Sidedressed Dairy Manure Effects on Corn Yield and Residual Soil Nitrate

Abstract

Application of livestock manure to an annual crop such as corn is typically limited to relatively short periods in the fall after harvest or in the spring before planting. Direct incorporation or injection into a growing corn crop at sidedress time offers another window of time for manure application—one that avoids planting delays associated with spring application and may reduce potential for nitrate leaching. We established a 2-year field study in northwestern Vermont to compare sidedressed liquid dairy manure directly incorporated with spreader-mounted S-tine cultivators (SD-Incorp) or surface applied (SD-Surf) to preplant-incorporated manure (PP-Incorp) and sidedressed fertilizer N (SD-FertN) to assess effects on corn silage yields, N uptake, and residual soil nitrate. The PP-Incorp manure N rate was higher than SD (212 vs. 150 kg ha−1) in Year 1 but similar (270 and 256 kg ha−1) in Year 2. In Year 1, N uptake for PP and SD-Incorp was similar and greater than SD-Surf and Control (no manure or additional fertilizer N); corn silage yields showed similar but nonsignificant trends. In Year 2, yield for SD-Incorp was equal to other manure and fertilizer N treatments and greater than Control; effects on N uptake were similar except that PP-Incorp was greater than SD manure. Postharvest residual NO3-N in the 1.2-m soil profile was highest in PP-Incorp and SD-FertN treatments; over-winter decreases in profile NO3-N were greater from SD-FertN than from incorporated manure treatments, suggesting higher leaching or denitrification losses. These results show that sidedressed manure can supply adequate N to meet the needs of a corn silage crop and may reduce excess residual NO3-N and potential for N losses.