The purpose of this study was to compare two commonly used runoff experimental methods, which have different scales, on measurements of runoff and associated fenamiphos and metabolite losses over a 2-year period. Methods used were 15 m wide by 43 m long (645 m(2)) mesoplots and 1.8 m wide by 3 in long (5.4 m(2)) microplots, under simulated rainfall (25 mm h(-1) for 2 h) at 1, 14, and 28 d after fenamiphos application. Mesoplots and microplots were established parallel to a 3% slope on a Tifton loamy sand (Plinthic Kandiudult). All plots were planted to corn (Zea mays L.). Target application rate for fenamiphos was 6.7 kg ha(-1). Runoff totals and maximum rates or meso- and microplots were similar with approximately 25% of the rainfall running off mesoplots and approximately 28% running off microplots. Runoff totals and maximum rates from meso- and microplots were each positively correlated (R-2 = 0.89). In both years, fenamiphos lost in runoff decreased with each rainfall event (1, 14, and 28 d after application). The majority of fenamiphos lost in runoff was in the fenamiphos sulfoxide form. Fenamiphos sulfoxide lost over both years from mesoplots ranged from 51% to 93% of the total fenamiphos lost, and loss from microplots ranged from 47% to 100% of the total fenamiphos lost. Runoff from meso- and microplots I d after fenamiphos application, a "reasonable worst-case" event, had the greatest fenamiphos losses among events. Total losses of fenamiphos or this event averaged 1.2% (CV = 26%) of applied amount for mesoplots and 1.3% (CV = 47%) of applied amount for microplots. Maximum (seasonal) fenamiphos losses for meso- and microplots were 1.4% of applied for mesoplots and 2.6% of applied for microplots. A positive correlation was obtained between microplots and mesoplots for total losses of fenamiphos + metabolites (R-2 = 0.88), fenamiphos parent (R-2 = 0.89), and fenamiphos sulfoxide (R-2 = 0.81). Relatively poor agreement was found for relatively small losses of fenamiphos sulfone between plot types (R-2 = 0.34). Microplots and mesoplots yielded statistically similar results in terms of runoff and fenamiphos losses; thus, microplot results can be extrapolated tip to larger mesoplot areas under these conditions. This has implications for field-scale management and watershed assessment in the Coastal Plain region of the southeast U.S. in that microplot and rainfall simulation results could be useful as statistically valid input datasets to estimate runoff and associated fenamiphos losses from larger areas.

Metam sodium alone and in combination with 1,3-dichloropropene plus 17% chloropicrin (1,3-D+C-17) were evaluated under polyethylene mulch film as alternatives for methyl bromide in tobacco and tomato transplant production for both efficacy against pests and crop safety. Eight different weed species, 10 genera or species of fungi and several agronomic criteria were evaluated at three different sites. In general both the metam sodium alone and in combination with 1,3-D+C-17 were highly efficacious when compared to methyl bromide. Short polyethylene film retention times and short aeration times resulted in poor stands and poor crop vigor while relatively long polyethylene film retention times and long aeration periods at the same rates typically resulted in high stand counts and vigor. Combination treatments were more phytotoxic to germinating seed of tobacco and tomato. Vigor and stand counts of the seedlings were higher as aeration time increased, suggesting phytotoxic residues dissipate with time. Method of application of metam sodium, either injected with chisels or sprayed onto the soil surface and incorporated with a tractor-powered tiller alone or co- applied with 1,3-D+C-17 chisel injected, did not affect the efficacy of the treatments. Caution regarding phytotoxicity must be exercised when seeding into soil fumigated with metam sodium alone or combined with 1,3-D+C-17. Additional work will be required to establish safety periods required prior to transplanting crops into fumigated soil.

