11111 1111111111111 1111 12111111211111 11.11 111111112 11 11.11111“. 1111:1111 1111 11111 $1.111. 111111....11111-1 LIBRARY Michigan State University Tm W 01" CULTIVATION AND HERBICIDE APPLICATION ON CERTAIN SOIL PROPERIIES AND IIELD OF FIELD CORN By Donald B. Herr AN ABTRACT Submitted to the School of Graduate Studies of Iichigan State University of Agriculture and Applied Science in partial fulfill-ant of the requirements for the degree of. IASTER OI" SCIENCE Department of Fern Crops 1962 ApperQ/Qké‘“ 7 m 2‘5 Donald 1. Herr field studies designed to determine the effect of cultivation on certain soil properties and the yield of corn were perforned on a fine textured soil during 1960 and 1961. Determinations were nade of bulk density and total porosity of soil that received varying amounts of cultivation. The effect of cultivation on height and yield of corn as well as the nutrient content of corn leaves was determined. Investigations were mde on the influence of varying weed papulatiom on yield of corn obtained by chemical and cultural methods. When weeds were controlled with pro-emergence herbicides cultivation decreased the yield of corn. Increased yield resulted from adequate cultivation when weeds were not controlled by chemical nethods. Cultivation by itself did not affect the nitrogen, phos- phorus or potassium content of corn leaves. Plant height measure- ments revealed that uncultivated corn had attained a greater height than cultivated corn on two of the three dates it see leasured. There was no difference in the bulk density of soil beneath that stirred by one or four cultivations or under the rear wheel track nde by the tractor during one cultivation. A higher bulk density resulted where the rear wheel of the tractor had passed four tines during cultivation. The soil beneath that stirred by one and four cultivation had the sale tetal porosity. However, one pass of the tractor wheel during the cultivation lowered total porosity and four passes caused an additional decrease in this soil preperty. Need population! of only one to two per square foot reduced the per cent of nitrogen in corn leaves but did not affect the Donald E. Herr per cent of phosphorus or'potassiul.present. The experimental areas used both years bad light natural infestations of needs. However, weeds caused significant reductions of corn yields in 1961. A destructive hail stern in mid-July 1960 nearly erased yield differences making it impossible to drae’conp clusions on yield data from this experiment. Liquid and granular forms of 2-chlero-4-ethylanino-6- isapropylanino-s-traisine (atrazine) and 2,L-dichlorqphenyozyacetic acid (2,4—9) applied pro-emergence at recommended rates provided satisfactory control of annual seeds. m INFLUENCE or CULTIVATION AND HERBICIE APPLICAIIW ON CERTAIN SOIL PWIB AND YIELD (P FIELD CORN By Donald I. Herr AWE Submitted to liehigan State University in partial fulfillment of the require-eats for the degree of mm (1‘36" Depart-entofl’ernGrOpe 1962 AW! The author wishes to express his appreciation to Doctor lillianr. Ieggittferhisguidanceandhelpfuladvise inplanning and conducting this investigation and for his valuable aid in the preparation of this meript. Sincere appreciation is also expressed to the administrative personnel of the Ohio Agricultural preriaent Station, especially Ir. Themes 1‘. londerling, for extending the opportunity of this undertaking and their genuine interest and cooperation in all plnses 'of this investigation. The author is also grateful to Doctors H. J. Iederski, D. I. Van Doren, C. R. leaver an! 6. D. Iriplett for their aid and use of equipnnt needed in this study. 1's all others who assisted in any way but go unentioned, the author is indeed grateful. INTRODUCTION REVIEI OF LITERATURE MATERIALS AND METHOIB RESULTS AND DISCUSSION SUM! BIBLIOGRAPHY APPENDIX A APPENDIX B TABIEOFCONTElflS 1. 3. 4. 5. 9. 10. 11. 12. 13. LISTOFTABLB Effect of cultivation on yield of corn when weeds were controlled with atrasine, 1961. Average height of corn plants on three dates as affected by various cultural treatments, 1960. Per cent of nitrogen in corn leaves from combination of chemical and cultural treatment, 1961. hill: demity, total porosity and blows required to obtain a core, from various areas of three cultural treatments, 1961. Rates of oxygen diffusion in microamperes on several dates in soil that had received varying amounts of cultivation, 1961. The effects of several herbicides on the control of broadleaf and grassy weeds in corn, 1960. The effect of three herbicides on the control of broadleaf and grassy weeds in corn, 1961. The degree of weed control obtained in corn with one, two “3‘60 four cultivations using sweeps and spear-point shovels, 1 . Degree of weed control attained in corn with one, two and four cultivations using sweeps, 1961. Effect of supplemental cultivation on yield of corn when wezds were not satisfactorily controlled with herbicides , 19 1. Average yields of corn from all combination of chemical and cultural variables included in 1961 experiment. Effect of varying amounts of cultivation on yield of corn using sweeps and spear-point shovels, 1960. Effect of pro-emergence and post-emergence herbicide treatments on yield of corn, 1960. iv 20 21 23 30 32 34 36 37 40 1. LIST OF FIGURES Appearance of uncultivated area that required an average of 13.2 blows to obtain core. An average of 82.1. blows were required to obtain a core in this area over which the rear wheel of tractor had passed four tines during the cultivation. Soil surface of plot receiving no cultivation. Soil surface of plot receiving one cultivation. Soil surface of plot receiving two cultivations. Soil surface of plot receiving four cultivation. Cozotrol of annual weeds was obtained with strains 80 l, 19 . Granular form of strains was as effective as the wettable powder. Damage to corn resulting from hail stern, July 19, 1960. 25 27 2'7 31 31 IITRODUCTION Thegrowizgofcornasacrophaerequiredthehelpofnn to reduce the pressure of competitive plants. Astee, lays and Inca Indians were growing corn before Columbus discovered America and weeds were probably removed by pulling or with crude instruments. Early settlers in America learned the methods of growing corn from the Indians and it constituted mob of their food supply. Iith the development of the country and the introduction of other food crops, particularly wheat, corn soon became our most important livestock feed rather than being used for human food. Early in the 19th Century crude cultivators were built, and for the first time an used a .611an in helping to controllweeds in corn. The use of horse-drawn hehines in corn culture necessitated planting in rows three to three and one-half feet apart, a practice that has persisted to the present. Iith the development of the tractor in the 1920' s , cultivating gradually shifted from the horse-drawn units to tractor-mounted oultivators . In spite of the continued improvement of cultivators in term of adjustment, control and shovel equipment available, it has been and still is difficult to satisfactorily control weeds in the corn row by mechanized cultural methods alone. The development of the selective phenoxy-type herbicides in the mid 1940's brought in chemical weed control as an aid to cultural weed control practices on a commercial scale. A recent survey by the United States Department of Agriculture iniicates that herbi- cides are now being used on approximately twenty per cent of the corn acreage in this country and 2,4-1) is still the most widely used herbicide. The prinry purpose in the use of 2,443 has been to supplement rather than replace cultural methods of weed control. Recently a series of s-triasine derived brbicides have been developed which when applied pre-emergence to corn have given out- standing control of annual weeds throughout the entire growing season. lith these herbicides available at economical prices, the value of cultivation becoaes questionable to the