Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2010
Publication Date: 5/1/2010
Citation: Wienhold, B.J., Gilley, J.E. 2010. Runoff Losses of N and P After Low Phosphorus Swine Slurry Application to No-Tillage Sorghum. Soil Science. 175:201-206.
Interpretive Summary: Manure is a byproduct of swine production that can be used as a fertilizer for crops. Once applied to a field there is a potential for nutrients in manure to pollute nearby water resources. Corn varieties have been developed that reduce the amount of phosphorus contained in manure. A study was conducted to compare nutrient losses from no-tillage sorghum plots after application of manure from swine fed a traditional diet, manure from swine fed a highly available phosphorus diet, or inorganic fertilizer. After each rain event during the 1999, 2000, 2001 growing seasons, runoff samples were collected and analyzed for nitrogen and phosphorus. There were differences among the years but runoff and sediment losses from these no-tillage plots were very low. Nutrient losses in runoff varied among years but were similar among the three nutrients treatments each year. Losses of phosphorus and nitrogen in runoff were very low and represented less than one-percent of the phosphorus and nitrogen applied. Feeding highly available phosphorus corn resulted in manure with lower phosphorus content but there was no significant reduction in runoff losses of phosphorus.
Technical Abstract: Swine (Sus scrofa) manure can serve as a fertilizer source for crop production. Manure typically contains more P relative to N than the crop requires. This imbalance often results in accumulation of soil P creating the potential for negative environmental impacts due to P losses in runoff. Low phytate corn (LPC) (Zea mays L.) has been developed to improve bioavailability of grain P resulting in lower P content in manure. A three-year study was conducted to compare runoff losses of NO3-N, NH4-N, total N, dissolved P, and total P under natural rainfall conditions from no-tillage sorghum plots [Sorghum bicolor (L.) Moench] receiving inorganic fertilizer, manure from swine fed a LPC diet, or manure from swine fed a traditional corn (TC) diet. Runoff varied among years (26.5 mm in 1999, 14.2 mm in 2000, and 1.6 mm in 2001) and was similar among treatments within a year. Sediment loss also varied among years (2.9 kg ha-1 in 1999, 0.9 kg ha-1 in 2000, and 0.4 kg ha-1 in 2001) and was similar among treatments within a year. Runoff nutrient losses differed among years but were similar among treatments within a year. Runoff losses of NO3-N (5.3 g ha-1 in 1999, 1.0 g ha-1 in 2000, and 2.6 g ha-1 in 2001), NH4-N (2.9 g ha-1 in 1999, 0.6 g ha-1 in 2000, and 5.6 g ha-1 in 2001), total N (89.7 g ha-1 in 1999, 8.4 g ha-1 in 2000, and 100.2 g ha-1 in 2001), dissolved P (1.5 g ha-1 in 1999, 0.5 g ha-1 in 2000, and 3.1 g ha-1 in 2001), and total P (3.8 g ha-1 in 1999, 0.9 g ha-1 in 2000, and 3.5 g ha-1 in 2001) from these plots were very low and represented much less than 1% of that applied each year. While use of LPC in a swine diet reduces manure P content the reduction did not result in a significant decrease in runoff P.