INFORMATION TO USERS The most advanced technology has been used to photo­ graph and reproduce this manuscript from the microfilm master. UMI films the original text directly from the copy submitted. Thus, some dissertation copies are in typewriter face, while others may be from a computer printer. In the unlikely event th a t the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyrighted material had to be removed, a note will indicate the deletion. Oversize m aterials (e.g., maps, drawings, charts) are re­ produced by sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps. Each oversize page is available as one exposure on a standard 35 mm slide or as a 17" x 23" black and white photographic print for an additional charge. Photographs included in the original manuscript have been reproduced xerographically in this copy. 35 mm slides or 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. 1 UMI A ccessing th e World's Information sin c e 1938 300 North Z eeb Road, Ann Arbor, Ml 48106-1346 USA O rder N u m b er 8807145 C h aracterization o f resid u al ph osp horus in som e M ichigan soils Yerokun, Olusegun Adedayo, Ph.D. Michigan State University, 1987 UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106 PLEASE NOTE: In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this docum ent have been identified here with a check mark V . 1. Glossy photographs or pag es_____ 2. Colored illustrations, paper or print______ 3. Photographs with dark background_____ 4. Illustrations are poor copy_______ 5. Pages with black marks, not original copy _ 6. Print shows through as there is text on both sides of p a g e _______ 7. Indistinct, broken or small print on several pages 8. Print exceeds margin requirem ents______ 9. Tightly bound copy with print tost in spine_______ / 10. Computer printout pages with indistinct print______ 11. Page(s)___________ lacking when material received, and not available from school or author. 12. Page(s) 13. Two pages numbered 14. Curling and wrinkled pages 15. Dissertation contains pages with print at a slant, filmed a s received 16. Other seem to be missing in numbering only as text follows. . Text follows. CHARACTERIZATION OF RESIDUAL PHOSPHORUS IN SOME MICHIGAN SOILS By Olusegun Adedayo Yerokun A DISSERTATION Submitted to Michigan State University In partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Crop and Soil Sciences 1987 CHARACTERIZATION OF RESIDUAL PHOSPHORUS IN SOME MICHIGAN SOILS By Olusegun Adedayo Yerokun AN ABSTRACT OF A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Crop and Soil Sciences 1987 ABSTRACT CHARACTERIZATION OF RESIDUAL PHOSPHORUS IN SOME MICHIGAN SOILS By Olusegun Adedayo Yerokun When that phosphorus (P) Is applied to the soil it undergoes render it more stable. Therefore only a fraction reactions of annual P application is removed by plants. Cultural practices have resulted in an accumulation of high levels of P residue in some agriculture. It was of interest to know the areas of intensive effectively available portion of this residue. Selected extractants - Bray PI, Bray P2, Olsen, AER, and CaClg were evaluated in a greenhouse study in relation to plant dry matter yield and P uptake, on 10 Michigan soils with various levels of residual soil P. 7.8. This group Furthermore, of heterogenous soils varied in pH from 5.6 to the chemical nature of P in these soils was determined by the solubility product principle. The was 1:20 amount of P extracted on each soil varied with extractant but highest with the Bray tests. In this case a soil:solution ratio for the Bray PI extracted P similar to Bray P2 (1:8) except calcareous method. Charity clay soil when more P was extracted by Generally the Bray method was more effective in soil testing low in P. the of on a latter detecting the OLUSEGUN ADEDAYO YEROKUN Plant weakly plant dry matter yield over ten consecutive 5-week crops was only correlated with soil tests, and soil characteristics as well physiological adjustments were found to have influenced as this observation. The Olsen, AER, and CaCl2 tests were better correlated with P uptake on this group of heterogenous soils. When the soils were separated by relative buffering capacity and P release mechanism it found that the Bray tests were affected more, as was correlations were improved. A mass balance comparison of P uptake with change in showed that the effectively available P was under soil estimated tests for the soils, except a Montcalm sandy loam soil. In this case it appeared that unavailable P was being extracted by the Bray tests. Generally the Bray PI from (1:20) and Bray P2 (1:8) more closely predicted plant P uptake the soils. Furthermore, the uptake from some uncultivated soils suggested that organic-P contributions were significant. The results of the solubility study showed that Al-P and Ca-P were important sources of P to plants, however, the high levels of residual increased the contributions from adsorbed P. P in some soils DEDICATION To my family. With love to my Wife, Dellia Judith The wind beneath my wings. With affection to my Daughter, Gbadero Aweni II The essence of my hopes and aspirations. In honor of my dear Mother, Gbadero Aweni I The essence of my Joy and struggle. In dear and loving memory of my Father, Simeon Alabi The pillar of my determination and a Monument of unageing intellect. Who taught me to Follow Knowledge like a sinking star To the utmost bounds of human thought. iv ACKNOWLEDGEMENTS Dr. Donald R Christenson served as my program and throughout my understanding Drs. Boyd graduate study. and support. I am most Indebted thesis to adviser him for his The members of my advisory committee Ellis, Norman Good, Bernard Knezek, and Darryl were Warncke. I thank them for their time and critical review of my program. I am grateful to the many people who helped me in the course of my project. I thank my Sisters and Brothers for their Interest in my goals encouragement of my pursuits. The patience and strength Mother through Though saddened that my Father was not present to witness through my years away from home eased the burden shown on my my by and my mind. progress this path that he set me off on, I rejoice in sharing with him the attainment of this milestone. My work could not have been completed without the selfless support of my Wife. She as much as I, has earned this. Saving the best and most for last, I give ceaseless praise and thanks to God Almighty who has made everything possible by the breath of life. v TABLE OF CONTENTS List of Tables--------------------------------------------- vii List of Figures-------------------------------------------- ix Introduction ---------------------------------------------- 1 CHAPTER 1: Availability of Residual Soil Phosphorus Introduction--------------------------------------------- 6 Literature Review---------------------------------------- 8 Materials and Methods------------------------------------ 17 Results and--Discussion---------------------------------- 22 Summary and--Conclusion---------------------------------- 49 CHAPTER 2: Solubility of Residual Soil Phosphorus Introduction--------------------------------------------- 52 Literature Review---------------------------------------- 54 Materials and Methods------------------------------------ 57 Results and Discussion---------------------------------- 58 Summary and Conclusion---------------------------------- 74 Appendix--------------------------------------------------- 75 Bibliography----------------------------------------------- 76 vi LIST OF TABLES Table 1. Median phosphorus levels for Michigan for soil samples tested at the MSU Soil Testing Laboratory. Table 2. Effect of applied phosphorus and potassium on yield of corn grain in a long term study conducted on a Conover loam, 19731983. Table 3. Soil classification of some Michigan greenhouse study of residual P. Table 4. Chemical and physical description of some Michigan soils used in a greenhouse study of residual P. Table 5. Summary of cumulative whole plant dry matter yield and phosphorus uptake of 10 consecutive crops grown in the greenhouse on 10 soils with various residual P levels. Table 6. Soil solution P levels for 10 soils with various levels of residual P, during a continuous cropping in the greenhouse. Table 7. Distribution of total dry matter yield of 10 greenhouse crops between plant tops and roots. Table 8. Phosphorus concentration of plant tops for crops grown in the greenhouse on 10 soils with various levels of residual P. Table 9. Phosphorus soil test values for 10 soils used in a greenhouse continuous cropping study of residual soil P. soils used in a consecutive (r) coefficients for the relationship Table 10. Linear correlation between dry matter yield and P uptake of 10 consecutive crops grown in the greenhouse, and the initial P soil test levels of 10 soils with various residual P levels. (r) coefficients for the relationship Table 11. Linear correlation between total dry matter yield and P uptake of 10 consecutive crops grown in the greenhouse, and the differences between initial and final P soil test levels of 10 soils with various residual soil P levels. (r) coefficients for the relationship Table 12. Linear correlation between P uptake of 10 consecutive crops grown in the greenhouse, and the initial P soil tests of 10 soils with various residual P levels, when the soils were stratified. vii Table 13. Linear correlation (r) coefficients for the relationship between P accumulation by 10 consecutive crops grown in the greenhouse, and the changes In soil test levels during cropping of 10 soils with various residual P levels. Table 14. Slope (b) values for the linear regression relationship between accumulation of P (x) by 10 consecutive crops grown in the greenhouse and changes In P soil test levels (y) during cropping of 10 soils with various levels of residual P. Table 15. Changes in the P content of 10 soils with various residual P levels, following P removal by 10 consecutive crops grown in the greenhouse. Table 16. Soil P solubility factors for 10 Michigan soils with levels of residual P. Table 17. Nitrogen and potassium application schedule for a study of residual P in 10 Michigan soils. viii various greenhouse LIST OF FIGURES Figure 1. Diagram of nutrient model by Russel (1971). Figure 2. Relationship between Bray and Kurtz PI (1:7) and P removal by 10 crops in the greenhouse. extractable P Figure 3. Relationship between Bray and Kurtz PI (1:8) extractable and P removal by 10 crops in the greenhouse. P Figure 4. Relationship between Bray and Kurtz PI (1:20) extractable and P removal by 10 crops in the greenhouse. P Figure 5. Relationship between Bray and Kurtz P2 (1:8) and P removal by 10 crops in the greenhouse. Figure 6. Phosphorus solubility of some Michigan after a greenhouse cropping study. Figure 7. Effect of greenhouse cropping practice on the P of a Charity high P soil. solubility Figure 8. Effect of greenhouse cropping practice on the P of an uncultivated Charity soil. solubility Figure 9. Effect of greenhouse cropping practice on the P of a Kalamazoo high P soil. solubility Figure 10. Effect of greenhouse cropping practice on the P of a manured Kalamazoo soil. solubility Figure 11. Effect of greenhouse cropping practice on the P of a Spinks high P soil. solubility Figure 12. Effect of greenhouse cropping practice on the P of an uncultivated Spinks soil. solubility Figure 13. Effect of greenhouse cropping practice on the P of a Capac high P soil. solubility Figure 14. Effect of greenhouse cropping practice on the P of a Montcalm high P soil. solubility Figure 15. Effect of greenhouse cropping practice on the P of an Oshtemo high P soil. solubility ix extractable P soils before and Figure 16. Effect of greenhouse cropping practice on the P of a Hillsdale high P soil. x solubility INTRODUCTION The importance of phosphorus (P) in crop production is well documented. Therefore it is common practice for farmers to Include P their annual fertilizer management programs. As early as suggested farming, 1841, that "it must be borne in mind that as a practice what is taken from the soil must be returned to in Leibig of it arable in full measure." Because P applied to the soil regresses into unavailable forms (Larsen et requirements capacities. (residual al., 1965), are usually annual applications supplied in order to in excess fulfill of plant plant growth Nonetheless, it is known that P from previous applications P) can become available in subsequent years. This raises the question of it’s Importance as an integral of production programs. Can residual P by itself sustain a season of production at the current levels? The practice of continuous fertilization has resulted establishment of high P levels in many regions of intensive in an agriculture (Table 1). This can bring about concerns about soil nutrient imbalances as well as for the environment (leaching and eutrophication), especially in a state such as Michigan with many game and recreational waters. On the other hand, such residual P may be as effective as P so, Inland fresh applications for crop production (Mattingly, 1971). When this is residual properties P is nonetheless valuable, affecting (Biswas the soil et al., 1970; Lutz and Haque, 1975).The 1 not physical nature of 2 Table 1. Year Median phosphorus levels for Michigan for soil samples tested at the MSU Soil Testing Laboratory*. Number of Samples PT -mg/kg1962 1963 1964 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1979 1980 1981 1982 1983 1984 1985 +Source: 6,792 10,397 14,172 15,021 13,753 18,668 14,063 12,216 12,323 12,139 14,140 24,446 19,263 27,207 29,953 24,755 24,319 27,574 24,631 29,580 24,886 22,038 Michigan State University Soil Testing Laboratory. TBray-Pl, 1:8, soilrsolution attraction. 