TqESlg T‘ i 4 -«-—--- — ”A“ / - v. :1 L. r: a wry-want” ‘3 73 1293 01905 3302 l g! are éaaézaéa £2, 5; z: I I I I a 5 5.3254223"! 95"?" 15"»- %f‘*?’*” '3 E A’éwvz-afia’ézafiéi 9.» 95/},sz [s g gig/4.949%; Iovmg-fiw g i err/5.5m- 1! 11/6 filéiy j This is to certify that the thesis entitled Effect of Soil Applied Herbicides on Corn Growth presented by Paul Edward Horny has been accepted towards fulfillment of the requirements for Master oLSe—ieneedegree in _CJ:Qp_a_nd_ Soil Science LL) VQL). (xv-N-.. }5‘\ :: ¢£t{:&. 2“ K3 Major professor William F. Meggitt Date 5-1743” 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution bV1ESI_J RETURNING MATERIALS: Place in book drop to LJBRARJES remove this checkout from ran-ungunnn. your record. FINES will be charged if book is returned after the date stamped below. Um‘t'! €175" EFFECT OF SOIL APPLIED HERBICIDES ON CORN GROWTH By Paul Edward Horny 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 1984 © Copyright by PAUL EDWARD HORNY 198“ ii ABSTRACT EFFECT OF SOIL APPLIED HERBICIDES ON CORN GROWTH By Paul Edward Horny The effect of alachlor (2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide, metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy—l-methylethyl) acetamide), acetochlor (2-chloro-N(ethoxymethyl)-6'-ethyl-o-acetotoluidide), butylate + R-25788 (S-ethyl diisobutylthiocarbamate + N,N-dially-2,2 dichloro acetamide), EPTC + R-25788 (S-ethyl diprOpylthiocarbamate + N,N-dially-2,2 dichloroacetamide), and pendimethalin (N-(l-ethylpropyl)-3,u-dimethyl-2,6 dinitrobenzenamine) on corn (Zea mays) germination, root and shoot fresh and dry weights, plant water stress, potassium and phosphorus content, and yield was studied in 1982 and 1983. Herbicides were applied at normal use (1X), increasing rates (2X, AX) except EPTC + 8-25788 and pendimethalin, and applied preplant incorporated and preemergence with the acetanilides. Most differences in root and shoot weights occurred “-5 weeks after planting. Acetochlor incorporated caused the greatest reductions in all parameters studied. EPTC + R-25788 caused reductions in root and shoot weights when compared to alachlor, metolachlor, butylate + R-25788 and pendimethalin. Alachlor incorporated showed a significant increase in the phosphorus content over that of plants treated with pendimethalin and preemergence alachlor, but all three were within corn sufficiency ranges. Though differences were observed with alachlor, metolachlor, butylate + 3-25788, EPTC + R—25788, and pendimethalin at all rates and methods of application, none significantly reduced yield. To Anita, Paul Jr. and Anna for their persistance. iii ACKNOWLEDGMENTS The author wishes to express his thanks to Dr. Michael Barrett for his faith and foresight in allowing me to begin this project, which has allowed me to finish a degree in which I never thought I would ever begin. Thanks for the chance Mike. The author also would like to thank Dr. William F. Meggitt for allowing me to continue on with and finish this project. I've learned alot from you Bill. The author would also like to thank Dr. Dean Krauskopf for his common sense approach to helping solve problems I have encountered during this course of study. Another thanks goes to Dr. James J. Kells for his guidance and friendship through this project. A special thanks to Mary Lauver for her advice and assistance, Jackie Schartzer for typing the tables twice, Frank Roggenbuck for the updated fishing information, and John Pawlak and Dennis Cosgrove for helping with the every day problems encountered. As for the rest of the weed science crew (you know who you are) thanks for your help and support in completing this project. iv TABLE OF CONTENTS LIST OF TABLES. LIST OF FIGURES INTRODUCTION. REVIEW OF THE LITERATURE. Plant population Root and shoot fresh and dry weights Plant water stress Corn leaf nutrient content Corn grain yield Varietal differences MATERIALS AND METHODS General information. Plant population measurements. Root and shoot fresh and dry weight determinations . . . . . . . Diffusive resistance measurements. Leaf water potential measurements. Corn leaf nutrient analysis. Corn grain yield RESULTS AND DISCUSSION. Plant population Root fresh weight. Shoot fresh weight Page viii O\U'IU'|U'| 0000\1 IO 10 l2 l2 13 1A 15 l5 l6 l6 l6 23 Diffusive resistance Leaf water potential Corn leaf nutrient analysis. Corn grain yield CONCLUSIONS SUMMARY LIST OF REFERENCES. APPENDICES l. The effect of soil applied herbicides at three rates on corn root dry weights, ~ two leaf stage . . . . . The effect of soil applied herbicides at three rates on corn root dry weights, three leaf stage . . The effect of soil applied herbicides at three rates on corn root dry weights, four leaf stage. . . The effect of soil applied herbicides at three rates on corn root dry weights, five leaf stage. . . . . . . . The effect of soil applied herbicides at three rates on corn shoot dry weights, two leaf stage . The effect of soil applied herbicides at three rates on corn shoot dry weights, three leaf stage . . . . . . The effect of soil applied herbicides at three rates on corn shoot dry weights, four leaf stage. . . . . . . . The effect of soil applied herbicides at three rates on corn shoot dry weights, five leaf stage. . . . . . . Rainfall data for 1982 and 1983, Crop Science Research Farm-East Lansing, MI vi Page 28 28 31 3A 36 39 Al U8 “9 5O 51 52 53 54 55 56 IO. 11. 12. 13. 1A. 15. The effect of soil applied herbicides three rates on corn grain yield, Voris 2381 . . The effect of soil applied herbicides three rates on corn grain yield, Great Lakes 422. . . . . The effect of soil applied herbicides three rates on corn grain yield, Voris 2331 . . . . . . . The effect of soil applied herbicides three rates on corn grain yield, Pioneer 3901 . Sample procedure for plasma emission spectroscopy The effect of soil applied herbicides three rates on diffusive resistance in corn, May 11 and June 23, 1982 vii at at at at at Page 57 58 59 6O 61 62 LIST OF TABLES RESULTS AND DISCUSSION 1. 10. 11. The effect of soil applied herbicides at three rates on corn plant population . The effect of soil applied herbicides at three rates on corn root fresh weights, two leaf stage The effect of soil applied herbicides at three rates on corn root fresh weights, three leaf stage The effect of soil applied herbicides at three rates on corn root fresh weights, four leaf stage. The effect of soil applied herbicides at three rates on corn root fresh weights, five leaf stage. . . The effect of soil applied herbicides at three rates on corn shoot fresh weights, two leaf stage The effect of soil applied herbicides at three rates on corn shoot fresh weights, three leaf stage . . . The effect of soil applied herbicides at three rates on corn shoot fresh weights, four leaf stage. . . . . The effect of soil applied herbicides at three rates on corn shoot fresh weights, five leaf stage. The effect of soil applied herbicides at three rates on diffusive resistance in corn The effect of soil applied herbicides at three rates on corn leaf water potential viii Page l7 19 2O 21 22 2A 25 26 27 29 3O 12. 