EVALUAHON 0F ZINC STATUS OF SEVERAL ECUADOREAN SOILS Thesis for the Degree of M. S. MICHIGAN STATE UNWERSiTY FERNANW PACEFICO TORRES 19-74 LIBR/iii’t" a Michigru Si. “3 Univc sit-f “ T7“ Ems 3v % m & SBNS' w BOOK BINDERY INC. {I :BRARY BINDERS .' ' ”WW-PORT. HICHISAI ABSTRACT EVALUATION OF ZINC STATUS OF SEVERAL ECUADORIAN SOILS BY Fernando Pacifico Torres A short-term greenhouse cropping procedure was developed to evaluate the zinc status of soils. In this procedure. corn plants are grown in sand culture in such a way that the actively—growing roots can be placed in contact with a small volume of soil (100 grams) for two weeks. This results in an exhaustive removal of available zinc from the soil. and the zinc content of the corn plants gives a measure of the zinc status of the soil. In each cropping experiment. a standard soil known to be de- ficient in zinc is included to provide a means for com— parison. By using this technique to evaluate the zinc sta- tus of 10 Ecuadorian soils. it was determined that 3 of the 10 soils were possibly deficient in zinc. Therefore. 1 Fernando Pacifico Torres field experiments are advisable at these locations to evaluate.possible zinc responses. Total zinc content of the soils was not related to the level of available zinc in the soils. However. linear correlation analyses indicated that any one of three methods of extracting available soil zinc (O.1 E HCl. EDTA. and DTPA) could be used to evaluate the zinc status of the soils. The results suggested that DTPA would probably be the most satisfactory extractant be- cause of a higher level of correlation and because the use of this extractant can be more easily adapted to rou- tine laboratory procedures. EVALUATION OF ZINC STATUS OF SEVERAL ECUADORIAN SOILS by Fernando Pacifico Torres A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Crop and Soil Sciences 1974 .39 a?” {2 {5‘ With all my love This thesis is dedicated to my wife. Carmen. and to my lovely children. who bolstered my spirit at times when I needed it. ii ACKNOWLEDGMENTS During the course of my research I have been for— tunate to receive the generous and able assistance of many persons. I am pleased to acknowledge here my indebtedness to them and to recognize those that provided special help. s Sincere gratitude is acknowledged to Dr. Eugene C. Doll. my major professor and chairman of my thesis commit- tee. for his immeasurable aid. unfailing courtesy. and ex- pert guidance in directing my thesis and making my work both pleasant and rewarding. General acknowledgement is due to INIAP (Instituto Nacional de Investigaciones Agropecuarias) for its finan- cial support and stimulation to pursue a higher degree of education. Appreciation is expressed to Dr. Bernard Knezek for his enthusiastic assistance. Thanks are also extended to Dr. Donald R. Christenson. Dr. Lynn S. Robertson. Dr. John Shickluna and Dr. Robert Rupple. members of my thesis committee. iii TABLE OF CONTENTS LIST OF TABLES . . . . . . . . . . . . . INTRODUCTION . . . . . . . . . . . . . . REVIEW OF LITERATURE . . . . . . . . . . Role of Zinc in Plants . . . . . . . Zinc in Soils. . . . . . . . . . . . Factors Affecting Zinc Availability. Phosphorus . . . . . . . . . . . Nitrogen . . . . . . . . . . . . Soil Reaction and Carbonates . . Soil Tests for Zinc. . . . . . . . . METHODS AND MATERIALS. . . . . . . . . . Cropping Procedures. . . . . . . . . Laboratory Analyses. . . . . . . . . Total Soil Zinc. . . . . . . . . Available Soil Zinc. . . . . . . iv Page viii 22 24 24 25 Table of Contents (cont'd.) O.1§HC1....... EDTA-Ammonium Carbonate. DTPA O O O O O O O O O Routine Soil Tests . . . . Soil pH. . . . . . . . Extractable Phosphorus Extractable Potassium. Magnesium. . . . . . Available Zinc and Manganese Available Copper . . . Plant Analyses . . . . . . RESULTS AND DISCUSSION . . . . . . Calcium Development of the Cropping Technique. First Experiment . . . . . Yields . . . . . . . . Zinc Content of Tissue Uptake of Zinc . . . . Second Experiment. . . . . Yields 0 O O O O O O O Zinc Content of Tissue Uptake of Zinc . . . . Third Experiment . . . . . Yields . . . . . . . . Zinc Content of Tissue Uptake of Zinc . . . . Discussion of Cropping Techniques. Page 25 . 26 . 27 . 27 . 27 . 29 . 29 . 31 . 31 . 32 . 32 . 34 . 34 . 35 . 35 . 35 Table of Contents (cont'd.) Page Evaluation of Zinc Status of Ecuadorian Soils by Cropping in the Greenhouse. . . . . . . . 38 Fourth Experiment. . . . . . . . . . . . . . . 38 Yields . . . . . . . . . . . . . . . . . . 38 Zinc Content of Tissue . . . . . . . . . . 38 Uptake of Zinc . . . . . . . . . . . . . . 39 Fifth Experiment . . . . . . . . . . . . . . . 39 Yields . . . . . . . . . . . . . . . . . . 39 Zinc Content of Tissue . . . . . . . . . . 42 Uptake of Zinc . . . . . . . . . . . . . . 42 Sixth Experiment . . . . . . . . . . . . . . . 42 Yields . . . . . . . . . . . . . . . . . . 42 Zinc Content of Tissue . . . . . . . . . . 43 Uptake of Zinc . . . . . . . . . . . . . . 43 Relation of Yield and Zinc Concentration to Z inc Uptake O O O O O O O O O O .0 O O O O O 43 Relation Between Available Zinc and Soil pH. . 46 Zinc Status of Ecuadorian Soils. . . . . . . . 47 Evaluation of Procedures for Measuring Available Soil Zinc. . . . . . . . . . . . . . . . . . . . . 47 Total Zinc . . . . . . . . . . . . . . . . . . 47 Available Soil Zinc. . . . . . . . . . . . . . 50 0.1 N HCl Extraction . . . . . . . . . . . 50 EDTA Extraction. . . . . . . . . . . . . . Sl DTPA Extraction. . . . . . . . . . . . . . 52 vi Table of Contents (cont'd.) Page Evaluation of Available Zinc Extractants . . . . . 53 CONCLUSIONS. . . . . . . . . . . . . . . . . . . . . . 54 LITERATURE CITED . . . . . . . . . . . . . . . . . . . 56 vii Table LIST OF TABLES Chemical analyses of Ecuadorian soils. These determinations were made in the Santa Catalina Experiment Station Laboratory. Quito. . . . . Chemical analysis of Ecuadorian soils. These determinations were made in the Michigan State University Laboratory . Yield. concentration. and uptake of zinc by corn plants grown on a Wisner loam without applied zinc and with 10 and 20 ppm zinc. . . . . . Yield. concentration. and uptake of zinc by corn plants grown on a Wisner loam with O. 10. and 20 ppm applied zinc at levels of 0 and 500 ppm applied phosphorus Yields. concentration. and uptake of zinc by corn plants grown on 5 different Michigan soils. Wisner loam without applied zinc and with 10 and 20 ppm applied zinc. and sand . . Yields. concentration. and uptake of zinc by corn plants grown on Ecuadorian soils. Wisner loam soil and sand. Yield. concentration. and uptake of zinc of corn plants grown on Ecuadorian soils. Wisner loam soil and sand. viii Page List of Tables (cont'd.) Table 8. 10. ll. 12. 