WI “I“ W H 125 130 .THS_ A CASE STUDY OF SOME BIOLOGECAE. INTERACTEONS EH EEO-TELL CORN Thesis Ear tines} agree 37." M. S. MECHE GAN SEAT E EEE EE/‘E R33: MOHAMED E‘W EEM SH‘ Mb 13 o 3 x1 A u. LIBRAR Y Michigan: Scan Uni'e'crsfity v “w mtg" “v ABSTRACT A CASE STUDY OF SOME BIOLOGICAL INTERACTIONS IN NO-TILL CORN BY Mohamed Nazeem Shams Corn (Egg mays L. 'Pioneer 3780') was grown in a very old fescue—bluegrass sod on Spinks loamy sand soil with No- Till, chisel plow, and moldboard plow treatments. The irri- gated corn yields averaged 13,100, 14,186, and 14,148 kg/ha . for the No-Till, chisel plow and moldboard plow treatments, respectively. Corn on No-Till plots was severely damaged by wireworms and had to be replanted, a fact which undoubtedly contributed to lower yields. Tillage systems influenced corn root weights which were higher in the plowed soil than in the No-Till soil at both the 0-15 and the 30-40 cm depths. Moldboard plowed or chiseled soils, initially loose and Open at the surface, became more compact with time. By late summer, bulk densities of the surface soil had increased until they were greater than in the No-Till soil. Mohamed Nazeem Shams The surface soil (0-5 cm) of the No-Till plots was slightly more acidic than the soil of other treatments. The organic C and total N levels at this depth were significantly higher in the No-Till plots. Soil samples were collected in the fall of 1975 and the spring of 1976 for evaluations of arthrOpod pOpulations. The numbers of soil Collembola and Acarina under a No-Till system were substantially higher at both the 0-5 and 0-15 cm depths than with plowed treatments. These investigations were exploratory and should stimulate interest in No-Till corn production and in the recycling of soil organic matter as related to tillage treatments. A CASE STUDY OF SOME BIOLOGICAL INTERACTIONS IN NO-TILL CORN BY Mohamed Nazeem Shams 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 1976 To my Father This thesis is dedicated to him. ii ACKNOWLEDGEMENTS Special recognition and appreciation are due to Dr. L. S. Robertson, Committee Chairman, for his patient guid- ance in these investigations, to Dr. R. J. Snider for his supervision and assistance in classifying soil fauna, and to Dr. R. E. Lucas for his c00peration in the field studies. Drs. B. D. Knezek, J. M. Tiedje, B. G. Ellis and A. E. Erickson and Renate Snider provided essential laboratory fa- cilities and supplies. The c00peration and advice of these individuals is appreciated. The writer also wishes to eXpress appreciation to Dr. A. R. Wolcott who contributed valuable time and advice in the preparation of this manuscript and to Dr. E. H. Kidder for his continued interest in my studies at Michigan State University. iii TABLE OF CONTENTS LIST OF TABLES ..... ....... .... ......... . ............ INTRODUCTION ............... .................... ..... REVIEW OF LITERATURE .. ............. . ....... . ...... .. No-Till Corn Yields ... ................ ......... Soil Conditions in No-Till Corn .... ........ .... Biological Interactions in No—Till Soil ........ MATERIALS AND METHODS ............ ............ . ...... Field Experimental Plots .......... .. ........ ... Laboratory Analyses ....... ....... .............. RESULTS AND DISCUSSION ... ......... ... ..... ..... ..... SUMMARY AND CONCLUSIONS .......... ...... ............. LITERATURE CITED ..... . ..... ..... ...... . ............. iv Page 12 12 14 16 30 10. ll. 12. LIST OF TABLES Corn grain yields under three tillage systems.... Corn root distribution as affected by two tillage systems ...................................... Soil temperatures at soil fauna sampling time as related to three tillage systems .... ..... Bulk density of surface soil as related to three tillage systems and grass cover ...... Distribution of total N, organic C and organic matter in soil under three tillage systems.. Soil pH levels under three tillage systems ... Average p0pulations (O to 15 cm) of dominant Collembola species as related to three tillage systems (Fall l975)............ ..... ... ..... Average p0pulations of dominant Collembola species as related to three tillage systems (Spring 1976)00.000000.00oooooooooooooooooo00.00.00. Average populations of Acarina as related to three tillage systems and sampling time..... Average populations of Acarina as related to three tillage systems and sample depth (Spring 1976)oooooooooooo ....... oooooooooooooooooooo Nematode pOpulations as related to three tillage systems and sampling time ........... Nematode populations as related to three tillage systems and sampling depth (Spring 1976).... Page 17 19 19 21 21 23 25 25 28 28 29 29 man, - (max (23%“ as thq lOS INTRODUCTION No—Till crop production is a recent innovation made possible by easily available specific herbicides and the development of Special planters. This minimum tillage method involves making a narrow slot in untilled soil so that seed can be planted where soil moisture levels are adequate for rapid germination. The most common device for doing this today is the fluted coulter, although equipment of other design exists. Many believe that No-Till should be used by more farmers because many hectares of arable land in Michigan and elsewhere are well suited to this practice. Despite this, adoption by farmers has been slow, probably because variable degrees of success and failure have been obtained with No-Till methods. The experience of farmers and researchers show that No- Till was most successful on medium and coarse-textured soil where herbicides were effective, where insect and disease problems did not develOp and where soil had desirable physi- cal properties. Many of the engineering, agronomic, and economic aspects of No-Till crOp production have been investigated but there is relatively little information available on the bio- logical processes. The purpose of this project was to inventory soil organic matter levels, species diversity and populations of soil fauna. This study should serve as a basis for future investigations. REVI EW OF LI TE RATURE No-Till Corn Yields Perhaps Sprague (1952) was the first to publish on No- Till methods when he reported on "Substitution of Chemicals ‘for Tillage in Pasture Renovation." The first work on corn was by Barrons and Fitzgerald (1952) of the Dow Chemical Company. Later Davidson and Barrons (1954) reported on the use of 2,2 -dichloroporpionic acid (dalapon) and (2,4-dichloro- phenoxy) acetic acid (2,4-D) in both corn and soybean produc- tion. Yields on conventionally plowed and chemically treated plots were similar. This report stimulated interest by both farmers and researchers alike in the concept that eventually was labeled "No-Till." The book "No Tillage Farming" by Phillips and Young (1973) has been the basic reference for farmers. The Opti- mistic evaluations of Opportunities with No-Till have led many to eXperiment with this crop production method. The authors state that this method should increase yields. The Soil Conservation Service of the United States Department of Agriculture (1975) promotes the No-Till concept on the basis of comparable yields while stressing 13 advantages including lower production costs and better erosion control. Agronomists at Michigan State University feel that the No—Till concept is well adapted to many sites and should be used more extensively. They, however, are less enthusiastic than others on the use of the concept on naturally, poorly drained soil that is relatively high in organic matter and on fine-textured soil. Research in several states has been summarized in a practical way by the COOperative Extension Service at Michigan State University. Four bulletins have been published under the series title, "No-Till Corn." 1. Guidelines (Nelson et 31.) 2. Fertilizer and Liming Practices (Vitosh and Warncke, 1976) 3. Soils (Robertson et 21., 1976) 4. Weed Control (Chase and Meggitt, 1976) These bulletins suggest that great care must be exer- cised if success is to be obtained. They interpret the statement by Lowell Burchett (1975) of Kansas State Univer- sity, as reported in the Soil Conservation Service bulletin, that "to switch to No-Till, two things have to change. . . your mind and your planter." The bulletins also reflect the thinking and research of Cook 33 31. (1949, 1950, 1951, 1958, 1964) pioneers in tillage investigations. Research reporting practical problems associated with No-Till is scant. Apparently researchers recognize some of the problems, but side step others by reporting primarily on projects where adequate crop stands were obtained, herbicides were effective, and where pests presented no special prob- lems. Numerous observations suggest that these are practical problems that must be recognized before comparable or improved yields can be obtained. Agreeing with the writings of Phillips and Young (1973), Doster (1972) reported higher yields from No-Till methods in a four-year continuous corn experiment. Shear and Moschler (1969) made similar observations. Triplett EE.El° (1968), while investigating effects of crOp residues, found that yields were improved by soil-water relationships associated with increasing return of crop residues. Publications, such as those cited above, stimulated interest in the No-Till concept. As a result there have been many workshOps and conferences organized on a state, regional or national basis. Jacobson (1967), Griffith (1972), and Linford (1973) organized and edited