com-rcial corn producer. The aim of the present experiment was to study the effects of cultivation on certain soil properties and yield of corn in send unction with various herbicide treatments . REVIEIOFLITERATURE The literature is voluminous on the control of weeds by chenical and cultural methods. This review will include only selected references dealing with the effects of cultivation and specific herbicides on the physical properties of soil and yield of corn. Effects of Cultivation on Iield of Corn Sons experiments were started at Urbana, Illinois as early as 1888 to determine the value of depth am frequency of cultivation. These emperiments were centimed until 1893 and according to Iiner and Harland (36) Gardner concluded that there seemed to be no advan- tage in cultivating any more frequently than required to destroy woods. The yield in those plots that received no cultivation, but where weeds were controlled by scraping with a hoe, was 96.9 per cent of that of plots cultivated shallow four to five tines. In six years of experiments with corn Iosier and Gustafson (20) found the average yield from uncultivated plots on various soil types was 98.9 per cent that of similar cultivated plots. Gates and Cox (6) con- cluded that mltivation was not beneficial to the corn plant except that weeds were removed. They also reviewed work at low York, lissouri and South Carolina concluding that there were no significant differences for cultivation of corn over hand cutting of weeds with a hoe at any of these station. In 1925 liner and Harland (36) pub- lished results of six years work where uncultivated plots, except with weeds controlled by scraping with a hoe, yielded 104.3 per cent of 3 cultivated plots. Borst arrl lcCIure (5) of Ohio concluded that on liami silty clay loan and other soils which pack, bake or becone crusted, culti- vation has a beneficial action in addition to controlling weeds. On these soils cultivation to nintain a broken condition of the soil surface my result in increased yields of corn. On Brookstom silty clay loam soils, well aggregated and supplied with organic matter, the chief purpose of cultivation is weed control an! that stirring the soil will not in itself increase the yield of corn. Similar viewswerereportedbylecers (18)whenhefoundthatongramlar soils no cultivation with weed growth controlled by scraping or very shallow cutting with a hoe gave unsurpassed yields. On soils with a high per cent of silt no cultivation resulted in decidedly reduced yields. Swamon and Jacobson (27) working on Cheshire loam in Connecticut found that cultivation had beneficial effects in addition to controlling weeds. Cultivation would be essential for maxi-n _ yields in season having high-intensity rains which result in paddling and packing d the soil, especiale if this is followed by a hot period. In season where the soil surface does not crust or on light textured or well aggregated soils the benefits of cultivation would be fewer. Blake an! Aldrich (2) studied the effect of culti- vation on corn yields and reported that where weeds were effectively controlled with herbicides a mini-1m cultivation still gave better yields of corn thn no cultivation. leggitt (16) investigating the influence of cultivation on corn yields when weeds were controlled with herbicides found that one and in some cases two cultivations were needed to provide laximm corn yields on most soil types with the exception of those which are ofalighttextureaflareinemcellenttilthasaresultofprevious cropping. In most cases there was no advantage of additional culti- vaticns beyond one. There were no differences between the one cultivation nde early in the growth of the plant or at lay-by as long as weeds were adequately controlled early in the season. Another aspect of cultivation, affecting the yield of corn, is the possibility of root pruning. Innu- and lelton (34) reported that cultivation to a depth of four inches gave a decreased yield every season but one, as compared with a similiar cultivation to a depth of one and one-half inches. The average decrease per acre was four buhels of grain and 183 pounds of fodder. In lissouri, Helm (10) reported that deep cultivation compared with shllow reduced the yield of corn six and one-half to thirteen bushels per acre. hasell and Associates (23) studied the absorption of soil moisture at a shallow depth directly beneath the corn hills. The sons of absoiption extended laterally until most of the available moisture at that depth was depleted. The lateral expansion of the noisture absorption acne occurred at successively lower depth as the growing season progressed. Iosier and Gustafson (20) found that the harsful effects of cultivation are always more pronounced during years of drought which would support the findings of hissell (23). Effects of Cultivation on Soil Moisture Iusgrave and Tree (21) investigated the effects of cultivation on the infiltration of water in larshsll silt loan and found that for a three and one-half hour period infiltration was as follows: without cultivation .78 inch per hour; with four-inch cultivation .99 inch per hour; and with six-inch cultivation 1.23 inches per hour. hiring the first thirty mimtes following application of water the effects were quite pronounced. After this initial period, howavcr, the effects of increased porosity induced by cultivation diminished rapidly. There were no significant effects of treatment found on three-hom- wet runs nde forty-eight hours after the initial runs. Pillsbury (22) was unable to get conclusive data on the effects of cultivation mi infiltration of water on 1010 loss. is concluded that the principal effect of ham! cultivation on infiltration was decidedly teqorary in nature. liese and Inc (33) studied the effect of chemical ad cul- tural weed control practices on soil moisture storage and losses on a calcareous reddish chestmt soil in the great plains and concluded that "when weeds were properly controlled the efficiency of moisture storage under chemical fallow was equal to that under subsurface tillage.” Iosier and Gustafson (20), in a series of experiments from 1907-1914, recorded the average yields of corn. Plots unculti- vated, but where weeds controlled by scraping, yielded 45.9 bushels per acre, plots cultivated shallow three times yielded 39.2 bushels and plots cultivated three times all! irrigated averaged 47.7 bushels. These investigators concluded that the uncultivated corn produced so well in comparison with the other treatnents that cultivation for comervation of moisture was a very secondary consideration. Iimer (35) coepared first an! second year corn yields of plots cultivated versus scraping and found that cultivation increased the yield but once during the four years when rainfall was below the nine- year average. Even though this increase amounted to 1.4.8 bushels per acre it was more than offset by the seven remaining cases where yield reduction totaled 58.8 bushels. floors (19) found that capillary conductivity is at a maxi-1m near saturation and decreases rapidly with the moisture content to about moisture equivalent. it moisture equivalent, conductivity is very low and remains practically content as the moisture content is further decreased due to the breaking of water films on the soil particles. Since most soils become plastic at moisture contents near the moisture equivalent, cultivation to conserve soil moisture cannot be done until the moisture leaving the soil by capillary conductivity has been lost. Yeihmeyer (29) studied the loss of water through evaporation under a wide range of condition and found that a dust nilch did not conserve a significant amount of soil water. Effects of Cultivation on Physical Properties of Soil According to Baver (l) the air supply to plant roots as well as soil microorganisms is augnented by cultivation. Cultivation decreased the bulk density of the soil and total porosity was increased. Ioreover, the percentage of large pores was increased