U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
2005
Citation
Agron. J. 97:542–548 (2005).
Abstract
To utilize manure P for crop production, P release and plant availability needs to be quantified. An incubation study was conducted to determine P availability from swine (Sus scrofa) and cattle (Bos taurus) feedlot manure in three soils. Treatments for each manure included temperature (11, 18, 25, and 32°C), water regime [constant 60% water-filled pore space (WFPS) vs. four dry-down cycles of 60 to 30% WFPS], time, and soils (Catlin silt loam, Sharpsburg silty clay loam, and Valentine fine sand). In another study, synthetic P fertilizer was used to determine the fraction of P that becomes unavailable with time to compare with manure P. Time, soil, and manure application were factors that influenced soil test P and water-soluble P during incubation. At the low synthetic P fertilizer rate of 6 μg g‒1, about 12 kg P ha‒1, none of the applied P remained available in the Catlin soil while about one-third remained plant available in the Sharpsburg soil and two-thirds in the Valentine soil. At the high P rate, 68 mg kg‒1, 38 to 83% of fertilizer P remained available in the three soils. Phosphorus availability was 60 to 100% of applied cattle manure P and 52 to 100% of swine slurry P in the three soils. Phosphorus availability in the Sharpsburg soil was 100% of P in both manure types. Phosphorus availability from manure is high, and manure can be used similar to inorganic P fertilizer in soils where P-based application is made in areas susceptible to P loss in runoff. In P-deficient soils, a P availability of 70% should be used.