Read J J, Brink G E, Adeli A, McGowen S L
USDA-ARS, Genetics and Precision Agriculture Research Unit, P.O. Box 5367, Mississippi State, MS 39762, USA.
J Environ Qual. 2008 Sep-Oct;37(5 Suppl):S180-9. doi: 10.2134/jeq2007.0553.
Bermudagrass [Cynodon dactylon (L.) Pers.] hay production is integral to manure management on southeastern swine farms. But swine effluent timing must be synchronized with crop nitrogen (N) demands to decrease the potential for soil N accumulation and nitrate (NO(3)) leaching. Field studies were conducted on a Prentiss sandy loam (coarse-loamy, siliceous, semiactive, thermic Glossic Fragiudult) to determine N-use efficiency (NUE) and residual soil NO(3)-N. Two rates of 10 and 20 cm yr(- 1) ( approximately 260 and 480 kg ha(-1) N, respectively) were applied in four timing treatments: April to September (full season), April to May, June to July, and August to September. Plots were harvested every 7 to 9 wk beginning in June, and soil was sampled in fall after a killing frost and the following spring. Annual uptake of N and P were least in the August to September timing treatment. Doubling the effluent rate increased N uptake 112% in 2000 (from 130 to 276 kg ha(-1)) and 53% in 2001 (from 190 to 290 kg ha(-1)), suggesting 10-cm did not meet crop N demands. Due to low rainfall and decreased forage yield in 2000, doubling the effluent rate led to increased soil NO(3)-N to 30-cm depth in fall 2000 and spring 2001. Averaged across timing treatments, soil NO(3)-N at 5-cm depth ranged from 8.5 mg kg(-1) in non-irrigated controls to 39.6 mg kg(-1) with 20-cm effluent. Results indicate low NUE in the order of 30 to 38% for applications in August to September increase the risk to surface and ground water quality from excess N remaining in soil.
狗牙根[狗牙根（L.）Pers.]干草生产是东南部养猪场粪便管理不可或缺的一部分。但是猪粪废水排放时间必须与作物的氮（N）需求同步，以降低土壤氮积累和硝酸盐（NO₃）淋失的可能性。在普伦蒂斯砂壤土（粗壤质、硅质、半活性、热性舌状脆磐土）上进行了田间研究，以确定氮利用效率（NUE）和土壤残留硝态氮（NO₃-N）。以10厘米/年和20厘米/年两种速率（分别约为260千克/公顷和480千克/公顷氮）进行四种排放时间处理：4月至9月（整个季节）、4月至5月、6月至7月以及8月至9月。从6月开始，每隔7至9周对小区进行收割，并在霜降后的秋季和次年春季采集土壤样本。8月至9月排放时间处理下，氮和磷的年吸收量最少。将废水排放速率加倍，2000年氮吸收量增加了112%（从130千克/公顷增至276千克/公顷），2001年增加了53%（从190千克/公顷增至290千克/公顷），这表明10厘米/年的排放速率无法满足作物对氮的需求。由于2000年降雨量少且牧草产量降低，废水排放速率加倍导致2000年秋季和2001年春季土壤中30厘米深度内的硝态氮增加。在所有排放时间处理中，5厘米深度土壤中的硝态氮含量，非灌溉对照为8.5毫克/千克，20厘米废水排放处理为39.6毫克/千克。结果表明，8月至9月进行施肥时，氮利用效率较低，约为30%至38%，这增加了土壤中过量氮对地表水和地下水水质造成污染的风险。