papers presented at such meetings. These compilations illustrate the numerous publications now available on this tOpic. Soil Conditions in No-Till Corn In the first publication on No-Till corn, Davidson and Barrons (1954) reported that the percent water stable aggre- gates in soil of uncultivated (No—Till) plots was signifi- cantly higher than in the cultivated plots, and that soil moisture levels were significantly higher. These conditions caused superior growth rates early in the season. Similar observations have been reported many times since then, although specific data to support the observations are some- what limited. By far the most common physical condition evaluated in studies on No-Till corn is that of bulk density. Thomas gt 31. (1975) did not measure any significant differences caused by tillage while others interpreted differences in terms of relative compaction. Chancellor (1971), for ex- ample, interpreted bulk density as one parameter which can be used to measure a state of compaction. Gill and Trouse (1972) related compaction to vehicular traffic. Therefore, No-Till soil normally is expected to be less compact than soil subjected to traffic with conventional equipment. The lower bulk density values associated with No-Till methods are related to several factors including the pre- sence of surface mulches as well as reduced traffic. Wood- ruff (1972) related wind erosion potentials to amounts of surface residues. The greater the residues the smaller the soil losses. Harrold (1972) reported similar observations in regard to water erosion. Edwards (1972) reported that surface residues reduce movement of hazardous chemicals. Several, including Lal (1974), observed the formation of strong crusts on conventionally tilled soil while, on No- Till, crusts usually failed to develOp due to surface mul— ches. If crusts were formed, they were of a different nature, being more thin and fragile. While the chemistry in No—Till soil has received con- siderable attention, the specifics seem to be related to time of application as well as placement of fertilizer, lime, and manure. Singh 2E.3l- (1966) showed that corn grown on untilled soil utilized superphosphate as well or better than corn grown on plowed soil. Ester (1972) observed higher K levels in the leaves of corn grown on untilled soil, He also reported that soil pH levels decreased in the 0—7.5 cm level as a result of sur- face applied N. Shear and Moschler (1969) and Thomas et 31. (1975) made similar observations. It seems that, with one possible exception, No-Till methods present no Special problems in using fertilizer. The exception is related to the practical use of banded planting time fertilizer. Vitosh and Warncke (1976) observed that placing fertilizer in a band 5 cm to the side and 5 cm below the seed was difficult to achieve with standard No-Till planters. They reported that some farmers solved the prob- lem by widening the tillage strip through the use of two fluted coulters. Corn root penetration into the soil is considered to be an indication of soil conditions. Mannering et 31. (1971) showed a close correlation between corn root distribution and tillage systems, especially at the 8 to 30 cm depth. In con- trast, Lal (1974) reported that different tillage treatments had no effect. In conclusion, it appears that whether or not No—Till methods greatly improve soil conditions as related to corn growth is dependent upon the nature of the soil. Biological Interactions in No-Till Soil Very few references are available on biological inter- actions in No-Till soil. Agronomists apparently have ignored this area. Entomologists and zoologists have been active in areas other than those involving tillage. At the moment it is necessary to extrapolate from p0pulation studies under forest or prairies conditions to those of intensive field crOp production. There are few guidelines for doing this. Where corn is planted in grain stubble or in sod fields, Nelson gt gt. (1976) report that rodents may cause problems where runways are obvious. In the present discus- sion, the role of macrofauna, especially mammals, is ignored because in soil used for field crOp production, pOpulations are usually low. Soil faunal activity may influence productivity by altering the physical and chemical composition of organic matter. The overall physical condition of the soil may be altered by increasing the size or number of pores, channels and burrows in the soil (Sommers and Biederbeck, 1972). Earthworms are important macrofauna, especially in undisturbed pasture or forest soils. Earthworms decompose organic litter located on the surface of soil as well as materials below the surface, in addition to stimulating the activity of other decomposing