13. Yield. concentration. and uptake of zinc by corn plants grown on Ecuadorian soils. Wisner loam soil and sand with 1000 ppm of phosphorus applied. . . . . . . . . . . Linear correlation coefficients (r) between yield. concentration of zinc. and uptake of zinc on the Ecuadorian and Wisner soils . Linear correlation coefficients (r) between 0.1 N_HC1. EDTA. and DTPA Zn extraction procedures and pH on the Ecuadorian soils. . Amount of zinc extracted from Ecuadorian and Wisner soils by four extractants . . . Linear correlation coefficients (r) between soil tests and uptake of Zn in the 3 ex- periments with Ecuadorian and Wisner soils . Linear correlation coefficients (r) between total zinc and available Zn in Ecuadorian soils as measured by 3 extraction procedures ix Page INTRODUCTION Many of the soils in the Andean mountain valleys of Ecuador require relatively heavy applications of phos- phorus fertilizer if maximum crop yields are to be obtain- ed. A number of field experiments with corn have been conducted in recent years in which heavy broadcast appli- cations of phosphorus were applied. In some instances. corn yields were reduced. or initial corn growth was re- tarded on plants which received high rates of phosphorus. On some plants. symptoms developed which were character- istic of zinc deficiency. As far as the writer knows. no studies related to the zinc status of Ecuadorian soils has been conducted. Therefore. samples from Ecuador were obtained from typical agricultural soils of the Ecuadorian Andean val- leys for further studies at Michigan State University. The study reported here was conducted to (1) develop a quick greenhouse procedure to determine the relative zinc status of different soils and (2) using this procedure. 1 evaluate the zinc status of the Ecuadorian soils. This method could then be used to evaluate the zinc levels in soils from many different locations to determine where more intensive field experiments would be warranted. REVIEW OF LITERATURE Most soils contain micronutrients in sufficient quantities to sustain normal plant growth. On the other hand. zinc (Zn) deficiency in agricultural crops is one of the most common micronutrient deficiencies. and can develop in some soils due to crop removal. leaching. chemical fixation. erosion. or an initial lack of primary minerals which serve as sources of Zn. Leeper (1952) listed several factors which affect the availability of micronutrients to plants. Depending on the ionic species. availability is influenced by low total content. low exchangeable content. organic matter and.calcite complexes. anion precipitation. aging and recrystallization. and competition among species. Role of Zinc in Plants Literature on the critical concentration of Zn for normal growth of plants indicates considerable varia- 3 tion among species and varieties. Ellis (1965) reported that in Michigan it has been shown that the Saginaw var- iety of navy bean may yield well in the same soil where the Sanilac variety develops marked Zn deficiency; with adequate Zn fertilizer. the highest yields can be obtained with the Sanilac variety. The following tentative classification of crops was given by Viets §E_gl. (1954) based upon sensitivity to Zn deficiency: Highly sensitive: beans. soybeans. corn. hops. grapes. lima beans. flax and castor beans. Moderately sensitive: potatoes. tomatoes. onions. alfalfa. grain sorghum. sudan grass. sugarbeets and red clover. Insensitive: peppermint. oats. wheat. barley. rye. peas. asparagus. mustard. carrots. safflower. and grasses. Boehle and Lindsay (1969) listed cotton and fruit crops. especially citrus and peach. as good indicators of Zn deficiency. Salisburg and Ross (1969) and Boehle and Lindsay (1969) stated that Zn is needed for the proper utilization of carbon in plants. It is needed for protein metabolism and forms part of the enzyme systems which regulate plant growth. It is a constituent of the enzyme carbonic an- hydrase. a catalyst which breaks down carbonic acid. Zinc is necessary for the formation of trytophan. a precursor of indoleacetic acid (IAA). IAA is the most prevalent hormone in plants and Zn deficient plants have greatly re— duced auxin activity. Auxin content is important because changes in water content of plants are directly related to changes in the auxin content. As cited by Price §£_al. (1972). B. L. Vallee first recognized the role of Zn as an essential component of a variety of dehydrogenases. proteinases. and peptid- ases. Epstein (1972) noted that Zn is the metal component of a number of metalloenzymes. including several dehydro- genases. among them alcohol dehydrogenase and lactic de— hydrogenase. Salisburg and Ross (1969) suggested that Zn is related to chlorophyll formation because the symptoms of Zn deficiency in several fruit trees is an interveinal chloroses in the leaves. Salisburg and Ross (1969). Lindsay (1972). and Epstein (1972) all state that while all nutrient defic- iencies reduce plant growth. a lack of Zn frequently re- duces growth so dramatically that terms like "little leaf." "rosette." "mottle leaf" or "yellows" have been applied to the condition. Zinc in Soils Swaine (1955) reported that the total Zn content of soils varies from 10 to 300 ppm and that only part of this Zn is available for plant growth. The incidence of Zn deficiency in the United States has increased since Beeson (1945) mapped those states where deficiencies occurred. Berger (1962). as cited by Kubota and Allaway (1972). Lindsay (1972) and Cox (1973) reported that Zn deficiencies had occurred in 30 states. and Viets in 1966 reported that at least two additional states could be added to this list because he had observed symptoms of deficiency in crops in areas where these symptoms had not been evident 2 or 3 years earlier. As cited by Lindsay (1972). Ryan §£_al. in 1967 reported that low Zn levels occur in 10 of 15 European countries and in Israel. As the search continues. the areas of deficiency throughout the world are expected to expand. Hibbard (1940). Mitchell (1964). Lindsay (1972) and others agree that in general. the Al horizon contains the greatest quantity of Zn because of the high organic matter content. Krauskopf (1972) pointed out that the common minerals which are the principal sources of Zn in soils are (l) sulfide as sphalerite (ZnS). (2) carbonate as smithsonite (ZnCOB). (3) silicate as hemimorphite (Zn + (OH)ZSin 0 -H20). Zinc occurs dominantly in both sili— 4 7 cates and sulfides. The carbonate and sulfide of Zn are slightly soluble. He also reported that Zn is found in a clay mineral (sauconite) in which it is an essential constituent. but the pure Zn mineral is rare. Zinc also occurs in sedimentary rocks as disseminated grains of sphalerite. often accompanied by galena. especially in carbonate rocks. Lindsay (1972) pointed out that Sphal- erite can form under reducing conditions where H S is 2 produced. According to Lindsay (1972) Zn deficiencies are frequently found in areas where the surface soil.has been removed. He added that farmers have found that liberal application of manure and other organic materials are often effective in correcting Zn deficiencies. On the other hand. Zn deficiencies are often noted on old corral sites that are high in organic matter. This apparent contradictory behavior is explained because organic matter can interact with Zn in two ways. First. soluble Zn can be mineralized and made available to plants. Second. Zn can be incorpor— ated into organic constituents that are immobile in soils and fix Zn in a form from which it is not readily released. Factors Affecting Zinc Availability