Submitted to: National Workshop on Constructed Wetlands/BMPS for Nutrient Reduction and ...
Publication Type: Proceedings
Publication Acceptance Date: September 8, 1999
Publication Date: N/A
Technical Abstract: Chemical transport from fields depends on factors such as the hydrology of the soil and the rate, timing, and placement of agricultural chemicals used in the cropping system. This research was conducted on the runoff-prone claypan soils of north-central MO. The 3 cropping systems evaluated included three rotations: a minimum till corn-soybean (FS1), a no-till corn-soybean (FS2), and a no-till corn-soybean-wheat (FS5). Each 0.35-ha plot was instrumented with runoff measuring and sampling equipment. For FS1, 190 kg/ha of nitrogen (N) was broadcast and incorporated with a chisel plow about 2 days before planting. For the 2 no-till systems, UAN solution was knifed in post-plant at a rate of 150 kg/ha. Atrazine on FS1 and FS2 in 1997 and 1998 was broadcast preplant at the rate of 2.24 kg/ha and incorporated on FS1. In 1997 for FS5, 2/3 of the atrazine was broadcast preplant, while the remainder was applied post emergent approximately 4 wks safter planting. In 1998 for FS5, 0.84 kg/ha atrazine was applied post emergent approximately 5 wks after planting. Measurements were limited to only the corn phase of the rotation. Data collected during the 45-day critical loss period after planting in 1997 and 1998 are presented. Mean runoff losses from the no-till systems were twice that of minimum till. Mean dissolved inorganic N losses from no-till were about 10% higher than minimum till due primarily to improved N placement. Mean atrazine losses for FS1, FS2, and FS5 were 0.03, 0.08, and 0.09 kg/ha, respectively. The lack of atrazine incorporation with FS2 and FS5 and much higher runoff accounted for these differences. The split and reduced atrazine rates associated with FS5 did not reduce atrazine losses as much as anticipated because runoff events occurred soon after application.