organisms (Burges, 1967). A comprehensive study of earthworms was made by Edwards and Heath (1963). They noted that large litter fragments were removed three times faster from bags to which earthworms had access than from others from which they were omitted. Darwin (1881) estimated the annual worm-cast produc- tion on four different soils. He stated that earthworms were able to produce an annual worm-cast of between 18,532 and 44,774 kg/ha. He also estimated that earthworm activity could bring about 0.5 cm annually to the soil surface. Graff (1969) observed a 20 to 25-fold increase in casting on No- Till plots over plowed barley stubble. Lal (1974) found that tillage resulted in a great decrease in numbers of earth- worm casts. Water infiltration rates were significantly lower in the plowed areas. Ehlers (1975) estimated the num- ber of earthworm channels in tilled and untilled soil at 4 depths. He found 333, 78, 63 and 4 percent more channels in the untilled areas at depths of 2, 20, 30, and 60 cm, respec- tively. These data partially explain the observations of 10 Lal (1974). Insect problems with No-Till are minor, at least in the thinking of many. Regardless of this, Lucas gt gt. (1976) reported that replanting in an old grass sod was necessary because of wireworm problems. Nelson gt gt. (1976) recommend planter seed box treatment for such pests as wire- worms, grubs, slugs, and cutworms. Ruppel (1975) reports that cornroot worms are likely to be problems "where corn follows corn without rotation." He recommends the use of insecticides where appropriate. Other fauna apparently derive their energy from feeding more on dead organic matter. Populations and activities as related to No-Till methods of cr0p production have not been well investigated. Collembola are among the most numerous of all soil fauna, (Snider, 1967). Hale (1963), Dunger (1956, 1958) and Schuster (1956) demonstrated that Collembola pOpulations increased rapidly when ample energy was present. As many as 100,000 Collembola per m2 produce an average of 183 cc of feces annually. Schaller (1950) showed that 0.2 cm of soil was brought to the surface annually by Collembola. Poole (1959) suggested that Collembola are active in the dissemination of fungi and in breakdown of excrement from large arthrOpods. He also found that soil fungi are readily decomposed by species of large Collembola, allowing the smaller species to feed in a direct manner on the humus. ll Burges (1967) found that Collembola may be involved in making chitinous material accessible for use again by other soil organisms. A good correlation between humus production and soil organism activity was observed by Wallwork (1970). MacFadyen (1963) showed that, while the small-sized decom- posers such as Collembola have a good decomposition capa- bility, the cryptostigmatid Acarina have a low metabolic rate. Ambrozad and Nosek (1967) showed that Collembola are involved in maintaining a favorable balance between bacteria and fungi. Most Cryptostigmata appear to be more active in the later stages of decomposition than in earlier stages (Edwards and Heath, 1963; Drift, 1963). Also they concluded that Cryptostigmata were not active in primary decomposition; how- ever, most of them correlate well in numbers with the later stages of decomposition. Mite activity is important in the dissemination of fungal spores, which may stick fast to the surface of the body or may be conveyed in the mite gut (Wallwork, 1967). Crossley and Witkamp (1964) suggested that mites create important conditions for the physical breakdown of litter with the transmission of organic material in their mouth- parts. Thus, soil fauna play an important role in the decom- position of organic matter as well as in altering the physi- cal condition of soil. MATERIALS AND METHODS Field Experimental Plots Field eXperimental plots were established on the Uni- versity farm in 1975 by Dr. R. E. Lucas, Department of Crop and Soil Sciences, Michigan State University. The area represented an old sod. While records are not available, the grass is believed to be a minimum of 15 years old. It was primarily fescue and bluegrass. The soil is a Spinks loamy sand (soil management group 4a) which is naturally well drained and droughty. The plots were irrigated in July and August with 7 cm of water each month. Tillage treatments, randomized and replicated 4 times, were made in the spring of 1975 and included a moldboard plow, chisel plow and a No-Till treatment which involved killing the grass with herbicides and then planting with an Allis Chalmers No-Till planter. Plots were 6 x 12 m in size. The No-Till and chisel plow plots were Sprayed with paraquat at the rate of one pint per acre, plus two pounds of atrazine. The plowed plots received only atrazine. 