12 12 15 18 17 16 20 22 26 27 29 32 34 34 35 48 54 49 50 52 54 53 residual soil P has been of Interest but not of concern. There Is no Indication of urgent considerations of the mobilization of residual soil P. This may be because of the availability of high quality P minerals at economical price. The high prediction of the availability and plant use of residual P on P testing soils Is not now well understood. Yet this knowledge is Imperative to economically manage the rising soil P levels. observations (Table 2) have indicated a lack of response to applications to more of these soils. Excessive fertilization result In yield. P This uptake by plant without acceptable gains has prompted some agronomic and in Recent further can dry P only matter economic concerns. Furthermore, the energy and raw materials used in commercial fertilizer production are limited resources and must not be wasted. Whereas amount of chemical soil test methods have been used to estimate P that can become available to crops, these are sometimes questionable. A reliable soil test should extract the P fractions are well correlated with the P removed by plants. For a single this may be adequate on similar soils but inconsistent the on which method, soils of differing properties. Moreover, these tests may not reflect the chemical and microbial transformations that contribute to P equilibrium and plant uptake. Berlnger (1985) has suggested that soil test interpretations and applications In the supplied continuing by exhaustive that be reviewed to suit the current levels of high effort to determine the amount of P fertility. that can be resorted to and relative cropping. The one set back to this approach is the residual fraction, some agronomists have it is retrospective. In order to use any parameter of soil P, it Table 2. Effect of applied phosphorus and potassium on yield of corn grain in a long term study conducted on a Conover loam, 1973-1983. Fertilizer3 Applied P2°5 k 2o Year 1973 1974 1975 1976 1977 1978 1979 1980 1981 1983 Average — lb/acre-0 0 124 175 139 150 182 183 160 190 175 179 166 0 50 100 150 150 150 128 125 122 171 179 176 142 138 147 151 158 147 173 180 178 178 169 180 156 155 166 187 192 190 178 178 186 176 170 180 164 164 167 b 100 100 50 150 0 75 c 123 125 123 124 168 173 177 177 157 147 144 135 159 158 160 151 165 158 171 176 182 179 177 178 157 151 152 154 196 191 190 190 170 175 185 171 175 177 175 181 165 164 165 164 LSD (5%) NSd aAnnual application except b and c below. **150 lb P20,-/acre applied in 1973, 1976, 1979 and 1982; none in other years. C225 lb ^O/acre applied in 1973, 1976, 1979 and 1982; none in other years. ^Year x treatment interaction. g Comparison of treatment averages. Source: Christenson and Vitosh (1984). NSe should be able to foretell and account for the variation in yield of and uptake by plants grown on soils of varying P levels. The following study was conducted to: 1. Evaluate the and plant use of residual soil P. residual soil P. 2. Monitor some availability transformations of CHAPTER 1 AVAILABILITY OF RESIDUAL SOIL PHOSPHORUS INTRODUCTION Frequent current use of inorganic fertilizers is an integral part intensive production programs. Of particular attention are macro-nutrients. The nature of P is such that only a fraction of the of that applied in a single season is available for plant use. A portion of the remainder can become available for plant use in subsequent seasons. This accumulating P fraction is available residual P. Soil characteristics influence the behavior of P. For this reason soils need to be treated differently in terms of P management. Soil test methods evolved out of the need to know the magnitude of plant available nutrients. Because interferences applicable. results. with of P the heterogeneity of extractants, there is soils no and one the universal This further complicates the interpretations of Therefore, possible attempts have been made to exhaustively soil test test remove P from soils with plants and relate these to soil test results. In Michigan where Increasing P levels can become of concern, it was of interest to examine the potentials of these soils and soil test perfomance. The following study was undertaken to; 1. Study P levels in soils of with varying fertilization histories. 2. Determine the effect cropping on P levels in soils. 3. Examine the relationship between P levels and plant performance. 4. Examine the influence of soil on plant P use. factors LITERATURE REVIEW Russell (1977) proposed a nutrient dynamics model (FIs 1) that could serve to Illustrate the fate of P fertilizers. This model suggests that following remains a plant removal and loss from the system, pool of plant available P residue. If no of P, further there nutrient input is made it would be expected that plants can obtain some nutrition from this because Many pool. slow factors Available residual soil P does not reactions render it unavailable in time interact to partition the P supply remain constant (Barrow, 1974). into the different removed in agricultural products depends on the kinds of Gifford et pools. Some of these are discussed below. The products al. P exported and cultivation practices. In Australia, (1975) reported that an average of less than 20?* of annual P application is removed in the same year. Larsen (1974) estimated 10?* for Denmark, and Davis (1962) put the figure at 25?* for the U.S. Various characteristics of plants influence their ability to use soil P. Some of these are rooting patterns, root physiology (Johnston and Olsen, 1972; McLachlan, 1976), and plant age (Barrow and Campbell, 1972). Phosphorus losses such as by leaching and erosion are usually small, in the vicinity of 2?* (Schumann et al., 1973). However, on sandy soils with low buffering capacities and low water retention, it could be high exceeding 80?* (Neller et al., 1951). Immobilization residual value of reactions between soil and fertilizer soil P. These reactions are reduce principally those adsorption, precipitation and fixation. In the final analysis, the type the and characteristics play an important part In the magnitude of soil of P N u trie n t input F(t ) u U n a v ailab le nu trient K XA A A v a ila b le n u trie n t Figure 1. Diagram of nutrient model by Russell (1977). L osses ►- from system Rem oved p la n t p ro d u c ts 10 immobilized. then Given possible to the current rates of fertilizer application estimate that residual soil P could it range is from insignificant to appreciable amounts. Phosphorus Reactions With The Soil: Available Inorganic Fractions Phosphate role with the soil constituents play an ultimate in P availability to plants. In this respect, Inorganic soil P maintained The reactions in three Important fractions pertaining to plant relationship is nutrition. between these fractions can be represented as: Soil solution P <«*«> Labile soil P <-*«> Non-labile soil P. Soil solution P Is the fraction from which plant roots directly obtain nutrition , usually In the orthophosphate form (Khasawneh et al., 1979). The P concentration in soil solution of fertile arable soils about 10 It is B is M. As this is considerably low compared to plant requirements, necessary to continuously replenish this pool to avoid P deficiency. The labile P fraction serves this purpose. Labile soil P consists of P weakly adsorbed on to This fraction is in equilibrium with solution P potentially available concentration for plant use soil surfaces. and is considered to be (Larsen 2 of P in this fraction could be 10 et al., 9 to 10 1965). times The greater them in solution (Mengel and Kirby, 1982). As a matter of time and soil P retention characteristics, the labile pool can become more stable and move into the non-labile pool (Barrow and Shaw, 1976). Non-labile P is strongly held on and within the clay lattices or is occluded by some other precipitation-recrystallization reactions. This fraction reverts non- slowly into labile P, and is considered avallable to plants. to be 11 When reaction step the soli P equilibrium Is disturbed by adding fertilizer, between fertilizer and soil take place In two steps. A rapid leads to the adsorption of P, and a slow reaction converts P the more firmly held form (Barrow, 1974; Hayward and into Trapnell, 1964). Large and continuous application of P over a period of time will likely reduce the amount and rate of P fixed by the soil , resulting in high available residual P. The ability of a soil to supply P to plants is governed by the soil buffering capacity (Holford and Mattingly, 1976). This parameter is ratio (I), between adsorbed P, quantity (Q), and soil solution P, at an equilibrium solution concentration. It is an the Intensity indication of the ability of the soil to replace a unit change in soil solution P; the relative amount of P needed to replace a unit change in soil solution P; and the soil P requirements to maintain a productive solution concentration. The soil P buffering capacity may be the limiting in P uptake (Holford, 1976; Nair and Mengel, 1984). buffering Soils capacities usually may only need to maintain low factor with high intensities because of their ability to quickly respond to changes in solution P, as long as levels there is adequate quantity. However, they do require of quantity to maintain the plant optimum intensities higher (Holford, 1976; White and Doll, 1971). Phosphorus isotherm 1980). buffering plots(Holford, capacities are derived 1976; Parfitt, 1978; Olsen from and adsorption Khasawneh, 12 Plant Vae Of Available Residual Soil Phosphorus Phosphorus applied to the soli is rendered partially unavailable as soil reactions previous defined partition it Into various pools. The fraction P applications that remains available for plant use as residual P. This fraction has also been shown from has to been play a recognizable role on crop nutrition and production (Barrow, 1980). In a (1974) review of residual P in Canadian soils, Sadler and Stewart compiled evidence that this residue can amount to agronomic economic importance. On some high P fixing soils of North and Carolina, Kamprath (1967) showed that residual effects can be noticed even 9 years following a large initial application. Learner (1963) was able to recover two thirds years of a 235 kg P/ha application to New Mexico soils, with of alfalfa and 1 year of sorghum. When the differences in 4 yields between a single large application and four annual small applications to Kansas soils though the were compared, Janssen et al. (1985) showed that significant yield from the large application in even the first year had disappeared, it was as effective as single applications in fourth year. applications large In an Matocha et al. (1970) observed that made over a ten year period was as effective as application observed Texas, five increase years later. Allessl of and 10# in grain yields due Power to a the small single (1980) the also effect of residual P in North Dakota soils, up to six years following application. In England, Mattingly (1971) even reported that residual effects were superior to fresh effects on potato/sugarbeet plots. When residual P not only as effective as fresh P, it is nonetheless valuable, affecting P status but also water holding capacity, organic matter, is not and 13 modulus of rupture (Lutz and Haque, 1975). Important as residual P appears, there Is a problem in predicting it's availability. Factors Affecting Plant Use Of Residual Soil Phosphorus The plant use and availability of residual P is affected by soil environment and other factors. These are mostly factors that affect solubility effects of fertilizer P and plant foraging ability. While the simple have been extensively discussed in the literature, there is no doubt that interactions prevail. The studies by Mattingly (1968, 1970) and Devine et al. (1968) compared fertilizer sources. They showed that the Initial effect of more water held soluble superphosphate was superior to rock P while the reverse true for residual effects. The dissolution of rock P can be especially in non-acid soils, allowing for a longer period with reduced chances of loss. Residual effects of granular were superior to the powdered form(Mattingly et al., 1971; of slow, supply fertilizers Terman et al., 1960). As the period of prior contact with the soil Increased, the residual effectiveness decreased (Barrow and Shaw, 1974 and 1975a). Mattingly superphosphate to and Wlddowson (1963) observed that the percentage fresh equivalent (the ratio of yield obtained with residual that obtained with fertilizer application) increased with the rates previously applied. However, the study by Kamprath (1967) suggests the rate residual fixing needed is relative to the soil characteristics. He that only effects following a large application of 612 lb P/A to high soils. By increasing the fertilizer rates, the length effectiveness of residual P may also be increased (Learner, 1963). P saw P of 14 The total decrease amount of added P recovered from soils appears as the soil clay content increases (Campbell, 1965; to Bar-Yosef and Akiri, 1978; Barrow and Shaw, 1976). However, Barrow (1973) found a slight trend toward Increased residual effectiveness with high buffering capacity. Increasing temperature contributed to a decrease in residual effectiveness (Barrow and Shaw, 1975b) as a result of enhancing the slow reaction. Barrow The relationship with soil moisture is not so (1974) dried simple. incubated soils at moisture contents ranging When from air- to water logged, before cropping them, he observed that the soil Incubated air dry had a better residual effectiveness. This was probably because the Increasing point limitation on the aqueous phase retarded water logging interactive effects. (Barrow it the residual effectiveness. Further to did not introduce marked decreases in residual value. In is Important to keep in mind it is dealing Involved and wilting up and When mechanism reactions. the water content of incubation up to the permanent decreased conclusion slow Shaw, in not exactly that possible increases these to eliminate with different soils, it is the immobilization of 1974), as this reduces factors helpful residual the P are additive that is the similar complications of Interpretations. Determination of Available Residual Soil Phosphorus It approach test has been a challenge to Soil Scientists to develop to predict the amount of available residual soil P. methods, complicated modifications, nature. and Interpretations Olsen et al. (1983), Novais and a reliable The many to its attest Kamprath (1978), 15 Bowman et (1984) have chemical al. (1978), Adepoju et al. (1982), and observed significant but variable Aquino and Hanson correlations soil tests (Bray, Olsen, Merlich) and P uptake and or While these tests were developed to incorporate the many soil that affect available soil P, they sometimes react with portions between fractions that to the plant. Furthermore,they do not indicate yield. are the not chemical and microbial transformations that may occur during the season. Isotoplc (32P) and resin extraction have also been well correlated with P and yield (Dalai and Hallsworth, 1976 and Bowman et latter approach strong