13. 14. The effect of soil applied herbicides at three rates on corn leaf potassium content, sampled at silking. The effect of soil applied herbicides at three rates on corn leaf phosphorus content, sampled at silking. The effect of soil applied herbicides at three rates on corn grain yield. ix Page 32 33 35 LIST OF FIGURES INTRODUCTION 1. Chemical structures of alachlor, metolachlor, acetochlor, butylate, R-25788, EPTC, and pendimethalin . MATERIALS AND METHODS 2. List of herbicide treatments. Page 11 INTRODUCTION Several effective grass control herbicides are registered for use in corn (Figure 1). Included are alachlorl (2-chloro-2',6'-diethyl-N-(methoxymethyl)acet anililde), metolachlor2 (2-chloro-N—(2-ethyl-6-methyl pheny1)-N-(2-methoxy-1-methylethyl)acetamide), acetochlor3 (2-chloro-N(ethoxymethy1)-6'-ethyl-o-acetotoluidide), butylate + R-25788u (S-ethyl diisobutylthiocarbamate + N,N-dially-2,2-dichloroacetamide), EPTC + 3-257885 (S—ethyl dipropylthiocarbamate + N,N-dially—2,2-dichloroacetamide), and pendimethalin6 (N-(l-ethylprOpyl)-3,U dimethy1-2,6 dinitrobenzenamine). Corn is tolerant to these herbicides under conditions of normal use, however data are being generated concerning comparative growth inhibition, corn injury, and stress from these materials. This causes concern over the use by growers who use these herbicides as a basis for grass control in their weed control programs. It is important to generate data that will establish the safety of these herbicides in comparison with each other and to an untreated control under normal field conditions. The purpose of this study was to: (l) evaluate the effect on corn growth from the different soil applied herbicides; (2) evaluate the effect on corn growth with l 2 increasing rates of herbicides; (3) evaluate the effect on corn growth with different application methods. lRegistered 2Registered 3Registered “Registered 5Registered 6Registered as as as as as as LassoR by Monsanto Company. DualR by Ciba-Geigy Corporation. HarnessR by Monsanto Company. Sutan+R by Stauffer Chemical Company. R Eradicane by Stauffer Chemical Company. ProwlR by American Cyanimid. Figure 1. Chemical structures of alachlor, metolachlor, acetochlor, butylate, R-25788, EPTC, and pendimethalin. CH'z—CH—CH3 CH3 CHg—CHz-S-fi-N O _ emu-1,: 0 CH2 fH‘CHI . 0 N-fi—CHza butylate O CHzCH3 alachlor 1'4 CHz—CH=CH2 °"“f“.i"“< c; o Cl-l,--CH=CH2 (:H3 (EH3 R-2S788 /CH-CH,O-CH, O N \c-CH,CI CHZCH, ll) metolachlor CH,CH,CH3 (ZHT13Fb-S-43-N o CHpHpH. CH3 EPTC C H _ CH-O-CH CH '2 5 N/ 2 2 3 NH—CH \ / \ ha. C-CHZCl CH2CH, II 0 ozw NO2 acetochlor CH, CH3 3”" pendimethalin REVIEW OF THE LITERATURE Plant Population Reduced germination of corn has been reported for alachlor (l9), metolachlor (26,35,58), butylate+R-25788 and EPTC+R-25788 (49,50,70). All reduced stands with normal and increased rates of herbicides. The reductions in plant population did not result in changes in root deveIOpment (74), water use and yield (55,69). Acetochlor caused the greatest reduction in germination (38), Lee and Alley (42) reported a 37% reduction in the corn stand. Root and Shoot Fresh and Dry Weights Root and shoot growth of corn at early growth stages is affected by all soil applied herbicides. Alachlor (22, 28,37,AO,A5), metolachlor (21,22,26,AO) and acetochlor (AO,68) reduce root and shoot growth early in the growing season. Increased rates of these herbicides produced corresponding reductions in corn growth (21,27,28). Differences between incorporated and preemergence treat- ments varied over different conditions (32,AA). Butylate+R-25788 and EPTC+R-25788 both caused reductions in the growth of corn. Although both of these herbicides without the added safener cause injury to corn, and with the addition of R-25788 corn injury is reduced substantially (2,66,67), they both have been reported to inhibit corn growth with the addition of the safener R-25788 (11,12,13,16). Buzio and Burt (14) observed that EPTC and R-25788 separated in the soil columns and cited this as a possible reason for injury from this herbicide (12,13). They also reported that corn was most sensitive to EPTC+R-25788 injury four weeks after planting. Pendimethalin applied preemergence caused reductions in corn root growth (43), especially after incorporation of the herbicide by rainfall (18,64), or by placing the corn seed at shallow planting depths (57). Pendimethalin incorporated does cause the most injury to corn (43), but is not recommended as a herbicide treatment for corn. Plant Water Stress The growth stage of corn that is most directly affected by water stress is pollination (34). Robins and Domingo (62) reported up to a 50% reduction in yield when the plants were under water stress during pollination. Denmead and Shaw (23) observed the same yield reduction from water stress at pollination but also found that water stress early in the growing season had an indirect effect on yield by reducing the amount of photoassimilates available for ear filling. Measuring plant water stress is difficult under field conditions due to the many factors involved (1,20,47,60, 65), therefore absolute values cannot be obtained. Instead, relative values (8) are measured under steady state conditions which lend themselves to analysis by multiple comparisons. Alachlor has been shown to increase transpiration of corn (3), oats (46), and potatoes (13), but the plants were not under severe water stress under normal field condi- tions. EPTC caused increased water loss in corn (9,41), but with addition of R-25788 the formation of epicuticular wax was not changed (31,41), and transpiration is not increased. Corn Leaf Nutrient Content Rehm et. al., (61) found that phosphorus uptake was closely associated with relative yield. Alachlor at higher concentrations increased the phosphorus content of corn plant shoots (59). Alachlor and trifluralin9 ( *,¢X, /- trifluoro-2,6-dinitro-N-N-dipropyl-p-toluidine) decreased phosphorus uptake (10) due to reduction of the total corn root mass (6). Reductions in phosphorus accumulation in corn caused by metolachlor have been observed by Ellis and Wilson (29). Balke (5) reported that both metolachlor and alachlor inhibited potassium absorption in cat roots. EPTC decreased the phosphorus content (6) in french bean seeds (Phaseolus vugaris var.), while alachlor increased the total phosphorus content in seeds of peanut (Arachis hypogaea). R 9Registered as Treflan by Elanco Co. Corn Grain Yield Alachlor (17, 75), metolachlor (24, 75), acetochlor (17), butylate+R-25788 and EPTC+R-25788 (52,75), and pendimethalin (43,57) at normal use rates have no effect on corn yield. Where yield differences were found plots were not hand weeded so the effect of the herbicide treatments on yield could be compared, not the effect of increased or decreased weed pressure. Weeds left growing have a deliterious effect on crop yield (48). Increasing rates of alachlor and metolachlor did not reduce yields (24). Incorporated acetochlor and alachlor did not show any difference in yield over preemergence treatments at the same rate (17). Varietal Differences Differences in corn varietal response to soil applied herbicides have been observed with alachlor (30,53,75), metolachlor (75), and acetochlor (7). More injury occurred with inbred lines than the hybrids, and injury was seen more often early in the season. Tolerance of different varieties to butylate+R-25788 (16,56,73,75) and EPTC+R- 25788 (l5,39,63,72,75) also showed most injury early in the grow1ng season, greater injury was seen with the inbreds than the hybrids.' Niccum (54) reported that alachlor and butylate were safe to use on commercial varieties but should not be used with the inbreds without knowledge of the possible consequences. Zawierucha and Hartwig (75) observed that injury and stunting in the early season from the differences in the varieties was not enough to cause a significant impact on yield. MATERIALS AND METHODS General Information The treatments for this experiment are as listed (Figure 2). On May 5, 1982 and May 17, 1983 the preplant incorporated treatments were sprayed, then one pass incorporated with an implement with danish S-tynes and rolling baskets, three inches deep. The preemergence treatments were sprayed on the same day. The preemergence and the control had one pass tillage prior to treatment for uniform seedbed preparation. The corn was planted on May 5 north to south and May 17 east to west with a four row planter. The plots were four rows, 3.04m by 18.24m long, with four different varieties per plot: Voris 2381, Great Lakes 422, Voris 2331, and Pioneer 3901. There were four replications of the treatments each year. All plots were hand weeded to eliminate weed competition. Before planting 505 kg/ha of urea (45-0-0) was incorporated in each year. Two hundred twenty three kg per hectare of 19-19-19 in 1982 and 223 kg/ha of 5-20-20 in 1983 was band applied with the planter. The soil was a loam texture, pH 6.5, with 3.3% organic matter. The soil temperature at planting time was 15.5C in 1982 and 12.7C in 1983. Insecticide was not applied at planting in 1982 to avoid any possible interactions with the herbicides, but 10 11 Treatment (kg/ha) Alachlor, preplant incorporated Alachlor, preemergence Metolachlor, preplant incorporated Metolachlor, preemergence Acetochlor, preplant incorporated Acetochlor, preemergence Butylate+R-25788, preplant incorporated EPTC+R~25788, preplant incorporated Pendimethalin, preemergence Untreated (hand weeded) 1X 2X 2.8 5. 2.2 4 2.8 5 2.2 4 2.2 4 1.7 3 3.4 6 6.8 1.7 4X 11. 8 11. 8. 8 6; 13. Figure 2. List of herbicide treatments. .8 8 .8 8 6 rootworms were a problem szthe experiment during 1982. Rootworm larvae damage was seen throughout the experiment but was worse in treatments with lower plant populations. The plots were sprayed at silking with carbaryl7 (l- naphthyl N-methylcarbamate) and crop oil to prevent the adult rootworms from damaging the silks. Rootworm insecti- cide, (O-ethyl S phenyl ethylphosphonodithioate)8 was band applied above the row in 1983. The split plot experimental design was employed both years. Data was analyzed with the Duncan's multiple range test at the five percent level. In each measurement, the average of the four varieties in each treatment is presented in the tables, except where noted. Plant Population Measurements On May 17, 1982 and May 31, 1983 the number of plants in 3.04m of row was counted for each of the four different varieties in every treatment. Root and Shoot Fresh and Dry Weight Determinations On May 19, 1982 and June 2, 1983, at the two leaf stage, five plants were dug from the north and east end of the plot. The plants were placed in plastic bags and sealed to reduce moisture loss. The five plants were 7Registered as Seving>by Union Carbide Agricultural Products Company Incorporated. .3 8Registered as DyfonateR by Stauffer Chemical Company. l3 washed and seedcoats were removed. The five plants were then blotted dry with a paper towel, separated at the root-shoot axis, roots and shoots weighed separately, oven dried, and weighed separately again. Plants were also harvested using the same process on May 26, 1982 and June 9, 1983, the three leaf stage, at the north and east end of the plot, June 2 and June 10, 1982 at the four leaf stage, and June 16 and June 23, 1983, the five leaf stage, at the south and west end of the plot. Plants were not removed from the acetochlor incorporated 2X and 4X treat- ments during 1982 so the few plants that remained could be used for further measurements. The comparisons of root and shoot dry weights closely paralleled the comparisons of the fresh weights. Root and shoot dry weights will not be included in the text of this paper, but are included in the appendices (1-8). Diffusive Resistance Measurements A porometer was used to measure stomatal diffusive resistance (seconds per centimeter) as an indicator of plant water stress. It is assumed that stomates will close under water stress thus causing a higher resistance value, or the diffusive resistance is inversely proportional to the stomatal aperature under steady state conditions. A LI-CORR LI-l600 steady state porometer was used for the measurements. After first setting the aperature (2.00m), and the pressure for the altitude (98.5 kPa), the diffusive resistance can be measured. Only one variety was 14 measured (Pioneer 3901) in the interest of time so measure- ments could be taken between 10 a.m. and 2 p.m., the time of highest light intensity and stress during the day. One plant was chosen in the Pioneer 3901 row for each treatment and was used for measurements on May 11, June 22 and June 23, 1982 and June 14, 1983. The newest emerged leaf (having a visible