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 herbic ide banding with interrow cultivation on runoff, sediment, and phosphorus ( P) losses for three different tillage systems. Tillage treatments were mold board- 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 ye ars. The herbicides alachlor [2-chloro-2'-6'-diethyl-N-(methoxymethyl)-acet anilide] and cyanazine [2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amin o-2-methylproprionitrile] were applied as a preemergent mixture by either b roadcasting or banding. All treatments were mechanically cultivated one tim e. The effects of tillage practice and herbicide application method on runo ff water quality were different before and after cultivation. Prior to cult ivation, crop residue associated with the ridge till and chisel plow system s reduced runoff, sediment, and P losses compared with the moldboard plow s ystem. Soil cover from weed growth between herbicide treated bands resulted in lower precultivation runoff, sediment, and P losses than broadcast heat ed plots, especially in the moldboard plow system. For runoff events occurr ing 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 los ses in tillage systems with little existing crop residue and during the per iod when crop canopy is minimal. There was no yield loss associated with ap plying herbicides in a band compared with broadcasting.