Herbicide banding and tillage effects on runoff, sediment, and phosphorus losses

Tillage and weed control methods affect hydrology by altering soil surface conditions. The objective of this study was to assess the effects of herbicide banding with interrow cultivation on runoff, sediment, and phosphorus (P) losses for three different tillage systems. Tillage treatments were moldboard- or chisel plow-based and ridge tillage. Tillage direction was up and down the slope of runoff plots and corn (Zea mays L.) was grown for two years. The herbicides alachlor [2-chloro-2'-6'-diethyl-N-(methoxymethyl)-acetanilide] and cyanazine [2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino-2-methylproprionitrile] were applied as a preemargent mixture by eithar broadcasting or banding. All treatments were mechanically cultivated one time. The effects of tillage practice and herbicide application method on runoff water quality were different before and after cultivation. Prior to cultivation, crop residue associated with the ridge till and chisel plow systems reduced runoff, sediment, and P losses compared with the moldboard plow system. Soil cover from weed growth between herbicide treated bands resulted in lower precultivation runoff, sediment, and P losses than broadcast treated plots, especially in the moldboard plow system. For runoff events occurring after cultivation, there were no differences among tillage practices or herbicide application methods on sediment or P losses. Weed cover between herbicide treated bands is effective in reducing runoff and contaminant losses in tillage systems with little existing crop residue and during the period when crop canopy is minimal. There was no yield loss associated with applying herbicides in a band compared with broadcasting.