collar) was used for the porometer measurements. Quantum readings, which measures the amount of photosynthetically active radiation (microeinsteins per square meter per second) were taken before each replica- tion. The diffusive resistance readings were taken in direct sunlight. Leaf Water Potential Measurements On June 22 and June 23, 1982 at the six leaf stage the pressure bomb was used along with the porometer. The pressure bomb was used to measure leaf water potential (bars) of a leaf in the same row as the plant used for the porometer measurements. No measurements were taken in 1983. It was not possible to use the same plant as the porometer measurements because the newest leaf (having a visible collar) was removed for the water potential measurement. The leaf was placed in a plastic bag to reduce moisture loss then cut to approximately 150m from the tip of the leaf so the leaves would be uniform. The- proximal end of the leaf had sections removed from both sides of the midrib, leaving an area approximately 3cm long and 1cm on both sides of the midrib so the leaf would 15 fit in the narrow latex grommet used to hold the leaf in place in the cylinder cover on the pressure bomb. The cylinder was then pressurized with nitrogen gas. When sap was expressed, the corresponding pressure (converted to bars) was recorded. Corn Leaf Nutrient Analysis The ear leaf was removed from two Voris 2331 plants in each treatment at silking.. This variety was chosen because of the higher average population across treatments. The leaves were rinsed in nondistilled water and rinsed again in two successive containers of distilled water to remove any dirt or chemicals on the leaf surface. The distilled water was changed periodically. The leaf samples were dried, and then ground to a 20 mesh particle size. Potassium and phosphorus was determined by plasma emission spectroscopy. The sample preparation procedure is listed in Appendix 14. Corn Grain Yield Corn was harvested on October 17, 1982 and October 25, 1983 with a one row research corn harvester. The amount of corn in 7.6m of row was weighed. A sample for moisture determinations was taken from each row in each treatment and sealed in a wax lined paper bag to reduce moisture loss. The yield data was then computed to kg/ha of corn at 15.5 percent moisture. RESULTS AND DISCUSSION Plant Population None of the herbicide treatments at the normal use rates (1X) reduced corn plant population as compared to the control. Incorporated acetochlor at the 2X rate in 1982 and the 4X rate both years significantly reduced the corn stand (Table l). Incorporated acetochlor at the 4X rate both years and the 2X rate in 1982 significantly reduced stand compared to preemergence treatment at the same rate. Alachlor incorporated at the 2X rate in 1982 significantly reduced stand compared to the preemergence treatment at the same rate (Table 1), however, the 4X rate did not show the same pattern. Root Fresh Weight At the 1X rates, no treatments were significantly different than the control harvest 1 (two leaf stage) in 1982, and harvest 1, 2 and 4 during 1983 (Table 2, 3, and 5). Acetochlor incorporated (1X) caused the most consistant reductions in corn root weights at harvest 2 and 3 (three and four leaf stage) in 1982, and harvest 3 during 1983 (Table 3-4). 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At the third harvest in 1983, EPTC+R-25788, butylate+ R-25788, acetochlor incorporated and preemergence reduced corn root fresh weights (Table 4). However, at the fourth harvest, the five leaf stage, in 1982 (Table 5) only EPTC+R-25788 and metolachlor preemergence treatments reduced corn root weights. Root weights of plants treated with acetochlor preemergence harvest 1, acetochlor incorporated and metolachlor preemergence harvest 2 were significantly less than plants treated with butylate+ R-25788 treatment at the 1X rate during 1983 (Table 2-3). Alachlor incorporated at higher rates reduced corn root fresh weights at harvest 2 during 1982 and harvest 3 and 4 both years. Preemergence alachlor at higher rates caused reductions in root weights the third harvest both years and harvest 4 in 1982 (Table 3-5). Higher rates of metolachlor resulted in decreased corn root weights at the second and fourth harvests during 1982 and the third harvest both years. The 4X rate of metolachlor especially when incorporated reduced root weights three of the four harvests in 1982 (Table 3-5). Acetochlor incorporated at higher rates reduced root weights all four harvests in 1982 and harvests 2, 3 and 4 during 1983. Preemergence acetochlor also reduced corn root weights harvest 2 during 1983 and harvest 3 and 4 both years (Table 2-5). Butylate+R-25788 caused root growth reductions only l9 .wscaH0 0>H0 0o scmHmzo .OZH opzwfiu comp .Hmop owcms oHdHque m.cmoczm wch: Ho>oH Rm on» no ucopouuHo zapconchme Ho: oLm LoHHoH osmm ecu an ooonHou cszHoo oco cquHz .moHuoHHm> Lsom no owmpo>m .mcmozm w w m.H 5.H o.H o.H m.H m.H m.H m.H mm0H IIIIIIIIIIIIIIIIIIIIIIIIIIIIII 093 comma ewIIIIIIIIIIIIIIIIIIIIIIII N am ohm cm on m.: 5.m mmmH w .m m m.H m.H o.m 5.H 5.H 5.H mama w m.: m 0.: m m.m m m.: m m.= mama am 0.H am 5.H no w.H a 0.0 n :.H 90 0.H gm 0.H pm 0.H pm 0.H pm m.H mme w m. m.: m.: mama oopmohuc: 000 .eHHmnsmsHeca0 H00 .00500I0+oe0m H00 .00500I0+000H0030 000 .00H200000< H00 .0oHnooumo< 000 .uoHcomH00mz H00 .0oHsomHonz 000 .hoHnoaH< H00 .0onomH0 nopmm :oHsaoHH000 use meHOHntm: 00000 000:9 pm mmeHoHntm: emHHnaa HHom 00 000000 was m.owmpm mama 039 .muanoz :mopm poom :H00 :0 .m manme .0000H0 0>H0 0o 0:0H030 .ozp ohstu oomo .0000 00:00 oHdHuHse 0.:mocso wCHm: Ho>oH Rm 0:0 00 acohouuHo mHocmoHuchHm 00: 000 00000H 0500 0:0 as ooonHou essaoo oco canHz .moHuoHLm> Lsom mo owmpm>w .mcmozm 0000 5.0 0 0.5 00 5.0 00 0.5 000 5.0 0 0.5 00000000: I I I I 000 0.0 0 0.0 000 .0HH0000EH0000 I I I I 000 5.0 0 0.5 H00 .00500I0+0H00 0 H.m 0 0.5 00 5.0 00 5.5 0 0.0 00 0.5 H00 .00500I0+000H0000 0 0.H 0 0.5 0 0.0 000 0.5 000 0.0 0 H.0 000 .00H0000000 000 0.0 0 0.0 00 0.0 I 00 0.0 0 0.0 . H00 .00H0000000 nu 0000 0.0 0 0.5 00 0.0 000 0.5 0 0.0 0 H.0 000 .00H000H000z 90 00000 0.0 0 0.0 0 0.0 00 0.0 00 0.0 00 5.0 H00 .00H000H0002 00 0.0 0 0.5 0 0.0 0 0.0 000 0.0 00 0.5 000 .00Hc00H0 00000 0.0 00 0.0 00 5.0 0 0.0 000 0.0 00 0.5 H00 .00H000H0 0000 0000 000H 000H 000H 000H IIIIIIIIIIIIIIIIIIIIIIIIIIIIII 003 50000 szIIIIIIIIIIIIIIIIIIIIIII x: 00 0H 00H000HH00< 0:0 00H0H0000 noumm 0.0wmum mama omace .mucwfioz :mon Doom :H00 :0 00000 00000 00 000H0H000: 00HH00< HHom 00 000000 000 .0 0H000 21 .0000H0 0>H0 00 000H03 o .03» mpszm 00mm .0000 00:00 0HQHHHBE 0.000030 0:00: H®>0H Rm 020 00 000000000 haucmoHuchHm 00: 000 000000 0500 0:0 00 ooonHom cezHoo 0:0 002003 .mmHuoHLw> H209 no owmpo>0 .mcwmzm 0 0.0 00 m.w 00 m.: 0 5.m 000 0.0 000 0.0 000 3.0 00 5.m mmmH m m.