12 13 Paraquat was applied before any tillage treatments were made but the atrazine was applied immediately after planting. Pioneer 3780 hybrid was planted on all plots on April 30. The No-Till plots had to be replanted on May 20 because of excessive wireworm damage. Fertilizer was applied as a basal treatment across all plots. One hundred Sixty pounds of 5-20-20 was used at planting time. Urea was sidedressed on May 30 and 31 at the rate of 130 pounds of nitrogen per acre. Average populations of corn plants were determined by counting the number of plants in 5 rows of each plot and are reported as plants per hectare. Corn grain yields were determined with hand harvest methods involving the weight of husked ear corn. A constant shelling percentage was assumed. Yields are for 15.5 percent moisture grain. Root samples were taken from only the moldboard plowed and the No—Till plots. In July, samples were collected at a distance of 7.5 cm to the side of a plant near the end of a plot. An iron frame measuring 10 x 10 x 15 cm was used to collect both soil and roots. Roots were separated by washing through a 40 mesh sieve. They were then dried at 720 C and weighed in agreement with standards outlined by Mengel and Baker (1974). In August a different method was used on the same plots. A 60 cm circle around a single plant to a depth of one meter 14 was excavated. Roots were separated from soil as previously described. Soil temperature evaluations were made by inserting a standard soil thermometer unto the soil to a depth of 5 cm at 5 locations per plot at each sampling time (Nov. 3, Nov. 11, 1975, and March 24, April 23, 1976). Bulk density evaluations were made by the Blake method (1965). A total of 20 cores were taken from each treatment' (5 per plot) to a depth of 7.6 cm in Summer 1975. Samples were dried at 1050 C for 48 hours. Soil samples for carbon, nitrogen, and pH evaluations were collected soon after the soil thawed in the early spring of 1976. Nine subsampleS were taken with a standard 2.5 cm probe at three increments of depth to 15 cm. Laboratory Analyses Organic carbon evaluations were made with the wet di- gestion method of Walkley (1947). Soil organic matter estimates were made by multiplying the organic carbon valve by 1.72. Total nitrogen was determined by the semi-micro Kjel- dahl method outlined by Bremner (1965). Soil reaction levels were evaluated with a Sargent (PBL model) potentiometer in a 1:1 soil to distilled water suspen— 15 Sion. Samples for evaluation of arthrOpod numbers were collec- ted in November 1975 and in March and April of 1976. Red flags were placed in the center of each plot as reference points for the samples. Samples were collected in the corn row using a standard, hand-driven sampler (6.25 cm in diam- eter and 15 cm deep). Three samples per plot were collected and placed in plastic bags which were taken to the labora- tory for extraction. The values reported are average numbers per sample per plot. The entire sample was used in the November sampling. However, in the Spring the samples were subdivided to repre- sent 0-5, 5-10 and 10-15 cm depths. Fauna extraction was achieved with a Tullgren funnel, as described by Kevan (1962). Heat from 25 watt light bulbs dried the soil, and the fauna moved downward and finally out of the soil falling into ethyl alcohol. After three days the wattage was increased to 30 for another 3-day period. Under the direction of Dr. R. J. Snider, soil fauna were identified and divided into several groups. With the aid of a microscope, the number in each group was determined. RESULTS AND DISCUSSION The first step in obtaining high yields with No-Till corn is to produce an adequate stand. Because wireworm dam- age greatly reduced pOpulationS on the No—Till plots--much more than on other plots--the No-Till plots had to be re— planted. Even after replanting, there were gaps down the row. Immediately after emergence, plants from border rows were tranSplanted into the gaps, thus making the populations on all treatments comparable. POpulations averaged 50,100 plants per hectare. Corn grain yields were high due primarily to the use of irrigation water on soil that because of its sandy nature is droughty and does not usually have soil structure problems. There was no difference in yields on the plowed plots (Table l). Yields on the No-Till plots were lower, averaging 13,100 kg/ha. The Slightly decreased yield was associated with the necessity to replant. When root samples were collected in July with the 10 x 10 x 15 cm sampler, the moldboard plowed plots contained Significantly more roots (2.30 gm) than the No-Till plots (1.68 gm). Whether this reflects tillage method or