Field studies were conducted to evaluate potential methyl bromide alternatives against multiple pests in a bell pepper (Capsicum annum L.) – squash (Cucurbita pepo L.) cropping sequence. Early in the growing season, the most effective treatments in suppressing purple nutsedge (Cyperus rotundus L.) emergence through the polyethylene mulch were methyl bromide, methyl iodide, and chisel-injected 1,3-dichloropropene plus chloropicrin [1,3-D+C35 (chisel)]. However by the end of the season in 1999, only methyl bromide treatment had less purple nutsedge emerging through the polyethylene than the nontreated control. Each soil-applied treatment resulted in nematode-susceptible pepper plants with lower root-gall indices [Meloidogyne spp. (root knot nematode)] than the nontreated control, while there were no differences among treatments with the nematode-resistant pepper cultivar. Total fungi isolated from soil was lower in all treated plots relative to the nontreated control, with the exception of methyl iodide. However, methyl bromide was the only treatment that was consistently effective against Pythium spp. and Fusarium spp. A treatment of metham prior to planting squash was beneficial in reducing root-gall indices in plots treated with 1,3-D+C35 (chisel) and methyl bromide prior to the pepper crop. Methyl bromide, methyl iodide, and 1,3-D+C35 (chisel) applied before pepper resulted in squash with lower root-gall indices than the nontreated control. Glyphosate applied between the first and second crop eliminated exposed weed foliage through the polyethylene mulch, possibly muting the effects of the second crop treatment on weed densities. Results of this study indicate that there are some potential methyl bromide alternatives available to growers for use in pest control, however there does not appear to be one broad-spectrum pesticide that will replace methyl bromide. Also, an effective control for nutsedge species within the pepper–squash cropping system is still elusive.

Metam-sodium, chloropicrin, 1,3-dichloropropene (1,3-D), 1,3-dichloropropene plus 17% chloropicrin (1,3-D+C-17) and 1,3-dichloropropene plus 35% chloropicrin (1,3-D+C-35) were evaluated alone and together under a polyethylene cover as alternatives for methyl bromide in tobacco, tomato and pepper transplant production over a two-year period. Eleven different weed species, 10 genera or species of fungi, two arthropods and four species of nematodes were evaluated in three different sites. All of the fumigant candidates were successful in controlling some of the pests. However, metam-sodium alone and in combination with 1,3-D+C-17, chloropicrin, and 1,3-D+C-35 were the most efficacious. Seventy-nine different parameters were measured over the two-year period including plant stands, vigour, plant heights and control of weeds, fungi, arthropods and nematodes. Metam-sodium and methyl bromide plus 2% chloropicrin (MeBrC) were not significantly different (P=0.05) from each other in 76 of the 79 parameters evaluated; MeBrC was significantly better than metam-sodium for three of the 79 parameters. The combination of metam-sodium plus 1,3-D+C-17 was not significantly different from MeBrC for 74 of the 79 parameters tested. MeBrC was more efficacious than metam-sodium plus 1,3-D+C-17, for two of the 79 parameters, and metam-sodium plus 1,3-D+C-17 was significantly better than MeBrC for three of 79 parameters.

Wheat, cotton, and peanut were arranged in three cropping sequences to determine the effects of fenamiphos (6.7 kg a.i./ha) and cropping sequence on nematode population densities and crop yields under conservation tillage and irrigation for 6 years. The cropping sequences included a wheat winter cover crop each year and summer crops of cotton every year, peanut every year, or cotton rotated every other year with peanut. The population densities of Meloidogyne spp. and Helicotylenchus dihystera were determined monthly during the experiment. Numbers of M. incognita increased on cotton and decreased on peanut, whereas M. arenaria increased on peanut, and decreased on cotton; both nematode species remained in moderate to high numbers in plots of wheat. Root damage was more severe on cotton than peanut and was not affected by fenamiphos treatment. The H. dihystera population densities were highest in plots with cotton every summer, intermediate in the cotton-peanut rotation, and lowest in plots with peanut every summer. Over all years and cropping sequences, yield increases in fenamiphos treatment over untreated control were 9% for wheat, 8% for cotton, and 0% for peanut. Peanut yields following cotton were generally higher than yields following peanut. These results show that nematode problems may be manageable in cotton and peanut production under conservation tillage and irrigation in the southeastern United States.