chemical. has al., been more reliable because of the That is not to attempt to refute the uptake 1978). The absence of importance quick chemical tests, just to indicate the problem that begins to as soil fertility level Increases beyond the range used for a of arise established interpretations. Kurtz and Quirk (1965) and Fox and Kamprath (1970) used the displacement of the adsorption isotherm and P requirements by previously fertilized used soils to estimate the residual effectiveness. Fitter the relationship between P aging and measured NaHC03-P to residual discussed effect of previously applied P. The efficacy were found to be dependent on soil of (1974) predict the tests characteristics and laboratory manipulations, therefore comparisons are on a relative basis. It is thus agreeable that total plant available P is best determined by plants. In order to more usefully quantify residual P, a relative cropping approach has been utilized. Because of the many factors affecting soil P equilibrium rather than a better approach would be to consider the the availability of residual soil P. Barrow effectiveness and Campbell (1972) of a suggest that the residual value should reflect the previous Mattingly application (1968), Mattingly relative to it’s initial and Widdowson (1963) and availability availability. Devine et al. (1968) measured residual P by comparing the effectiveness of previous to fresh P applications for plant growth. The value was refered to as "percentage fresh superphosphate equivalent." This approach assumes that fresh P can duplicate the behavior of residual P. But Mattingly (1971) in another set of experiments found that residual P improved yields over fresh P application. Other concerns of using this approach are that oftimes it is important to know the fertilization history and the must be such that they will respond to fresh P applications. The of soils effect variations in seasons will influence the measurement of initial residual effects. calculations and Arndt and McIntyre (1963) made adjustments in their to allow for this. They decided that a single season mean yield when multiplied by the ratio of the mean of control plots for the seasons over the mean of control plots for a single better reflect yields had seasons been similar. all season, would More recent investigations have concentrated on determining the P supplying power of soils, as an index for further cultivation practices. MATERIALS AND METHODS Ten soils previously were used in the study, seven of which cropped and three uncultivated. The descriptions had been follow in Tables 3 and 4. Soil pH was measured in a 1:1 soil: water suspension and 1:10 soil: analysis 0.01M CaClg suspension using a glass electrode. Textural was made by the hydrometer method (Bouyoucos, 1962). The soil CEC was determined by NH40Ac saturation and alkaline steam distillation. Total N was analyzed for by the micro Kjeldahl Mulvaney,1982). Organic method matter was determined by a (Bremner modified and Walkley- Black procedure (Page, 1974). Greenhouse Experiment A greenhouse Investigation was conducted using the soils described above to monitor plant use patterns of residual soil P in some soils. Michigan In order to accomplish this, surface soil samples (0-15cm) collected screened from to the field in the autumn. The soils were pass through a 4 mm sieve. Havlin and were air-dried Westfall and (1984) observed that P being rather immobile accumulated in the top 7.5cm, and Ozanne top et al. (1965) suggest that plant roots proliferate in the soil, so it was felt that the surface samples should be a good indicator of P supply. The experimental design was a randomized complete block with replicates. Three kilograms of soil were placed in pots four lined with plastic bags. Each pot was watered to the soil water content at 0.03 MPa (field moisture capacity), and maintained by weighing dally and adding water as needed. Following the initial watering, seeds were planted and thinned to fifteen following emergence. Nitrogen as NH^NOg and potassium 17 18 Table 3. Soil classification of some greenhouse study of residual P. Soil Series Texture Charity Charity (uncultivated) c scl Kalamazoo (manured) 1 Spinks si Spinks (uncult ivated) si Montcalm 1 si Oshtemo Hillsdale Family Aerie Haplaquept, fine mixed, mesic Kalamazoo Capac Michigan si soils used in Previous Treatment Small grains rotation Grass-shrub fallow Typic Hapludalf, fineloamy, mixed, mesic Small grains Grass fallow Psammentlc Hapludalf, sandy, mixed, mesic a Small grains Woody vegetation Aerie Ochraqualf, fine-loamy, mixed, mesic Small grains Eutric Glossoboralf, sandy, mixed, frigid Potato Typic Hapludalf, coarse-loamy, mixed, mesic Small grains Typic Hapludalf, coarse-loamy, mixed, mesic Small grains Table 4. Chemical and physical descriptions of some Michigan soils used in a greenhouse study of residual P. Particle Size pH Soil h 2o CaCl2 S Si C — mg/ kg- CEC Total-N cmol(+)/kg soil O.M. Total-P Moisture Capacity g/kg — lag/K g — Charity 7.8 7.2 80 330 590 26.1 1.7 19 927 290 Charity (uncultivated) 7.6 7.1 90 340 570 35.3 2.7 35 804 300 Kalamazoo 6.6 6.0 510 280 210 9.4 1.0 17 585 180 Kalamazoo (manured) 6.3 5.8 380 410 210 18.3 2.4 24 631 260 Spinks 5.6 4.8 490 360 150 7.9 0.9 13 608 160 Spinks (uncultivated) 6.7 6.4 690 210 100 11.3 1.2 25 401 90 Capac 6.6 4.8 480 370 150 7.1 0.9 16 619 280 Montcalm 6.5 5.7 630 240 130 6.6 0.8 12 631 140 Oshtemo 6.8 6.2 430 380 190 9.7 1.4 17 691 200 Hillsdale 6.6 6.2 790 100 110 3.8 0.6 9 381 70 +f.m.c. at 0.03 MPa. 20 as KC1 and (Appendix cropping K2S04 were supplied at different rates during cropping Table 17). Lime applications at 2 g/culture were made the Spinks soil and at the end of the third cropping before for all soils except the Charity soil. A sequence bicolor). 2 followed. Each of 3 sudax (Sorghum Sudanese), 1 sorghum oats (Avena satlva var Korwood), 3 sudax, and 1 cropping period was for 35 days. Plant tops (Sorghum oats and was roots were harvested separately by cutting the plant tops just above the soil, and the roots. The roots were thoroughly washed with distilled water. All plant matter was then passing the soil through a 4 mm sieve to separate dried for 48 hours at 60 °C, weighed and ground to pass through 0.60 mm a sieve using a Wiley mill. Following the removal of plant roots the soil In each pot was re­ mixed and alr-drled for approximately 2 days before the subsequent crop. Soil samples were removed when crops 1, 3, 9, and 10 were harvested. Following is a description of pertinent analyses. Plant Analyses: Of the dry and ground in 5 mL of a plant tissue, 250 mg was digested H2S04:H202 mix (Parkinson and Allen, 1975). The concentration was then determined by the ascorbic acid method of P Murphy and Riley (1962) and measured on a Bausch and Lomb Spectronlc 20 at 880 urn. Bray and Kurtz-P: Two grams of soil samples were shaken at ratios of 1:7, 1:8 and 1:20 (soil:extractant) in Bray and Kurtz-Pl (0.025 N HC1 + 0.03 N N NH4F) solution and a ratio of 1:8 in Bray and Kurtz-P2 HC1 + 0.03 N NH4F) solution, for 5 minutes at 220 rpm on an (0.10 oscillating shaker. The suspensions were then filtered and P determined as above. 21 Resin Exchangeable P : One gram of soil (<2u) in contact with resin (Dowex 2 g 2-X4, basic anion) was shaken in 100 mL of water of for hrs. The soil and resin were then separated by washing the soil 24 through a 0.3mm sieve with distilled water. The resin was washed in hot 10$ NaCl solution (Amer et al.,1954) The volume was diluted to 100 mL with the NaCl solution and P determined as above. Water Soluble P : Five grams of soil was shaken in 50mL of 0.01 M solution for 1 hour. The samples were filtered and P CaClg determined as above. Total Soil P : Two hundred milligrams of soil was digested in 3 HClOg (1972). on an aluminum digest block according Following digestion at 203 °C for to Sommers 90 minutes, mL and of Nelson samples were cooled, diluted and P was determined as above. Statistical Analyses Analyses of data was performed using the Michigan State University MSTAT computer programs. Interpretations were essentially by the methods described by Snedecor and Cochran (1967) and Steele and Torrie (1980). RESULTS AND DISCUSSION A greenhouse residual sites soil in Investigation was conducted to study plant P on a range of soils. Samples were collected South-Central Michigan. Seven of these soils use from had of ten received annual inorganic P fertilization in the field for an undetermined length of time, but no less than 10 years. One of the soils had once been site for soils. a dairy operation and the remaining two were unfertilized The soils were characterized in the laboratory by methods have been used to estimate the intensity, quantity and capacity of soil P. accounting These values were then compared for quantitatively their for available soil P as the that factors Importance measured by in plant uptake. Crop Yield and Phosphorus Uptake Dry matter availability differences yield and P uptake were used to evaluate of residual soil P. It is recognized that there in dry matter production between soils, due would to tests physical/chemical characteristics of the soils was envisioned as means to evaluate the availability of P in a group of be inherent differences between soils. However, comparison of P removal, soil and the a heterogeneous soils. There cropping during dry were (Table significant 5). differences in crop The cumulative yield figures yields throughout suggest that only the first cropping was there a probable effect of residual P matter accumulation. At this time yields were higher on fertilized soils when compared to the uncultivated soils. previously As cropping progressed, the uncultivated Charity and manured Kalamazoo were as 22 on good Table 5. Summary of cumulative whole plant dry matter yield and phosphorus uptake of 10 consecutive crops grown in the greenhouse on 10 soils with various residual F levels. 1 Crop+ • 3 Crops 9 Crops 10 Crops Yield Uptake Yield Uptake Yield Uptake Yield Uptake g/culture mg/culture g/culture mg/culture g/culture mg/culture g/culture mg/culture Charity (high P) 27.2 35.5 31.7 65.2 60.7 135.8 66.2 154.0 Charity (uncultivated) 15.5 14.1 31.8 33.3 65.2 93.5 71.5 110.3 Kalamazoo (high P) 36.5 41.9 58.3 87.0 89.5 160.7 94.2 182.4 Kalamazoo (uncultivated) 34.3 31.5 62.9 82.6 92.0 117.3 97.2 124.7 Spinks (high P) 30.9 32.7 55.0 71.1 85.3 130.2 89.4 150.5 Spinks (uncultivated) 10.4 7.5 17.2 14.3 40.6 44.9 44.3 51.7 Capac 30.0 40.7 46.3 84.5 83.7 176.6 88.0 194.3 Montcalm 26.3 35.0 33.8 51.2 58.4 103.1 61.3 117.0 Oshtemo 36.0 53.1 53.9 108.5 90.7 203.4 94.3 224.2 Hillsdale 11.0 8.7 19.2 16.3 40.4 48.5 43.8 57.5 4.6 3.8 9.0 15.0 9.5 17.3 9.0 18.5 Soil LSD (5%) +Each crop was grown for 5 weeks before harvesting tops and roots. 24 as their fertilized counterparts, while the fertilized Spinks remained superior. The former were under grass/shrub fallow, nutrient cycling may nutrient supply. On the other hand, the uncultivated Spinks have been active enough to therefore maintain adequate soil under wood vegetation. The Capac and Oshtemo soils performed Hillsdale soils were poorer than expected. The current would suggest influencing that the residual accumulation P did not play an Montcalm observation important of dry matter on these was relatively well as the soil tests would suggest. Dry matter yields on the and soil soils role in over the cropping period. To further support this is the weak correlation between soil tests and Nevertheless, it dry is matter yields across the possible that the influence soils of (r»0.23). residual P was concealed. When soils significant be with significantly varying soil P levels do difference in dry matter yields, a number of factors responsible. Among these are: (1) sufficiency of P at levels in not soil solution, (2) plant top and root the show could critical partitioning as a response to nutrient limitations, (3) soil physical characteristics, and (4) plant examine and or soil nutrient imbalances. Thus it was decided how these factors may have influenced the observations in to this study. The soil soil buffering capacity is an inherent characteristic solution P supply. Therefore on various soils, the P maintain higher solution P concentration while stronger buffered maintain lower millet will vary. Weakly limiting solution that concentration of buffered concentrations (Holford, 1976). Rajan grown on well buffered Hawaiian soils soils (1973) had the soil usually soils observed solution P requirements and ranging from 0.06 - 1.94 X10-5 M. Fox and Kamprath Ozanne lack and Shaw (1967) established that near maximum yields of response to further P applications could be expected soil solution P is maintained at 6.45 - 9.68 soil (1970) or when a the X10~^ M. Table 6 shows the solution P values observed at intervals over the cropping period. Even though critical levels were not determined for the soils used, when compared to values in the literature only the Hillsdale , uncultivated Kalamazoo point this and Montcalm soils exhibited critical concentrations during was the study. Judging from their production of not a permanent situation. The low P at dry matter, concentrations in uncultivated Charity and Spinks, manured Kalamazoo, and Hillsdale coincided with deficiency symptoms at the fertilized their any the soils termination of the study. The Charity and Capac soils also had low P concentrations, P capacities and soil buffering capacities would be but expected sustain production on these soils. For this reason, it is presumed to that the Influence of solution P is not now conclusive. Some studies that have been conducted with P as nutrients have revealed that limitations of soil nutrient introduce variations in the ratio of dry matter plant tops and roots. Asher and Loneragan (1967) plant tops respond with content partitioning observed to P, the total weight of roots may other be can between that when reduced. Furthermore, Williams (1948) showed that photosynthate translocated down is trapped and used for root growth when P is limiting. Ozanne (1980) suggested that having large root growth may be an evolutionary advantage for survival and growth under limiting conditions. Large root growth may subsequently influence foraging ability and water use. The total shoot and root weights are given in Table 7. It would appear that the lower P 26 Table 6. Soil solution P levels for 10 soils with various levels of residual P, during a continuous cropping In the greenhouse. Period of Sampling Soil Original Soil Crop 3 Crop 1 _ tp yi + Crop 9 Crop 10 n- ^____ Charity (high P) 1.50 0.20 0.90 0.30 0.23 Charity (uncultivated) 0.20 0.20 0.10 0.50 0.20 Kalamazoo (high P) 3.25 5.56 5.00 3.43 3.10 Kalamazoo (uncultivated) 0.70 0.01 0.01 0.73 0.30 Spinks (high P) 5.00 2.58 0.88 3.35 1.55 Spinks (uncultivated) 1.50 0.96 1.10 2.53 0.97 Capac 6.10 4.35 4.90 1.38 0.20 Montcalm 3.90 1.64 0.01 2.03 2.13 7.75 7.23 4.18 3.53 0.01 0.01 1.45 0.80 Oshtemo Hillsdale 12.2 0.30 •f Soil sample following plant harvest. 