Corn Silage Yield, Shallow Groundwater Quality and Soil Properties Under Different Methods and Times of Manure Application

The effects of four method-and-time combinations of dairy cattle liquid manure application on corn silage yields, shallow groundwater quality, and soil composition were studied in a Typic Haplaquent soil during a three-year period and for two additional residual years when no treatments were applied. Manure was applied at the rate of 90 t ha~^y~^ by fall plowdown, preplant broadcast followed by disking, and post-emergent sidedressing by injection and broadcasting between rows. Additional treatments included a control and preplant broadcast chemical fertilizer application to provide approximately the same smount of NH^-N as the manure. Manure applied by the above methods had no significant effect on yields. This was mainly attributed to the previous alfalfa crop at the experimental site. Yields tended to be slightly higher with the two post-emergent sidedress treatments compared to the fall-plow and preplant broadcast treatments. Shallow (1.2 m deep) groundwater NO^-N concentrations were always greater than the drinking water limit of 10 mg L~^ with all treatments, including the control, indicating that this limit is unlikely to be met with the normally recommended manure and fertilizer applications for corn production. Treatment effects on soil composition were not significant at the moderate manure application rate used in this study.