the necessity to replant is not known. Regardless, the average yields produced were directly related to corn root weights in July. The circular sampling procedure was used in August 16 17 Table 1. Corn grain yields under three tillage systems. Tillage Treatment Yield kg/ha Moldboard plow 14,186 Chisel plow 14,148 No-Till 13,100 LSD (0.01) 692 18 in an attempt to more realistically sample root growth. Average root weights in the surface soil of both treatments were remarkably Similar (Table 2). This possibly reflected a Similar stage of develOpment in all plots that may have been attained by this time but not when samples were collected a month earlier. The difference in root weight at the 30-40 cm depth was statistically significant and possibly reflects the longer growth period of corn on the moldboard plowed plots. Soil temperatures regulate many biological as well as chemical reactions. Temperature evaluations were made when the soil was sampled for soil fauna. Average temperatures in the No-Till plots were significantly lower than in the chisel or the moldboard plowed plots at each time of measurement (Table 3). This was possibly due to the differences in organic matter in and on the surface of the soil. Whether a difference of approximately 2 degrees signifi- cantly affects biological activity is not well known. Consi- dering the time span, theoretically, the total effect on bio- logical activity could be great. The direct relationship between temperature of surface soil and both yields and root weights probably should be somewhat discounted because of deve10pmental differences resulting from the necessity to replant the No-Till plots. Average bulk density values are reported in Table 4. As an after thought samples were also taken 10 to 20 meters out of but adjacent to the plot area. The "grass" treatment in this table reflects the original condition of the soil before herbicide use. Table 2. Corn root distribution as affected by two tillage systems Tillage Treatment Sample Depth No—Till Moldboard LSD plow (0.05) cm ---------------- gm 0—10 17.14 17.65 NS 10—20 5.28 5.44 NS 20—30 1.10 1.49 NS 30-40 0.12 0.39 0.14 Table 3. Soil temperatures at soil fauna sampling time as related to three tillage systems. Tillage Treatment Date of . Measurement Moldboard Chisel No-Till LSD plow plow (0.01) ------------ Degrees C --- November 3 14.1 13.7 13.2 0.38 November 11 13.3 12.9 12.3 0.43 March 24 11.4 10.7 9.4 0.47 April 24 16.8 15.6 14.7 0.43 20 Bulk density values tended to be directly related to soil temperature, root weights and yield although for reasons previously mentioned, some caution is urged in relating bulk density to root weights and yields. Total N and C analyses are reported in Table 5. Since moldboard plowing represents more of a mixing action than other treatments, the lower values for both N and C in the 0-5 cm sample were anticipated, although both elements were higher than expected in this Spinks soil. It was assumed that N and C had built up to these levels over a period of many years during which the plot area had been under contin- uous grass cover. This concept appears valid when it is realized that the average C level for similar soil used for corn production in Michigan is only 0.75 percent (Mokma gt g1., 1976). The higher N and C values in the surface samples of the No-Till and chisel plowed plots represent a more concentrated source of food and energy for many kinds of soil organisms. In the moldboard plowed soils, total N did not change with depth. In the soil of the chiseled plots total N levels were highest in the 0-5 cm level. This was also the case with the soil in the No-Till plots. In regard to C, levels increased with depth in the moldboard plowed plots. In the No-Till plots C levels de- creased with depth. Since chisel plowing represents a more drastic tillage treatment than No-Till and a leSS intensive treatment than moldboard plowing, the intermediate values were eXpected. 21 Table 4. Bulk density of surface soil as related to three tillage systems and grass cover. Tillage Treatment Bulk Density Moldboard plow 1.54 Chisel plow 1.49 No-Till 1.42 Grass (control) 1.35 LSD (0.05) 0.085 Table 5. Distribution of total N, organic C and organic matter in soil under three tillage systems. %C ZN ZO.M. Tillage Treatment Depth (cm) Depth (cm) Depth (cm) 0—5 5-10 10-15 0-5 5—10 10—15 0—5 5-10 10-15 Moldboard plow 1.11 1.18 1.24 0.11 0.10 0.11 1.91 2.03 2.14 Chisel plow 1.63 1.17 0.91 0.13 0.10 0.11 2.81 2.02 1.57 No-Till 1.93 1.15 0.90 0.15 0.10 0.12 3.33 1.98 1.55 LSD (0.05) 0.31 NS 0.21 0.02 NS NS 0.51 NS 0.31 22 Soil organic matter levels are reported primarily for interest and to suggest the location and quantity of food available to soil organisms. The