©H 0 O 00 0 n 0 m.ma m.HH 0.0 H.:H m.mH H.MH m.HH mama 0 0.0 00 0.0 o H.© 0 0.: 00 0.5 00 5.0 000 5.5 02 0.0 m00H m m.©H on o.MH on a.ma o 0.0 con >.HH 00 0.0 009 :.HH 000 N.HH mama 0 0.0 00 H.0 00 0.0 00 H.5 00 0.5 O N.© 000 m.5 000 0.5 000 m.5 000 5.5 000H 6 0 0 00 mm 0 m.oH o.mH ©.NH N.:H a.mH ~.HH a.ma a.ma m.MH ©.ma Nmma IIIIIIIIIIIIIIIIIIIIIIIIIIIIII op: cmmpm ewIIIIIIIIIIIIIIIIIIIIIIII 00000000: 000 .cHH0000EH0000 H00 .00500I0+0e00 H00 .00500I0+000H0000 000 .00H0000000 H00 .00H0000000 000 .00H000H000z H00 .00H000Ho00z 000 .00H000H0 Ham .LoazomH< nmpmm :oHumoHH00< 0:0 moHoHnLo: a.mwmum 9004 0:00 .mucwfioz smonm 000m :H00 :0 00000 00000 00 000H0H0000 00HH00< HHom 00 000000 000 .0 0H000 22 .000000 0>00 00 0000020 .030 00zw00 00m: .0000 00:00 00000005 0.:00::0 w:00: 00>00 Rm 0:0 00 0:0000000 000:00000cw00 00: 000 000000 0500 0:0 0: 00300000 :50000 0:0 :0:003 .0000000m> 0:00 00 0mm00>0 .0:0020 0 2.20 0 0.0m 0 2.20 0 0.00 0 2.20 0 0.0m 00000000: I I I I 0 0.00 00 0.00 000 .c000c00500c00 I I I I 0 0.00 0 0.00 000 .00000I0+0000 00 0.00 00 2.00 000 0.00 n 0.00 0 0.00 00 0.00 000 .00000I0+00000000 0 0.00 0 0.00 00 0.00 00 0.00 0 0.00 00 0.20 000 .0000000000 0 0.0 I 0 0.00 I 0 m.00 00 0.20 000 .0002000000 00 2.00 00 2.00 000 0.00 00 0.00 0 0.00 0 0.20 000 .00000000002 00 0.00 0 0.00 000 0.00 00 0.00 0 0.00 00 0.00 000 .00000000002 00 0.00 00 0.00 00 0.00 0 0.20 0 0.00 00 0.00 000 .00000000 00 0.00 0 0.00 00 0.00 0 2.00 0 0.00 00 2.00 000 .00000000 m000 0000 M000 0000 0000 0000 IIIIIIIIIIIIIIIIIIIIIIIIIIIIII 003 :0000 smutIIIIIIIIIIIIIIIIIIIIII x: 00 00000000000 0:0 00000000: 0000: 0.0w00m 000A 0>0m .00:w003 :000m 000m :000 :0 000mm 000:5 00 000000000: 000000< 000m 00 00000m 0:9 .m 00000 23 at the 2X and 4X rates the third harvest both years and harvest 4 in 1982 (Table 3-5). More of the incorporated treatments in 1982 were significantly different from the control than the preemergence treatments at the same rate than in 1983. Only one incorporated treatment, acetochlor at the 4X rate, was less than the preemergence treatment at the same rate in 1983. Acetochlor showed the most differences between incorporated and preemergence at all rates, with differences between application methods observed also with alachlor at the 2X rate and metolachlor at the 4X rate both in 1982 (Table 2-4). Shoot Fresh Weight None of the herbicide treatments at normal use rates (lX) produced significantly lower shoot fresh weights than the control during both years. However, EPTC+R-25788 caused reductions in shoot fresh weights in one instance both years (Table 7 and 9) as compared to other treatments at the same harvest. Acetochlor incorporated and preemergence was also reduced as compared to other treat- ments at the same harvest at the 1X rate (Table 6—7). Higher rates of alachlor, metolachlor or butylate+ R-25788 did not reduce shoot fresh weights, except alachlor the second harvest at the 4X rate (Table 7). Acetochlor caused shoot fresh weight reductions all four harvests (two, three, four and five leaf stage) both incorporated and preemergence (Table 61%). 2U .mpcmaa m>fic co pzwfimzo .ozu mhswam womb .pmou omcmb bananase m.:mocso wcfiw: Hm>ma am on» no ucopoumfio haucmOHuficme no: mLm mepmH msmm ocu an omonHou cesaoo mco cfinpfiz ammfiumfipm> Lsou no mwmpm>m .mcmozm w m o.m w.~ mama one m.m one ~.m ohm m.m o w.= ohm 0.0 com m.m m m.m on H.m mama Q .m .m o.m o.m m.H m.H mama m m.m m H.@ m o.m m >.m m :.m mama am o.m am m.H pm o.m m m.m n o.H n o.H pm H.m pm m.H pm o.m pm w.H mama .m m m.m m.w w.m 0.0 :.m m.m >.m H.m m.m H.m mama IIIIIIIIIIIIIIIIIIIIIIIIIIIIII op: smock ewIIIIIIIIIIIIIIIIIIIIIIII ompmopucz mma .cfifimnumsfiocma Ham .wmsmmnm+oeam Ham .mmsmmum+mpamspsm mma .poH;00umo< Ham .coH200pmo< mmm .poanomHOsz Ham .soanomfioumz mmm .poacoma< Ham .soHnomH< xm nmamm :ofiumofiaoo< paw opfiOfioLo: mmsmm omens pm mmefiofinpm: omfifiaa< HHom co pomccm one m.owmum mama 039 .mucwfioz nmmpm poozm :Loo co .0 magma 25 .mucmaa m>fic co ucwfimzo .03» opswfiu womb .ummu omen; mfiofiuflzs m.cmo::o wean: Ho>oH mm on» pm pcopmuufip haucmofiuficwfim go: mum Louuoa mean on» an boonHou cesaoo mco Cased: .mmfiuofipm> snow no mwwam>m .mcmmzm m 0.: pm o.m pm H.m n o.m 2m M: an c.m ; m.m n m.m Mme. w w :.m c.oH m.m c.o ~.cH 0.x o.~H m.m mama llllllllllllllllllllllllllllll o»: :mopu Emil:IIIIIIIIInIIIIIIIIIII m 0.: pm :.m w z.m om m.m w ©.m pm m.oH m >.m I m >.m ow m.m m w.m no o.m w H.: m o.oa a o.m n m.» mum” mwmfi no 0.: am w.m n.:.m w m.: pm w.m n m.m 2m m.m am >.m no o.= aw H.= mama m =.m coummpuca m N.HH mmm .cfiflmzumsfiecma a 5.» Hum .mmsmmum+oeam m m.m Ham .wwsmmum+mumflspzm m ~.m mam .LoH2009moa a m.m Ham .Loanoo»mo< m ~.m mam .poacomfiouo: m :.m Ham .poazomfloumz m H.m mma .soficoma< m m.m . Ham .hofizoma< mama xm xH boom: :oHumOfiHQo< cam mpfiofiobm: a.mmmum mood mouse .mpsz03 :mmnm poosm :Loo co mmsmz amuse um mmofiofinnmz emfifiaa< Hfiom co uomcum one .s magma 26 .mpcmfla m>fic co unmfimzo .03» mpswfim womb .umou mmcmn mfiofipHSE w.:mo::Q wcfim: Ho>mH am on» um ucopoumac haucmofiuacwam go: one Lcuuoa msmm oz» an cozoaaou cezHoo oco Canvas .mofipmfipm> pzom no mmprm>m .mcmmzm a =.c_ a e.m= m :.OH m o.m: m :.©H m o.m: emsmoescs . n u u m o.sH m a.mm mam .cfifimsumefiecma I I - u m o.mH m :.wm Ham .mmsmmum+oeam pm a.mfi 2m m.om am H.MH pm m.Hm w H.0H m a.mm Ham .mwsmmum+mpmaspsm on m.m an m.om pm a.mfi m m.o: m a.mfi m a.mm mma .poHcooumo< o s.s ; m.sa a m.o a m.mfi m =.HH m :.Hm Ham .poanooumo< m a.mfl a m.>m pm m.MH am a.mm m o.oH m a.mm mam .soacomHOpmz pm 5.:H a N.cm pm m.=fl pm m.nm m m.:H m m.sm Ham .poacomHOpmz om H.=H a H.m: m m.©fl pm o.om m a.mH m m.om mam .pofinomfia one :.HH an m.cm pm a.mfi m a.mm m m.mH w 0.0m Ham .soflnoma< mam. meal mama mwofi mama mama llllllllllllllllllllllllllllll op: cwmpu ewIUIIIIIIIIIIIIIIIIIIIIII x: xm cofiumOHHaaa new mofloansm: noumm .owmum mama Lzom .muzwaoz samba poonm :goo co moumm mmgce um mmpfioanpo: omaaoo< Hfiom no uoommm one .w magma 27 .mucmao m>Hm no uzmmmzo .03» waswfiu mom a .owob mmcmL oaofiuazs m.:mo::o wcfim: Hm>oa mm on» pm ucopmMMHU amucmoaumcwfim so: mLm Lmupma mean on» an pmzoaaou CESHoo mco :quaz .mofiuofipm> Lsom mo mwmgm>m .mcmozm m m.ma m a.a:H pm m.ma m a.a=H m m.ma pm a.a:m emummcuc: I I I I m H.om a m.amH mam .cfimmsumsmecmm I I I I a 3.0m n a.Ha Ham .aammmIa+09mm m m.aa m :.amfi pm a.ma m m.oom a m.am pm m.:am Ham .aammmIa+mpmHapsa o a.am m a.moa a m.ma a m.HmH m a.aa pm a.mmH mam .pomcoopmoa on 0.0a I n a.ma I m a.ma pm o.mHH Hmm .poHnOOpmoa one a.ma m a.mmfi om m.:m m m.HaH m m.am pm m.aoa mam .poanomHOumz 09m H.aa a m.aoH pm o.am m a.a:H m m.aa m a.mma Ham .coacomHOpmz 0am a.ma .m m.amm m :.mm m a.