27 Table 7. Distribution of total dry matter yield of 10 greenhouse crops between plant tops and roots. consecutive Dry Matter Yield Soil Top Root Root Top --- ----g/culture— Charity (high P) 52.6 14.6 0.28 Charity (uncultivated) 52.2 19.3 0.37 Kalamazoo (high P) 64.8 29.5 0.45 Kalamazoo (uncultivated) 61.6 35.6 0.58 Spinks (high P) 61.5 27.9 0.45 Spinks (uncult ivated) 26.8 17.5 0.65 Capac 62.0 26.0 0.42 Montcalm 43.2 18.2 0.42 Oshtemo 68.5 26.0 0.38 Hillsdale 29.5 14.3 0.48 5.3 6.7 LSD (5%) 28 soils have a relatively larger root weight, especially the uncultivated Charity and manured Kalamazoo compared to their fertilized counterparts. There is a possible subtle effect of residual P here. As this observation is still inconclusive, further considerations were made. Ozanne (1980) suggested that an absence of yield differences could be Imparted by the amount of available water in soils. The soils in this study were through of cropping. imbalances indicates were different soil moisture capacity such Care was taken not to and introduce as compaction, flooding or moisture that thus any physical stress. P uptake was more on the fertilized soils not always that. Comparison of the soil water maintained Table but holding 5 yields capacities (Table 4) shows that except for the uncultivated Spinks soil other soils testing lower in P have relatively higher water contents at field moisture capacity. Perhaps this amount of available water influenced the production of comparable dry matter on the lowerP soils. It then plausible that the soil solution P in the lowerP soils may enough to trigger a relatively larger root growth on low which in turn improved water use efficiency. This have these resulted seems been soils, in the that no production of similar dry matter yields on the low P soils. Lastly, detectable the nutrient imbalances occurred. Cropping was uncultivated Hillsdale not visual observations made during cropping suggest terminated Charity, manured Kalamazoo, uncultivated when Spinks and soils showed P deficiency symptoms. The fertilized soils did demonstrate P deficiency at this point. Therefore, it is concluded that residual P is beneficial, but such benefits will be observed over a period of time. The length of cropping or production should then be important factor in estimating the availability of residual soil P. an 29 Phosphorus uncultivated uptake was higher on the fertilized soils than on soils, except for the Montcalm and Hillsdale soils the (Table 5). Since dry matter accumulation on the uncultivated soils was equal to that on some fertilized soils the P concentration was higher fertilized soils (Table 8). The decrease in uptake vs yield on correlation as cropping progressed (r« 0.92,0.88,0.83,0.81, respectively) indicates that other soil factors played seemingly increasing roles in dry matter yields as cropping progressed. The direct Influence of residual P can be observed in P uptake on the soils. The magnitude of this uptake did correspond that to the order of magnitude of soil testlevels, indicating soil characteristics will influence the rate of removal of P. Montcalm soil was notably intermediate in performance not The considering the high soil test level. Soil Test Values The However, Bray PIextraction with the fertilization, method method is increasing levels commonly of used soil itwas of Interest to compare the P P in Michigan. fertility and detected by this to theplant P use. Christenson and Vitosh (1984) have reported an absence of crop response to further P fertilization. This observation would suggest that only a disproportionately small amount of the soil was extracted. Thus it was decided to compare ratio of 1:20 to a extractant compared. (Bray The a wider soil:solution 1:8 ratio. Also increasing the acid strength of and Kurtz-P2) but retaining the Olsen method commonly used on current calcareous P ratio soils, the was resin extraction and soil solution P were Included in this comparison. Phosphorus soil test values are shown in Table 9. The soils differed significantly in the levels of available soil P as estimated by 30 Table 8. Phosphorus concentration of plant tops for crops grown In the greenhouse on 10 soils with various levels of residual P. _________________ Period of Sampling_________________ Soil Crop 1 Crop 3 Crop 6 Crop 9 Crop 10 %■ Charity (high P) 0.16 0.23 0.21 0.23 0.39 Charity (uncultivated) 0.12 0.10 0.18 0.24 0.30 Kalamazoo (high P) 0.13 0.21 0.25 0.20 0.63 Kalamazoo (uncultivated) 0.11 0.13 0.15 0.10 0.16 Spinks (high P) 0.11 0.16 0.22 0.20 0.69 Spinks (uncultivated) 0.07 0.11 0.16 0.12 0.25 Capac 0.16 0.27 0.28 0.29 0.54 Montcalm 0.14 0.28 0.24 0.19 0.66 Osh temo 0.17 0.30 0.31 0.29 0.74 Hillsdale 0.07 0.13 0.16 0.12 0.38 0.01 0.01 0.01 0.08 0.15 LSD (5%) Table 9. Phosphorus soli test values residual soil P. for 10 soils used In a greenhouse continuous cropping study of Soil Test_______________________________________ _____________Bray-Pl____________________ 1:7 Soil Initial 1:8 Final Initial 1:20 Final Initial Bray P-2 Final Initial Final NaHCO^P Initial AER-P+ Final Initial Final mg/kgCharity (high P) Charity (uncultivated) 43.4 17.7 49.6 21.7 86.0 47.9 171 114 28.0 11.3 60.8 30.5 8.2 6.3 10.2 9.8 23.4 25.6 98.3 84.2 10.4 9.9 24.1 19.1 Kalamazoo (high P) 136 83.5 133 89.1 178 130 172 126 46.9 37.9 102 82.2 Kalamazoo (uncultivated) 51.9 45.9 56.2 46.1 86.0 80.6 88.2 71.9 18.8 16.9 44.8 36.5 Spinks (high P) 132 85.6 129 89.9 170 131 172 128 48.9 23.4 57.5 47.2 Spinks (uncultivated) 45.2 46.7 48.0 45.8 61.7 67.4 75.8 81.6 15.1 14.2 38.7 27.7 Capac 134 56.0 131 60.5 170 99.5 167 121 51.0 24.9 60.8 51.1 Montcalm 239 179 227 220 322 280 307 263 50.3 52.2 97.9 104 Oshtemo 160 96.0 157 99.7 206 136 205 142 51.8 38.2 113 78.7 Hillsdale 75.9 66.4 77.2 68.2 110 106 95.7 92.8 18.0 17.8 32.7 53.5 +Anion exchange resin extractable P. 32 each method. As expected, the uncultivated soils tested lower In inorganic-P than their fertilized counterparts. Bray PI extractions at 1:7 and 1:8 were similar for each soil. Increasing the ratio to 1:20 resulted In more P being extracted. In turn the Bray PI (1:20) and Bray and Kurtz-P2 (1:8) extracted similar amounts of P, except on the high clay and carbonate content Charity soils, where more P was extracted by the latter method. The principle of test Is based on the ability of the F” to reduce Al3+ the Bray activity by competing with it thus releasing P in Al-P. The H+ then solubilizes Ca-P - but not apatite-P (Thomas and Peaslee, 1980). Therefore in clay soils possibility with high base exists for the saturation, neutralized before the effectively solubilize Ca-P (Pratt and Garber,1964; The Council on Soil observed be soils, can and to calcareous of it Testing H+ or cases Plant Analysis,1980). This is perhaps the reason for the Increases in extractable P with wider soil:solution ratio and stronger acid concentration on the Charity soil. The similar P extracted from the acid to neutral soils by the Bray and Kurtz-Pl (1:20) and and Kurtz-P2 predominance despite the stronger acid in the latter of Al-P in these soils. The Bray Bray underscores and Kurtz the method effectively detected that the uncultivated Charity soil was a low P soil with the potential for crop response to further P application. Thus this method provides a good degree of confidence as a soil test method on this group of soils. Olsen-P behind this result of suggest values were lower than all Bray method involves Increasing the solubility of precipitation of Ca3+ that while HCOg- and F" values. as CaCOg. Thomas and The principle Ca-P Peaslee appear to largely remove the as a (1980) same P 33 compounds, HCOg~ ions. rather was F~ will react more vigorously and remove P The ranking of the soils by magnitude of unavailable P extracted similar between the Olsen and Bray methods. However this less effective in detecting which soils would to is method respond to P application. This method would not be a suitable soil test on this group of soils. It action has been suggested that resin extraction simulates and may thus be a better indicator of available plant soil root P. This approach does not Include the use of strong chemicals, which reduces the incidence of extracting unavailable P compounds. In this case comparison of magnitude is higher only than the Olsen P and variable with the Bray PI (1:7, 1:8). Soil solution P, an intensity factor, was determined by extraction with 0.01M CaClg-P (Table 6). As expected the values here are much lower than for the other tests. Capacity factors could be as much as 10 —2 ° to 10~3 times more than Intensity factors (Mengel and Kirby, 1982). The 10. relationships among and between soil tests are given in Linear significant. the correlation coefficients are moderate Table to good, but This suggests that the extractants removed P mainly from same compounds on each soil, even though in different magnitudes. Furthermore the differences between soil tests before and after cropping were well correlated (Table 11), and P removal by plants from similar compounds may account for this relationship. The test effect of cropping the soils was a general reduction levels Kalamazoo cropping (Figures soil 2-5). The uncultivated soils however have slopes approaching zero. and On did not account for decreases in Inorganic P test the in soil manured these soils levels. In Table 10. Linear correlation (r) coefficients for the relationship between dry matter yield and P uptake of 10 consecutive crops grown in the greenhouse, and the initial P soil test levels of 10 soils with various residual P levels. Bray PI Uptake 1 Total Uptake Total Yield Bray PI - 1:7 0 .60^ 0.42^ 0.23nS - 1:8 0 .61^ 0.43^ 0.23nS 1.00^ - 1:20 0.60^ 0.40^ 0.20ns 0.99^ 0 .99^ Bray P2 0 .65^ 0.47^ 0.18ns 0.89^ 0 .86^ 0.92^ NaHC03-P 0 .82^ 0.74^ 0 .50^ 0.88^ 0 .88^ 0 .85^ 0.80^ AER-P 0 .83^ 0.68^ 0.43^ 0.80^ 0.81^ 0.80AA 0 .79^ 0.83^ CaCl2-P 0. 7 5 ^ 0 .75^ 0.48^ 0.54^ 0. 5 6 ^ 0 .52** 0.56^ 0 .75^ +Anion exchange resin P. ♦♦Significant at = 0.01. ♦Significant at “ = 0.05. nc Not significant at ® = 0.05. 1:7 1:8 1:20 Bray P2 NaHCOg-P AER-P+ 0.74^ CaCl2~P Table 11. Linear correlation (r) coefficients for the relationship between total dry matter yield and P uptake of 10 consecutive crops grown in the greenhouse, and the differences between initial and final P soil test levels of 10 soils with various residual soil P levels. Bray PI Uptake Yield Bray PI - 1:7 0.77** 0.49** 1.00 - 1:8 0.86** 0.63** 0.82** 1.00 - 1:20 0.87** 0.55** 0.96** 0.88** 1.00 Bray P2 0.87** 0.57** 0.80** 0.73** 0.89** 1.00 NaHC03-P 0.67** 0.49** 0.61** 0.82** 0.70** 0.63** 1.00 AER-P 0.68** 0.50** 0.29ns 0.52** 0.47** 0.61** 0.47** **Significant at * = 0.01. us Not significant at “ = 0.01. 1:7 1:8 1:20 Bray P2 NaHC03-P AER-P 1.00 Charily Soli Test Level (mgP/kg toll) rirjhCharts OJ o\ an 140J i f o ' is o z & o '220 Cumulative P uptake (mg/cuKure) Figure 2. Relationship between Bray and Kurtz PI (1:7) extractabte P and P removal fay 10 craps in the greenhouse. 329- i Charily virgin Charity o Kalamazoo ■ monund Kalamazc A ey w A virgh Spfcik i o Soil Test Level (mgP/kg soil) 305285265- ♦ 245- * A 225- X 205185- w '-j • 165145 125 105 85 65 45 25 5 r "■“t r *"i i 140 160 180 200 220 Cumulative P Uptake (mg/culture) Figure 3. Relationship between Bray and Kurtz P1 (1:8) extractable P and P removal by 10 crops in the greenhouse. Soil Test Level (mgP/kg soil) Charily viyHi UKiny Kalamazoo monurad Kolomazc Spinks virgin Spinks OJ 00 T— *— I— '— T-i— I— '— I— »— I— '— I— '— I— '— r 60 80 100 120 140 160 180 200 220 Cumulative P Uptake (mg/culture) Figure 4. Relationship between Bray and Kurtz P1 (1:20) extractdble P and P removal by 10 crops in the greenhouse. Charily Soil Test Level (mgP/kg soil) vigil viNllljr Kalamazoo manured Kolamazc «pnRi virgin Spinldi 205u> VO I— '— I 140 160 T" 1— r 200 220 Cumulative P Uptake (mg/culture) Figure 5. Relationship between Bray and Kurtz P2 (1:8) extractable P and P removal by 10 ten crops in the greenhouse. 40 fact, test beginning soluble levels during cropping were sometimes higher of P cropping (Table 15). There is a from organlc-P was being strong released than at the suggestion into the that Inorganic-P fraction of the soil P. Relationship Between Soil Tests and Plant Response There was a weak correlation between initial soil tests and plant over all soils (Table 10). In many cases dry matter yields performance rather than nutrient uptake is the measure of returns on investment. However, because of the singular interest in P removal from the soil and the appreciable correlation between yield and uptake, it was decided to use P uptake as the index for plant use of residual soil P. The linear correlation between soil tests and P uptake over all soils was weak to moderate (r- 0.40 to 0.74). In this case the Bray Kurtz method pattern was least effective (r-0.40) in establishing among this group of soils. A broad range of a an linear correlations have been reported in the literature (Dalai and Hallsworth, 1976). Increasing the soil:solution increasing increased the ratio did not seem to improve the acid sensitivity strength introduced to on the Charity Ca-P slight correlation, but improvement. soils by the The latter approach contributed to the improvement in correlation. On the basis of correlation with plant P uptake the Bray and Kurtz method has been shown to be inferior to some other methods on heterogeneous 1980). soils (Holford, Therefore it was of interest to test this hypothesis. The soils were thus grouped into more similar units of comparison. When the soils were were soils arbitrarily separated by clay content (<20$>), the improved for each group, but significantly for the correlations higher (Table 12). The Bray method has been found to overcompensate clay for Table 12. Linear correlation (r) coefficients for the relationship between P uptake of 10 consecutive crops grown in the greenhouse, and the initial P soil tests of 10 soils with various residual P levels, when the soils were stratified. % Clay >20 Bray PI (1:8) mg/kg Soil <20 >100 <100 Set 1+ Set 2T Bray PI - 1:7 0 .83^ 0.50^ 0 .57^ 0.37ns 0 .86^ 0.23ns - 1:8 0.84^ o.sr* 0.56^ 0.30nS 0.87^ 0.24ns - 1:20 0 .86^ 0.44^ 0 .60^ 0.08nS 0 .88^ 0.24ns Bray P2 0 .83^ 0.47^ 0 .59** 0 .12** 0.82^ 0.40ns NaHC03-P 0.92^ 0 .86^ 0.27ns 0.53 0.59* 0.63* AER-P 0.91^ 0 .70^ 0 .22ns 0 .58** 0.83** 0.41nS CaCl2-P 0.91^ 0 .91^ 0.69^ 0.16ns 0.73** 0.67^ 20 20 20 20 12 n ♦♦Significant at * = 0.01. ♦Significant at “ = 0.05. «o Not significant at ® = 0.05. dumber of soils in stratum +Set 1 = Kalamazoo, Spinks and Oshtemo soils. TSet 2 = All other soils. 