There are several factors affecting zinc availa- bility. ”Phosphorus (P) level. nitrogen (N) status. and soil pH seem to be the most important. Phosphorus Brinkerhoff (1969) found that high rates of P reduced plant weight. Zn uptake. and yield only when the . "l Zn supply in the soil was limited. In a greenhouse ex- periment. Ellis §t_§l. (1964) found that application of 10 pounds of Zn per acre increased the yield of field beans when the treatments included high levels of either applied or residual P. Judy gt_§1. (1964). Ellis (1965). Lessman (1965). and Melton §£_al. (1970) reported that heavy application of P may induce Zn deficiency. but when i.4 Zn was applied at a rate of 4 pounds per acre at each rate of P fertilizer. yields were increased. Lessman and Ellis (1971) found that the percent— age of fertilizer Zn which remained water soluble in the soil increased with increasing rates of Zn until a Zn/P ratio of 1:29 was reached. and then decreased with in— creasing quantities of ZnO incorporated in ammonium poly- phosphate (APP). Langin §£_al. (1962) stated that the more effec- tively the applied P is utilized by the crop. the more severe is the reduction in Zn utilization. On the other hand Boawn §£_31. (1954) and Seatz g£_§l. (1959) reported that P fertilization did not affect Zn response. Vinande et a1. (1968) found that with a high P level. the yield 10 of red kidney beans was increased slightly when Zn was applied. Langin §£_§1. (1972) and Stukenholtz §£_31. (1966) stated that the deleterious effect of P on Zn utilization is considered to be largely physiological in nature. pro- bably a plant root adsorption phenomenum. rather than an external Zn-P precipitation. The actual cause of P-induced Zn deficiency is still unknown. but fortunately the disorder can be alle- viated by application of 3 to 4 pounds of Zn per acre in the inorganic form or approximately one—fifth as much Zn in a chelate form (Judy g£_§1. 1964; Ellis 1965: Langin .E£_§L- 1962; Brinkerhoff §t_al. 1967; Melton §t_al. 1970; and Lindsay 1972). Nitrogen The effect of nitrogen (N) fertilizers on the availability of native and applied Zn is related to changes in soil.pH. according to Viets gt_al. (1957). Zinc uptake by three crops of milo and four clippings of Ladino clover was highest when ZnSO was applied with ammonium sulphate. 4 In a greenhouse experiment. Ellis et a1. (1964) found 11 that an application of ammonium nitrate banded.with Zn sulphate resulted in a significantly higher yield and Zn contents of navy beans than when ZnSO4 was banded alone or with monocalcium phosphate or with potassium chloride. Boawn gt_al. (1960) found that the influence of N carrier l"- on Zn uptake varied with crop grown. They compared ammo- nium sulfate. ammonium nitrate. and calcium nitrate as N HI! carriers- When an N carrier effect was observed. it was found to be most closely correlated with changes in soil pH. that is. N sources that reduced soil pH increased Zn availability. .Langin g£_§l. (1962) concluded that N has a bene— ficial action as a controlling factor of Zn deficiency in the corn plant. Soil Reaction and Carbonates -Recommendations for applications of micronutrients are often based on soil tests. of which soil pH is.an im- portant consideration. According to Lucas and Knezek (1972). Zn deficiency in crops is not common on acid soils. Lessman (1967). stated that as soil pH increases as a re— sult of liming. Zn availability decreases. 12 Camp (1945) stated that the critical pH above which Zn may become unavailable is from 5.5 to 6.5. In the soils studied by Nelson (1956). plants grew normally at pH 5-7 but were chlorotic at pH 7.3. Terman and Mortvedt (1965) found that Zn defic- iency. except in very sandy soils. is not usually a prob- lem below pH 6.0. but noted that the incidence may in- crease as the pH increases. especially in calcareous soils. They found that the response of corn to Zn was lowered as the soil pH was decreased by the various fer- tilizers. Hodgson §£_§l, (1966) stated that Zn defic- iencies are generally more widespread on calcareous soils. According to Ellis (1965). in Michigan the most severe Zn deficiency occurs in a region where the soils are usually calcareous; also Ellis (1964) suggested that in this area pH and free calcium carbonate may be re— lated to the occurrence of Zn deficiencies. Judy (1967) and Langin g£_gl. (1962) state that liming. high pH. and calcareous soils are among the fac- tors which affect the Zn concentration in the plants. Melton et a1. (1970) found that heavy P applications gen- 13 erally induced a greater Zn deficiency on soils test- ing above pH 7.0 which contained free CaCO Seatz et a1. 3. (1959) noted response by flax and sorghum to Zn fertili- zation as the rate of liming was increased from 2 to 6 tons of CaCO3 per million pounds of Hartsells soil. 1‘ Wear (1953) found that an application of 2000 pounds of CaCO3 per acre considerably decreased the Zn w! content of sorghum. The pH of the soil was increased from 5.7 to 6.6 and the calcium content of the plants was increased from 0.78 to 1.09 per cent. He concluded that the reduction of Zn uptake by the plants is a pH effect and not a calcium effect. Soil Tests for Zinc According to Lindsay (1972). the prime objective of a Zn soil test is to determine whether a given field will show Zn deficiency for certain crops. Bray (1948) proposed that a good soil test should meet the following requirements: 1. The extracting solution and the procedure used should extract the total amount (or 14 a proportionate part) of the available form or forms of a nutrient from soils with variable properties. 2. The amount of a nutrient in the extract should be measured with reasonable ac- curacy and speed. 3. The amount of extracted nutrients should be correlated with the growth and the re- sponse of each crop to the nutrient under various conditions. Cox and Kamprath (1972) concluded that eventually the soil test should predict the amount of fertilizer needed to achieve maximum economic production. Wear and Sommer (1947) found a good correlation between the occurrence of Zn deficiency symptoms and the quantity of Zn extracted with 0.1 N HCl or 0.04 N acetic acid. However. they noted that substituting 0.1 N HCl for 0.04 N acetic acid reduced the time of extraction and the volume of extracting liquid. making it possible to complete a set of determinations within a single working day and reducing the danger of contamination of the rea- 15 gent. Using a dithizone extraction procedure. Massey (1957) found no correlation between uptake of Zn and total soil Zn. Barrows and Drosdoff (1966). using a polarogra- phic method for the determination of extractable Zn in mineral soils. obtained significant correlations between extractable Zn in the soil and total Zn in leaves of tung trees. Martensug£_31. (1966) working with 57 Wisconsin soils compared four extractants and found that the re- lative amount of soil Zn extracted was in the order Aspergillus niger > 0.1 N_HCl > dithizone > 0.2 MLMgSO4. They concluded that much of the additional Zn extracted by 0.1 N_HC1 as compared to dithizone is not extractable by plants. In most Hawaiian soil profiles. the highest concentrations of Zn extractable with 0.1 N_HC1 was found .to vary from 0.1 to 17.0 ppm and total Zn from 51 to 288 ppm (Kanehiro and Sherman. 