High‐intensity storms that occur shortly after chemical application have the greatest potential to cause chemical runoff. We examined how effectively current chemical transport models GLEAMS, Opus, PRZM2β, and PRZM3 could predict water runoff and runoff losses of atrazine [6‐chloro‐ N ‐ethyl‐ N ′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] under such conditions, as compared with observations from a controlled field runoff experiment. The experiment was conducted for 2 yr using simulated rainfall on two 14.6‐ by 42.7‐m plots within a corn ( Zea mays L.) field on Tifton loamy sand (fine‐loamy, kaolinitic, thermic Plinthic Kandiudults) under conventional tillage practices. For each plot‐year, atrazine was applied as surface spray immediately after planting and followed by a 50‐mm, 2‐h simulated rainfall 24 h later. A similar preapplication rainfall and four subsequent rainfalls during the growing season were also applied. Observed water runoff averaged 20% of the applied rainfall. Less runoff occurred from freshly tilled soil or under full canopy cover; more runoff occurred when nearly bare soil had crusted. Observed total seasonal atrazine runoff averaged 2.7% of that applied, with the first posttreatment event runoff averaging 89% of the total. GLEAMS, Opus, PRZM2β and PRZM3 adequately predicted water runoff amounts, with normalized root mean square errors of 29, 29, 31, and 31%, respectively. GLEAMS and PRZM3 predicted atrazine concentrations in runoff within a factor of two of observed concentrations. PRZM2β overpredicted atrazine concentrations. Opus adequately predicted atrazine concentrations in runoff when it was run with an equilibrium adsorption submodel, but significantly underestimated atrazine concentrations when it was run with a kinetic sorption submodel.

The microencapsulation of alachlor and metolachlor in the polymers cellulose acetate butyrate, ethyl cellulose, poly(methyl methacrylate), and poly(alpha-methylstyrene) with different emulsifiers is described. The controlled-release properties of these formulations were measured under greenhouse conditions on barnyardgrass, crowfootgrass, smallflower morningglory, and Palmer amaranth. The emulsifiers had little effect on the activity of the herbicides. The herbicidal activities of the poly(methyl methacrylate) and poly(alpha-methylstyrene) formulations were consistently lower on all weed species when compared to the activities of the cellulose acetate butyrate, ethyl cellulose, and commercial formulations. The ethyl cellulose formulation of alachlor exhibited controlled-release properties. The results with metolachlor were similar to those with alachlor except that none of the metolachlor formulations exhibited efficacy superior to that of the commercial formulation or controlled release properties.

Abstract The potential for utilizing selected peanut cultivars in multiple-cropping sequences was studied on a Bonifay sand and Tifton loamy sand soil in cropping sequences with grain sorghum, tomato transplants, and cucumbers. The peanut cultivars Pronto, Comet, and Florunner always produced more pods under a 114-day growing period than for a 99-day growing period. In a 99-day growing period, Pronto and Comet produced significantly more peanuts than Florunner. Total sound mature kernels (TSMK) percentages were always greater for a 114—day growing period. Seeding rate did not affect TSMK or OK characteristics. On restricted growth periods (99 days), early-maturing peanut cultivars resulted in higher percentages of TSMK than the late-maturing cultivars. Under small production scale research units, Pronto peanut was planted early – April, or late June – under both clean and conservation type tillage. The moldboard land preparation portion of a tillage experiment resulted in greater yields when peanut was planted early or late in 4-row seeding, but not statistically more than 2-row seeding. Grain sorghum grown at a population of approximately 200,000 plants/ha produced greater yields when planted in July than in August planting. Greater grain yields of sorghum were produced using moldboard land preparation.

Abstract Most peanut (Arachis hypogaea L.) fields of the Southern Coastal Plain are treated with either vernolate (S-propyl dipropylthiocarbamate) or benefin (N-butyl-N-ethyl-a,a,a-trifluoro-2, 6-dinitro-p-toluidine) or a combination of these two herbicides to control certain weeds. The nematicide DBCP (1,2-dibromo-3-chloropropane) is also used in some fields. Field and greenhouse experiments were conducted to determine the effect of vernolate, benefin, DBCP, and Rhizobium sp. on nodulation, yield, quality, and chemical composition of ‘Starr’ peanuts. The application of herbicides, nematicide, and inoculant had no significant effect on yield, sound mature kernels, or ether extract of ‘Starr’ peanuts. The N content of the leaf and seed and the number of nodules were not affected by the treatments. Nematode infestation was low and did not affect yield. In the greenhouse studies, the application of lime, herbicides, or fertilizer did not affect certain morphological characteristics of the plant or N content of the peanut leaves. Nitrogen fertilization increased the weight of the peanut foliage.

are common in the southeast Coastal Plains and south- ern Piedmont. Given the extensive area that is treated High-intensity storms that occur shortly after chemical application with pesticides in this region, particularly during the have the greatest potential to cause chemical runoff. We examined months of March, April, and May, it is likely that a how effectively current chemical transport models GLEAMS, Opus, PRZM2b, and PRZM3 could predict water runoff and runoff losses storm of sufficient magnitude to cause surface water of atrazine (6-chloro-N-ethyl-N9-(1-methylethyl)-1,3,5-triazine-2,4- runoff will occur on some fields that have recently been diamine) under such conditions, as compared with observations from treated with pesticides. a controlled field runoff experiment. The experiment was conducted Field studies of pesticide runoff typically depend on for 2 yr using simulated rainfall on two 14.6- by 42.7-m plots within the occurrence of natural rainfall because simulated a corn (Zea mays L.) field on Tifton loamy sand (fine-loamy, kaolinitic, rainfall cannot be generated at hectare and larger scales. thermic Plinthic Kandiudults) under conventional tillage practices. Micro-scale plots (microplots), typically 5 to 50 m2, are For each plot-year, atrazine was applied as surface spray immediately commonly used with rainfall simulators. While valuable after planting and followed by a 50-mm, 2-h simulated rainfall 24 h in specific pesticide transport studies, microplots are later. A similar preapplication rainfall and four subsequent rainfalls thought to overestimate pesticide runoff as compared during the growing season were also applied. Observed water runoff averaged 20% of the applied rainfall. Less runoff occurred from freshly with typical field studies. This is more likely due to the tilled soil or under full canopy cover; more runoff occurred when severe conditions often used in microplots (Wauchope nearly bare soil had crusted. Observed total seasonal atrazine runoff et al., 1995; Wauchope and Burgoa, 1995). Moreover, averaged 2.7% of that applied, with the first posttreatment event microplots cannot adequately represent typical agricul- runoff averaging 89% of the total. GLEAMS, Opus, PRZM2b and tural management practices and the major characteris- PRZM3 adequately predicted water runoff amounts, with normalized tics of a typical field. In the early 1990s, Coody et al. root mean square errors of 29, 29, 31, and 31%, respectively. GLEAMS (1990, 1994) developed a rainfall simulator for use on and PRZM3 predicted atrazine concentrations in runoff within a intermediate-scale plots, typically 500 m2, sometimes re- factor of two of observed concentrations. PRZM2b overpredicted ferred to as "mesoplots." This equipment made it feasi- atrazine concentrations. Opus adequately predicted atrazine concen-