28 42 buffering (Holford, available P 1980). This results In an on well buffered soils and an over under estimation estimation on of weakly buffered soils. It is suspected that this Is the reason that correlation with the more buffered soils is Improved. Also stratification by soil test level () slightly improved correlations. appears that interfered by removing the Charity soil with carbonate with P extraction and the uncultivated soils with contributions, there was better correlation with It which organic-P P uptake. Extracted P from the Charity soils continued to Increase with soil:solution ratio as well as acid strength, indicating that available P is indeed more detected uptake as suggested by uptake values (Table 15). On the other than hand, data suggests that unavailable P may have been extracted on Montcalm and Hillsdale soils. These two facts may the contribute to explaining the poor uptake correlations with the Bray method. The correlation (r-0.74) of P uptake with the Olsen method and better than for the Bray method. Similar was moderate observations superiority have been reported in the literature (Sims and Ellis, Holford, of 1983; 1980). This method is more sensitive to buffering and this reflected in intensity factor. correlation method. the better correlation (Table 10) with Separation of soils by clay the content CaC12-P, Holford an improved in this case as well, but less markedly than for (1980) showed that the Olsen test exhibits the a is the Bray similar sensitivity to buffering as do plants, thus its superiority over a range of soils. Resin uptake this extraction was moderately correlated (r« 0.68) with plant (Table method 10). A good degree of confidence has been for its effectiveness in extracting plant expressed available P in P 43 (Bowman et al, 1978). In this study, comparatively, it performs well. This method also showed a slight response to stratification by buffering (clay content) (Table 12). The good correlation with Intensity further supports the sensitivity to soil buffering. Also, this method proved as effective as the Olsen method on heterogeneous soils. The CaC12-P had a moderate but significant correlation with (r«0.75). Separation correlation, cropping of soils by clay contents uptake increased the but without difference between groups. Also the length made no difference (Table 11). Williams and Knight (1963) Holford (1980) have suggested that the intensity factor may be of and a more important factor in evaluating P uptake on a set of heterogeneous soils, but Dalai and Hallsworth (1976) expressed some reservations about generalization. correlation. They propose that soil heterogeneity can this offset the Olsen et al. (1983) observed the quantity parameter to be better correlated with plant P uptake than the intensity factor. In this study, the intensity factor gave better correlation values with P uptake on a group of heterogeneous soils. Accumulation values (Figures of P was plotted against changes in Bray 2-5). As P accumulation increased soil soil test test values decreased. Table 13 shows that the variations in soil test changes well as were correlated with plant P uptake. The uncultivated soils did not well. They show weaker and more variable correlations. It suspected that uptake from organic P which was not detected by the methods here may have contributed to the lower and more suggested in that correlations between test methods (Table the Bray and Kurtz method sometimes 13). over is test variable correlations on these soils. The Montcalm and Hillsdale soils also variability do It show was estimates 44 Table 13. Linear correlation (r) coefficients for the relationship between P accumulation by 10 consecutive crops grown In the greenhouse and changes In soil test levels during cropping of 10 soils with various residual P levels. Bray PI Soil 1:7 1:8 1:20 Bray P2 Charity (high P) - 1 .00** -0.99** -0.99** -0.90* Charity (uncultivated) -0.73ns -0.19nS -0.17nS -0.44ns Kalamazoo (high P) -0.95* -0.99** -0.99** -0.99** Kalamazoo (uncultivated) -0.34ns -0.97** -0.85nS -0.87ns Spinks (high P) -0.95* -0.98** - 1 .00** -0.96** Spinks (uncultivated) -0.36ns - 0 .79nS - 0 .20nS -0.29ns Capac - 0 .86nS -0.93* -0.94* -0.98** Montcalm -0.92* -0.54ns -0.89* -0.80ns Oshtemo -0.96** - 1 .00** - 1 .00** -0.99** Hillsdale -0.52ns -0.94* -0.69ns -0.70ns **Signifleant at « = 0.01. *Signifleant at “ = 0.05. ns Not significant at « = 0.05. 45 available P on weakly buffered soils. It Is likely that unavailable P was detected on these soils contributing to the low correlation. Similarities In P release mechanism on these soils can be predicted by similarities soils be of the slopes of regression (Table 14). The Charity show variable slopes over the test methods. This fluctuation the result of carbonate interference with extraction discussed above. Also the uncultivated soils varied over but similar among soils, suggesting a possible were uptake may which test was methods similarity in on these soils. The possible influence of organic P as a source of P for plant use has been suggested. The Kalamazoo, Spinks, Capac Oshtemo soils methods. more each showed similarities in slopes between Furthermore the Kalamazoo, Spinks and Oshtemo soils similar slopes among soils, which suggests that these P and the test exhibited soils are more similar in P release mechanism. The validity of this suggestion was tested by comparing the correlation between uptake and soil tests these three soils against the other soils. Table 12 shows that the and Kurtz-P compared correlation with uptake was better on these to all soils. The correlation decreased for the three on Bray soils Olsen method which is better suited to alkaline soils. In with order to further compare plant use of residual P in soil test results, it was worthwhile to compare the the soils differences between initial and final soil test values and P uptake (Table 15). The change was expected in available P values is variable from soil to soil. given characteristics, the different soil buffering This capacities and and plant performance. Higher testing soils appear have larger changes in available P values, and this coincides with P removal from these soils. The uncultivated soils showed little to more change 46 Table 14. Slope (b) values for the linear regression relationship between accumulation of P (x) by 10 consecutive crops grown In the greenhouse and changes In P soil test levels (y) during cropping of 10 soils with various levels of residual P. Bray PI Soil 1:7 1:8 1:20 Bray P2 Charity (high P) -0.48** -0.51** -0.69** -0.99** Charity (uncultivated) -0.09ns -0.03ns -0.03ns - 0 .21ns Kalamazoo (high P) -0.78** -0.75** -0.75** -0.78** Kalamazoo (uncultivated) -0.06ns -0.27nS -0.16ns -0.39* Spinks (high P) -0.81** -0.84** -0.78** -0.87** 0 .21ns -0.18ns 0.09ns -0.18nS Spinks (uncultivated) Capac -0.99* -0.93** -0.99** -0.69** Montcalm -1.41** -0.39ns -1.47** -1.17ns Oshtemo -0.81** -0.81** -0.96** -0.81** Hillsdale -0.33ns -0.60** -0.75** -0.30ns **Signifleant at « = 0 .01. *Signifleant at « = 0.05. ns Not significant at « = 0.05. 47 In soli test values despite plant P uptake and this strengthens the speculation of organic P contributions to available P In these soils. No explanation can be offered for the increase In test values detected by the Olsen and resin methods on the Montcalm and Hillsdale soils. The supplied Charity, Kalamazoo, Spinks, Oshtemo and Hillsdale more P for plant uptake than the changes In soil soils test values Indicate (Table 15). There was slightly less uptake from the Capac than as methods. suggested by the Bray PI method, but more than by the The Montcalm soil consistently showed less effectiveness soil other than as suggested by soil test differences. Delta indice values (initial - final soil test values) moderately but significantly correlated with uptake coefficients correlation between soil test methods suggest that similar pools sources. were from r- 0.67 to 0.87. 11). correlation compounds ranged (Table were detected, and plant P uptake was largely The from only The good of P similar Table 15. Changes in the P content of 10 soils with various residual P levels, following P removal by 10 consecutive crops grown in the greenhouse. Bray PI Soil Uptake 1:7 1:8 1:20 Bray P2 NaHC03-P AER-I 77.1 83.7 114.4 173.4 49.8 90.9 1.0 -6.7 42.3 1.4 14.8 Charity (high P) 154 Charity (uncultivated) 110 Kalamazoo (high P) 182 156.9 132.6 144.0 136.8 27.0 58.4 Kalamazoo (uncultivated) 125 18.1 30.3 16.1 49.8 5.6 25.1 Spinks (high P) 151 138.3 114.9 117.6 131.1 76.5 30.9 6.7 -17.0 -17.3 2.6 33.3 Spinks (uncultivated) 52 5.64 -4.35 Capac 194 233.7 210.0 211.8 138.3 78.3 29.0 Montcalm 117 178.8 21.0 125.1 130.8 -5.6 -18.0 Oshtemo 224 191.7 171.3 208.3 187.5 40.5 104.7 58 28.4 27.1 10.9 8.6 0.6 -62.1 Hillsdale SUMMARY AND CONCLUSION A greenhouse study and laboratory analyses were conducted to measure plant use of residual soil P on heterogeneous soils with various management chemical histories, soil test and examine the methods in suitability detecting the of some effectively current available residual soil P. Measurements made were plant dry matter yield, P uptake and extracted soil P. In week the greenhouse, dry matter production over 10 consecutive crops varied significantly but not linearly with the level residual P on soils used while P uptake was higher on soils with residual values. increases in plausible Plant physiological root mass reasons for and water use of higher adjustments such as efficiency were proposed similarities in yields relative as between the uncultivated soils and some high P soils. The study was terminated when P the five deficiency occurred on some lower residual P soils and a moderate Hillsdale sandy loam soil. Since production would have continued on other soils, it is conclusive that the influence of residual P on yield would be to prolong the ability of soils to but not necessarily to increase seasonal support production. P the crop production, Even though residual P improved P uptake by plants, this was not effectively noticed in dry matter yields over the period of this study. In in the laboratory, the effectiveness of the chemical test detecting available residual P was variable. methods Increasing the extractant volume or acid strength of the Bray method revealed more P in the soils, available confirms especially residual the P in the Charity clay soil. values suggested by the By methods reasoning that only a proportion of the 49 comparison, varied. available the This P is 50 detected by dependent further extraction methods. The usefulness of any method on P how well it predicts the likelihood of crop Is thus response application to that soil. In this study the Bray and to Kurtz method was more effective In detecting the low P soil. Phosphorus correlated aspect than extracted with by CaClg, an Intensity factor, the plant use of residual P over all was soils. the NaHC0g-P method was similar to the resin method Bray However, and Kurtz-P method on this set of of the Bray and Kurtz-P method was superior to the NaHC03-P. residual P levels P uptake was not In the soils. Deviations this better heterogeneous soils. greatly release the improved and absolutely were In and by Identifying some soils with similarities in P correlation better related introduced by to the Montcalm sandy loam soil which tested high In P but plants didn't remove much of it. The by amount of P removed from most soils was closely accounted changes in soil test values. Actual plant P uptake was indicated by soil test changes. deviated, showing larger higher Again, the Montcalm sandy changes in soil test than for than loam uptake. soil It is suspected that unavailable P was detected on this soil. The uncultivated Charity and organic-P Spinks , and manured Kalamazoo soils gave indications mineralization and plant use. Soil tests on these soils of were stable through cropping. In conclusion, practices current with have levels this raised study confirms that the residual P levels in intensive Michigan would be adequate to support long term P sufficiency levels, but generally, the soils. cropping other management practices. The Bray and Kurtz method detects cultural current The along effectively soil test methods under-estimate the effectively available residual P and this may lead to residual over-estlmatlons in P recommendations and application. P values of soils can be actively lowered by plant slow reactions do not appear to be rapid in this case. Such a will reduce the possibilities of P pollution. uptake The as reduction CHAPTER 2 SOLUBILITY OF RESIDUAL SOIL PHOSPHORUS INTRODUCTION The with soli reactions and regions, among other factors. Any interest to detect such a P compounds that dominate soil solution P vary compound may emanate from the desire to know the source of important contributions to plant P uptake and the soil management implications for crop P use. approaches understanding to explain soil P compounds. First, the principle and Out of the movement for such an solubility (Aslyng, 1954) has been beneficial in attempting predict the fractionation chemical behavior of soil P. came product to Secondly, explain the method (Chang and Jackson, 1957; Williams et two soil al., P 1971) has contributed to detecting quantitative changes in soil P compounds. It soil is essential to have a general understanding of the P within development modification have various and regions. Such knowledge will assist adoption of soil testing practices in new of soil test practices in areas where nature in the areas, the cultural introduced changes in soil reaction and cultivation of practices practices in resulted in general. In Michigan, accumulation interest following of intensive high P cultivation practices levels in some soils. have Therefore it was to study the chemical nature of P residue in these soils. study was developed to: 1. Predict 52 the P compound of The most probably controlling the soil P. 2. Determine the effect of cropping on the soil P solubility. 