TECHNICAL ARTICLESEXTRACTABLE PHOSPHORUS FOLLOWING SOIL AMENDMENT WITH MANURE FROM SWINE FED LOW-PHYTATE CORNGollany, H. T.1; Schmitt, M. A.2; Bloom, P. R.2; Randall, G. W.2; Carter, P. R.3Author Information 1Columbia Plateau Conservation Research Center, USDA-ARS, P.O. Box 370, Pendleton, OR 97801. 2Dept. of Soil, Water, and Climate, University of Minnesota. 3Agronomy Science Manager, Pioneer Hi-Bred International, Johnston, IA. Dr. Gollany is corresponding author. E-mail: [email protected] Received March 13, 2003; accepted June 24, 2003. Soil Science: September 2003 - Volume 168 - Issue 9 - p 606-616 doi: 10.1097/01.ss.0000090801.06903.67 Buy Metrics Abstract Manure application rate recommendations have been based almost exclusively on nitrogen (N) management considerations, which can result in over-application of phosphorus (P) and its accumulation in soil. Low-phytate (LP) corn (Zea mays L.) was introduced into swine (Sus scrofa domesticus) feed to reduce the amount of P in manure. Unlike ruminants, swine cannot utilize phytate, the major form of P in normal hybrid corn. The objectives of this study were to determine extractable P following swine manure application from different manure sources and compare the relative P availability of LP-manure to standard (S) manure. A laboratory incubation study was conducted using a Waukegan silt loam, a Verndale sandy loam soil, and five levels of total P (Pt) from three P sources (KH2PO4, S-manure, LP-manure). Extractable P from manures of swine fed low-phytate corn and standard corn diets were compared with a soluble P (KH2PO4) source. Slope ratio procedure was used to determine a phosphorus availability index (PAI). The effect of the P application rate on extractable Bray-1 P was linear (r2>0.97). Small but significant P mineralization was observed for the Verndale sandy loam soil. Mineralization of organic P was detected only at the highest LP-manure application rate for the Waukegan silt loam soil. Relative to KH2PO4, the LP-manure and S-manure had PAI of 0.55 and 0.61, respectively. Swine manure P availability was about 60% that of the KH2PO4 source for both manure sources. The total P concentration for the LP-manure was 42% lower than that for the S-manure. The important factor in the difference between manure sources is the 42% lower total P content for the LPmanure, not a difference in availability. Further evaluation of available P from LP-manure is needed under field conditions. © 2003 Lippincott Williams & Wilkins, Inc.