to a greater extent than the total pore space. As a result, the total volume of air within the seedbed was raised. Supporting views were expressed by Swanson and Jacobson (27) who studied the effects of soil hardness and connection on corn growth and found that breaking of the soil crust permitted free novenent of air in the soil. Blake and Aldrich (2) in a study of levels of cultivation on physical properties of soils, reported virtually no difference in air space though volume weights were lowest in the noncultivated soil. The composition of soil air is dependent on the extent of biological processes taking place in the soil and the ease with which atmospheric air diffusion can take place. In poorly aerated soils, a decrease in oxygen content is accompanied by an increase in carbon dioxide because the conditions that restrict oxygen diffusion also restrict removal of carbon dioxide produced by roots and microorganisms. As a result it is difficult to distinguish the relative effecte of low oxygen and high carbon dioxide in a poorly aerated soil. The influence of the composition of soil air on plant processes is illus- trated by Chang and Loo-is (7) who found that bubbling carbon dioxide through water cultures for ten minutes out of each hour reduced the absorption of water by roots by fourteen to fifteen per cent. The effect of carbon diouide seemed to be associated with the water- absorption mechanism rather than transpiration, a conclusion also reached by Eraser (11). Gingrich and Russell (9) investigated the effect of soil moisture tension and oxygen concentration on growth of corn roots and found, when the effects were averaged over all moisture tensions, each successive increase in oxygen produced a significant increase in radical elongation, fresh weight and dry weight. Imwton (12) studied the effects of soil aeration on growth and absorption of nutrients by corn plants and found that increasing the soil moisture content reduced the growth of tops and roots of corn. Under the same conditions the per cent potassium, nitrogen, calcium, magnesium alxl phosphorus absorbed by the plants decreased. lhen air was forced through the soils held at high moisture the growth rate of tops and roots increased. Blake and Aldrich (2) used the amount of sodium, potassium and calcium absorbed in potato leaves as an indicator of soil aeration. They found when potatoes were cultivated zero, one, two and six tines, each of the three mtrients was lowest in potatoes cultivated six tines. Cultivation reduced total porosity both years it was measured. Ieaver and Jamison (32) investigated the effect of moisture on tractor wheel compaction of soil. The greatest increase in bulk density occurred during the first four passes of the tire where a maximu- of ten passes were imposed. The average bulk density of Cecil clay increased from 1.22 to approximately 1.1.0 at a depth of 2.75 to 5.25 inches below the bottom of the wheel track. This data was taken below the lower plastic limit in the moisture range con- sidered optima for working the soil. nod-co and Rubin (3) studied the effects of compression and shear on Tole silty clay loan at three moisture levels. At the high moisture content of twenty-seven per cent which is practically equal to the moisture equivalent, pore space was reduced from sixty-six per cent to virtually acre by an applied pressure of 21.3 pounds per square inch. The reduction in pore space decreased with moisture but still was considerable at moisture contents favorable for cultivation and at pressures snorted 10 by fars tractors. According to never (1) the work of Beak illustrates the importance of pore space where coarse sand with a pore volume of 55.5 per cent v... 1000 times more permeable to air than sand with a pore volume of 37.9 per cent. Blake and Aldrich (2) reported that differences in bulk densities of potato plots cultivated five to seven times were not significant, but there was a tendency for these plots to have higher bulk densities than plots cultivated only once. Veihmeyer and Henrickson (30) studied the effect of soil demity and root penetration and concluded that the density above which roots fail to penetrate was not the same for all soils. lo roots were found at densities of 1.9 or above and in several cases densities of 1.7 or 1.8 inhibited the penetration of sunflower roots. There was no penetration of sunflower roots in clay soils when demities reacbd values of 1.6 or 1.7. The lowest density in which roots failed to penetrate was 1.46. Effectof'eeds ennelds chcrn liner and Harland (36) reported the six-year average yield of oornwhereweedswere allowedtogrowwas 0n1113.7percentcfsimilar plots cultivated with shovels. Corn on plots where weeds were not controlled yielded 15.6 per cent of plots receiving three shallow cultivations. Results were cited by Bondarenko (1.) where a band of pigweeds in the corn row reduced the yield 30.2 bushels per acre. Corn yield reductions of 22.9 bushels per acre were reported when an average of 5/. giant ragweed plants were growing per foot of corn row. As the population of each of the two weeds was reduced, corn yields becaae 11 progressively higher, approaching that of the weed free checks. Yangris et a1. (31) reported that even at high nutrient levels weeds suppressed the growth of corn and resulted in decreased yields. He also presented data indicating that any weeds are more efficient in nutrient uptake tlrmn corn. Characteristics and Effectiveness of Herbicides Used on Corn Lovely and Staniforth (15) found that granular 2,4-dichloro- phenoayecetic acid (2,l.-D) applied pro-energence was about as effec- tive as liquid. Slightly better control was obtained with 2,I.-D at rates below two pounds per acre with liquid for-nations than with gramles. Granular applications, in conjunction with shallow cultivation, when corn was at the one-to-three leaf stage were equal to or better than spray. Liden (14) applied 2,4—D pre- and post-emergence and compared these with the same treat-ants supplemented with cultivation. The treatments with cultivation outyielded those without at two out of three location. lie concluded that 2,4-D pro-energence application should be supple-ented with cultivation for maximal yields and that 2,443 applied pro-energence at one pound per acre with two culti- vations gave good results both in yield of corn and value returned for treatment. leggitt (1?) concluded free a test involving several herbicides applied pre-euergenee on corn that 2-chloro-4-etlvlanine-6-isopr0pyl- uino-s-triasine (atrasine) at two pmnds per acre provided excellent weed control throughout the season without injury or reduction in yield of field corn. Stroube (26) reported that a granular formhtion 12 of strains applied pre-eaergence at recommended rates gave results equal to the corresponding wettable powder for-alation where unifore distribution of granules was obtained. Schneider (25) showed that atrasine was taken up by roots when a sufficient anount of aoisture was present to carry the herbicide to the root sone. To obtain best results soil moisture should be adequate at the tins of application and rainfall or over-head irrigation within two weeks was necessary to carry the herbicide to the root acne. Generally at least one-half inch in one shower was required although the rapidity of evaporation and soil moisture at tine of application affects the ascent required. Interaction reported by Schneider (24) indicated that atrasine as a post-eaergence herbicide was sore effective against broadleef than grassy weeds. Ltrasine perforeed favorably when applied at two pounds of active material per acre on an overall basis to broadleaf and grassy weeds which were not sore than one and one-half to two inches high at the tine cf application. 