=HH m m.am pm a.mmm mam .coanomma onw a.mm m c.aoH pm a.ma m a.mOH m a.ma pm =.aHH Ham .toflcomma mama mama mama mama mama mama IIIIIIIIIIIIIIIIIIIIIIIIIIIIII ouz cwmgu ewIIIIIIIIIIIIIIIIIIIIIIII am am :ofiumoamama new anaemncm: noumm m.owmum mama m>am .wunwmmz zmopm pooam :Loo co mmpwa amaze um mmemofinbm: ommamma Hmoa ao uomaam was I.m magma 28 Differences between incorporated and preemergence treatments occurred only during 1982. Preemergence alachlor harvest 1 and 2, and acetochlor preemergence harvest 2 and 3 showed significant increases in shoot fresh weights compared to the incorporated treatment at the same rate (Table 6-8). Shoot and root fresh weight values were lower in 1983 than in1982. The greatest differences were in shoot weights rather than the root weights. The temp- eratures were lower early in the growing season in 1983, combined with more rainfall (Appendix 9) and later planting date in 1983 could all cause reductions in plant weights. Diffusive Resistance Differences in root and shoot growth with the various herbicide treatments did not translate into differences in diffusive resistance as measured with the porometer (Appendix 15). Herbicide treatments did not alter the diffusive resistance with the exception of acetochlor at the “X rate preemergence on June 22, 1982 (Table 10). Acetochlor increased the diffusive resistance, indicating increased water stress. Leaf Water Potential None of the herbicide treatments significantly affected the leaf water potential as measured with the pressure chamber from that of the control (Table ll). However, incorporated acetochlor had a significantly lower 29 .03» mpswfim womb .Ho>mH am on» um ammo omcmg magauazE m.:mocsa wcfim: pcopoumap maocmofiufizwem no: mam Loppoa oEmm on» an omzodaom cesfioo mco Casuaz mcmozm a am.a p mm.m m am.H m mm.m a am.H m mm.m empmmcuc: I I I I m mm.m m mH.m mam .cfiamzumsmecmm I I I I m mm.m m aa.m Ham .aammmIa+oema m 2m.a gm om.m m aa.H m ao.m a am.m m m:.m Ham .aammmIm+mumHmpza m cm.a a mm.m m ma.H m ma.a m a=.H m ma.H aam .moHcooumo< m cm.m pm mfl.m m Ho.m m ma.m m aa.H m am.m Ham .poH500umoa a ma.m cm mm.m m aa.m m am.m m ma.m a mH.m mam .bomnomHOsz m mm.m 2m om.m a am.H a oa.m m mm.H a ma.m Ham .eofizomHOsz m ma.H pm mm.~ m om.m m mm.m m ma.m m mm.H mam .momcomma a mm.a pm :a._ m :m.fi m :a.m m aa.m m mz.m Ham .sofizomma aa\=m\a ma\mm\a aa\:H\a ma\mm\a aa\:H\a ma\mm\a IIIIIIIIIIIIIIIIIIIIIIIIIIIIIII Eo\mpcoommIIIIIIIIIIIIIIIIIIIIIIIII as, am am cofiumommmm< new mefiomnsm: noumm m.cgoo :fi mocmumammm m>amsuwfia co mmpma omega pm mmgmoanpm: emfimmm< Hmom co pomaaa was .oa magma 3O .H0>0H mm on» »m »mm» ma»cmcauficwfiw »o: mum L0»»mH 05mm .03» mpswam 00m» mwcwp mHQH»H:E m.:mo::Q mafia: »:m»muufip on» an 0030Haom cesaoo mco :H£»H3 mcwozm a a.m m a.m m a.m m a.m pm a.m m a.m empmmtpca I I I I am a.m m a.m mam .cfimmzpmsaecmm I I I I am m.a m a.m Ham .aammmIa+oema a m.m m :.o» m a.m a a.m» pm a.m m a.m» Ham .aammmIa+m»mHa»sm m ».a m :.m m :.m a m.m n m.a m m.m mam .moflsoo»mo< m m.a a a.m m m.a m m.m m m.a m m.m Hmm .comnoo»mo< m m.m m a.m m a.m m m.a pm a.m m a.m mam .pomcomHOsz a m.m a a.m m a.m m m.m pm a.m m m.m Ham .pomzomao»mz a a.m m a.m m a.m m 2.0» gm a.m m m.m» mam .coHcomfia a :.m m a.m m a.m m m.a pm m.m m a.m Ham .moanomm< ma\mm\a ma\mm\a ma\am\mpmnma\mm\a ma\am\a maxmm\a as am a» cofimeHHmma ecm moHOHnsm: po»mm m.amm»:m»om L0»m3 mama :Loo co mmuma mates pm mmemomnsma emmmmm< Hfioa mo »omaaa was .HH mmnme 31 water potential at the 1X rate on June 23, 1982. Corn Leaf Nutrient Analysis Potassium content was not significantly affected by the herbicide treatment except for acetochlor preemergence at the 4X rate in 1982 (Table 12). All of the herbicide treatments in 1982 with the exception of acetochlor incorporated at the RX rate were within the normal (36) range of 1.7 to 2.5 percent potassium. All of the values for 1983 were Just at or below the normal range and were considered low in potassium content, 1.26 to 1.70 percent. The percent possible analytical error as determined from the blank sample (Appendix 15) was 0.03 percent both years. Plants treated with acetochlor preemergence in 1982 were significantly higher in potassium concentration than plants in the incorporated treatment at the MX rate. No herbicide treatment significantly reduced phosphorus content from that of the control (Table 13). All values were within the normal range of 0.25 to 0.50 percent phosphorus (36). The percent analytical error as determined from the blank sample was 0.02 and 0.003 percent in 1982 and 1983. Plants treated with alachlor incorporated were significantly higher in phosphorus content than plants treated with pendimethalin both years, alachlor and metolachlor preemergence, and EPTC+R-25788‘ in 1982. Alachlor incorporated at the 2X in 1982 and the “X rate in 1983 produced higher phosphorus contents than 32 .03» madman 00m» .»mo» owcma oaaa»a:E m.:mocsm moan: ao>0a am on» »m »:mamuma0 aa»cmoaaa:wam »oc mam L0»»oa 05mm on» an 003oaaou casaoo 0:0 Ca£»a3 mcmozm m m.a on m.a m m.a m a.a pm m.a m.a cmpmmcaca I I I I am m.a m.m mam .caamspmsaecmm I I I I am m.a a.a amm .aaammIa+09mm m a.a 02a m.a m m.a m a.a pm m.a a.a amm .aaammIa+m»maauzm a m.a m m.m m :.a a a.a am m.a a.a mam .poasooumo< a m.a o m.a m m.a m a.a pm m.a a.a amm .coacoopmoa a a.a onm m.a a m.a a a.a m a.a m.m mam .poasomaoamz m m.a onm a.a m a.a m a.a om a.a m.a amm .moazomaoamz m a.a pm a.m m m.a m m.m pm a.a m.m mam .moanomaa m a.a onm a.a m m.a m m.a n m.a a.m amm .toanomaa aama mama mama mama mama mama IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII a aIIIIIIIIIIIIIIIIIIIIIIIIIIIIII a: I am coaamoaamma ecm meaoanmm: 00»mm m.m:axaam »m 00amewm .»co»:oo Esammm»om mama :L00 :0 mmpma mmcze um moeaoanpm: cmaamm< aaom ao aomaam was .ma magma 33 .03» mazwam mom» .»mm» owcmp oaaa»a=E m.:moczo wCam: ao>ma Rm 0:» »m »:oammma0 >a»:moauacmam »0: mam L0»»0a mean on» a» 0030Ha0m cesaoo 0:0 can»a3 mcmwzm cam mm.o a aa.o am.o pm am.o am am.o cam ma.o cmpmmpaca I I I I n am.o o mm.o mam .caamzsmsaocmm I I I I am am.o on mm.o amm .aammmIa+oema pm mm.o am.o mm.o pm aa.o pm am.o com aa.o amm .aaammIa+m»mamusa on am.o ma.o am.o pm oa.o pm am.o one aa.o mam .coazooamoa gm mm.o ma.c oa.o n am.o pm am.o onm mm.o amm .boacoo»mo< cam am.o ca.o am.o pm oa.o m am.o on mm.o mam .soanomaonz m ca.o ma.o oa.o pm ma.o pm am.o pm ma.o amm .goanomao»mz o mm.o aa.c am.o p am.o pm oa.o on oa.o mam .poacomaa m ca.o aa.o mm.o a ma.o a aa.o m o:.o amm .LOacoma< mama mama mama mama mama mama IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII m aIIIIIIIIIIIIIIIIIIIIIIIIIIIIII aa ceaamoaamm< cam mcaoansma co»mm m.w:axaam »m owaaemm .»