Crop Rotation, Manure, and Agricultural Chemical Effects on Dryland Crop Yield and SOM over 16 Years in Eastern Nebraska
This chapter examines the effectiveness of using crop rotations and manure as substitutes for fertilizer and describes the effect of crop rotations that include legumes on soil characteristics and crop yields. The experiment was designed to compare chemical-free farming practices that use crop rotation and manure, crop rotation practices that use chemicals, and continuous corn with a chemical-based cropping system. Rotation management systems had higher corn yields than continuous corn; however, crop rotation did not significantly influence soil organic carbon and Kjeldahl nitrogen levels. Plots usually were disked twice to 10 to 15 cm for weed control and incorporation of fertilizer or manure. Soybean yield was substantially lower during the first rotation cycle for the R/Man system compared to the R/FH and R/F management systems. This relationship remained consistent throughout the 16-year period, although yield differences were less between the R/Man system and the other systems.