2-ehloro-4, 6-bis-(ethylalino)-s-triasine (silasine) at recouended rates will give longer control than atrasine in areas heavily infested with barnyard grass, several species of Panicua and crabgrass. Although controlled early in the season by atrasine, these species will soaetiwes reappear before fall as they have been observed to tolerate higher rates of atrasine than silaaine. In regard to the soil residual activity of strains as a selective herbicide, Strcube (26) reported that nest rotational crops can be planted and grown one year after an application of atrasine at the race-ended rates. Tillage practices such as plowing, harrowing 13 and cultivating will reduce the possibility of adverse soil residual effects. However, the possibility exists that smll pains seeded in the fall after corn harvest may be injured. Bondarenko (4) reported 2 chloro-N, n diallylacetanide (can) is especially effective in controlling annual grasses in corn. Best results were obtained when slight to moderate rains followed appli- cation. Rainfall of three-fourths inch or more shortly after application reduced the effectiveness of this herbicide considerably. The effectiveness of CDLA was also affected by temperature and in cool moist nether con failed to control fortail, a 00.021 amal grass in Ohio. MW AND HETmlB This study was conducted during the 1960 and 1961 growing seasons on the lorthwestern Substation of the Ohio Agricultural ExporiIent Station located at Boytville, Ohio. The soil type was Hoytville silty clay loan and the topography level. lechanical analysis of this soil type in the A horizon (zero to nine-inch depth) was as follows: sand 20.6 per cent, silt 1.1.8 per cent and clay 37.6 per cent. The areas used for the 1960 and 1961 experinents were surface drained and had underground tile drainage system with laterals spaced fifty and forty-two feet apart respectively. The 1960 experiaent followed corn renoved as silage. The area was fall plowed and the followim spring 100 pounds of nitrogen was applied previous to the secondary tillage operations. The 1961 experiaent followed an alfalfa-timothy sod that was seeded in cats in the spring of 1959. This area received an application of sixty pounds of nitrogen and 330 pounds of 0-20-20 price- to spring plowing on lay 17, 1961. Secondary tillage on the 1961 site consisted of twice over with a double disk and cultipacker pulled by a track-type tractor at right angles to planting direction. Care was exercised so that all areas received identical tillage treat-ant. Soil comistency at the tins of the tillage operation us hard and a mininum tilled seedbed resulted. In 1960, Ohio I 64 was planted on By 24 in 1.2-inch rows with 1!. 15 a row application of 300 pounds of 4-16-16. The following year Ohio I 62 was planted on June 6 with a row application of 165 pounds of 5-10-10 per acre. A split-plot design with four replication was used in the 1960 experisent. The following cultural treat-outs made up the sail plots which were four rows wide. O'HHU Cultivated once, at three-leaf stage with sweeps. Cultivated twice, same as L and 10 days later. Cultivated four times, the first two the same as in i and B, with the last two cultivation at further ten-day intervals. Check, no cultivation. Cultivated onee, sane time as A, with shovels. Cultivated twice, same tine as B, with shovels. Cultivated four tines, same tine as O, with shovels. Check, no cultivation. The sub-plots , fourteen feet wide and twenty-eight feet long, were made up of the following chemical treatments: 1. 2. 3. L. 5. '7. Atrasine 80 I, pre-eaergence, two pounds per acre. Atrasine 8 G, pre-eaergenee, two pounds per acre. itrasine 80 I, pest-eeergence (four-six leaf stage) two pounds per acre. 2.4-9, low volatile ester, pro-emergence, two pounds per acre. 2,44! granular pro-emergence, two ponds per acre. 2,4-0 amine, post emergence, i pound per acre. lo herbicide. 16 In 1961, a partially balanced incomplete block with four repli- cations was used. Plots were four 1.0-inch rows wide and twenty-e ight feet long. lash replication contained sixteen treatments made up of all combinations of each of the following cultural and chemical variables . Cultural Variables . lo cultivation. Cultivated one tine at three-leaf stage with sweeps. Cultivated two tines, same time as B, and ten days later. UOyb Cultivated four times, same time as B and C, with last two cultivations at further ten-day intervals . Che-ical Variables 1. Atrasine, 80' pro-emergence, three pounds per acre. 2. GOAL, pro-emergence, two pounds per acre. 3. 2,4-9 amine post-energenee, one-half pound per acre. 4. lo herbicide. All rates of 2,443 are expressed on an acid equivalent basis, and rates of atrasine and CDAA are in term of active ingredient. All liquid formlations were applied with a hand been delivering thirty-four gallons of solution per acre. Granular ferns used in 1960 were applied with a 1.0-inch Candy spreader. All herbicides were applied overall both years. In 1960 all pne-energence treat-ants were applied on ky 25, the day following planting. Post-energence applications were ads on June 20 when the corn plants were in the five-leaf stage. Pre- energence applications in 1961 were made on June '7 and the 2,4-9 post-energenoe treatsent was applied on July 6 and repeated on August 1.. 17 The cultivation in both experinents was performed with a nounted two-row cultivator. This cultivator was equipped with eight shanks on the front rigs and three on the rear. For the cultivation with sweeps in 1960 and all cultivation in 1961 the four shanks adjacent to the two rows were equipped with cultiguards and the renining four equipped with ten-inch sweeps. Three 12-inch sweeps were nounted on the rear shanks equipped with cultilevelers to level the soil surface behind the large sweeps. In 1960 the cultivation with shovels was performed with the ease cultivator except that spear-point shovels were installed on the front rigs and narrow bull-tongue shovels on the rear. The cultivation with shovels stirred the soil to a depth of two to three inches while the cultivation with sweeps worked the soil from one to no and one-half inches deep. In all cases the first cultivation was closest to the corn row with succeeding cultivation further free the row. During 1960 the four cultivation were made on June 16, June 27, July 5, and July 12. In 1961, the dates were June 22, June 30, July 10, and July 21. Each year stand counts were made and the entire erporinent was thinned to a cannon stand. In 1960 poor stands were obtained and in order to have the sane population in all plots the corn was thinned to 12,000 plants per acre on July 2. The corn in the 1961 aperinent was thinned to a population of 15,170 plants per acre on July 11. The total number of broadleafaud grassyweeds growing on eighty square feet of area between the rows were counted on each plot (rill. II 18 of the 1960 experinent. In addition, weed counts were made in an eight-inch band fifty-six feet long centered on the corn row. Similar counts were made in 1961 on all plots receiving no cultivation and on all plots receiving no herbicide. Ieasurements were made from the soil surface to the tip of the tallest leaf extended on thirty-five marked plants in each cultural treatment on July 6, l2 and 18, 1960. No plant height measurenents were taken in 1961. Leaf samples, from the leaf below the ear frcn ten plants selected at random, were analyzed for nitrogen, phosphorus and po- tassium in 1961. Samples were obtained from all plots treated with atrasine and all other plots receiving no and one cultivation. By the use of the platimun microelectrode method (13) the rate of oxygen diffusion was measured in 1961 on one plot each where it was not cultivated, cultivated once and cultivated four times. Readings were taken on July 21., 25, 26, 28, August 18, September 10 and 26, with the electrodes placed four inches below the soil surface. On September 3, 1961 nine soil cores were obtained fron plots treated with atrasine in each of the following areas: one cultivation in and outside the rear wheel track made by the tractor during cultivation and four cultivation in and outside the wheel track. The umber of blows of a twelve pound humor on the core sampler required to obtain a core were recorded. hilt ddnsity an! per cent porosity were determined from the cores. Plots in both experiments were trinnd to twenty-five feet and the center two rows hand harvested for yield determination on 19 October 17, 1960 and October 16, 1961. Per cent moisture in the corn at harvest was determined by gravinetric nethods. 