1967). Martens (1968) found that Zn uptake was more closely related to soil Zn extracted with 2 N MgCl 2 0.663) than to soil Zn extracted with 0.1 N_HC1 (r (r 0.297) or with 1.0 g HCl (r = 0.301). 16 On soils that varied widely in texture and pH. neither 0.1 N_HC1 nor dithizone-extractable zinc was found to give a reliable estimate of the plant availa- bility of soil Zn. On the other hand. a direct relation- ship was shown to exist between plant uptake of Zn and soil Zn extracted with 0.1 N HCl on soils of similar texture and pH by Martens and Chesters (1967). and by Massey (1957). Wear and Evans (1968) extracted Zn from coarse- textured soils with 0.05 N_HC1 plus 0.025 NLH . with 2504 0.1 N_HC1. and with 0.05 M EDTA at pH 7.0. The highest correlation for corn and sorghum was obtained with the first extractant. Correlation coefficients (r) for corn for the 3 above extractants were 0.89. 0.82. and 0.62 re- spectively. and correlation coefficients for sorghum were 0.70. 0.63. and 0.44 respectively. Extraction with NH4NO3. KCl and disodium ethyl- enediamine di (0 - hydroxyphenol acetic acid) was found by Ravikovitch §£;3;, (1968) to give the most significant multiple correlation coefficients for six different crops growing on 15 different calcareous soils. Melton (1968) reported that a 0.1 N_HC1 extraction procedure was found 17 to be adequate soil test for plant-available Zn in Michigan. Trierweiler and Lindsay (1969) developed the EDTA-ammonium carbonate soil test for Zn. This soil— test was evaluated on Colorado soils and was compared favorably with the dithizone and 0.1 N_HC1 methods. More recently Lindsay and Norvel (1969) reported the use of DTPA as an extractant for diagnosing the Zn. Fe. Mn. and Cu status of soils. Brown §£_§1, (1971) compared several analytical methods for determining available soil Zn. Soils from 92 fields in California were analyzed for extractable Zn using the DTPA. ammonium acetate-dithizone. 0.1 N_HC1. and NaZEDTA methods. They found a "predictible value" of 83. 79. 73. and 72%" respectively for these tests. On this basis. DTPA was preferable to the other methods. As cited by Viets and Lindsay (1973). Laner found that the mean labile Zn content of soil determined by corn «plants. DTPA extraction and 0.1 N HCl was 4.6. 4.3. and 7.7 ppm of Zn respectively. The labile Zn values in the corn plants and in the DTPA extraction were highly corre— 2 . lated (r = 0.97). Lindsay (1972) concluded that in ac1d 18 soils. the 0.1 N HCl and the dithizone methods are about equally effective in predicting Zn deficiency.- When soils containing CaCO3 are included. the EDTA. DTPA-and dithizone extractions are superior to the 0.1 NDHCl ex- traction. The EDTA and DTPA procedures are much more con- venient to use than dithizone. The DTPA extractant appears to be one of the more promising soil tests for Zn. is- METHODS AND MATERIALS Soil samples were obtained from 10 locations in Ecuador where field experiments had been conducted. and the results of soil analyses made in the laboratory at Santa Catalina. Quito. Ecuador were available for all ex- cept 3 locations (Table 1). Approximately 8 kg of soil was Obtained from the Ap horizon from the following lo— cations in the mountain area of Ecuador: Parroquia Canton Provincia £35m. Aloag Mejia Pichincha Aychapichu Cutuglahua Mejia Pichincha Santa Catalina Machachi Mejia Pichincha Chisinche Tumbaco Quito Pichincha Clementina Atuntaqui Antonio Ante Imbabura Atuntaqui La Merced Ibarra Imbabura Granja Experimental Guamani Quito Pichincha Monjas Pifo Quito Pichincha Alagarin Cutuglahua Mejia Pichincha El Retire El Chaupi Mejia Pichincha Umbria The soil samples were air-dried. placed in cotton bags. and shipped to Michigan State University. The sam- 19 20 nlllerI Ir m.m was o.m o.m. mos Hmma mma ma vs m.o «.6 manna: m.H mmm o.m n.6H mmm mmoa 6mm a as 6.6 m.m onflumm Hm III III III III III IIII III II II III III cflummmad o.m mas m.m m.m Has maoa sum as mm m.o 6.6 mascoz III III III III III IIII III II II III III .mxm mncmuw III III III III III IIII III II II III III Asvmucsum m.m ea m.~ m.m mom mum mmm m mm m.o m.s mcaucmsmao v.m mas 6.~ m.~ was coma mam oa we m.o e.o mroqflmflro o.m sum H.o H.m mm mooa mas ma as o.H s.m mcflamumo mucmm o.m ANN o.m 6.N mos moms mmm m ms m.o m.o snoammromm IIIIIIIIIIIIIIIIIIIIIIIII EQQIIIIIIIIIIIIIIIIIIIIIII mooa\me .2: 0s so an m: mo M m z m+a< mm maaom some 0H03 mcoflumcflfiumumo mmmne .ouflso .wuoumnonma coflumum unmEHmexm mcflamumo mucmm 0:» Ga .maflom cmfluoomsom mo mommamcm Hmowfiwno .H magma 21 ples were treated by steam sterilization by the Quaran- tine Division of the United States Department of Agri- culture in Miami. Florida. After the soil samples were received at Michigan . State University. they were crushed by rolling with the glass bottle. and then stored in cardboard containers. A sample of a Wisner loam from Bay County. Michigan taken from an area where a marked Zn response was obtained in field experiments was used as a soil for comparison purposes in these experiments. For the third experiment. samples from 5 Michigan soils varying in texture and fertility level were used; the soil series and locations are listed below: §pil Type County 1. Nester loam Clare County 2. Nester sandy loam Gladwin County 3. Kent silt loam Mason County 4. Selkirk loam Mason County 5. Montcalm sandy loam Mecosta County White silica sand from Wedron. Illinois was wash- ed 6 times with 6 N HCl. 3 times with 0.1 N_HC1. 3 times with distilled water and 3 times with deionized water. 22 then oven dried and stored in plastic bags. Preliminary cropping (following the procedures given below) to com- pare washed sand and unwashed sand indicated that the sand did not contain enough plant-available Zn to justify the washing procedure. Consequently all subsequent ex- periments were conducted using unwashed sand. Cropping Procedures At Michigan State University. the Ecuadorian and Michigan soils were cropped in the greenhouse to evaluate their Zn-supplying ability. Six separate experiments were carried out using a cropping procedure adapted from that described by Stanford and DeMent (1957). Five hundred grams of silica sand were added to l6-ounce wax cartons. into each of which a bottomless 16- ounce carton had been inserted. Fifty m1 of Hoagland's nutrient solution without Zn (Hoagland and Arnon. 1950). was added to each container. 6 corn seeds (Var: Midh 500 2X R 121) were spread on the surface and covered with silica sand. which was added until the total weight of the carton was 750 g; last 80 ml of deionized water was added. 