Biological Systems Engineering


Date of this Version



Published in Applied Engineering in Agriculture 22:4 (2006), pp. 555-560. Copyright 2006 American Society Agricultural Engineers. Used by permission


On a national scale, the damage caused by corn rootworm (Diabrotica virgifera virgifera LeConte), can cause economic loss of up to $650 million annually. To limit these losses, corn producers apply terbufos insecticide to approximately 11% of all corn acres at a time when there is a high probability of intense precipitation. When combined with low vegetative cover and disturbed soil surfaces, there is a high potential for terbufos transport into surface water bodies. Increased public concern for environmental contamination from the use of agricultural chemicals has prompted many crop growers to look for crop production practices that minimize the transport of insecticides by surface runoff. A field experiment was conducted at the Haskell Agricultural Laboratory in northeast Nebraska in the spring of 1989 to develop best management practices for applying corn rootworm insecticides. The objective of the study was to determine the influence of three tillage practices (DISK, NOTILL, and PLOW) and two insecticide placement methods (BAND and FURROW) on the transport of terbufos insecticide (Counter®) with runoff water resulting from high intensity simulated precipitation after chemical application. A randomized complete block design of four replications was utilized. Treatments were laid out in a split-plot fashion with tillage as the main plot and insecticide placement as the subplot. Corn was planted up-and-down hill in 0.76 m row spacings on a Nora silt loam (fine-silty, mixed, mesic Udic Haplustoll) with a field slope of 6 %. Water runoff was not significantly affected by either tillage practice or insecticide placement method (P < 0.05). Sediment losses from NOTILL plots were significantly less than from the DISK and PLOW treatments. Overall, terbufos transport was significantly affected by tillage practice with the NOTILL treatment resulting in less terbufos transport than the PLOW or DISK treatments. However, terbufos transport was not affected by placement method. Samples collected 10 and 20 min after runoff initiation indicated that sediment-adsorbed terbufos accounted for more than 90% of total terbufos transport. No significant differences in the sediment-adsorbed levels were noted due to tillage treatment or insecticide placement method (P < 0.05). Tillage and insecticide placement methods significantly affected the dissolved terbufos concentration, especially for samples collected 20 min after runoff initiation where the BAND placement was greater than the FURROW placement. Within tillage treatments, the PLOW treatment had greater dissolved terbufos concentration than the NOTILL treatment after 20 min of runoff.