3. Study the relationship between soil test P and P solubility. 4. Examine the relationship between factors and plant P uptake. soil P solubility LITERATURE REVIEW Phosphorus exists In the soil primarily as compounds aluminum and specific compound depends upon the region, weathering pH, iron. The presence in the soil and of calcium, availability of intensity, soil and cultivation practices. Since plants obtain P directly from soil solution, it is not certain that the compound present is except indirectly as far as it's solubility is concerned. this It can help to explain the chemical the Important Nevertheless, information can be useful in fertilizer and residual P practices. a behavior management of soil P (Lindsay and Moreno,1960). When P is applied to the soil, it undergoes reactions that render it less soluble. Devine et al. (1968) represented the transformation as: Fertilizer --- > Soil solution --- > Metastable solid ----> stable solid. The mechanism involved in this transformation is Initiated by the movement vapor rate of soil water into the fertilizer particle via transport capillary or 1959). The depends on the soil P status and (Lehr et al., 1959; Kolaian and Ohlrogge, of dissolution in the soil then water solubility of the fertilizer (Lawton and Vomocil, 1954; and Hashimoto, ordinary 1979). Lehr superphosphate, et al. (1959) monocalcium showed phosphate Khasawneh that granules of and concentrated superphosphate would dissolve rapidly. In contrast, rock phosphate would dissolve particles, with until slowly (Khasawneh and Doll, 1978). As water P would move out resulting in soil moves solution into supersaturated respect to various P compounds. Phosphate movement would continue the granule concentration decreases to a level at which there no osmotic gradient and diffusion ceases (Huffman and Taylor, 1963). 54 the is 55 The initial reaction products formed in the reaction of P with soil are metastable. In time they revert into more stable compounds. Reaction products commonly in order > dicalcium phosphate (DCP) > octacalcium phosphate (OCP) > B tricalcium phosphate (TCP) phosphate solubility are: found dlcalcium > hydroxyapatite (varlsclte) However, in neutral to calcareous soils phosphate (HA) dihydrate (Lindsay, 1979). (DCPD) Aluminum and iron phosphate (strengite) predominate in most P compounds contain impurities acid which of soils. considerably influence their solubilities. For Instance, carbonate impurities render hydroxyapatite more soluble than in the pure state (Khasawneh and Doll, 1978). The occurrence of a compound in the soil can be predicted solubility the product principle (Aslyng, 1954; Withee and Ellis, 1965). graphical representation of this makes for convenient Samples that fall above an isotherm are considered to be with by respect to it. Conversely samples below an A comparisons. supersaturated Isotherm are undersaturated and the compound in this case is considered to control P in the sample. Metastable forms of P fertilizer residue have been suggested to DCPD and DCP(Brown and Lehr, 1959 and Bouldin et compounds do not remain in the soil for extensive al., 1960). periods be These following fertilization (Bell and Black, 1970). In many soils with fertilization, P residue has been shown to be in the form of OCP or TCP and Westfall, 1984). Apatite is the expected thermodynamic end (Havlin point Ludwick histories of P fertilizers in neutral to calcareous soils. Yet, of Fixen and (1982) suggest that under arable conditions this end point may not be reached as evidenced by the continued uptake of residual soil P. 56 Variscite and strengite are possible end products In acid soils. (Chakravarti and Talibudeen, 1962; Lindsay et al., 1959). Numerous products compositions can influence the upon contact with the soil. Ammonium ortho- and fertilizers completely 1959; fertilizer without calcium or micronutrient cations reaction polyphosphate would dissolve leaving no residue in the granule site (Bouldin and Sample, Khasawneh et al., 1974). The reaction products of manyfertilizer compounds have been compiled by Sample et al. (1980). The ultimate goal of any form of determination of soil P is ascertain sufficiency for production. Solubility phase products are quantitative, but they are capable of suggesting soil P supply not pattern and adequacy. Cumulative works have shown that if the solid phase is equilibrium with OCP, then the soil P should it exceeds known optimum ranges be adequate (Olsen for as 1980). In their studies, Olsen et al. (1978) and Havlln (1984) demonstrate that available residual soil P may be present in state with respect to the metastable fertilization will modify soil P, therefore as soils fertilized parent material and indicators of the soil P chemistry. weathering Khasawneh, and Westfall compounds. are intensity in crop production undersaturated and to an Annual continuously become poor MATERIALS AND METHODS A laboratory study was conducted on ten soils from South-Central Michigan to describe the solubility of residual P. A description of soils and greenhouse study has been given in chapter 1 of this the thesis. Soil samples were obtained from each experimental unit in the greenhouse before and during cropping (after crops 1, 3, 9, and 10) for analysis in the laboratory. It is important to point out again that lime application was made to the Spinks soil before the initial cropping, and to all other soils except the Charity at the end of the third cropping. Soil Analyses The Five grams of soil was shaken in SOmL of 0.01M CaClg for one hour. suspension glass electrode. pH Samples was were then immediately centrifuged and determined filtered. using The a electrical conductivity was measured on a conductivity bridge with a cell constant of 1. Phosphorus concentration was measured by the ascorbic acid method (Murphy and Riley, 1962) using a Spectronic 20 spectrophotometer at 880 microns. Calcium was measured on an atomic absorption spectrophotometer. Ionic strengths of the solutions were estimated as a product of the electrical Jurinak, conductivity values and a constant (0.013) 1973). Activity coefficients were calculated by (Griffin the and extended Debye-Huckel equation (Lindsay, 1979). The standard solubility isotherms were established from solubility constants given by Lindsay (1979). Soil phosphate potential (pHgP04 + 0.5pCa) and lime potential (pH - O.SpCa) were calculated by a computer program supplied by Dr. B.G. Ellis1. 1 Dr. B.G. Ellis, University. Professor of 57 Soil Chemistry, Michigan State RESULTS AND DISCUSSION Chemical Nature Of Phosphorus Residue In Solis The studied. chemical The nature of residual P In some Michigan soils ranged In soil reaction from pH 4.8 to soils 7.2 16), and varied In other soil characteristics (Table 4). The was (Table solubility product principle which has been used by many Investigators was used to attempt to explain the chemical behavior of soil P. Figure 6 shows the nature of P residue in these soils as they when collected from the field. The location of a soil near an would were isotherm suggest that P in the soil is in a state of equilibrium with the discrete solid phase or a compound of similar solubility. Changes in the P controlling Where compound thereafter are gradual and not counterpart uncultivated soils are available it instantaneous. becomes obvious that fertilization has increased the solubility of P in these soils. The clustering of soils as observed in this Figure gives the indication that there pH is an association with the soil reaction. Generally, soils below 6.0 are located around the varlscite and strengite isotherms, while soils above pH 6.0 fall around the Ca-P compounds. Susukl et al. observed soils. a similar They trend in fractionation studies of some (1963) Michigan showed that the soils with pH 6.0 and above tended to be higher in Ca-P while those below were higher in Al-P. It is interesting here that some of the soils fall well above varlscite isotherm. compounds control This would suggest that more soluble the P in these soils. However, given the the aluminum high soil tests and P activity it is more probable that adsorbed P controls the in these soils Lindsay et al. (1959) established 58 that more P soluble 59 Table 16. Soil F solubility factors for 10 Michigan soils with various levels of residual P. Soil pH (CaCl2) PH 2P 04 CaCl2-P pCa pH P0 4 + 0.5 pCa pH 0.5 p( mg/kg Charity 7.2 5.3 0.48 2.3 6.5 6.1 Charity (uncultivated) 7.1 6.2 0.06 2.3 7.3 6.0 Kalamazoo 6.0 4.6 1.01 2.3 5.7 4.9 Kalamazoo (manured) 5.8 5.3 0.20 2.3 6.4 4.7 Spinks 4.8 4.4 1.55 2.3 5.5 3.7 Spinks (uncultivated) 6.4 5.0 0.47 2.3 6.1 5.3 Capac 4.8 4.3 1.88 2.3 5.4 3.6 Montcalm 5.7 4.5 1.19 2.3 5.6 4.6 Oshtemo 6.2 4.1 3.78 2.3 5.2 5.0 Hillsdale 6.2 5.7 0.09 2.3 6.8 5.0 3.00 — 12345678910- 4,00 — o 5.00 — o a. in 6.00— Charity uncultivated Charity Kalamazoo uncultivated Kalamazoo Spinks uncultivated Spinks Capac Montcalm Oshtemo Hillsdale 7.00- o a. CM X a 8. 000.00— 10.00 — ♦After cropping * Before cropping 11. 00 - 2.bo lo o s5o 4.00 4^o s.00 sio eJ» eio 7.00 tAg pH - 0.5pCa Figure 6. Phosphorus solubility of some Michigan soils before and after a greenhouse cropping study. 61 aluminum compounds are very unstable, there fore it is not expected that precipitated P would be currently active enough in these soils. It is strengite. often questionable which is more soluble, varlscite Lindsay (1979) suggests that in less weathered kaolinite-sillca is soils apt to control soil aluminum, varlscite and where would be more soluble. Furthermore, in Michigan soils Juo and Ellis (1968) showed that strengite was less soluble than varlscite for plant P uptake; while Susukl et al. (1963) observed that Fe-P did not contribute to P removal by suggest plants. The preceedlng premise was established in order that to P in the soils which fall below the strengite line is more likely controlled by varlscite. Contrary to previous suggestions that arable soils never have P equilibrium with hydroxyapatite, two soils are located near in this isotherm. The plausible explanations for this observation are that P in the manured Kalamazoo soil is Influenced by organic-P cycling, and P in the Hillsdale soil, a sandy loam was rather low and may also have been The P in the alkaline soils is clearly controlled by OCP/TCP. This influenced by organic-P. would be expected given the soil characteristics. In the final analysis, because expected of the chemical nature of P in these soils , it should be that Al-P and Ca-P are more important sources of P to plants. The extent to which either dominates on a soil could be affected by soil management practices, as observed below. Effect Of Cropping On Soil Phosphorus Compounds There was a general decrease in phosphate potential and solubility with the period of cropping (Fig. 6). As result of lime applied, by end of the study, most of the soils showed P in equilibrium the with 62 OCP/TCP. Despite the changes in lime potential it is important that phosphorus potentials of the soils was buffered around compounds the that are considered to be soluble. Even though the soils were not cropped P exhaustion, attained there is no Indication that they equilibrium with may have HA. The pattern observed on to eventually each soil is further discussed below. While soil there is a fluctuation in phosphate potential, remains buffered between OCP and TCP (Fig. 7). The the P Charity solubility pattern on this soil follows what would have been expected, however deviation This at sample 2 may have been the result of resistance to change experimental Increases the likelihood the error. of OCP as the discrete mineral phase. Furthermore it shows a greater P capacity factor than other soils which fluctuate about isotherms (Fixen 1982). The current observation would suggest source that of P P in this that and Ludwick, Ca-P was theimportant soil. Also, the nature of P solubility Indicates would be readily available on this soil. The shiftin soil pH between initial and final cropping was from 7.2 to 7.5. Phosphorus in the uncultivated Charity soil is clustered around TCP (Fig. 8). here. It The variability in phosphate potential is conceivable, but a speculation at is more best pronounced that organic-P mineralization may have been responsible for the pattern observed Otherwise solubility no at explanation can be offered for the acute in requirements. did not respond to further P fertilization despite a low (3 NaHC03-P) soil that increase sample 4. Halm et al. (1972) observed that some native grasslands in Saskatchewan released P that exceeded plant They here. test level. Also, Lindsay and Moreno disturbances of P equilibrium by biological (1960) processes mg/kg suggested could be 63 340— i 1-Before cropping 2-After Crop 1 3-After Crop 3 4-After Crop 9 5-After Crop 10 440- O o CL m 5.00•4 0 — o + 7.00- o0. 8.00- cm 8.0010.00 11.0 0 2 4 0 2Js0 3.l)0 i t o 4 ^ 0 4.to 5 .i» s i o 8.1)0 s ilo 7J1O 7 .U pH - O.SpCa Figure 7. Effect of greenhouse cropping practice on the P solubility o? a Charity high P soil. 3.00— l-Before cropping 2-After Crop 1 3-After Crop 3 4-After Crop 9 5-After Crop 10 440— o 540 — o in o + o C L CM X a. e.007.008.008.00— 10.00 — 11.0 0 2.b0 2.50 3.00 3.^0 4.1)0 4.