=0»:oo msaonamonm mama :L00 :0 mmumm amaze pm mmoaoanmmm emaamma aaoa no uomaam was .ma manmE 34 other treatments at the same HX rate during 1983 (Table 13). Corn Grain Yield At normal use rates, no herbicide treatment reduced corn grain yield. At higher rates, acetochlor incorporated and preemergence was the only herbicide treatment to significantly reduce corn yields (Table 14). Preemergence acetochlor treatments had higher yields than the incorpor— ated treatment at the same rate during 1982 and 1983. The yields of the four varieties are listed in the appendix (10-13). 35 .03» magma» mom» .»mo» omcma oaaa»a:E m.cmo::Q wCam: am>oa am on» »m »:oamuua0 ma»:moamacwam »o: 0L0 Lo»»oa 05mm 0:» a» 0030aa0m Cezaoo 0:0 :ac»a3 .mma»oapm> Lsou no mwwao>m .mcmozm gm oamm m ommm m oamm m ommm m oamm m ommm em»mmm»:: I I I I m aoam a mmaa mam .caamsamsaocmm I I I I m maam m amaa amm .aammmIa+oemm pm amam w amaa m aoam m omam m ammm m moam amm .aammmIm+m»maaasa a mam: m :ima m mama m maam a mmmm m aaaa mam .poanoo»mo< o mamm n amam m amma n aamm m mmmm m :m:: amm .moasoopmoa m mama m mcmm m amam m mmmm m ammm m ammo mam .LOanomao»wz pm aamm m comm m mmam m mama m ammm m amam amm .LOazomao»mz pm ammm m mmaa m ammm m mmmm m mama m omaa mam .aoanomaa pm amam m mmmm a oamm pm oaom m aaam m mmaa amm .soacomaa mama mama mama mama mama mama IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII m:\wxIIIIIIIIIIIIIIIIIIIIIIIIIIII am am xa coaamoaamm< ecm meaoancmz 00»mm {It‘ll III; IIIIIIIIIIIIIIIIIII [lull 0.0aoa> camao :Loo :0 momma amaze am mmcaoansm: cmaaama aaom ao uomaam mze .aa magma CONCLUSIONS Herbicide treatments produced reductions in germination, growth, water stress and nutrient uptake that affected corn plants during the growing season, which is in agreement with the authors cited. The reductions in root and shoot weights were more evident at the third harvest, which is similar to the results obtained by Buzio and Burt (13) who found that the greatest injury to corn from EPTC+R-25788 occurred four weeks after planting. However, corn grain yield was not significantly changed as a direct result of any of the parameters studied at normal use rates under normal field conditions. Alachlor, metolachlor, butylate+R-25788, EPTC+Ra25788 and pendimethalin at normal use rates are all comparatively safe and the differences observed do not have a direct effect on yield. Denmead and Shaw found that early season stress could indirectly affect corn yield (23). Yield of corn could be indirectly affected by any one or combination of the parameters studied. Several questions concerning the comparative effects of the soil applied herbicides in corn are still unanswered. Some comparisons that should be given consideration for further study are: 1. Effects of the soil applied herbicides under 36 37 increasing/decreasing water stress. 2. Effects of the soil applied herbicides on plant nutrient uptake under high and low fertility levels. 3. Effects of the persistance or injury caused by the soil applied herbicides should be measured in the plant and soil and expressed as a function of the parameters involved in corn growth i.e. a certain plant process is affected by a herbicide up through a certain growth stage. 4. Effects of extenders or lay by applications which could possibly allow the active herbicide to be in the soil and plant through pollination which could affect yield. 5. Effects on the biomass of corn for silage or the effect of the soil applied herbicides on the maturity of corn. Greater differences were observed during corn growth with increased rates of herbicides (2X, AX) as compared to the normal use rates (1X). Though the herbicides are not recommended at these rates, these data present a good indication of the margin of safety of these herbicides. I From the overall observations of the‘author, the herbicide that showed the least reduction at higher rates in growth and stress in the corn plants earlier in the growing season was butylate+R-25788. However, the butylate+R-25788 treat- ment did not show any increases in yield as compared to the alachlor or metolachlor treatments. Acetochlor produced the greatest reductions in growth and stress as compared 38 to the other herbicides at the higher rates. The differences between incorporated and preemergence treatments may have occurred in the drier year, 1982, (Appendix 9) because the preemergence herbicides were not placed in the root zone of the corn as well as the incorporated treatments. Since the root growth is affected more than shoot growth by the soil applied herbicides as seen in this study, if a herbicide were not in the root zone of a corn plant, the plant would not be affected as much by a preemergence treatment. Differences between incorporated and preemergence treatments did not result in significant changes in yield, with the exception of acetochlor at higher rates. Yield was most directly affected by the stand loss caused by the acetochlor treatment. SUMMARY The effect of alachlor (2-chloro-2',6'-diethyl-N- (methoxymethyl)acetanilide), metolachlor (2-chloro-N- (2-ethy1-6-methylpheny1)-N-(2-methoxy-l-methylethyl) acetamide), acetochlor (2-chloro-N(ethoxymethy1)-6'-ethyl- o-acetotoluidide), butylate + R-25788 (S-ethyl diisobutyl thiocarbamate + N,N-dially—2,2-dichloroacetamide), EPTC + R-25788 (S-ethyl dipropylthiocarbamate + N,N-dially-2,2- dichloroacetamide), and pendimethalin (N-(l-ethylpropyl)- 3,u dimethyl-2,6 dinitrobenzenamine) on corn plant population, root and shoot fresh and dry weights, diffusive resistance and leaf water potential, leaf nutrient content at silking, and yield was studied in 1982 and 1983. Herbicides were evaluated for their effect on corn growth with herbicide treatments at normal use rates (1X), increasing rates of herbicides (2X, AX) excluding EPTC + H-25788 and pendimethalin, and both preplant incorporated and preemergence with alachlor, metolachlor, and acetochlor. Hoot weights were affected more than the shoot weights. Root and shoot weights were less in 1983 than in 1982 at the same harvest, with the shoot weights showing greater differences between the two years. Differences in root and shoot weights were observed more 39 H0 the third harvest. Acetochlor preplant incorporated showed the greatest reduction in all of the parameters studied. EPTC + R-25788 showed greater reduction in root and shoot weights than alachlor, metolachlor, butylate + R-25788 and pendimethalin. Alachlor preplant incorporated was significantly different in phosphorus content as compared to pendimethalin and preemergence alachlor treatments, but all three were within the sufficiency ranges for corn. Though differences were observed with alachlor, metolachlor, butylate + R-25788, EPTC + R-25788 and pendimethalin at all rates and methods of application, yield was not significantly reduced by any treatment. In conclusion, alachlor, metolachlor, butylate + R-25788, EPTC + R-25788 and pendimethalin should be considered comparatively safe in their effect on corn growth under normal conditions and at recomended rates. In reporting data on corn growth one should consider the total picture portrayed on the growth of corn as it is affected by soil applied herbicides. lO. 11. LIST OF REFERENCES Acevedo, E., T. C. Hsiao and D. W. Henderson. 