35301.13 AND DISCUSSION All data presented in this section is the average of four replications unless otherwise mentioned. Duncan's (8) multiple range test of statistical significance at the five per cent level was used to determine the mean significantly different when an analysis of variance indicated differences existed. Iced counts were expressed as weeds per square foot and corn yields as bushels per acre at 15.5 per cent moisture. Iffeot of Cultivation on Iield of Corn The effect of cultivation on yield of corn can be determined by examining the yields in Table 1 from plots where weeds were controlled with atrasine. Table 1. lffect of cultivation on yield of corn when weeds were controlled with atrasine, 1961. lo cultivation 119.9 a One cultivation 116. 5 b ho cultivation . 112.7 c rm gltintigm 192.5 g fllean not significantly different are indicated by similar lower case letters . Under proper nanagenent this soil type has good structural qualities and remain in a friable condition throughout the growing 20 21 season. Because of this characteristic no benefit was obtained from stirring the soil as is usually the case on coarser textured soils. Root pruning and its interference with the absorption of moisture as well as the adverse effects of cultivation on soil properties could be factors responsible for the reduction in yields resulting from cultivation. Iffects of Cultivation on Height of Corn Plant height neasurements from the soil surface to the tallest leaf are given in Table 2. Table 2. Average height of corn plants on three dates as affected by various cultural treatments , 1960 . W W. W lo cultivation 1.1.57 a 54.83 a 67.81 a Four shovel cultivation 40.21 a 53.43 b 65.63 b One sweep cultivation“ 39.85 a 52.70 b 65.49 b Two sweep cultivation 40.00 a 52.49 b 64.91 b c One shovel cultivation 39.58 a 52.42 b 64.85 b c Two shovel cultivation 39.51 a 52.40 b 64.12 b e W 1 ”-MW More not significantly different are indicated by sinilar lower case letters. Increased bulk densities and lower porosity of soil incurred by the tractor during cultivation and the effect of these properties 22 on processes essential to plant growth are probable causes of reduced height of corn. Results of corn leaf samples indicate significant differences in the amount of nitrogen present in the various treatments. See Table 3. Table 3. Per cent of nitrogen in corn leaves from combination of chemical uni cultural treatment, 1961. Treatments M W Atrasine two cultivation 2.97 a Atrasine none 2.95 a Atramine one cultivation 2.91 a b lone one cultivation 2.89 a b c CDAA one cultivation 2.87 a b c Atrasins four cultivation 2.80 a b c 2,4-D none 2.77 a b c 2,4-D one cultivation 2.77 a b c lone none 2.70 b c M 3.51—4— ‘Ieans not significantly different are indicated by similar lower case letters . ' The presence or absence of weeds was the major influence on the amount of nitrogen present in the corn leaves. In Table 3 the two treatments with the highest per cent nitrogen were essentially weed free and contained a significantly greater anount of nitrogen 23 than the last two treatments which had the greatest infestation of weeds. Cultivation by itself had no effect on the per cent of nitrogen. No significant differences were obtained in the amount of phosphorus and potassium present in the leaf samples. A routine soil test of the area occupied by the experiment made in January 1960 Minted high amounts of phosphorus and potassium present. Apparently this reserve plus bulk and row application in 1961 provided suffi- cient amounts of these two elements . lffects of Cultivation on Soil Properties The effects of cultivation on some physical properties of the soil are shown in Table 4. Before the cores were taken the soil through which the cultivator had passed was removed so that the cores contained soil immediately below the cultivated layer. A total of nine cores were taken on September 3, 1961 from each of the areas sealed. Table 4. Bulk density, total porosity and blows required to obtain a core, from various areas of three cultural treatments, 1961. Ho cultivation, no wheel track __ __ 13.2 a Four cultivation, no wheel track 1.142 a 49.62 a 27.9 b One cultivation, no wheel track 1.225 a 48.30 a 31.3 b One cultivation, in wheel track 1.220 a 44.70 b 28.0 b *neem not significantly different are indicated by sinilar lower case letters. 21. Soil from the no cultivation treatment was very friable and either fell from the core when the sampler was removed or while the core was being trimed to length. Consequently, bulk density and total porosity were not determined from this treatment. Analysis of the data in Table 1. indicates that repeated pressure exerted by even small farn tractors results in increased bulk densities. The resulting increase in density occurs deep in the plow layer considerably below that stirred during cultivation. Taylor et a1. (28) determined sons physical properties of Hoytville silty clay loan at the Northwestern Substation in 1956 an! reported a bulk demity of 1.29 at the sero to nine inch depth and 1.45 at the nine to 18 inch depth. Results obtained in this study show that four passes over a given area with the rear wheel of a tractor resulted in a plow layer bulk dens ity equal to that normally encountered nine to eighteen inches below the soil surface. Cultivation by itself had no effect on the bulk demity or total porosity of the area immediately below the plow layer, however, one pass with the tractor wheel significantly lowered porosity and four passes of the tractor wheel again lowered porosity a significant amount. The najor portion of the reduction in total porosity probably took place as a result of a reduction in non-capillary pores. These pores are especially ilportant in heavy soil as they provide the lost direct route for the exchnge of oxygen and carbon dioxide with the atmosphere. Although the number of blows does not indicate any specific soil property it does provide a relative indication of the condition 25 of the soil in the areas sampled. Analysis of this data in Table 1. indicates that only between the three center treatments were the number of blows required not significantly different. The other two neans indicate the extreme variation in penetration resistance encountered by the core sampler. The appearance of the two extremes of compaction after the cultivated layer of soil had been removed is shown in Figures 1 and 2. .4' ' W V . . . _ s ‘5' - , _ .A A. 3 ‘ ‘ x ' *' -' “5 ' .3 '. at». 1‘s . - s l J w 4 T ~ . .5- r .4 ' "k" l s ‘ ‘ t .7 . . ' . . C . .‘ , ‘ .- ' F. , . . .“e 'I, \ t \' . 7 . a t . '1 ‘ gt“ 5 ‘ .i I _ .2?! ,‘V ‘ a v r a _ 0" af‘...» in l‘ ., ,- can. 95 .. 's ' ”‘7‘... \O‘J- x)" ”W I ta" ' -' ' - .‘.",‘$’ .._115 ‘ LE ._—__. . ~ . :M 7 - Hashins, Figure 1. Appearance of uncultivated area that required an average of 13.2 blows to obtain core. Data in Table 1. indicates that the properties of soil are drastically changed by repeated pressures exerted by farm tractors. In order to provide as near an ideal environment as possible for corn roots the nunber of operations performed after plowing should be kept 26 .V..__ ,‘_.. ‘_ 4 cummmus “ '7 4""1911"; 10‘ “1312!