A study of irrigated strip-till soybean production compared gross margins over nematicide expense for a continuous triticale-soybean system versus a two-year rotation system alternating triticale-soybean with triticale-cotton. Half of the replicated plots under each system received nematicide treatment. Gross margins were calculated using recorded yields and Georgia average market prices by marketing years. Mean gross margins for untreated plots were not significantly different between crop-sequence systems. Within each system, however, mean gross margins were significantly higher for plots not receiving nematicide treat- ment versus treated plots, even when treated plots produced greater yields. Soybean crops are especially susceptible to attack by many nematode genera (Schmitt and Noel, 1984). In the Georgia Coastal Plain, the nematodes causing economic damage to soybean include root-knot (Meloidogyne spp.), soybean cyst (Heterodera glycines Ichinohe), Columbia lance (Hoplolaimus columbus Sher), reniform (Rotylenchulus reniformis Linford and Oliveira), and sting (Belonolaimus longicaudatus Rau). Soybean losses to nematodes in Georgia were estimated at $3.75 million in 1995, representing more than half of the total disease losses for the crop and 6.5% of the 1995 total crop value (Bertrand, 1996). Management of nematodes has been achieved through selection of resistant soy- bean cultivars, crop rotations, and use of nematicides (Boquet and Hutchinson, 1993; Dabney et al., 1988; Edwards, Thurlow, and Eason, 1988; Schmitt and Noel, 1984). Unfortunately, no regionally adapted soybean varieties exist with resistance to all

A rainfall simulator was used to apply 5 cm of rainfall in 2 hours to two replicate 624 m 2 plots at six times during each of the growing seasons of 1992 and 1993. Because the simulator generated reproducible and time‐invariant rainfall intensities, the resulting 24 hydrographs reproducibly reveal the effects of tractor wheel compaction, tillage, soil reconsolidation, surface sealing, and corn canopy development. A time series data set including weather, crop development, soils properties, evapotranspiration, and antecedent soil water is available. These data should provide hydrologie modelers, particularly those interested in modeling runoff with time resolutions of <1 day, with a useful validation data set.

Runoff from crop land can enhance eutrophication of fresh water and hypoxia in sea water. We simulated rain at 25 mm hr(-1) for 2 hr, 8 d prior and 1, 14, 29, 49 and 108 d after fertilization and planting of corn (Zea mays L.). Experimental sites received 50 kg N, 45 kg P, and 125 kg K ha(-1) as granulated fertilizer broadcast and incorporated to a depth of 150 mm. An additional 118 kg N ha(-1) was surface-banded as solution fertilizer at Day 28, which was Id prior to the Day 29 rain. The study was conducted for 2 yr on a Tifton loamy sand (fine-loamy, siliceous, thermic Plinthic Kandiudults) with a slope of 4.5%, on micro- (5.57 m(2)) and meso-scale (622 m(2)) plots. Runoff was equal for the two scales of plots. There were greater runoff losses of soluble-P from meso- (1.4 kg ha(-1)) than from micro-plots (1.0 kg ha(-1)). Nitrate-N losses averaged 2.7 kg ha(-1) and bioavailable-P losses were 2.3 kg ha(-1). Greatest NO3-N and soluble-P losses occurred the day after application of the solid fertilizer, whereas bioavailable-P Loss was greatest at Day 14 and 29. No increase in NO3-N losses was found 1 d after the application of urea ammonium nitrate solution, possibly indicating that liquid fertilizers are not as susceptible to runoff losses as solid fertilizers. Results of this study should encourage the use of small plots, thereby saving research time and expense and provide data useful for estimating losses at similar sites.

Comprehensive models for agrichemical transport necessarily include runoff predictions to partition rainfall between infiltration and runoff as this ability is fundamental to predictions of chemical runoff and leaching. We compared GLEAMS, Opus, and PRZM-2 model runoff predictions with runoff measured in a precisely controlled field site used for chemical runoff studies. In 1992 and 1993, two 14.5 m x 42.9 m corn (Zea mays, L.) field plots with 3% slope on Tifton loamy sand (fine-loamy, siliceous, thermic Plinthic Kandiudult) received six severe, artificial rainfall events over the growing season with each event consisting of a 25 mm h(-1) rainfall for 2 h. Runoff was monitored continuously using a collector and flume. Model performance criteria included sensitivity analysis, graphical comparison and statistical analysis including mean, ratio of means, root mean square error (RMSE), and a paired difference t-test. Observed runoff averaged 20% of added rainfall. Lowest values occurred with freshly plowed soil or full canopy covet; while 24 to 34% runoff occurred when nearly bare soils had crusted over. Using an initial moisture condition-II curve number (CN) of 85, GLEAMS and Opus predicted runoff within 10%, overall, and produced a pattern of high and low runoff that closely followed observed. PRZM-2 overpredicted runoff by 90%, overall, and predicted its highest runoff when observed runoff was lowest. Paired difference t-tests indicated a significant difference between measured and predicted runoff for PRZM-2 (p<0.001 at alpha = 0.05), but none for GLEAMS (p = 0.761) or Opus (p = 0.194). Mean, ratio of means, and RMSE showed that GLEAMS and Opus performed better than PRZM-2. All three models were very sensitive to CN values which were empirical and subjective, but less sensitive to measurable soil physical properties. With careful parameterization, GLEAMS and Opus could be used to simulate runoff from similar row-crop and soil conditions.