1971. Immediate and subsequent growth responses of maize leaves to changes in water status. Plant Physiology u8z63l-636. Akinsorotan, A. 1976. The Influence of temperature and soil moisture on thiocarbamate injury to corn, with and without protectant. Weed Abstracts 28:1”38. Ashley, R. A. 197a. Effect of alachlor on water loss by sweet corn (Zea mays var. Rugosa L.). Proc. North- east. Weed Sci. Soc. 28:107-110. Ashley, R. A., and C. S. Vavrina. 1976. Effect of alachlor on water loss by potatoes. Proc. Northeast. Weed Sci. Soc. 30:118-121. Balke, N. E. 1979. 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IIIII-I;I:|I am xa scapaoaamma 0:0 00a0a000: :0»0m 0.000»m :00: 0>am .0»:ma03 0:0 »oo:m ::00 :0 m0»0m 00::E »0 000a0a::0: 00aa00< aaom :0 »o0::m 0:9 .m xa0:000¢ Appendix 9. 56 Rainfall Data for 1982 and 1983, Crop Science Research Farm - East Lansing, Michigan. April May June Dax 1982 1983 1982 1983 l 82 1963 1 .41 l 41 .02 2 1.16 3 .30 11 4 .79 02 .12 .65 5 .04 .02 6 .50 .13 .22 7 .31 .06 .18 8 .31 .94 12 9 10 .40 .20 ll .02 12 13 .14 .20 .12 14 .88 15 .11 .08 .10 16 .19 .72 .18 17 .04 .15 .06 18 .05 19 .14 .73 20 .16 .57 .83 21 22 .42 23 .09 1.00 24 25 .04 26 .32 27 .04 .14 .32 28 .38 .44 3.28 29 .63 .39 .35 .16 30 .06 .07 31 .16 TOTAL 1 14 4.15 2.38 5.59 3.97 5.03 57 .03» 0:3wa: 00m: .»m0» 00:0: 0a0a»a3E m.:0o:30 w:am3 a0>0a am 0:» 00 »:0:0::a: ma»:00a:a:ma0 »0: 0:0 :0»»0a 0E00 0:» a: 003oaa0: :E3aoo 0:0 :a:»a3 0:0020 0 mmaa 0 aaam mma: 0 aaom mmaa 0 maoa 000000000 I I I I amam 0 mama mam .caa0000sa0000 I I I I aaom 00 mama a0: .aaammIa+0:ma 0 amm: 0 ammm mama 00 amma mm:: 00 0maa am: .aammmIa+000am0sa 0 aac: 0 amaa aaam 0 mmoa mmaa 00 0ama mam .0oanoo00oa 0 aaam 0 aacm mmaa 0 aaam aaaa 0 aaam H00 .00a0000000 0 0aaa 0 maaa maom 0 mama aama 00 amma 000 .0oa000a000z 0 mmam 0 amzm aaam 0 aama mom: 00 mmmm a0: .0oa000ao00z 0 mamm 0 mmaa amaa 0 mama amma 00 amma 000 .0oa000aa 0 0aa= 0 amma aama 0 mama mmma 00 maaa a0: .0oa000aa mama mama mama . mama mama mama IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 0:\mxIIIIIIIIIIIIIIIIIIIIIIIIIIIII a: -II am xa coa000aamm< 0:0 00a0a000a :0»0m m.aamm 0a0o> .0a0a: :a000 :000 so 00000 000:: 00 000a0a000: 00aa00< aaoa :0 000000 0:: .0a xaoc0am< 58 :0 »:0:0::a0 ma»:00a:a:maw .03» 0:30a: 00m: .»00» 0w:0: 0a0a»a3E 0.:0o:30 w:a03 a0>0a Rm 0:» »0: 0:0 :0»»0a 0:00 0:» a: 0030aao: :E3a00 0:0 :a:»a3 0:0020 0 mmam 0:0 maaa 0 mmam 00 maaa mmam maaa 000000000 I I I I amam ammm mam .caa0200sa0c00 I I I I ma0a mmoa a0: .aammmIm+0ema 00 amam 00 aama 0 0mmm 00 amaa aa0a 00a: amm .aaammIm+000am0sm 00 ma:: 000 m000 0 aamm 0 maaa maam mama mam .:oa:00000< 0 00m: 0 aaam 0 amam 0 a0am aaaa aamm a0: .0oac00000a 0 maaa 000 aaaa 0 amam 00 aama aa0a mmaa mam .0oa000a000z 0 amma 000 mam: 0 aa0a 000 mamm aaaa 00mm amm .0oac00a000z 0 amaa 0 amma 0 aaaa 00 mm0a mmmm m0mm mam .0oa000aa 0 aama 000 amam 0 maaa 00 maam oaaa aaaa amm .0oan00aa mama mama mama mama mama mama IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 0:\mxIIIIIIIIIIIIIIIIIIIIIIIIIIIII x: coa000aaam< 0:0 00a0a000: 000m 0 00000 000:: 00 000a0a000: 00aa00< aaoa :0 000000 0:: 0.mm: 00:0: »00:0 .0a0aw :a0:0 ::00 :0 .aa xa00000< 59 00 0:00000a0 ma0ca0a0acaa0 .03» 0:3wa: 00m: .»00» 0w:0: 0a0a»a3E 0.:00:3Q w:am3 a0>0a am 0:» »0: 0:0 :0»»0a 0:00 0:» a: 0030aao: :E3aoo 0:0 :a:»a3 0:0020 000 mamm 000 aama mamm 00 aamm mamm 000 aama 000000000 I I I I maam 00 amma am: .caamc005a0000 I I I I ammm 000 0amm a0: .aaammIa+0ema 000 000a 000 mmmm aamm 0 am0a m0ma 000 amma amm .aaammIa+000aa0sm 00 aaaa 00 0mm: amam 00 00:: aamm 000 aaaa mam .00a000000a 0 a0aa 0 aamm maam 0 mmmm mmaa 0 0am: a0: .0oa000000a 0 maaa 00 aama maam 0 aama aaam 0 0a0a mam .0oa000a000z 000 mmmm 0000 0aaa 00am 00 aama mmam 00 aa0m H00 .00ac00a000z 000 aamm 0 mmam 0 0mam 00 aama 0 aaam 000 mmma mam .00a000aa 000 ma0a 00 aa0m 0 mmmm 00 0am: 0 00ma 00 000a am: .00a300aa mama mama mama mama mama mama IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 0:\wxIIIIIIIIIIIIIIIIIIIIIIIIIIIII am am xa coa000aa00< 0:0 00a0a000: :0»0m . .ammm 0a0o> .0a0am ca000 c000 :0 00000 000a: 00 000awa000: 00aa00< aaoa 00 000000 0:: .ma xa0c000< .03» mpswmm mmma .ammm mwcmp maaauase m.:wocza maam: Hm>mm mm vs» um p:mLmLaac zmacmoaaacwam uo: mLm quumm mEmm man an omzommou cssmoo mco Caspaz wcmmzm 6O pa aamm m :aaa am aamm a aaaa a aamm m zaaa cmpmmaaca I I I I m aaam m mama mam .caamnamancmm_ I I I I m amoa aamm amm .aaammIa+omma om ammm amma am amaa am mama m ammm mama amm aaaammIa+3maaa=a am aaam aama m amaa m mama m mamm mmoa mam .poanooamoa o mmcm ammm n mas: o amaa m mma: moaa amm .LOanooamo< m mama aama om aamm om mama m mama maaa mam .aoacomaoam: am mmam m aama am ammm om aaaa m mmam m omaa , amm .aoanomaoamz am maam m ammm pm ommm a ammm m mama m mama mam .LOacoma< a maam m amaa am mmmm on maam m oamm m mmma amm .poazomaa mama mama mama mama mama mama IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII m£\wxIIIIIIIIIIIIIIIIIIIIIIIIIIIII II. Ma. II xm xa :Oapmoaamm< new moaoanama nmumm m.aomm amocon .OHmH» :HmLo :L00 :0 amama means am mmoaoanpma amaamaa aaoa ac aomamm one .ma maccmmm< 6l *1 ' 0 *4 m m E} (I) [I1 E3 FJ (a (n [.1 O "3 Appendix 1M. Sample Procedure fo- Spectroscopy. '4 Weigh 1.000 g of ground plant tissue (20 mesh) in numbered crucible. 2. Dry ash @ 500 C for 5 hrs. in a muffle furnace (include 2 blanks for every batch of 20-25). LU Cool. Add 5 ml 6NHN03. Swirl. u. Let stand for 1 hour. 5. Pour through small glass funnel into 10 ml volumetric flask. 6. Adjust volume to 10 ml mark with lOOOppm LiCl (6.08 g LiCl/l). 7. Filter through #2 filter paper into labled vials. 8. This is lOX dilution for micro nutrients. 9. Pipette 0.4 ml of 10X solution to another vial. 10. Add 19.6 ml of 1000 ppm LiCl. 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