^0 1ST s.S» 8.00 e.ko 7.U 7 Sw pH — 0.5pCa Figure 8. Effect of greenhouse cropping practice on the P solubility or an uncultivated Charity soil. 64 frequent. In this case, while Ca-P may have been responsible for some uptake, organic-P must have been more Important. Soil pH shift was from 7.1 to 7.5. Generally, the P solubility was in agreement with what would have been expected on this low P soil. The would high P level of the Kalamazoo soil suggests that adsorbed be more Important than precipitated P at the Initiation study. Nevertheless compound. sample It of Figure 9 indicates that Al-P may have been is suspected that the shift above the varisclte Phosphorus this the line 3 was due to the influence of NH^+-N fertilization on the P P at soil. potential remained stable. With the application of lime OCP is precipitated and appears to control soil P. Aluminum P probably was as Important as Ca-P for plant use because of the better crop performance registered early in cropping. Soil pH shift was from 6.0 to 7.2. as a result of liming. It was responsible earlier for hydroxyapatite phosphate shift may the location of the manured Kalamazoo have the reduce the effected TCP The P addition from organic sources may account for the isotherm soil been near potential. precipitation. suggested that organlc-P cycling (Fig. 10). Cropping continued However, liming after sample to 3 in phosphate potential, and the solubility was in proportion to the slightly moderate P level in the soil. Organic P would have played a significant role in P uptake here. Soil pH increased from 5.8 to 6.9. Cropping soil was not very effective in reducing the PP on the (Fig. 11). Because of the sandy nature and low buffering Spinks of this soil, it would appear that in order to maintain the level of solubility, there test had to be an appreciable amount of free P in solution. level supports this thinking. This soil was limed before The soil cropping 65 3.00 1-Before cropping 2-After Crop 1 3-After Crop 3 4-After Crop 9 5-After Crop 10 pH2P04 + 0.5pCa 4.00 8.00 6.00 7.00 8.00 9.00 10.00 11.00 2^ o sJ» 3.ko 4A0 4A0 sJ» skaeJ)o o i» 7.)» r lc pH — 0.5pCa 3.00 Figure 9. Effect of greenhouse cropping practice on the P solubility or a Kalamazoo high P soil. l-Before cropping 2-After Crop 1 3-After Crop 3 4-After Crop 9 5-After Crop 10 4.00 pH2P04 + 0.5pCo 8.00 800 7.00 800 9.00 10.00 11.00 2.00 z io s ix ) sJw 4.Lo 4 ^0 sJ» 8 ^0 oJ» 880 7 M v io pH - 0.5pCa Figure 10. Effect of greenhouse cropping practice on the P solubility of a manured Kalamazoo soil. 66 and a consequent Increase in lime potential is observed. sample 3 resulted in an increase in solubility, and Liming this after would only suggest the solubilizing of varlsclte. Because of the soil test and soil characteristics it is unlikely that TCP could have controlled P in soil. It is more probable that Ca-P did not Octacalclum phosphate would precipitate. Furthermore, have the been proximity effectively expected to the a this precipitate. more likely variscite isotherm increases the belief that varlsclte was in control of soil P through the cropping period. Thus Al-P and Ca-P were Important for P uptake. Soil pH increased from 4.8 to 6.5 as a result of liming. Variscite is suspected to have controlled the P activity in the uncultivated Spinks soil at the beginning of the study (Fig. 12). Liming resulted in a gradual increase in the lime potential gradually decreased the P solubility. However liming Increased the P solubility by solubilizing variscite. The phosphate potential is suspected to have been mineralization, which appears to have been suggested by Table 15. Soil pH and after enhanced cropping sample rather by high organic-P beneficial for plant use was increased from 6.4 to 3 7.3 as as a result of liming. Adsorbed P appears to have been an Important fraction in the soil. may The solubility state at sample 1 (Figure 13) seems have been due to experimental error. Sample 2 would Capac unlikely and suggest that variscite may have controlled soil P. The shift at sample 3 , again have been resultant of the effect of ammonium fertilization on may soil reaction. Lime application after this period initiated the precipitation of OCP. Al-P and Ca-P contributed to P uptake from this increased the soil pH from 4.8 to 7.0. soil. Liming 67 3.00 — 1-Before cropping 2-After Crop 1 3-After Crop 3 4-After Crop 9 5-After Crop 10 pH2P04 + 0.5pCa 4.00— 5.00 — 8.007.00- 8.009.0 0 10.0 0 11.0 0 2.00 2.50 3.00 3 ^0 4.1)0 4.io 5.00 5.50 6.1)0 C.S0 700 7.1o pH — O.SpCa Figure 11. Effect of greenhouse cropping practice on the P solubility o f a Spinks high P soil. 3.00 — 1-Before cropping 4.00 — 2-After 3-After 4-After 5-After pH2P04 + 0.5pCa 5 .0 0 - 6.00— 7 .0 0 - 8.009.00 — 10.00 — 11.0 0 - 2.00 I S 3.00 4.00 4J0 5.00 S£0 8.00 8 ^0 7.00 7 ^0 pH — 0.5pCa Figure 12. Effect of greenhouse cropping practice on the P solubility o f an uncultivated Spinks soil. Crop Crop Crop Crop 1 3 9 10 68 Crop performance on the Montcalm soil was disappointing considering the soil test compounds sampling error. levels. While the soil was buffered (Fig. is 14) for the most part, the around deviation not understood. This could have been due However, if this soil stayed In this state for soluble at the P third to experimental any appreciable period during cropping, then this may have contributed to the poor crop growth. cropping. With after sample 3, OCP was gradually precipitated. The high P soil liming test Variscite level Aluminum controlled soil P at initiation supports the high state of P of solubility In this soil. P and Ca-P played important roles in P uptake from this soil. The soil reaction was Increased from 5.7 to 7.3 as a result of liming. Adsorbed Oshtemo P appears to have been an Important fraction soil. Because of the soil reaction and P potential in Al-P the might have been present. Initial cropping slightly reduces the solubility, but the effect of ammonium fertilization on the soil reaction resulted in deviation at sample 3 (Figure 15). The phosphorus potential was and at a rather high level of activity. Liming after sample 3 a stable increased the lime potential, and cropping decreased the phosphorus potential. The precipitation test and reaction good of OCP or a more soluble compound reflects the high ready availability P from this soil. The as a result of liming was from 6.2 to 7.3. performance change This in soil in accordance with the current observation. soil soil showed Plant P uptake appears to have been equally supported by both Al-P and Ca-P. The Hillsdale soil is a weakly buffered soil, and this is reflected in the inability Varlsclte is 16). rapid The to maintain a good solution P activity (Table suspected to have controlled soil P at sample drop in solubility is not understood. 1 6). (Figure However the 69 3.001-Before cropping 2-After Crop 1 3-After Crop 3 A-After Crop 9 5-After Crop 10 pH2P04 + 0.5pCo 4.00 — 3.00- 6.00— 7.00 — 8.00— 0.00— 10.0 0 11.0 0 2.00 l lo 3.1>0 330 4.00 4 .lo 5.00 330 6.00 6.50 7.00 7 ^0 pH — 0.5pCa Figure 13. Effect of greenhouse cropping practice on the P solubility o f o Capac high P soil. 3.001-Before cropping 2-After Crop 1 3-After Crop 3 A-After Crop 9 5-After Crop 10 4.00- pH2P04 + 0.5pCa 5.00 — 6.007.00- 6.000.00— 10.0 0 11.00 ■ 2.00 2.50 3.00 s lo 4.1)0 4.50 5.(10 5 ^0 6.00 630 7.00 T i . pH - 0.5pCa Figure 14. Effect of greenhouse cropping practice on the P solubility of a Montcalm high P soil. 70 3.00 1-Before cropping 2-After Crop 1 3-After Crop 3 A-After Crop 9 5-After Crop 10 4.00- pH2P04 + 0.5pCa 5.00-6.00- 7.008.00 8.0010.00 — — | | | | | | | | | | | 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 11 .0 0 - pH — 0.5pCa Figure 15. Effect of greenhouse cropping practice on the P solubility o f an Oshtemo high P soil. 3.001-Before cropping 2-After Crop 1 3-After Crop 3 A-After Crop 9 5-After Crop 10 4.00- pH2P04 + 0.5pCa 5.006.00 - 7.008.00- 9.00 — 10.00 — 11.00- “1 1 1 1 1 1 1 1 1 1 1 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 pH — 0.5pCa Figure 16. Effect of greenhouse cropping practice on the P solubility o f a Hillsdale high P soil. 71 Increase In solubility following lime application after sample 3would suggest the solubilizing of variscite. Two observations with thissoil are questionable - the very low level of P at samples 2 and 3, and rather high level of solubility following lime application. It may be possible that there was addition to soil solution P by the then organlc-P cycling. Al-P and Ca-P were used by plants. The initial soil reaction of 6.2 was Increased to 7.4 as a result of lime application. In summary, removal of P and liming resulted in the reduction of solubility in the soils. As expected, the soil pH was an estimate of the P compound that controlled soil P activity. of limewhile solubilizing increasing lime potential of soils P effective Application initiated of variscite and precipitation of OCP/TCP. The the nature of the pattern of solubility observed would suggest that plant P uptake was from Al-P and Ca-P, each being more Important before and effects, respectively. contributed It would appear that organic-P a significant portion of the P uptake on after liming mineralization the uncultivated soils as suggested in Table 15. Relationship Between Soil P Compounds And Soil Test Levels they It was of interest to examine the soluble soil P compounds and how may be related to or have influenced the soil tests. The Bray and Kurtz method is given consideration here because of it’s application in Michigan. Correlation of the soil tests with plant uptake was weak (Table 10). This implies that as far as solubility is concerned, there may have been an inadequate detection or over estimation of the P compound most Important to plant uptake across all soils, by the extractant. Soil test results are given in Table 9. Significantly more P was extracted on the 72 Charity soil as soil:extractant ratio and acid strength were It Is then obvious that the acid In the extractant was carbonate may neutralized and there was Interference with available P contribute Increased. detection. to discrepancies In the correlation, moreso as been establishedthat Ca-P was Important by This It has for plant use on this soil. Of further concern would be the uncultivated soils. Even though they showed relatively less available P, and little change In soil tests before after cropping (Table 9), the soils had and moderate phosphorus potentials. It Is believed that organic P could have contributed to this potential. The soils appreciable stability In P detected on the acid to neutral confirms the sensitivity of the Bray extractant to Al-P. It been suggested that Al-P played a significant role In P supply on has these soils. It is interesting that the levels of P solubility appear to reflect the range since of soil test levels. This is a complex index there is arange of PP for each discrete phase to establish and the soil buffering capacity ultimately affects P activity. Nevertheless, it could be a rough estimation of the level of potential P solubility in Havlin testing while and Westfall (1984) suggested that neutral to calcareous > 32 mg/kg NaHC03-P are more likely to be clustered around soils testing lower would be around TCP. A comparison soluble phases with the NaHC03-P soil tests in this study shows for their observation (Fig. 6 , Table 9). In the case of the Kurtz-P soils. (1:8) a test level of 20 mg/kg would more adequately of neutral soils would suggest an equilibrium with OCP the support Bray and separate the CA-P Isotherms. A test level of 130 mg/kg Bray and Kurtz-P for to soils variscite. acid The 73 general trend Is of a reduction In solubility with decreasing soil level. test SUMMARY AND CONCLUSIONS Laboratory analysis were conducted to examine the chemical nature of available residual soil P. This study would indicate the potential supply capacity on heterogeneous soils with variable residual P as P levels, well as verify the suitability of current chemical soil test method (Bray and Kurtz-P) for use in Michigan. The results suggest that P fertilization has raised the P potentials in the soils, and the P activity is consequently governed by adsorbed P or a very soluble P compounds. The soil reaction value was a good indicator of the dominant P compound and Al-P and Ca-P would appear to be the more important sources of P for plant use. The acid to neutral reaction of most of these soils and other Michigan soils appropriateness estimation it’s of the Bray and Kurtz-P method for soil of available P by this method can be Improved confirms the testing. The by sensitivity for Ca-P which is of equal importance for improving plant use, especially with the adjustment of soil reaction to be more alkaline. Crop production on these soils contribute to a decline in P solubility, however this decline is not of a rapid or an alarming nature even with substantial P removal. On soils where P deficiency was observed the solubility was yet maintained close to the TCP isotherm, a soluble P compound. On the higher residual P soils it is certain potential can support long term production. 74 that APPENDIX 75 Table 17. Nitrogen and potassium application schedule for a greenhouse study of residual P in 10 Michigan soils. ____________________Fertilizer Application___________________ ______ Before Planting______ Crop Nitrogen+ 2 Weeks_________ Potassium* Nitrogen Potassium 10 •mg/kg- 1 120 50 50 2 120 50 - 3 50 10 6 50 10 7 25 10 - - 8 25 10 - - 9 - - 20 10 10 _ - 4 5 ; +Nltrogen as ammonium nitrate. ^Potassium as potassium chloride (crops 1-3) and potassium sulfate (crops 6-9). BIBLIOGRAPHY BIBLIOGRAPHY Adepoju.Y.A., and S.V.Matigod. 1982. Availability and extractlbility of phosphorus from soils having high residual phosphorus. Soil Sci. Soc. Am. J. 46:583-588. Alessi,J., and J.F.Power. 1980. Effects of banded and fertilizer phosphorus on dryland spring wheat yield in the plains. Soil Sci. Soc Am. J. 44:792-796. residual northern Amer,F., D.R.Bouldin, C.A.Black, and F.R.Duke. 1955. Characterization of soil phosphorus by anion exchangeable resin adsorption and 32P equilibration. Plant Soil 6:391-408. Aquino,B.F., and R.G.Hanson. 1984. Soil phosphorus supplying capacity evaluated by plant removal and available phosphorus extraction. Soil Sci. Soc. Am. J. 48:1091-1096. Arndt,W., and G.A.McIntyre. 1963. The initial and residual effects of superphosphate and rock phosphate for sorghum on a laterltlc red earth. Aust. J. Agrlc. Res. 14:785-795. Asher,C.J., and J.F.Loneragan. 1967. Response of plants to phosphate concentration in solution culture. I. Growth and phosphorus content. Soil Sci. 103:225-233. Aslyng,H.C. 1954. The lime and phosphate potentials of soils: the solubility and availability of phosphates, p 1-50. In Year-book Royal Veterinary and Agricultural College. Copenhagen, Denmark. Bar-Yosef,B., and B.Akiri. 1978. Sodium bicarbonate extraction to estimate nitrogen, phosphorus and potassium available in soils. Soil Sci. Soc. Am. J. 42:319-323 Barrow,N.J. 1973. Relationship between a soils ability to adsorb phosphate and the residual effectiveness of superphosphate. Aust. J. Soil Res. 11:57-63. Barrow,N.J. 1974. The slow reactions between soil and anions. I. Effect of time, temperature and water content of a soil on the decrease in effectiveness of phosphate for plant growth. Soil Sci. 118:380-386. Barrow,N.J. 1980. Evaluation and utilization of residual phosphorus in soils, p. 333-359. In The role of phosphorus in agriculture. American Society of Agronomy. 76 77 Barrow.N.J., and N.A.Campbell. 