Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2008
Publication Date: 6/17/2008
Citation: Paschold, J.S., Wienhold, B.J., Mccallister, D.L., Ferguson, R.B. 2008. Crop N and P utilization following application of slurry from swine fed traditional or low phytate corn diets. Agronomy Journal. 100:997-1004.
Interpretive Summary: Swine production generates large amounts of waste. This waste contains nutrients that may serve as fertilizer when applied to agricultural fields. Proper application is difficult because the ratio of nutrients in the waste is different than what a crop requires. Application of waste to meet the nitrogen needs of a crop results in application of excess phosphorus which increases the potential for environmental contamination. Corn containing phosphorus in forms that can be more readily utilized by swine has been developed. Swine fed corn diets with more highly available phosphorus produce waste that has a nitrogen to phosphorus ratio closer to what a crop needs than swine fed traditional corn diets. Two field studies were conducted to compare crop use of nitrogen and phosphorus in waste from swine fed highly available corn diets to that in waste from swine fed traditional corn diets. Sorghum receiving annual applications of highly available phosphorus waste utilized similar amounts of nitrogen and phosphorus as did sorghum receiving traditional waste. Irrigated corn utilized similar amounts of nitrogen and phosphorus from the two waste types the year of application and very little the year following application. These studies demonstrate that highly available corn diets modify the nitrogen to phosphorus ratio in swine waste but crop utilization of these nutrients is similar when compared to traditional corn diets. Use of highly available corn in swine diets results in waste containing nitrogen and phosphorus that is readily utilized by the crop while reducing the rate of phosphorus accumulation in swine waste treated soils.
Technical Abstract: Field application of swine (Sus scrofa) slurry provides essential nutrients for crop production. The N:P ratio for slurry is lower than needed by most crops resulting in P accumulation when applied at N rates required for crop growth. Low phytate corn (Zea mays L.) (LPC) contains similar amounts of total P but less phytate P than traditional corn (TC) resulting in improved P bioavailability and reduced P excretion by monogastric animals. While manure from swine fed LPC diets has a higher N:P ratio than that from TC diets, field studies comparing crop utilization by nutrients from LPC manure have not been conducted. A field study was conducted to compare N and P utilization by no-tillage rainfed sorghum (Sorghum bicolor (L.) Moench.) receiving three annual surface applications of nutrients (inorganic fertilizer, LPC slurry, and TC slurry) and by irrigated corn receiving one incorporated application of nutrients. Sorghum grain and total dry matter N utilization exhibited a year-by-treatment interaction but total dry matter N utilization was similar for both manure types in all years (61.2 ± 2.6% for TC and 53.8 ± 2.6% for LPC). Grain P utilization was similar for inorganic fertilizer and manure but differed among years (44.4 ± 7.0% in 1999, 25.1 ± 1.4% in 2000, and 57.0 ± 2.2% in 2001). Corn grain N and P utilization did not differ among nutrient sources in the year of application (50.7 ± 2.4% for N and 40.4 ± 3.0 for P) and increased little in the year following application (62.2 ± 3.0% for N and 50.2 ± 4.5% for P). Crop N and P utilization from LPC manure and TC manure is similar and nutrient guidelines developed for TC swine slurry should also apply for LPC slurry.