values were obtained by multiplying total C by 1.72. Carbon and N levels in the 0-5 cm depth were inversely related to bulk density, temperature, root weights, and grain yield. The significance of this is not clear except as related to characterizing the environment for soil organ- isms. With organic matter levels higher on the No-Till plots, more food and energy iS available for soil organisms. Soil organisms, in turn, do influence soil physical prOper- ties. For example, animal traffic can serve to maintain pore systems in undisturbed soil, thereby contributing to lower bulk densities than in soil disturbed by tillage. Moldboard plowing had two effects upon the surface soil. First, the organic matter near the surface was diluted by mixing with lower mineral soil layers. Secondly, the sur- face Soil was exposed more directly to both wind and sun which increased drying rates after a rain. This would have influenced soil organism pOpulationS and activities. Drier soil conditions may explain, at least partially, why damage from wireworms was less evident on the moldboard plowed plots. The data in Table 6 illustrates the variation in soil pH associated with tillage treatments and depth. The soil in the moldboard plowed plots had the highest and most uniform 23 Table 6. Soil pH levels under three tillage systems. Treatment Depth (cm) 0-5 5-10 10-15 Moldboard plow 7.26 7.10 7.11 Chisel plow 6.79 6.56 7.05 No—Till 6.43 6.86 7.10 LSD (0.05) 0.06 0.49 NS 24 pH. Levels in the soil of the No-Till plots probably re- flect the leaching of basic cations from the 0—5 and 5-10 cm depths. All pH levels, regardless of treatment, were con- sidered to represent a good root environment for corn. The larger faunal forms such as earthworms were not well represented with the sampling technique used. Only a limited number of fauna related to suspected economic losses such as wireworms were found. With the sampling methods used it appeared that pOpulations of those fauna were not related to tillage treatments. Various Species of Collembola (Springtails), including Isotoma (Desoria) gp. "S" and virdis, Isotomurus palustris, Sminthurinus elegans and henshawi, Entomobrya multifasciata and unostrigata, Lepidocyrtus paradoxus and violaceous, and Tullbergia gtanulata, were identified under the supervision of Dr. R. J. Snider. The dominant species in the November 1975 samples were Isotoma (Desoria) gp. "S" and Tullbergia granulata. In Tables 7 and 8, Isotoma (Desoria) gp. "S" repre— sents a Species, that to date, has not been described. The Isotoma Species and Tullbergia granulata were present in larger numbers than any other Species. From these data, it is obvious that plowing, whether it be with a moldboard or a chisel plow, greatly reduces collembolan pOpulationS (at least temporarily). In the Spring of 1976, the same two Species were again 25 Table 7. Average populations (0 to 15 cm) of dominant Collembola spe- cies as related to three tillage systems (Fall 1975). Tillage Isotoma Tullbergia Treatment (Desoria) g2, "S? granulata Numbers/30.7 cm2 Moldboard plow 1 3 Chisel plow 16 13 No-Till 77 8 LSD (0.05) 59 NS Table 8. Average populations of dominant Collembola species as related to three tillage systems (Spring 1976). Isotoma Tullbergia Tillage (Desoria) _p. SS" granulata Treatment Depth (cm) Depth (cm) 0-5 5-10 10-15 0-5 5-10 10-15 Numbers/30.7 cm2 Moldboard plow 6 3 4 14 13 15 Chisel plow 16 10 7 36 21 7 No-Till 104 18 3 17 18 5 LSD (0.05) 88 NS NS NS NS NS 26 dominant (Table 8). In this sampling, the cores were divided into three parts representing 0-5, 5-10 and 10-15 cm depths. In all cases, the sum for the three depths in Table 8 is sub- stantially greater than the numbers found to 15 cm the pre- vious fall (Table 7). The largest relative increase for both species oc- curred in the moldboard plowed plots where total numbers were 13 to l4-fold greater in the spring than in the fall. With the other two treatments, the increase was about 2-fold for the Isotoma species and 5-fold for T. granulata. AS in the fall, the No-Till surface soil (0-5 cm) appeared to be a particularly favorable environment for the Isotoma species. In the case of T. granulata, differences for treatment were not Significant, although the data suggest that this species had increased in numbers to greater depth in soil tilled with the moldboard plow. On the other hand, chisel plowing may have been the most favorable treatment for T. granulata in shallow surface layers (0-5 cm). Numbers of Collembola, in general, were directly re- lated to C and N levels and inversely related to bulk den- sity and temperature. The implications of such observations as related to soil management and crOp yields is not well known. The only