23 After 10 days. a mat of corn roots had developed at the bottom of the inside carton containing the corn seedlings. These cartons with the root mats were removed - from the outer cartons and the roots placed on top of 100 g of soil. which was in other 16-ounce waxed cartons. The plants were allowed to grow into the soil for 14» days. For treatments to which Zn was applied. either 5 or 10 ml of 20 ppm solution of Zn as ZnSO4'7 H20 was added to the soil prior to cropping. This was equivalent .to 10 or 20 ppm Zn. respectively. in the soil. When P was to be added to the soil. 0.209 or 0.418 g of Ca (H2PO4)2'H20 was mixed with the soil (to give 500 or 1000 -nppm P). and the soil was then wetted to field capacity with deionized water. allowed to air dry. remixed. and then rewetted. In the last experiment the soils were in- cubated for 12 days after phosphorus was applied; during this time they were wetted to field capacity with deion- ized water and air-dried at room temperature once every 4 days without further mixing. Additional nutrient solution was added during the 24-day growing period. After 5. 11. and 18 days. an addi- tional 50 m1 of nutrient solution as cited above which did 24 not contain Zn was added. The cultures received deion- ized water every day to replenish moisture losses. Each culture also received 3 additional incre- ments of nitrogen (50 m1 of 0.0054M'Ca(N0 ) and iron as 3)2 Fe citrate (50 m1 of a solution containing 6.7 nge citrate per liter) when the appearance of the plants in— dicated a need for N and Fe. After the mat of roots had been in contact with the soil for 14 days. the corn plants were harvested. The plant material was oven dried at 65 C. weighed. and ground to pass a 20-mesh sieve. Laboratory Analyses Total Soil Zinc Total Zn was determined on the Ecuadorian soil and the Wisner soil by boiling 5 g of soil in 50 m1 of 12 N_HC1. The suspension was boiled until approximately 5 m1 of solution remained and then filtered into 200 ml volumetric flasks. The soil and the filter paper were washed with 1.0 N_HC1 and deionized water. Zinc was de- termined using a Perkin Elmer Model 290 Atomic Absorption 25 Spectrophotometer. This procedure was shown by Melton (1968) to give a reasonable approximation of total soil Zn. Available Soil Zinc Available Zn was determined by using the follow- ing extraction procedures: 0.1 N HCl.--Soils were extracted using a 1:10 soil:solution ratio. shaking for 10 minutes and filtering. EDTA-Ammonium Carbonate.--The extracting solution (Trierweiler and Lindsay. 1969) was prepared as follows: 1. Dissolve 32.8 g of EDTA in deionized water and dilute to 1000 m1. 2. Dissolve 1141.1 9 of (NH4)2C03-H20 in 500 ml of deionized water. 3. Combine l and 2 dilute to 10 liters. 4. The solution was adjusted to a pH 8.6 using HCl or NH4OH. 26 Soils were extracted using a 1:2 soil:solution ratio. shaking for 30 minutes and filtering. DTPA.--The extracting solution (Viets and Lind- say. 1973) was prepared as follows: 1. Dissolve 19.65 g of DTPA (Diethylenetriamino- pentacetic acid) in 8 liters of deionized water. Add 5.55 of CaClz. Mix until dissolved. Add 133 ml of concentrated TEA (Triethanol Amine). Dilute to 10 liters. Adjust the pH to 7.30 using HCl or NH4OH. Soils were extracted using a 1:2 soil:solution. shaking for 2 hours and filtering. Zinc was determined on all solutions using an atomic absorption spectrophotometer. Routine Soil Tests At Michigan State University in the soil test lab- oratory. the Ecuadorian soil samples were routinely anal— 27 yzed for pH. lime requirement. extractable P. K. Ca and Mh. Zn. Mn and Cu (Table 2). Using the procedure de— scribed below: Soil pH.--Ten grams of soil were mixed with 10 ml of water (1:1 ratio). After 15 minutes. the mixture was stirred again. and the pH of the suspension determined using a glass electrode pH meter. The lime requirement of samples testing below pH 6.8 was determined by the method of Shoemaker. McClean. and Pratt (1961). Extractable Phosphorus.-—Phosphorus was extracted for 5 minutes from samples with Bray P-l reagent (0.025 N_HC1 and 0.03 N_NH4F). using a 1:8 soil:solution ratio. Phosphorus in the extract was determined by using the Spectronic 20 colorimeter at 880 m and the ascorbic acid reduced blue color described by Watanabe and Olsen (1965). Extractable Potassium. Calcium. and Magnesium.-- Cations were extracted for 5 minutes with 1.0 N_NH4OAc (pH 7.0) using a 1:8 soil:solution ratio (Jackson. 1958). Potassium. Ca and Mg in the extract were determined by means of a Perkin Elmer Model 290 atomic absorption spectrophotometer. 28 as 66 o.ma has vaoa 66H 6N s.6 manna: oa m6 N.HH mmm msma was ma m.6 onuumm as ea S6 «.6 smm M66 mam m 6.6 cuummma< 6H 66 6.6 was mms mam ma 6.6 mmmco: oa mma 6.63 m¢6 66am «ma mm 6.5 .mxm ancmuo ma ms 6.6 mam eama man 6 6.5 asvmucsum m 66 6.6 oam 6H6 mma a 6.6 maauamsmao oa mm 6.6 so M66 6~H as 6.6 wroaumano am we s.oa so sacs 66H 6H 6.6 mauamumo mucmm NH 66 6.6 mas «Hos 66a NH a.m snoummrusa IIIIIIIIIIIIIIIIIIIIIIIIII EQQIIIIIIIIIIIIIIIIIIIIIII so a: an m: mo x m mm mauom mHmB mcofiumcfleumpmp smash .wnoumuonmq muHmH0>HCD mumum cmmHAOHZ 0:» CH some .mHHOm cmfiuoomsom mo mamMHmcm HMOHEUQU .N OHQMB 29 Available Zinc and Manganese.—-Available Zn and Mn were extracted for 10 minutes with 0.1 N HCl using a 1:10 soil:sOlution ratio. (Nelson,et a1" 1959). Zinc and Mn in the extract were determined by means of a Perkin Elmer Model 290 atomic absorption spectrophotometer. Available Copper.--Availab1e Cu was extracted for 1 hour with 1.0 N_HC1 using 1:10 soil:solution ratio. Copper in the extract was determined by means of a Perkin Elmer Model 290 atomic absorption spectrophotometer. Plant Analyses One g of plant material was ashed in a muffle furnace at 550 C for 8 hours. The ashed samples were treated with 10 m1 of 1.0 N_HC1. and the resulting solu- tion filtered into 100 ml volumetric flasks and washed with deionized water. Zinc in solution was determined using the atomic absorption spectrophotometer. RESULTS AND DISCUSSION Six separate experiments were conducted in the greenhouse; the first 3 to develop the cropping technique. and the last 3 to evaluate the relative Zn status of 10 Ecuadorian soils. The pots were systematically arranged in four replications. The data for yields. Zn content of the tissue. and Zn uptake per pot were analyzed by means of the analysis of variance. even though it was recognized that this was not completely justified since the pots were not arranged randomly. Development of the Cropping Technique First Experiment Three levels of Zn (none. 10. and 20 ppm) were applied to a Wisner loam which was known to be deficient in Zn from the results of previous field experiments. 30 31 Yields.--Yields were significantly higher when :20 ppm Zn was applied than When no Zn was applied. but Vvere not significantly higher when 10 ppm was applied (Table 3). (Table 3. Yield. concentration. and uptake of zinc by <:orn plants grown on a Wisner loam without applied zinc .and with 10 and 20 ppm. Rate of Yield Zinc in Plants Applied Zn Concentration Total uptake ppm 9/ pot ppm mg/ pot 0 2.50 16 0.045 10 2.60 31 0.082 20 2 66 23 0.064 :3 3:; CV ( %) 23 2.51 2.10 Zinc Content of Tissue.--Concentration of Zn (ppm) tended to increase in the tissue when Zn was ap- plied. but this increase was not significant. The highest concentration of Zn was obtained when 10 ppm of Zn was added to the soil (Table 3). 32 Uptake of Zinc.