“ 'Bodiling Green, ..1 22291 - l Figure 2. An average of 82.1. blows were required to obtain a core in this area over which the rear wheel of tractor had passed four times during the cultivation. to a minimum. Iinimum seedbeds that require less secondary tillage and often eliminate the need of rotary hocing to facilitate emergence is a practice that results in fewer operation performed an! conse- quently less compaction of the soil. Other helpful nnagement techniques are the application of pro-emergence herbicides from planter attached equipment and if additional weed control operatiom are necessary that it be done with equipment that will run in tracks made during planting. An observation apparent during late summer was the amount of cracking of the soil in the treatments receiving zero, one, two and four cultivations. Figures 3, 1., 5 and 6 are photographs taken September 12, 1961 of this phenomena. ‘~ . ‘w e . f , {:0 . " ’ — I! . N0 CULTIVATION ‘ .25 Q- ‘ - 4 ‘1’ ‘ ’ ‘ v" e - ' a l ' T" ‘, a. t I ,I'> Ma '1 - 4.4. . ‘4 ‘ t. . - . . I Ar.- ,’ ‘I I I L_s._- .9444” :1_ 1: 1.~_l.z_,1;,5"" v . Bowling Green, Ehone 2-229‘1 - Haskins, Phone . ./' A“ fig: 4" s _&___ Zgzzii I Figure 3. Soil surface of plot receiving no cultivation. l.» a ’ .a- .1 .4 v ‘ ‘1?»345" ‘ a ' ‘L' 0‘ N 5;" ONE CULTIVATION . ' 4 1' 12' 16;;1M ‘xk'44. hi " 9"20 3; fl. _-.-_ _ I» 1 .. 118i " 'I“ _ Bowling Cree-n, Phone 2-2291 - Hashim, Phone 36331 - v7— rigure 4. Soil surface of plot receiving one cultivation. \ ; - _8.V__g-_ix..,_ I! '_'1 2.4.1" I‘ . E'IIH Bowling Green, Phone 22291 - Has ' , Figure 5. Soil surface of plot receiving two cultivations. -. 1:. H ‘ \14"L1‘.5L_i.¢5___\ Plume 2.5.3.39] - Hashins. P} “ml: [my (be; '1. Figure 6. Soil surface of plot receiving four cultivations. 29 By use of the Platinmum microelectrode method (13) the rate of oxygen diffusion was determined on plots treated with atrasine that were not cultivated, cultivated once and cultivated four times. The readings obtained were in.microamperes and resulted from the flow of electrons through the circuit as oxygen is reduced at the electrode. Therefore the readings are proportional to the rate of oxygen diffusion into the immediate vicinity of the electrode. A.total of 39 readings were taken per plot on each date with the electrodes four inches below the soil surface. Table 5 lists the means of these readings. Table 5. Rates of oxygen.diffusion in.microamperes on several dates in soil that had received varying amounts of cultivations, 1961. W Dates 0 t - - - - - - lo cultivation 6.37 5.93 5.98 6.07 5.42 5.84 1.49 One cultivation 5.61 4.68 5.79 5.85 4.82 6.39 1.61 PM munum 4e83 5e28 5e36 5e66- 5e50 5e99 1e41- * 8 I'B N’s N N's Iide variation of readings within a treatment resulted in a large error term, consequently, only the means obtained on.July 24 were significantly different. The sequence of readings in late July was interrupted by a rain on.July 29. However, the means obtained July 24 indicates that the rate of orygen diffusion was slightly higher in.the uncultivated plot with one and four cultivations following in that order. . h ' l . A w - w I s '- a v e s- Q I t s s m - v . .. . u r . e s s . ~ _ . . 30 Effectiveness of Chemical Treatments Used in Controlling Heads The effectiveness of the various herbicides used in the 1960 experiment on the control of grassy and broadleaf weeds is indicated in Table 6. Table 6. The effects of several herbicides on the control of broadleaf and grassy weeds in corn, 1960. Atrasine, 80 I 2 pre-emergence .01 .11 2,44) 1.7.3. 2 pro-emergence .19 .09 2,4-0 Granular 2 pro-emergence .19 .12 Atrasine, 8 G 2 pre-emergence .11 .21 Atrasine 80 I 2 post-emergence .19 .30 2,4-D Amine f post-emergence .43 .45 W .24.._.____J.Q__ " pro-emergence treatments applied lay 25. Post-emergence application made June 20. ”Need counts nde July 5. Rainfall during the week following application of herbicides was: lay 27, .55; It! 28, .333 lay 29, .01; and lay 30, .28 inch. Rainfall following post-emergence treatments was: June 22, 1.52; and June 24, .02 inch. Results with atrasine applied as a spray and in granular fans were essentially equal. Figure 7. Control of annual weeds was obtained with atrasine 80 I, 1960. .- 3.3, Q4 ‘ :: 19rf-,_‘ . . mat-mm: 'r" _ ' ‘ we 75h{ 7, - v. m .u , 1'-' w . o ’— Figure 8. Granular fen of atrasine was as effective as the wettable powder. 32 A light natural infestation of weeds on the 1960 experimental site nde a critical evaluation of the herbicides impossible. However, pro-emergence application of the herbicides in liquid and granular form were slightly more effective than post-emergence applications. Total rainfall during June and July 1960 was 3.94 inches and 6.47 inches respectively. In some plots treated with strain, infestations of barnyard grass (Echinoohloa crusgalli) averaging one- half plant per square foot, occurred in late July. Apparently this shallow rooted grass germinated in the surface soil from which the atrasine had been leached by the high amount of rainfall. The herbicides used in 1961 were selected with the intent to create different types of weed populations: i.c. strains to control all annual weeds, 2,4-D post-emergence to control only breed- leaf and CDAA to control only grasses. The effectiveness of the herbicides used in 1961 is indicated in Table 7. Table 7. The effects of three herbicides on the control of broadleaf and grassy weeds in corn, 1961. W Atrasine 80 I 3 pre-emergence .07 .04 2,4-D amime i- post-emergence .19 .42 CDAA 2 pro-emergence .85 .49 W M yrs-emergence treatments applied June 7. Post-emergence treatment applied July 6 and repeated August 4. “Iced counts were made on July 25. 33 Rainfall during the week following application of the pre- emergence herbicides was: June 8, .34; June 13, 1.09; and June 14, .99 inch. Following the two post-emergence application precipitation was as follows: June 13, .05; July 14, .45; August 5, 1.10; August 6, .22; August 10, .07; and August 11, .07 inch. Atrasine 80 I gave good control of annual weeds. Satisfactory control of broadleafs was obtained with 2,443 amine post-emergence. Broadleaf weeds in the 2,443 plots were upright spotted spurge (mphorbia maculata), conon milkweed (Asclepias syriaca) and horse nettle (Solemn carolinense) . Heavy rainfall following application of CDAA reduced its effectiveness considerably as evidenced by the presence of annual grasses in these plots. Annual grasses in the plots treated with CDAA consisted primarily of yellow foxtail (Setaria lutescens). Infestation in the check plots consisted of all the weeds mentioned above in addition to lambsquarter (Chenopodium album), red root (Amarenthus retroflexus) , smartweed (Polygonum pensylvanicn) , ground cherry (Physalis subglabrata) and green foxtail (Setaria viridis). Effectiveness of Cultural Hethods in Controlling Reeds In the 1960 experiment the use of shovels and sweeps were included as cultural variables as shown in Table 8. leads were not a serious problem on the site of the 1960 experiment, however, the data in Table 8 indicates that sweeps on the cultivator were more effective in controlling weeds than shovels. The added width of the sweeps compared with shovels made it more difficult for weeds to slip by the sweeps without being destroyed. 34 Table 8. The‘degree of weed control obtained in corn with one, two, and four cultivations using sweeps and spear-point shovels, 1960. W leeds per square foot between the row Treatment Broadleaf i_ng§§z;__ m Re cultivation .74 .30 One cultivation .03 .02 Two cultivations .00 .00 Four cultivations .00 .00 some Ho cultivation .74 .30 One cultivation .14 .09 Two cultivations .13 .03 c t ti .011_ .99____ Sweeps were used on the cultivator for the cultural treatments in 1961. The natural infestation of woods on the site of the 1961 experiment while not heavy was greater than in the 1960 experiment. Table 9. Degree of weed control attained in corn with one, two and four cultivations using sweeps, 1961. Ieeds per square foot leads per square feet between the row in the row m = a: s = -' Ho cultivation 1.31 .69 1.31 .69 One cultivation .62 .07 .91 .26 Two cultivations .35 .01 .70 .14 - w ‘ -. a - w w . I ‘ r . O t . ' w a r . a a - - - u s e ‘ e ‘ . ‘ D V . 