In two separate studies, the herbicide cyanazine was microencapsulated within the following polymers: cellulose acetate butyrate (CAB); ethyl cellulose of two different viscosities (EC22 and EC100); low and medium molecular weight poly(methyl methacrylate) (PMML and PMMM); poly(alpha-methylstyrene) (PMS). Pesticide efficacy studies on five weed species (barnyardgrass, smallflower morningglory, crowfootgrass, Florida beggarweed, and Palmer amaranth) were conducted under greenhouse conditions over a period of 12 weeks for study 1 and 25 weeks for study 2, using the commercial formulation Bladex 90 DF for comparison purposes. In both studies, the poly(alpha-methylstyrene) formulations were consistently comparable or superior to the commercial formulation in long-term control.

In simulations on the fate of agricultural chemicals applied to crops, accurate partitioning of rainfall between infiltration and runoff is fundamental to chemical runoff predictions. We evaluated the Root Zone Water Quality Model (RZWQM version 3.1) against measured runoff from two field plots (15×45 m with 3% slope) on a Tifton loamy sand (fine-loamy, siliceous, thermic Plinthic Kandiudult). Six simulated rainfall events, each 25 mm h−1 for 2 h, were applied to maize (Zea mays, L.) each year. In the uncalibrated mode, RZWQM under-predicted runoff by 40% on average, with the closest fit for events that occurred after full canopy. Saturated hydraulic conductivity (Ks) accounted for the majority of the uncertainty in predicted runoff. When Ks of the surface crust was back calibrated from the measured runoff, RZWQM predicted runoff closely for the remaining plots and events. Alternatively, using different Ks values for wheel track and crop beds, running the model for each and, then, proportionally assigning runoff also led to predictions that agreed with measured runoff. When spatial and temporal changes in Ks were calibrated to specific conditions at the site, RZWQM effectively predicted runoff.

Triticale cv. Beagle 82, cotton cv. McNair 235, and soybean cv. Twiggs were arranged in three cropping sequences to determine the effects of fenamiphos and cropping sequence on nematode population densities and crop yields under conservation tillage for 4 years. The cropping sequences were triticale (T)-cotton (C)-T-C, T-soybean (S)-T-S, and T-C-T-S. Numbers of Meloidogyne incognita second-stage juveniles declined on trificale but increased on cotton and soybean each year. Root-gall indices of cotton and soybean ranged from 1.00 to 1.08 (1 to 5 scale: 1 = 0%, 2 = 1% to 25%, 3 = 26% to 50%, 4 = 51% to 75%, and 5 = 76% to 100% of roots galled) each year and were not affected by fenamiphos treatment or cropping sequence. Numbers of Pratylenchus brachyurus were maintained on trificale and generally increased more on soybean than on cotton. Population densities of Helicotylenchus dihystera were near or below detection levels in all plots during the first year and increased thereafter in untreated plots in the T-C-T-C and T-S-T-S sequences. Generally, yields of triticale in all cropping sequences declined over the years. Yields of cotton and soybean were not affected by fenamiphos at 6.7 kg a.i./ha. Cotton and soybean were grown successfully with little or no suppression in yields caused by nematodes in conservation tillage following triticale harvested for grain.

A plant-weighing procedure was used to measure the total mass of spray mixture intercepted by small whole corn and cotton plants. Mixtures of water and water plus crop oil concentrate or spreader–sticker were applied at spray volumes of 280 to 28,000 L/ha. The plants were weighed before and after passing under the spray and leaf areas, and shoot fresh and dry weights for each plant were measured. Spray deposition increased with spray volumes but not proportionally. Corn plants were larger than cotton plants and retained more spray per plant; however, cotton retained more spray per unit leaf area. The two adjuvants had similar effects on deposition, tending to increase it in corn and decrease it in cotton.

