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 NO3-N in drainage the 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, NO3-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.