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Plant availability of phosphorus in swine slurry and cattle feedlot manure

Eghball, B., Wienhold, B.J., Woodbury, B.L., Eigenberg, R.A.
Agronomy journal 2005 v.97 no.2 pp. 542
pig manure, cattle manure, nutrient availability, plants, phosphorus, plant nutrition, nutrient uptake, soil temperature, soil water content, temporal variation, soil texture, runoff
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.