The objective of this experiment was to determine the effects of fenamiphos 15G and short-cycle potato (PO)-sweet potato (SP) grown continuously and in rotation with peanut (PE)-grain sorghum (GS) on yield, crop quality, and mixed nematode population densities of Meloidogyne arenaria, M. hapla, M. incognita, and Mesocriconema ornatum. Greater root-gall indices and damage by M. hapla and M. incognita occurred on potato than other crops. Most crop yields were higher and root-gall indices lower from fenamiphos-treated plots than untreated plots. The total yield of potato in the PO-SP and PO-SP-PE-GS sequences increased from 1983 to 1985 in plots infested with M. hapla or M. arenaria and M. incognita in combination and decreased in 1986 to 1987 when root-knot nematode populations shifted to M. incognita. The total yields of sweet potato in the PO-SP-PE-GS sequence were similar in 1983 and 1985, and declined each year in the PO-SP sequence as a consequence of M. incognita population density increase in the soil. Yield of peanut from soil infested with M. hapla increased 82% in fenamiphos-treated plots compared to untreated plots. Fenamiphos treatment increased yield of grain sorghum from 5% to 45% over untreated controls. The declining yields of potato and sweet potato observed with both the PO-SP and PO-SP-PE-GS sequences indicate that these crop systems should not be used longer than 3 years in soil infested with M. incognita, M. arenaria, or M. hapla. Under these conditions, these two cropping systems promote a population shift in favor of M. incognita, which is more damaging to potato and sweet potato than M. arenaria and M. hapla.

There is need to evaluate the effects of agricultural production activities on sedimentation, pesticide, and nutrient losses under controlled simulated rainfall on plots large enough (generally exceeding 50 m(2)) to incorporate realistic slope lengths and dominant processes that control runoff and sediment yield from ''field-size'' areas. Therefore, a rainfall simulator system was developed for 600-m(2) plots (mesoplots) to evaluate runoff (water and sediment) and agrichemical movement from fields for different tillage practices and chemical applications. The rainfall simulator applies water with irrigation sprinklers spaced 3 m apart on two irrigation laterals arranged 14.6 m apart along the plot length. Runoff and sediment were collected in a V-shaped trough and directed to a flume for measuring and sampling. Simulated rainfall of 25 mm/h with a median drop diameter of 1.52 mm had a coefficient of uniformity of 91 over the plot area. Water was applied and sediment and runoff collected from two mesoplots for sir events over a corn-growing season.

Pearl millet is used mainly as a temporary forage crop in the southern United States. A new pearl millet hybrid has potential as a major grain crop in the United States. The effects of nematodes, irrigation, a nematicide, and nitrogen rates on a new pearl millet grain hybrid, HGM-100, and nematode population changes were determined in a 2-year study. Root-knot nematodes (Meloidogyne incognita race 1) entered the roots of pearl millet and caused minimal galling, but produced large numbers of eggs that hatched into second-stage juveniles. Root-gall indices ranged from 1.00 to 1.07 on a 1-5 scale and were not affected by irrigation or rates of nitrogen. Yield of pearl millet was up to 31% higher under no supplemental irrigation than under irrigation, 16% higher in fenamiphos-treated plots than untreated plots, and 56% higher in plots treated with 38 kg nitrogen/ha than plots treated with 85 kg nitrogen/ha. In southern Georgia, pearl millet appears to be resistant to ring nematode (Criconemella ornata) but favors development and reproduction of M. incognita.

A double-crop rotation of cotton-triticale-soybean-triticale was grown for 4-5 yr in three experiments on loamy sand soil. Tillage treatments were conventional (moldboard plowing 20-25 cm deep after burning triticale residues), no-till, row-till, and ridge-plant. Triticale residues were managed by burning or cutting the straw short (20 cm) or tall (60 cm) at harvest. Population densities of Rhizoctonia solani anastomosis group (AG)-4 in soil after triticale were low to moderate and similar among treatments. Population densities of Pythium spp, in soil were high and variable among treatments. Root and hypocotyl disease severity in cotton and soybean seedlings was low to moderate each year. In most years and crops, tillage and residue management treatments did not influence seedling disease or inoculum densities of pathogens. When there were differences, burning triticale residues and moldboard plowing improved seedling health.