35 The degree of weed control attained in 1961 by cultural methods is indicated in Table 9. In spite of the light infestation of weeds it was evident that as the number of cultivations increased the number of weeds in the area cultivated decreased. The difficulty of controlling weeds in the row by cultural methods even with several cultivations is also indicated by the data. Weeds in the row not covered during the first cultiva- tion usually are too large to be covered by subsequent cultivation. Effect of Needs on Corn The presence of weeds influenced the yield of corn signi- ficantly even though the maximum number present was only two per square foot. The weeds grew vigorously due to lack of competition and by late summer many specimen of Redroot (Amaranthus retro- flexus) and Velvet Leaf (Abutilon theophrasti) had attained heights in excess of five feet. These weeds were competing for moisture during late August when the ears were developing. The effect of these weeds and supplemental cultivation on corn yield is presented in Table 10. The no cultivation treatments 1nd the heaviest infestation of weeds and comparatively low yields of corn resulted. The low yield of the treatment no cultivation with CDAA was caused by one unmlainable yield more than ten bushels below the yield of the other plots that made up this mean. Treatments receiving one cultivation had essentially the same yields as the no culti- vation treatments. Apparently the weeds left in the row plus those that germinated after cultivation hold these yields close 36 to the no cultivation yields. Table 10. Effect of supplemental cultivation on yield of corn when weeds were not satisfactorily controlled with herbicides, 1961. No Herbicide CDAA tur atment n. d i M so cultivation 104.5 99.9 One cultivation 105.4 105.9 Two cultivations 114.9 113.6 Wt to innL. On treatments where weeds were not eliminated by herbicides two cultivations controlled weeds to the extent that maximum.yie1ds were obtained. Additional cultivation beyond two resulted in lower yields due to the adverse effects of cultivation already mentioned. Combined Effects of all Factors on Corn Iields The previous discussion had indicated that cultivation is beneficial only insofar as it controls weeds and the presence of weeds decreases the yield of corn. These two facts largely explain the yields obtained from.all treatments in the 1961 experiment, as shown in Table 11. In Table 11 treatments with high comparative yields were weed free. This condition was obtained either by herbicides alone or a combination of herbicides and adequate cultivation. This fact emphasises that one of the primary prerequisites for maximum corn yields is effective control of weeds. lhen adequate weed control was obtained by use of herbicides without the aid of cultivation 37 the highest yield resulted. leads in this treatment were killed as they emerged thus eliminating early competition, a factor operatirg in all but those treated with atrazine. The highest yield from the atrasine treatment and no cultivation also indicates that cultivation on this mil type is beneficial only to the extent that it controls weeds. Table 11. Average yields of can from all combination of chemical and cultural variables included in 1961 experiment. Bate Time of Nmnber of Iie1d* Herbicide 1bfl, Application cggmtgm MA, Atrasine 80 I 2 pro-emergence 0 119.9 a Atrazine 80 l 2 pro-emergence 1 116.5 b 2 ,4-0 f post-emergence 2 116.0 b c No herbicide - ------------- 2 114.9 b c CDAA 2 pro-emergence 2 113.6 b c d Atrasine 2 pre-emergence 2 112.7 c d e f CD“ 2 pro-emergence 4 111.1. g d e 1' 2,44) £- pcst-emergence 4 111.0 g e f 2 ,4-D £- post-emergence 0 110.6 g e f Atrasine 2 pro-emergence 4 109.5 g f 2,443 $- post-emergence 1 109.4 g h f No herbicide - ------------- 1. 108.3 g h i CDAA 2 pro-emergence 1 105.8 h i J No herbicide - ............. 1 105.4 1 1 No herbicide - ---------- -- 0 104.5 j 92;; 2 Dre-ewe O 99.9 k “Means not significantly different are indicated by similar lower case letters. 38 Around the median yield are treatments that have acceptable yields but significantly lower than the treatments just discussed due primarily to cultivation in excess of that necessary to control weeds. Low comparative yields resulted from treatments where weeds were not satisfactorily controlled with herbicides or adequate cultivation. Results of the 1960 experiment were influenced by a destruc- tive hail storm on July 19. This storm seriously defoliated the corn plants which reduced total yields and largely erased differences between various treatments. The damage resulting from this storm is illustrated in Figure 9. Figure 9. Damage to corn resulting from hail storm, July 19, 1960. 39 The influence of the cultivation.variables that made up the cultural whole plots in 1960 on the yield of corn is presented in Table 12. Table 12. Effect of varying amounts of cultivation on yield of corn using sweeps and spear-point shovels, 1960. .1, Cultural Treatments Mag—— One cultivation with sweeps 81.5 a Two cultivations with shovels 80.8 a b Four cultivations with sweeps 80.0 a b Four cultivations with shovels 78.4 a b o Two cultivations with sweeps 77.8 a b c One cultivation with shovels 76.6 b c d Check, no cultivation 75.1 c d he t vatio 72,§ g *leans not significantly different are indicated by similar lower case letters. Ho consistent trend was established by the cultural whole plots in the 1960 experiment. In 1960 various herbicide treatments made up the split plots. The effect of these herbicide treatments on corn yields is indicated in Table 13. Differences in yield of corn between the herbicide treatments were not great, however, treatments with the lowest yields had the greatest infestations of weeds. 40 Table 13. Effect of pro-emergence and post-emergence herbicide treatments on yield of corn, 1960. M Yield“ He atme Atrazine 8 G, pre-emergence 80.0 a Atrazine 80 I, pro-emergence 79.5 a 2,443 granular, pro-emergence 79.1. a 2,4-1) L.7.E., pro-emergence 77.9 a Atrasine 80 I, post-emergence 77.3 a b No herbicide 76.7 a b - t-e e c m man not significantly different are indicated with similar lower case letters . Analysis of the yield data showed a highly significant herbicide 1 culture interaction indicating that both the presence of weeds and the effect of cultivation were influencing corn yields. SUM! The effect of cultivation on the yield of corn and some physical properties of soil were investigated. In addition the effectiveness of several herbicides was determined in controlling weeds in corn, with varying amount of supplemental cultivation using sweep and spear-point shovels. The effect of weeds on the yield of corn and the influence of supplemental cultivation on the height and nutrient content of corn leaves was determined in this study. These investigations may be sumarised as follows: 1. lhen weeds were controlled with herbicides , cultivation did not increase and in some cases decreased the yield of corn. 2. lo significant difference existed in the bulk density of the soil beneath that stirred by one or four cultivations or under the rear wheel track made by the tractor during one cultivation. The bulk density of soil over which the rear wheel of the tractor had passed four times during cultivation was significantly higher. 3. No difference existed in the per cent total porosity to the soil directly beneath that cultivated one or four times. The soil beneath the wheel track made by one cultivation had a signifi- cantly lower porosity and four passes of the tractor wheel during cultivation lowered the porosity an additional significant amount. 1.. Cultivation by itself did not affect the nitrogen, phosphorus or potassium content of corn leaves. 5. The height of corn plants on uncultivated plots was significantly greater than corn on cultivated plots on two of the 41 three dates it was measured. 6. Ch treatments where weeds were not controlled by herbicides , cultivation to the extent that weed control was obtained increased corn yields. 7. The yield of corn was inversely proportional to the population of weeds present except where yields were decreased by excessive cultivation. 