-—The uptake of Zn (mg Zn/pot) was <2alcu1ated as follows: Weight of plants x ppm mg Zn/pot = of zinc in plants 1000 The uptake of Zn was significantly increased when :Zn was applied to the soil as compared to the treatment in which no Zn was applied (Table 3). Uptake was less. ibut not significantly less. when 20 ppm Zn was applied than when 10 ppm was applied; this decrease is a reflec- tion of the lower Zn content of the tissue when 20 ppm 'was applied. Second Experiment Wisner loam was again used from the same location as that used in the first experiment. and 3 levels of Zn (none. 10 and 20 ppm) were applied at each of two levels of phosphorus (none and 500 ppm P). Yields.--When no P was applied. no significant yield increases were obtained when Zn was applied. al- though the yield tended to be higher when 10 ppm Zn was applied (Table 4). When P was applied. the yield was 33 significantly higher when 20 ppm Zn was applied than when :no Zn was applied. and the yield when 10 ppm was applied tended to be higher. The highest yield was obtained with the highest levels of both Zn and P. and the lowest yield *when P was applied without Zn. ITable 4. Yield. concentration. and uptake of zinc by corn plants grown on a Wisner loam with 0. 10. and 20 ppm applied zinc at levels of 0 and 500 ppm applied phosphorus. Rate of Rate of Yield Zinc in Plants .Applied P Applied Zn Concentration Total Uptake ppm ppm 9/ pot ppm mg/ pot 0 0 3.15 42 0.133 0 10 3.23 54 0.174 0 20 3.08 65 0.199 500 0 2.95 39 0.120 500 10 3.06 48 0.153 500 20 3.46 61 0.210 23:23:; “3.2 2 3:31: cv ( %) 0.26 0.20 0.22 34 Zinc Content of Tissue.--The concentration of Zn in the tissue increased with each increasing increment of Zn at both levels of P (Table 4). At each level of applied Zn. the concentration of Zn in the tissue was significantly higher when no P was applied. than when P was applied; Zn tended to be higher when neither Zn nor P were applied than when only P was applied. Uptake of Zinc.-—Zinc uptake increased with each increment of applied Zn at both P levels (Table 4). The uptake of Zn with none or 10 ppm Zn was higher when no P ‘was applied than when P was applied. No difference in Zn uptake due to P level was noted when 20 ppm Zn was applied. due apparently to the yield levels obtained for these two treatments. Sflhird Experiment Five different Michigan soils together with the VVisner reference soil were cropped as before without Zn Iapplications. except that the same 3 levels of Zn (0. 10 and 20 ppm) were applied to Wisner loam. Two check treatments in which sand was used instead of soil were also included. 35 Yields.--Yields increased as the rate of Zn in- cxreased on Wisner loam. The lowest yield was obtained ‘vwith Nester loam and the highest with Nester sandy loam (HTable 5). No other significant differences were noted loetween soils when no Zn was applied or when sand was lised instead of soil. Zinc Content of Tissue.--Zinc concentration was significantly higher when Zn was applied on Wisner loam 'than when no Zn was applied (Table 5). Using the Wisner :soil to which no Zn was applied as the reference for (comparison. significantly higher Zn concentrations were rioted with Nester loam and with the Kent and Selkirk soils. (Uptake of Zinc.--Uptake of Zn was significantly .increased as each increment of Zn was applied to Wisner Iloam (Table 5). The higher uptake of Zn when sand was Iased instead of soil cannot be explained. but it does illustrate the need for extreme care in both the cropping .and analytical procedures to prevent Zn contamination. Again using the Zn deficient Wisner soil as a standard :for comparison. no differences in Zn uptake were noted laetween the Wisner soil and Nester sandy loam. The Kent 36 3.0 3.6 8.6 1.x. 0 >0 ”WE M w... mg a... 600.0 Hm mm.a 0 6:66 >60.0 6v mm.H 0 6:06 mma.0 m6 00.~ 0m Emoa Hmcmflz HNH.0 M6 mm.H 0H EmoH Hmcmflz 650.0 mm mm.a 0 smoa nonmflz 650.0 06 mm.H 0 Emoa awash Eamoucoz 060.0 mm m6.a 0 Emoa xuflxamm H60.0 mv 06.H 0 Emoa uHHm ucmx 650.0 mm 00.N 0 EMOH xvcmm Hmummz 660.0 mm hm.a 0 EmoH Hmummz pom\ms 6mm pom\m 8mm mxmumb Hmuoa codumuucmocoo 2N pmflamm< Haom . 6H0HM mo mumm . mucmam as ocHN mucmsumoue .6266 cam .ocHN pmaammm Sam 0N mam OH £ua3 mam ocflu pmflammm DSOADAB EmoH “mamflz .mafiom cmmflnoflz ucmHmMMHw m so azoam mucmam zaoo an ocfls Lo spasms was .aoflrmauamoaoo .mnfimas .m magma 37 soil. or the Montcalm soil. suggesting that these soils might also be deficient in Zn. Discussion of Cropping Technique The results of these first 3 experiments indicate that differences in the uptake of Zn can be obtained us- ing the modified Stanford-Dement cropping technique. The results of the first 2 experiments (Table 3 and 4) show that differences in uptake can be obtained when different rates of Zn are applied to the same soil. The third ex- periment (Table 5) demonstrates that differences can be obtained in Zn uptake between different soils to which no Zn is applied. The total dry weight of the plants. the concentrations of Zn in the tissue and the total uptake of Zn varied considerably between the 3 experiments. This illustrates the necessity of following a carefully controlled cropping technique in conducting experiments of this type. Furthermore. a soil for comparison. known to be deficient in Zn. must be included in each experi- ment to establish a level of Zn uptake for comparison. Usually. a level of 20 ppm Zn in plant tissue is consid- 38 ered to be the critical level below which growth re— sponses to added Zn can be expected. Concentration of Zn in the plants grown in these experiments was above this level in the second and third experiments. This further illustrates the necessity of including a soil of known Zn response for comparisons. Evaluation of Zinc Status of Ecuadorian Soils By Cropping in the Greenhouse Fourth Experiment In this experiment. the Zn status of 10 Ecua- dorian soils was evaluated. The Zn—deficient Wisner soil and another treatment in which sand was used instead of soil were included for comparison. Yields.-—The highest yield was Obtained with the Monjas soil. which was the only soil with which the yield was significantly different from that with the Wisner soil. The lowest yield was obtained with the sand cul- ture without soil (Table 6). Zinc Content of Tissue.--The highest concentra— tion of Zn was in plants grown on Aychapichu soil and the 39 lowest in those on the Granja Experimental soil (Table 6). The concentration of Zn was higher in plants grown on all soils than on Wisner soil except for the Clemen- tina. Granja Experimental. and Monjas soils. from which the Zn concentration in plants was not different from that in plants grown in Wisner soil. Uptake of Zinc.