Nitrogen Recovery and Partitioning with Different Rates and Methods of Sidedressed Manure

Animal manure is an important source of N for crops in areas with intensive livestock production. Variable manure N availability can incite over‐application of manure or supplemental fertilizer leading to low N recovery and possible negative environmental and economic impacts. To improve manure N use efficiency, the effects of rate and method of sidedress application of liquid swine ( Sus scrofa ) manure (LSM) on N recovery by corn ( Zea mays L.) were determined. We used in‐row injection (INJ) or topdressing (TD) to sidedress LSM from 1999 to 2002 at rates ranging from 0 to 93.5 m 3 ha −1 , and measured grain N uptake and NO 3 –N in drainage tile water, stalks, and topsoil postharvest. Apparent recovery of manure total N (LSM‐N) ranged from 0 to 57% and was greatest with injection of 37.4 m 3 ha −1 (194 kg LSM‐N ha −1 ). Injection rate to achieve 95% of maximum grain yield averaged 216 kg LSM‐N ha −1 over 4 yr. Transport of LSM‐N to ground‐ and surface waters was minimized when sidedressed at or below rates for optimal yield. When injected N exceeded crop demand, NO 3 –N increased to over 10 mg kg −1 in topsoil, 20 mg L −1 in drainage water, and to excessive (3.6 g kg −1 ) levels in stalks. Due to greater LSM‐N recovery, injection (59%) is recommended rather than topdress (41%) for sidedress application of manure.