8. The presence of weeds significantly decreased the per cent of nitrogen in the corn leaves, however, there was no significant difference in the amount of phosphorus and potassium present in any of the treatments sampled. 9. A tractor-mounted cultivator equipped with sweeps was more effective in controlling weeds timn one equipped with spear point shovels. However, neither satisfactorily controlled weeds in the corn row. 10. Atrazine 80 I applied pro-emergence at recommended rates gave virtually 100 per cent control of annual weeds. Acceptable results were also obtained with 2,443, 1.3.3., 2.4-!) granular and atrasine 8 G when applied pro-emergence at recommnded rates. 1. 3. 1.. 5. 9. 10. 13. BIBLIOGRAPHY Baver, L. D. Soil physics, third edition. New York, New Iork, John liley and Sons. 1956. Blake, G. R., R. J. Aldrich. Effects of cultivation on soil physical properties and crop yields. Soil Science Society of America Proceedings 19:400-403. 1955. Bodman, G. B., J. hibin. Soil paddling. Soil Science Society of America Proceedings 13:27-36. 1948. Bondarenko, D. D. Need control by herbicides. Agricultural Extension Service, Ohio State University, Rilletin 3%. 1960. Borst, H. I», G. I. IcClure. Cultivation of corn. Ohio Agricultural hperiment Station, Bimonthly Billetin 1623 75-77. 1933. Gates, J. 8., H. R. Cox. The wood factor in cultivation of corn. United States Department of Agriculture Bulletin 257. 1912. Chang, H. T., l. I. Ieomis. Effect of 002 ha absorption of water and nutrients by roots. Plant Physiology 20:220-232. 1945. Duncan, D. B. lultiple range and multiple 1" tests. Biometrics 231-4. 1955. Gingrich, J. 11., I. B. Russell. Effect of soil moisture tension and 02 concentration on growth of corn roots. Agronoq Journal 48:517-520. 1956. Helm, C. A. Corn in Iissouri. Missouri Agricultural Experiment Station Bulletin 185. 1921. Kramer, P. J. Causes of decreased absorption of water by plants in poorly aerated media. American Jour-l of Botany 27: 216-220. 1949. Lawton, I. The influence of soil aeration on the growth and absorption of nutrients by corn plants. Soil Science Society of America Proceedings 10:263-269. 1945. lemon, 1. R., A. I. Erickson. The measurement of omygen diffusion in the soil with a platinum microelectrode. Soil Science Society of America Proceedings 16:160-163. 1952. 43 15. 16. 17. 18. 19. 25. 26. U. Liden, C. H. Iced control using various combinatiom of cultivation, 2,4-0, and calcium cyanamid. Proceedings Northeastern Weed Control Conference 62209-216. 1952. lovely, I. 6., D. I. Staniforth. Cc‘amilar herbicide formi- lations for weed control in corn. Proceedings of Joint meeting North Central Iced Control Conference ani Hestern Canadian Weed Control Conference. 1959. Isggitt, l. P. The influence of cultivation on corn yields when weeds are controlled by herbicides. Proceedings of the 14th Annual Meeting of the Northeastern Iced Control Conference. 1960. . leggitt, I. 1'. Progress report on herbicides for weed control in corn and soybeans. Proceedings 14th Annual fleeting of the Northeastern Iced Control Conference. 1960. Iocers, C. A. Depth and method of soil preparation and culti- vation for corn and cotton. Tennessee Agricultural Experiment Station Bulletin 191. 191.4. loore, R. 0. later conduction from shallow water tables. Hilgardia 12:383-426. 1939. Rosier, J. G., A. F. Gustafson. Soil moisture and tillage for corn. University of Illinois, Agricultural Experiment Station Bulletin 181. 1915. lusgrave, G. 1L, G. 11. Free. Some factors which modify the rate and total amount of infiltration of field soils. Agronomy Journal 28:727-739. 1936. Pillsbury, A. 1'. Factors influencing infiltration rates into 1010 loam. Soil Science 64:171-181. 1947. Russell, H. 3., F. E. Davis, R. A. Bair. The use of tensiometers for following soil moisture conditions under corn. Agronmy Journal 32:922-930. 191.0. Schneider, 3. 0. Comparison of simasine and atrasine for weed control in corn. Proceedings of Joint meeting North Central Iced Control Conference and lestern Canadian Iced Control Conference. 1959. Schneider, E. 0. Simsine and related triasine herbicides. Proceedings 15th Annual looting, North Central Iced Control Conference 10-11. 1958. Stroube, s. s. Herbicides to control weeds in field crops . Agricultural Extension Service leaflet L75. 1962. 27. 30. 31. 32. 33. 45 Swanson, C. 1..., H. G. Jacobson. Effect of soil hardness and compaction on corn growth. Soil Science Society of America Proceedings 20:161-167. 1956. Taylor, G. 3., T. Coins, ll. Holowaychak. Drainage character- istics of Toledo and Hoytville soils. Ohio Agricultural Experiment Station Research Bulletin 876. 1961. Veihneyer, F. J. Some factors affecting the irrigation require- ments of deciduous orchards. Hilgardia 28125-284. 1927. Veihneyer, F. J. , A. H. Hendrickson. Soil density and root penetration. Soil Science 65:487-493. 191.8. Vengris, J ., I. G. Cobly, I. Drake. Plant mtrient capetition between weeds and corn. Agronomy Journal 47:213-216. 1955. Weaver, R. A., V. C. Jamison. Effects of moisture on tractor wheel compaction of soil. Soil Science 71:15-23. 1951. liese, A. 1., T. J. Amy. Effect of tillage and chenical weed control practices on soil moisture storage and losses. Agronomy Journal 50:465-468. 1958. William, C. G., F. A. lelton. Corn experimnts. Ohio Agricul- tural Experiment Station Billetin 282. 1915. Iiner, D. C. Uhy cultivate corn? University of Illinois Extension Service Circular 597. 191.6. liner, 1). c., n. B. Harland. The cultivation of corn. Illinois Agricultural Experiaent Station Bulletin 259. 1925. Source Total Ihole plot Reps. Culture Error a Split plot Herbicides H z:C Error b Total lhole plot Rope. Culture Error a Split plot Herbicides K 1:0 Error b APPENDIX .A Analysis of variance on 1960 data Iielg g; 09:3 $3 at us 13,705.27 223 1,282.05 3 1,728.25 7 246.89 1,202.69 21 57.27 817.25 6 136.21 2,955.75 42 70.38 5,719.28 11.4 39.72 E2is!i.s£.:1:n&a_2s.£nlz;§ 40,725.90 195 1,968.38 3 2,315.13 6 385.86 2,880.60 18 160.03 5,224.67 6 870.78 7,704.16 36 214.00 20,632.96 126 163.75 4.311” 3.429** 1.772" 2.411 n.s. 5.318** 1.307’n.s. Source Total lhole plot Rape. Culture Error a Split plot Herbicides H’xrc Error b Total lhole plot Reps. Culture Error a Split plot Herbicides H 1:6 Error b 47 ts on Jul e ht SS df 54,340.98 195 6,458.45 3 3,756.01 6 2,592.87 18 4,273.40 6 10,192.44 36 27,067.81 126 H ht o o 67,244.96 195 7,162.46 3 7,067.35 6 4,179.35 18 3,236.31 6 12 9 038 e 05 36 33,561.44 126 626.00 144.05 712.23 283.12 214.82 1,177.89 232.19 539.39 334.39 266.36 4.346** 3.315** 1.318 n.s. 5.073 2.025 n.s. 1.255 n.s. Source Total Rape. Treatments Error Total Reps. Treatments Total Rape . Treatments Error Total Reps. Treatments Error 48 APPENDIX’ B Analysis of variance on 1961 data 11.18 of 06;; 55 or us. 8 2,748.15 63 195.93 3 1,558.37 15 103.89 4.704** 993.85 45 22.09 921sL1astAsslzsis.fs:1!11:2222 96.57 39 8.37 3 39.38 9 4.3756 2.420** 48.82 27 1.8081 WW 11.686 39 2.294 3 2.438 9 .27089 1.052 n.s. 6.954 27 .25756 W 59.50 39 5.19 3 22m 9 263 2w5ma 32.23 27 1.1937 Source Total Between Error Total Between Error Total Between Total Between Error Total Between Error Total Between B to b C 35 or as F 27,616.20 44 25,463.90 4 6,365.97 118.32** 2,152.30 40 53.80 Pageant Porosity 634.70 35 377.90 3 125.9 15.70** 256.80 32 8.0 De it .591 35 .472 3 .157 42.31** .119 32 .00371 to o e D 0 on 411.87 116 30.63 2 15.31 4.58* 381.24 114 3.34 t D 0 on J 320.02 116 12.54 2 6.27 2.33 n.s. 307.48 114 2.69 366.77 116 5.39 2 2.69 .84 n.s. Source Total Between Error Total Between Error Total Between Error fitg 9f mgen Diffusion on Augggt 18 SS df 18 314.19 116 8.73 2 4.36 305.46 111. 2.76 fig of gaggg Dmgiog on September 19 494.85 116 6.22 2 3.11 488.63 114 4.28 fits of gages; Diffusion 0g Septemgr 36 25.95 .83 25.12 50 116 2 111+ .41 .22 1.62 n.s. .72 n.s. 1.86 n.s. g . £9?” ' ”in? UF _,""h‘ MICHIGAN STATE UNIVERSITY LIBRARIES l lllll llllNll lljlllllilll 14 3 1293 03015 1