-—The highest uptake of Zn was obtained with the Aychapichu soil and the lowest in the Wisner soil (Table 6). On 5 soils—-Clementina. Atunta- qui. Granja Experimental. El Retiro. and umbria—-the uptake of Zn was not significantly different from that with Wisner soil. This suggests that these soils may also be deficient in Zn. Fifth Experiment The preceding experiment was repeated in order to check the reproducibility of the results. Yields. Yields obtained on 3 soils--Chisinche. Clementina. and Monjas--were significantly higher than that obtained on Wisner soil (Table 7). Yields on all soils were significantly higher than that with sand. 40 Table 6. Yields. concentration. and uptake of zinc by corn plants grown on Ecuadorian soils. Wisner loam soil and sand. Zinc in Plants SOil Yield Concentration Total Uptake 9/90t PPm mg/pot Aychapichu 2.83 52 0.147 Santa Catalina 2.73 48 0.131 Chisinche 2.86 43 0.123 Clementina 2.82 40 0.113 Atuntaqui 2.70 38 0.103 Granja Exp. Imbabura 2.67 34 0.099 Monjas 2.92 41 0.120 Alagarin 2.50 45 0.121 El Retiro 2.55 46 0.117 Umbria 2.52 43 0.109 Wisner soil 2.58 38 0.098 Sand 2.31 45 0.093 38:83 “3.: 3 2:32: CV ( %) 0.16 0.16 0.24 41 Table 7. Yield. concentration. and uptake of zinc of corn plants grown on Ecuadorian soils. Wisner loam soil and sand. Zinc in Plants SOil Yield Concentration Total Uptake 9/ pot ppm mg/ pot Aychapichu 2.05 46 0.094 Santa Catalina 2.10 51 0.106 Chisinche 2.15 42 0.090 Clementina 2.16 41 0.088 Atuntaqui 1.82 38 0.069 Granja Exp. Imbabura 2.10 39 0.082 Monjas 2.21 50 0.110 Alagarin 1.94 42 0.081 El Retiro 1.99 52 0.103 Umbria 1.97 58 0.114 Wisner soil 1.94 40 0.077 Sand 1.54 38 0.058 LSD (0.05) 0.19 3 0.011 (0.01) 0.26 4 0.014 CV ( 99 0.13 0.10 0.17 42 Zinc Content of Tissue.—-The highest concentra- tjxon of Zn was found in the Umbria soil. and the Zn con- centration in this soil. together with Aychapichu. Santa Catalina. Monjas. El Retiro. was significantly higher than that from the Wisner soil (Table 7). Uptake of Zinc.--The greatest uptake of Zn was obtained with the Umbria soil. on which the uptake was not significantly different from Wisner in the fourth experiment. The uptake of Zn with the Atuntaqui. Granja Experimental and Alagarin soils was not significantly different from that with Wisner (Table 7). Except for the Alagarin and Umbria soils. these results are in agreement with those obtained in the preceding experiment. Sixth Experiment This experiment was conducted concurrently with the preceding experiment. but 1000 ppm of phosphorus was applied to each of the Ecuadorian soils and to the Wisner soil. A treatment in which sand was used instead of soil was also included. Yields.--Yields obtained with the Chisinche and El Retiro soils were significantly greater than that with 43 the Wisner soil (Table 8). Yields on all soils except the Clementina soil were significantly more than that with sand. Zinc Content of Tissue.--The highest concentra- tion of Zn was in plants grown on the Santa Catalina soil. The concentration of Zn was higher on the Aycha- pichu. Santa Catalina. Monjas. E1 Retiro and Umbria soil than in the Wisner soil (Table 8). The Atuntaqui soil had the lowest concentration of zinc. Uptake of Zinc.--The highest uptake of Zn was obtained with the Santa Catalina soil and the least with the Atuntaqui (Table 8). The uptake of Zn from the Clementina. Atuntaqui. Granja Experimental and Alagarin soils was either not different or lower than that from the Wisner soil. Uptake of Zn from all soils except Clementina and Atuntaqui was significantly higher than that from Wisner soil. Relation of Yield and Zinc Concentration to Zinc Uptake Yield and Zn content were not correlated in any of the last 3 experiments (Table 9). nor were yield and 44 'Table 8. Yield. concentration. and uptake of zinc by corn plants grown on Ecuadorian soils. Wisner loam soil and sand with 1000 ppm of phosphorus applied. Zinc in plants SOil Yield Concentration Total Uptake g/pot PPm mg/pot Aychapichu 2.39 38 0.090 Santa Catalina 2.54 39 0.099 Chisinche 2.69 34 0.091 Clementina 2.17 29 0.062 Atuntaqui 2.42 25 0.060 Granja Exp. Imbabura 2.49 30 0.074 Monjas 2.55 36 0.091 Alagarin 2.49 28 0.069 El Retiro 2.65 36 0.094 umbria 2.56 36 0.092 Wisner soil 2.33 32 0.074 Sand 1.85 29 0.053 E8183 8'32 2 8:83 CV’ ( %) 0.16 0.18 0.23 45 Zn uptake except in the sixth experiment. Zinc concen- tration and uptake were highly correlated (0.01 level) in all 3 experiments (Table 9). Table 9. Linear correlation coefficients (r) between yield. concentration of zinc. and uptake of zinc on the Ecuadorian and Wisner soils. Comparisons Experiment Experiment Experiment 4 5 6 Yield vs Zn content 0.050 0.148 0.424 Yield vs uptake 0.380 0.477 0.689* Zn content vs uptake 0.910** 0.938** 0.936** *Significant at 0.05 level **Significant at 0.01 level This means that actual yields were not as greatly affected by Zn level in soil as was the concentration of Zn in the plant. Also. differences in Zn status of soils are reflected by differences in Zn absorption by the plants. not in growth. This would be expected since the concentrations of Zn in the plants was always considerably I higher than the generally accepted critical level of 20 ppm. Either concentration or total uptake could be used 46 to evaluate Zn status of soils. However. Zn uptake will be used herein as a means of evaluating the Zn status of the soils. since it was felt that this value would probably reflect the Zn level in the soils more accurately than concentration should some other factor affect yield. Relation Between Available Zinc and Soi1_pH Available Zn extracted with 0.1 N.HC1 was not correlated with soil pH (Table 10). Significant (0.05 Table 10. Linear correlation coefficients (r) between 0.1 N_HC1. EDTA. and DTPA Zn extraction procedures and pH on the Ecuadorian soils. Correlation coefficient Comparisons r pH vs 0.1 N HCl -0.29 pH vs EDTA -0.69* pH vs DTPA -0.62* *Significant at 0.05 level. 47 level) correlations were noted between soil pH and Zn extracted with EDTA and DTPA. in which level of Zn de- creased as pH increased. However. these correlations were not as high as those obtained between Zn uptake by cropping and the Zn extracted by these two methods. Zinc Status of Ecuadorian Soils In all 3 of the experiments with Ecuadorian soils (Tables 6. 7. and 8). the uptake of Zn from the Atuntaqui. Clementina. and Granja Experimental soils was not significantly different from Zn uptake from the Zn—deficient Wisner soil. This would suggest that those soils might be deficient in Zn. and so would be the soils on which further field experiments would be warranted. Evaluation of Procedures for Measuring Available Soil Zinc Total Zinc Total zinc was extracted from the soil with 12.0 .N HCl. More Zn was extracted from the Wisner soil than from any of the Ecuadorian soils (Table 11). The amounts 48 Table 11. Amount of zinc extracted from Ecuadorian and Wisner soils by four extractants (ppm). Soils 12.0 N HCl 0.1 N HCl EDTA DTPA Aychapichu 53.3 7.73 4.37 3.07 Santa Catalina 57.6 9.33 6.69 3.95 Chisinche 46.5 4.93 2.74 1.47 Clementina 52.6 3.60 0.80 0.51 Atuntaqui 37.3 3.73 0.74 0.48 Granja Exp. 57.1 8.13 2.10 1.36 Monjas 42.9 7.46 4.56 2.75 Alagarin 48.5 4.80 2.29 1.44 E1 Retiro 52.8 9.73 5.44 4.08 umbria 43.4 7.60 4.64 2.96 Wisner loam 69.3 5.60 1.76 1.17" 49 of total Zn extracted from the Ecuadorian soils varied from 57.6 ppm in the Santa Catalina soil to 37.3 ppm in the Atuntaqui soil. Total Zn was not correlated with either Zn uptake (Table 12) or with the "available" Zn extractions (Table 13). Table 12. Linear correlation coefficients (r) between soil tests and uptake of Zn in the 3 experiments with Ecuadorian and Wisner soils. Comparisons Experiment Experiment Experiment 4 5 6 12.0 N HCl vs uptake 0.090 0.150 0.060 0.1 N_HC1 vs uptake 0.208 0.676* 0.790** EDTA vs uptake 0.476 0.704* 0.925** DTPA vs uptake 0.469 0.813** 0.893** *Significant at 0.05 level **Significant at 0.01 level 50 Table 13. Linear correlation coefficients (r) between total zinc and available Zn in Ecuadorian soils as measured by 3 extraction procedures. Comparisons r 12.0 N HCl vs 0.1 N HCl 0.26 12.0 N HCl vs EDTA 0.05 12.0 N HCl vs DTPA 0.07 0.1 N HCl vs EDTA 0.87** 0.1 N HCl vs DTPA 0.90** EDTA vs DTPA 0 . 