Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2010
Publication Date: 7/6/2010
Citation: Cambardella, C.A., Moorman, T.B., Singer, J.W. 2010. Soil Nitrogen Response to Coupling Cover Crops with Manure Injection. Nutrient Cycling in Agroecosystems. 87:383-393. Interpretive Summary: Large-scale pork production is a major agricultural enterprise in the Midwest. Large numbers of confined hogs produce about 50 million tons per year of swine manure in Iowa alone. The most commonly used manure management practice in the Midwest involves fall application to land where corn will be grown in the subsequent growing season. Fall planted annual cover crops can capture manure nitrogen (N) and release it the following spring, helping to synchronize manure N availabilty with corn N uptake. We conducted experiments to evaluate the effects of integrating a rye/oat cover crop with liquid swine manure injection on retention of manure N in a corn-soybean cropping system. We found that a fall planted rye/oat cover crop reduced soil inorganic N after liquid swine manure injection. Cover crop effects on soil N were observed within a month after application and persisted into the following spring. Results of this research will impact producer decisions about nutrient management in farming systems that utilize manure.
Technical Abstract: Coupling winter small grain cover crops (CC) with manure (M) application may increase retention of manure nitrogen (N) in corn-soybean cropping systems. The objective of this research was to quantify soil N changes after application of liquid swine M (Sus scrofa L.) at target N rates of 112, 224, and 336 kg N ha-1 with and without a CC. A winter rye (Secale cereale L.)-oat (Avena sativa L.) CC was established prior to fall M injection. Surface soil (0-20 cm) inorganic N concentrations were quantified every week for up to 6 weeks after M application in 2005 and 2006. Soil profile (0-120 cm in 5, 20-cm depth increments) inorganic N, total N, total organic carbon and bulk density were quantified for each depth increment in the fall before M application and before the CC was killed the following spring. Surface soil inorganic N on the day of application averaged 318 mg N kg-1 soil in 2005 and 186 mg N kg-1 soil in 2006 and stabilized at 150 mg N kg-1 soil in both years through mid-November. Surface soil NO3-N concentrations in the M band were more than 30 times higher in the fall of 2005 than in 2006. The CC reduced surface soil NO3-N concentrations after manure application by 32% and 67% in mid- November 2005 and 2006, respectively. Manure applied at 224 kg N ha-1 without a CC had significantly more soil profile inorganic-N (480 kg N ha-1) in the spring after M application than manured soils with a CC for the 112 (298 kg N ha-1) and 224 (281 kg N ha-1) N rates, and equivalent inorganic N to the 336 (433 kg N ha-1) N rate. We conclude that CC can enhance plant nutrient uptake and reduce N leaching potential in farming systems utilizing manure.