1972. Methods of measuring residual value of fertilizers. Aust. J. Exp. Agrlc. Anlm. Husb. 12:502-510. Barrow.N.J., and T.C.Shaw. 1974. Factors affecting the long effectiveness of phosphate and molybdate fertilizers. Commun. Soil Plant Anal. 5:355-364. term Sci. Barrow.N.J., and T.C.Shaw. 1975a. The slow reactions between soil and anions. 5. Effects of period of prior contact on the desorption of phosphate from soils. Soil Sci. 119:311-320. Barrow.N.J., and T.C.Shaw. 1975b. The slow reactions between anions. 2. Effect of time and temperature on the decrease In concentration In soil solution. Soil Sci. 119:167-177. soil and phosphate Barrow.N.J., and T.C.Shaw. 1976. The slow reactions between soil and anions. 2. The effect of time and temperature on the decrease In isotoplcally exchangeable phosphate. Soli Sci. 119:190-197. Bell,L.C..and C.A.Black.1970. Transformation of dibasic calcium phosphate dlhydrate and octacalcium phosphate In slightly acid and alkaline soils. Soil Scl.Soc.Am.Proc. 34:583-587. Berlnger,L. 1985. Adequacy of soil testing for requirements. Plant Soil 83:21-37. predicting fertilizer Biswas,T.D., B.L. Jain and S.C. Mandal.1970. Role of phosphatlc fertilizers In improving soil physical properties. Bull. Indian Soc. Soil Sci.8:83-89. Bouldin.D.R.,J.R.Lehr,and E.C.Sample.1960. The effect of associated salts on transformations of monocalcium phosphate monohydrate at the site of application. Soil Scl.Soc.Am.Proc. 24:464-468. Bouyoucos,G .J. 1962. Hydrometer method improved for making particle size analyses of soils. Agron. J. 54:464-465. Bowman,R.A., S.R.Olsen, and F.S.Watanabe. 1978. Greenhouse evaluation of residual phosphate by four methods In neutral and calcareous soils. Soil Sci. Soc. Am. J. 42:451-454. Bremner,J.M., and C.S.Mulvaney. 1982. Nitrogen -Total, p. 595-624. In Methods of soil analysis, Part 2. American Society of Agronomy monograph no. 9. Brown,W.E.,and J.R.Lehr.1959. Application of phase rule to the chemical behavior of monocalcium phosphate monohydrate in soils. Soil Scl.Soc.Am.Proc. 23:7-12. Campbell,R.E. 1975. Phosphorus fertilizer residual effect on crops in rotation. Soil Sci. Soc. Am. J. 29:67-70. irrigated 78 Chalwanakupt,P ., and W.K.Robertson. 1976. Leaching of phosphate and selected cations from sandy soils as affected by lime. Agron. J. 68:507511. Chakravartl,S.N., and O.Tallbudeen. 1962. Phosphate equilibria In soils. J. Soil Sci. 13:231-240. acid Chang,S.C., and M.L.Jackson. 1957. Soil phosphorus fractionation In some representative soils. J. Soil Sci. 9:109-119. Christenson,D.R., and M.L.Vitosh. 1984. Fertilizer needs under high and K accumulation in soils. Report to T.V.A., Mich. State Univ. P Dalai,R.C., and E.G.Hallsworth. 1976. Evaluation of the parameters of soil phosphorus availability factors in predicting yield response and phosphorus uptake. Soil Sci. Soc. Am. J. 40:541-546. Davis,J.F. 1962. How much fertilizer carry over in your cropping system? Crops and Soils. Devine,J.R., D.Gunary, and S.Larsen. 1968. Availability of phosphate as affected by duration of fertilizer contact with soil J. Agric. Sci. 71:359-364. Fitter,A.M. 1974. A relationship between phosphate requirement, the immobilization of added phosphate , and the phosphate buffering capacity of colliery shales. J. Soil Sci. 25:41-50. Fixen,P.E., and A.E.Ludwick. 1982. Residual available near-neutral and alkaline soils: I. Solubility relationships. Soil Sci. Soc. Am. J. 46:332-334. phosphorus in and capacity Fox,R.L., and E.J.Kamprath. 1970. Phosphate sorption isotherms for evaluating the phosphate requirements of soils. Soil Sci. Soc. Am. J. 34:902-907. Gifford,R.M., J.D.Kalma, H.R.Aston, and R.J.Millington. 1975. Biophysical constraints in Australian food production.Implications for population policy. Search 6:212-223. Griffin,R.A.,J.J.Jurinak.1973. Estimation of activity coefficients the electrical conductivity of natural aquatic systems and extracts. Soil Sci. 116:26-30. from soil Halm,B.J.,J.W.B.Stewart,and R.H.Halstead.1972. The phosphorus cycle in a native grassland ecosystem, pp 571-586. In Isotopes and radiation in soil-plant relationships including forestry. IAEH. Vienna. Havlin,J.L., and D.G.Westfall. 1984. Soil test phosphorus and solubility relationships in calcareous soils. Soil Sci. Soc. Am. J. 48:327-330. Hayward,D.0., and B.M.W.Trapnell. 1964. Butterworths, London. Chemisorption. 2nd ed. 79 Holford.I.C.R. 1976. Effects of phosphate buffer capacity of soli on the phosphate requirements of plants. Plant Soil 45:433-444. Holford.I.C.R. 1980. Greenhouse evaluation of four phosphorus soil tests In relation to phosphate buffering and labile phosphate in soils. Soil Sci. Soc. Am. 44:555-559. Holford.I.C.R., and G.E.G.Mattingly. 1976. Phosphate plant availability of phosphate. Plant Soil 44:377-389. Huffman,E .0., and A.W.Taylor.1963. The behavior phosphate in soil. J.Agrlc.Food Chem. 11:182-187. adsorption of and water-soluble Janssen,K.A., D.A.Whitney, and D.E.Kissel. 1985. Phosphorus application frequency and sources for grain sorghum. Soil Sci. Soc. Am. J. 49:754758. Johnston,W.B., and R.A.Olsen. 1972. Dissolution plant roots. Soil Sci. 114:29-36. of fluoroapatite by Juo,A.S.R.,and B.G.Ellis.1968. Chemical and physical properties of Iron and aluminum phosphates and their relation to phophorus availability. Soil Scl.Soc.Am.Proc. 32:216-221. Kamprath.E.J. 1967. Residual effects of large applications of phosphorus on high phosphorus fixing soils. Agron. J. 59:25-27. Khasawneh,F .E ., I.Hashlmoto, and E.C.Sample. 1979. Reactions of ammonium ortho and polyphosphate fertilizers in soils : II. Hydrolysis and reactions with soil. Soil Sci. Soc. Am. J. 43:52-58. Khasawneh,F.E.,and E.C.Doll.1978. The use of phosphate rock for direct application to soils. In Advances in Agronomy 30:159-206. N.C.Brady (ed). American Society of Agronomy. Academic Press, New-York. Khasawneh,F.E.,E.C.Sample,and Isao Hashimoto.1974. Reactions of ammonium ortho and polyphosphate fertilizers in soils.I. Mobility of phosphorus. Soil Scl.Soc.Am.Proc. 38:446-451. Kolalan,J.H.,and A.J.Ohlrogge.1959. Principles of nutrient uptake from fertilizer bands: IV. Accumulation of water around the bands. Agron J. 51:106-108. Kurtz,L.T., and J.P.Quirk. 1965. Phosphate adsorption fractions in field soils of varying histories fertilization. Aust. J. Agrlc. Res. 16:403-412. and of phosphate phosphate Larsen,S. 1974. Food. Neth. J. Agrlc. Sci. 22:270-274. Larsen,S., D.Gunnary, and C.O.Sutton. 1965. The rate of immobilization of applied phosphate in relation to the soil properties. J Soil Sci. 16:141-148. 80 Lawton,Kirk, and J.A.Vomocil.1954. The dissolution and migration of phosphorus from granular superphosphate In some Michigan soils. Soil Scl.Soc.Am.Proc. 18:26-32. Learner,R.W. 1963. Residual effects of phosphorus fertilizer In irrigated rotation In the southwest. Soil Sci. Soc. Am. J. 27:65-68. an Lehr,J.R.,W.E.Brown,and E.H.Brown.1959. Chemical behavior of monocalcium phosphate monohydrate In soils. Soil Scl.Soc.Am.Proc. 23:3-7. Leiblg,Justus. 1841. The organic chemistry and agriculture and physiology. It’s application on Lindsay,W.L., and E.C.Moreno. 1960. Phosphate phase equilibria in soils. Soil Sci. Soc. Am. J 24:177-182. Lindsay,W.L.,A.W.Frazier, and H.F.Stephenson.1962. reaction products from phosphate fertilizers Scl.Soc.Am.Proc. 26:446-452. Identification of in soils. Soil Lindsay,W.L.,J.R.Lehr,and H.F.Stephenson.1959. Nature of the reactions of monocalcium phosphate monohydrate in soils:III. Studies with metastable triple point solution. Soil Scl.Soc.Am.Proc. 23:342-345. Lindsay,W.L..M.Peech,and J.S.Clark.1959. Solubility criteria for existence of variscite in soils. Soil Scl.Soc.Am.Proc. 23:357-360. Lindsay,W.L.1979. New-York. Chemical Equilibria in soils. John Wiley and the Sons, Lutz.J.F., and I.Haque. 1975. Effect of phosphorus on some physical chemical properties of clays. Soil Sci. Soc. Am. J. 39:33-36. and Matocha,J.E., B.E.Conrad, L.Reyes, and 6.W.Thomas. 1970. Residual value of phosphorus fertilizer on a calcareous soil. Agron. J. 62:572-574. Mattingly,6.E.G. 1968. Evaluation of phosphate fertilizers. II. Residual value of nitrophosphates, Gafsa rock phosphate, basic slag, and potassium metaphosphate for potatoes, barley, and swedes grown In rotation, with special reference to changes In soil phosphorus. J. Agrlc. Sci. 70:139-153. Mattingly,G.E.G. 1970. Residual value of basic slag, Gafsa superphosphate in a sandy podzol. J. Agrlc. Sci. 75:413-418. rock and Mattingly,G.E.G. 1971. Residual value of phosphate fertilizer on neutral and calcareous ground. In Residual value of applied nutrients. Tech.Bull. 20:1-9. Ministry of Agriculture, Fishries and Food, HMSO, London. Mattingly,G.E.G., A.Penny, and Marie Blakemore. 1971. Evaluation of phosphate fertilizers. III. Immediate and residual values of potassium metaphosphate and magnesslum ammonium phosphate for potatoes, radishes, barley and ryegrass. J. Agrlc. Sci. 76:131-141. 81 Mattingly,G.E.G., and F.W.Vlddowson. 1963. Residual superphosphate and rock phosphate on an acid soil. I. phosphorus uptake In the field. J. Agrlc. Sci. 60:399-407. value Yields of and McLachlan.K.D. 1976. Comparative phosphorus responses In plants to a range of available phophorus situations. Aust. J. Agrlc. Res. 27:323341. Mengel,K., and E.A.Klrkby. 1982. Principles of plant nutrition. 3rd International Potash Institute, Switzerland. ed. Murphy,J., and J.P.Riley. 1962. A modified single solution method for determination of phosphate in natural waters. Anal. Chlm. Acta 27:31-36. Nair,K.P.P., and K.Mengel. 1984. for phosphate uptake by rye. Soil Importance of phosphate buffer power Sci. Soc. Am. J. 48:92-95. Neller.J.R., D.W.Jones, N.Gammon, and R.B.Forbes. 1951. Leaching of fertilizer phosphorus In acid sandy soil as affected by lime. Clrc. Fla. Univ. Agrlc. Exp. Stn. no. S-32. Novais.R., and E.J.Kamprath. 1978. Phosphorus supplying capacities of previously heavily fertilized soils. Soil Sci. Soc. Am. J. 42:931-935. Olsen,S.R., and F.E.Khasawneh. 1980. Use and limitations of physicalchemical criteria for assessing the status of phosphorus in soils, p. 361-410. In The role of phosphorus in agriculture. American Society of Agronomy. Olsen,S.R., F.S.Watanabe, and R.A.Bowman. 1983. Evaluation of fertilizer phosphorus residues by plant uptake and extractable phosphorus. Soil Sci. Soc. Am. J. 47:952-958. 0zanne,P.G. 1980. Phosphate nutrition of plants - A general treatise, p. 559-589. In The role of phosphorus in agriculture. American Society of Agronomy. 0zanne,P.G., and T.C.Shaw. 1967. Phosphate sorption by soils as a measure of the phosphate requirements for pasture growth. Aust. J. Agrlc. Res. 18:601-612. 0zanne,P.G., C.J.Asher, and D.J.Klrton. 1965. Root distribution in a deep sand and its relationship to the uptake of added potassium by pasture plants. Aust. J. Agrlc. Res. 16:785-800. Page,N.R. 1974. Estimation of organic matter in Atlantic Coastal soils with a color difference meter. Agron. J. 66:652-653. Plain Parfitt,R.L. 1978. Anion adsorption by soils and soil materials. Advances in Agronomy 30:1-50. N.C.Brady (ed). American Society Agronomy. Academic Press, New-York. In of 82 Parkinson,J.A., and S.E.Allen. 1975. A wet oxidation procedure suitable for the determination of nitrogen and mineral nutrients in biological material. Comm. Soil Sci. Plant Anal. 6:1-11. Pratt,P.F., and M.J.Garber.1964. Correlations ofphosphorus availability by chemical tests with Inorganic phosphorus fractions. Soil Sci. Soc. Am. J. 28:23-26. Rajan.S.S.S. 1973. Phosphorusadsorption characteristics of Hawaiian soils and their relationship to equilibrium phosphorus concentrations required for maximum growth of millet. Plant Soil 39:519-532. Russell,J.S. 1977. Evaluation of Agrlc. Res. 28:461-475. residual nutrients Insoils. Aust. J. Sadler,J.M., and J.W.B.Stewart. 1974. Residual fertilizer phosphorus In western Canadian soils: a review. Saskatchewan Inst, of Pedology no. R136. Sample,E.C.,R.J.Soper,and G.J.Racz.1980. Reactions of phosphate fertilizers in soils, pp 263-319. In The role of phosphorus in agriculture. F .E .Khasawneh,E .C.Sample,and E.J.Kamprath (eds). American Society of Agronomy. Madison,WI. Schuman,G.E., R.G.Spomer, and R.F.Plest. 1973. Phosphorus losses four agricultural watersheds In Missouri valley loess. Soil Sci. Am. J. 37:424-427. from Soc. Sims, J.T., and B.G. Ellis. 1983. Adsorption and availability of phosphorus following the application of limestone to an acid, aluminous soil. Soil Sci. Soc. Am. J. 47:888-893. Snedecor,G.V., and W.G.Cochran. 1967. Statistical methods. 6th ed. Iowa State University Press. Ames, Iowa. the Sommers,L.E., and D.W.Nelson. 1972. Determination of total phosphorus in soils: A rapid perchloric acid digestion procedure. Soil Sci. Soc. Am. J. 36:902-904. Steel,R.G.D., and J.H.Torrie. 1980. Principles and procedures of statistics: a biometrical approach. 2nd ed. McGraw-Hill Book Co. NewYork. Susuki,A.,K.Lawton,and E.C.Doll.1963. Phosphorus uptake and soil tests as related to the forms of phosphorus in some Michigan soils. Soil Scl.Soc.Am.Proc. 27:401-403. Terman,G.L., J.D.Dement, L.B.Clements, and J.A.Lutz. 1060. Crop response to ammoniated superphosphates and dicalcium phosphate as affected by granule size, water solubility, and time of reaction with soil. J. Agrlc. Food Chem. 8:13-18. The Council on Soil Testing and Plant Analysis. 1980. Determination phosphorus by Bray PI extraction. Athens,GA. of 83 Thomas,G.W., and D.E.Peaslee. 1973. Testing soils for phosphorus, p. 115-132. In Soil testing and plant analysis. Walsh,L.M., and J.D.Beaton (eds). Soil Sci. Soc. Am., Inc. White,R.P., and E.C.Doll. 1971. Phosphorus and potassium affect soil test levels. Res. Rep. 127. Mich. State Univ. Sta. fertilizers Agr. Expt. Williams,E.G., and A.H.Knight. 1963. Evaluations of soil phosphate status by pot experiments, conventional extraction methods, and labile phosphate values estimated with the aid of phosphorus 32. J. Sci. Food Agrlc. 14:555-563. Williams,J.D.H., J.K.Syers, R.F.Harris, and D.E.Armstrong. 1971. Fractionation of inorganic phosphate in calcareous lake sediments. Soil Sci. Soc. Am. J. 35:250-255. Williams,R.F. 1948. The effects of phosphorus supply on the rates of Intake of phosphorus and nitrogen and upon certain aspects of phosphorus metabolism in gramineous plants. Aust. J. Sci. Res. (series B) 1:333341. Withee,L.V.,and Roscoe Ellis,jr.1965. Change of phosphate potentials of calcareous soils on adding phosphorus. Soil Scl.Soc.Am.Proc. 29:511-514.