98** **Significant at 0.01 level. Available Soil Zinc 0.1 HCl Extraction.—-The amount of Zn extracted from the Ecuadorian soils varied from 9.73 ppm in the El Retiro soil to 3.73 ppm in the Atuntaqui soil (Table 11). Of the 3 soils which were considered to be potentially Zn deficient from the cropping experiments. lower levels of extractable Zn were obtained from the Atuntaqui and Cle- mentina soils than for the Wisner soil. but a higher level was noted for the Granja Experimental soil. Also the 51 Chisinche and Alagarin soils have lower levels of Zn than the Wisner soil. Linear correlation analyses between Zn extracted with 0.1 N HCl and Zn uptake during cropping (Table 12) showed no correlations in the fourth experiment. a sig- nificant correlation in the fifth experiment. and a highly significant correlation in the sixth experiment when P was applied. EQTA Extraction.--The amount of Zn extracted varied from 6.69 ppm in the Santa Catalina soil to 0.74 ppm in the Atuntaqui soil. Of the 3 potentially Zn- deficient soils. lower levels of extractable Zn were noted from the Atuntaqui and Clementina soils. but a slightly higher level was obtained for the Granja Exper- imental soil. All of the other soils also had higher levels of extractable Zn than the Wisner soils. Less Zn was extracted from the soils with EDTA than with 0.1 N HCl. The linear correlation coefficient between ex- tractable Zn and uptake of Zn was not significant for the fourth experiment (Table 12). but significant coeffic- ients were Obtained in the fifth and sixth experiments. 52 Again. a higher correlation was obtained when P was applied to the soils than when no P was applied. DTPA Extraction.--The amount of Zn extracted with DTPA varied from 4.08 ppm in the El Retiro soil to 0.48 ppm in the Atuntaqui soil. Of the 3 potentially Zn- deficient soils. less Zn was extracted from the Atuntaqui and Clementina soils than from the Wisner soil. and again slightly more was extracted from the Granja Experimental soil. Also. higher Zn levels were obtained for all the other soils than from the Wisner soil. Less Zn was ex- tracted from the soils with DTPA than with either 0.1 E HCl or EDTA. The linear correlation between Zn uptake and Zn extracted with DTPA was not significant for the fourth experiment. but highly significant correlations were ob- tained for both the fifth and sixth experiments (Table 12). Again. a higher correlation was Obtained when P was applied. 53 Evaluation of Available Zinc Extractants The total amount of Zn in the soils does not appear to be related to the level of available Zn (Tables 12 and 13). All 3 of the methods for deter— mining available soil Zn were correlated with Zn uptake by cropping (Table 12). indicating that any one of the 3 could probably be successfully correlated with yield response to Zn. The correlation coefficient of 0.98 between EDTA and DTPA extractable Zn (Table 13) indic- ates an almost perfect correlation between these 2 ex- tractants; this would be expected since both are com- plexing or "chelating" agents which would be expected to react similarly with soil Zn. On the basis of these results. either of these two extractants would probably be somewhat more satisfactory for routine testing than 0.1 NLHCl. Since the DTPA extracting solution is easier to make up in the laboratory and is less susceptible to decomposition with time. it is prObably the most practical for routine use. CONCLUS IONS The short-term cropping procedure developed by Stanford and Dement (1957) can be used to measure dif- ferences in Zn uptake by corn from soils having differ- ent levels of available soil Zn. or from soils to which different levels of Zn have been applied. However. the techniques used in following this procedure must be standardized and carefully followed in each experiment if reproducible results are to be obtained. Since the plants are grown for only a short time (2 weeks in con- tact with soil). growth differences are not obtained so that comparisons must be made between the total Zn up- take from the different soils. In order to separate soils which may respond to Zn applications in the field from those which will not respond. a soil known to be deficient must be included in all experiments as a means of comparison. Using this technique. Zn uptake from 10 Ecuador— ian soils was determined and uptake from 3 of the 10 54 55 (Atuntaqui. Clementina. and Granja Experimental) was either lower or not different from Zn uptake from the Zn deficient soil (Wisner loam). This suggests that these soils may be deficient in Zn. and that field ex- periments are justified on these soils. The uptake of Zn from these soils was correlated with Zn extracted using 3 different extracting solu- tions: 0.1 N HCl. EDTA. and DPTA. Any one of the 3 extractants could be satisfactorily used as a soil test for available Zn. It is suggested that DTPA would be the most satisfactory extractant to use. since slightly higher correlations were obtained with DTPA than the other extractants. and since the solution seems to be more adapted to laboratory routine procedures than the EDTA solution. LITERATURE CITED LITERATURE CITED Barrows. H. L. and Drosdoff. M. 1960. A rapid polaro- I graphic method for determining extractable Zn I in mineral soils. SSSAP 24: 169-171. Beeson. K. C. and Kenneth. C. 1945. The occurrence of mineral nutritional diseases of plants and ani— mals in the U.S. Soil Sci. 60: 9—13. Berger. K. C. 1962. Micronutrients deficiencies in the United States. J. of Agri. and Food Chem. 10: 178-181. Boawn. L. C.. Viets. F. G. Jr.. and Crawford. C. L. 1954. Effect of phosphate fertilizers on Zn nutrition of field beans. Soil Sci. 78: 1—7. Boawn. L. C.. Viets. F. G. Jr.. Crawford. C. L. and Nelson. J. L. 1960. Effect of nitrogen carrier. nitrogen rate. zinc rate and soil pH on zinc uptake by sorghum. potatoes and sugar beets. Soil Sci. 90: 329-337. Boehle. J. Jr. and Lindsay. W. L. 1969. Micronutri- ents--the fertilizer shoe nails. Solutions 6-12. Bray. R. H. 1948. Requirements for successful soil tests. Soil Sci. 66: 83—89. Brinkerhoff. F. H. 1969. Zinc. iron and phosphorus relationship in pea beans. Master thesis. Michigan State University. Brinkerhoff. F. H.. Ellis. B.. Davis. J.. and Melton. J. 1967. Field and laboratory studies with zinc fertilization of pea beans and corn in 1966. Quart. Bull. Mich. Agr. Exp. Sta.. East Lansing. Mich. 49: No. 3. 262-275. 56 57 Brown. A. L.. Quick. J. and Eddings. J. L. 1971. A comparison of analytical methods for soil zinc. SSSAP 35: 105-107. Camp. A. F. 1945. Zinc as a nutrient in plant growth. Soil Sci. 60: 157-164. Cox. J. 1973. Get zinc into your garden and into your diet. Organic gardening and farming. P. 112-117. Cox. F. R. and Kamprath. E. 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