other group of soil fauna found in large numbers were the Acarina (mites). Mite pOpulationS as re- lated to tillage treatments were similar to the Collembola in that plowing greatly and Significantly reduced numbers 27 (Table 9). This was the situation in both the fall and Spring samplings. Average Acarina pOpulations in the Spring of 1976 were two to three-fold greater than in the fall of 1975. AS in the case of the collembolan Isotoma species, untilled surface soil was particularly favorable for their development (Table 10). A poor representation of nematode populations was ex- pected with the extraction methods used. However, a number were casually observed in some of the samples. A summary of the observations presented in Tables 11 and 12 is reported here, because some Species of nematodes are known to cause production problems. Using standard statistical evaluation methods, it appeared that tillage treatments did not affect nematode populations. Nevertheless, by selecting the 10 percent level of confidence in place of the standard 5 percent level, nema- todes were recovered in larger numbers from the surface soil (0-5 cm) of the No-Till plots. It is realized that this ob- servation should be checked with acceptable standard methods for collecting nematodes. 28 Table 9. Average populations of Acarina as related to three tillage systems and sampling time. Sampling Time Tillage Treatment Fall Spring 1975 1976 2 Numbers/30.7 cm Moldboard plow 17 34 Chisel plow 21 62 No—Till 91 194 LSD (0.05) 8 93 Table 10. Average populations of Acarina as related to three tillage systems and sample depth (Spring 1976). Tillage Depth(cm) Treatment 0—5 5-10 10-15 2 Numbers/30.7 cm Moldboard plow 19 9 7 Chisel plow 37 18 8 No—Till 160 18 14 LSD (0.05) 98 NS NS 29 Table 11. Nematode populations as related to three tillage systems and sampling time. Sample Time Tillage Treatment Fall Spring 1975 1976 2 Numbers/30.7 cm Moldboard plow 2 22 Chisel plow 4 5 18 No-Till 4 40 LSD (0.05) NS NS Table 12. Nematode populations as related to three tillage systems and sampling depth (Spring 1976). Tillage Depth (cm) Treatment 0—5 5-10 10-15 Numbers/30.7 cm2 Moldboard plow 12 3 7 Chisel plow 10 5 3 No-Till 28 7 5 LSD (0.05) NS NS NS S UMMARY AND CONCLUS I ONS The purpose of this project was to inventory some soil conditions as affected by moldboard plowing, chisel plowing and No—Till, and to relate those conditions to specific bio- logical activities in the soil. Field eXperimental plots were established on a Spinks loamy sand soil. Corn was grown under irrigation. Treat- ments were replicated four times. By replanting the No—Till plots after wireworms affec- ted stands, pOpulations were similar averaging 50,100 plants per hectare for all three treatments. Corn grain yields were high due to irrigation and averaged 14,186, 14,148, 13,100 kg/ha, respectively for the moldboard plow, chisel plow and No-Till treatments. The lower yield of the No-Till treatments was attributed to the necessity to replant. Root weights were higher on the plowed plots in July but were similar in August except at the 30-40 cm depth, when again they were higher in the plowed plots. Bulk density values increased with intensity of tillage. The No—Till plots averaged 1.42 the chisel plowed plots 1.49 30 31 and the moldboard plowed plots 1.54. Tillage methods affected the distribution of both N and C. Carbon levels were highest in the 0-5 cm depth of the No-Till soil and lowest in the moldboard plowed soil. Ex- cept for the plowed soil, levels decreased with depth. Ni- trogen levels were also highest in the 0—5 cm depth on the No—Till plots and lowest on the moldboard plowed plots. Average pH levels were lowest in the No-Till plots and increased with depth. The highest levels were in the moldboard plowed plots which had similar levels down to 15 cm. Soil fauna populations Showed a close relationship to position and source of food in that the highest pOpulationS were found in the soil of the No—Till plots at a depth of 0-5 cm. Also in these plots the soil was more porous than on any others because the bulk density values were the lowest. In the fall samples, the Collembola Isotoma (Desoria) gp. "S" were present in largest numbers followed by Tull- bergia granulata. POpulations of both increased by the time samples were collected in the spring. The populations of Acarina were similar to the Collembola and also increased greatly in the Spring sampling. This increase may be ex- plained by the undisturbed condition of the soil Since the previous spring coupled with available organic matter for food and an increase in fecundity. Nematode pOpulationS represented relatively small numbers. 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