Plant Availability of Phosphorus in Sewage Sludge Compost1
- J. L. McCoy,
- L. J. Sikora and
- R. R. Weil2
Field and greenhouse studies were conducted to compare the effectiveness of Blue Plains sewage sludge compost (BLU), Parkway sewage sludge compost (PAR), and triple superphosphate (TSP) as sources of P for corn. These amendments were applied to a Sassafras sandy loam (Typic Hapludults) in a field study and to the Sassafras soil and a Christiana silty clay loam (Typic Paleudults) in a greenhouse study. First-year application rates in the field study ranged from 0 to 1500 kg total P/ha. Plots were split the second year with one-half receiving no additional P and one-half receiving P equal to 1st-yr rates. Nitrogen as NH4NO3 was applied at variable rates to plots so that the total assumed available N equaled 180 and 219 kg N/ha for the 1st and 2nd yr, respectively. Dry matter yield and P uptake were measured at the eight-leaf stage (V8) and at maturity. Below the 100 kg P/ha rate, there were no significant differences in P uptake or yield among the different sources and rates of P. Above the 100 kg P/ha rate, TSP but not the composts, significantly increased growth and P uptake by corn in both field and greenhouse studies. The TSP was approximately four to seven times more effective than either compost in raising tissue P concentration in corn (Zea mays L) ear leaves. A maximum of 2.05 and 11.2% of the P applied as compost and TSP, respectively, was taken up by the corn. Soil P extracted by the dilute double acid (0.5 M HCl and 0.0125 M H2SO4) and 0.5 M NaHCO3 methods increased with increasing P application from all sources. Extractable soil P by both methods correlated well with total P uptake from TSP but did not correlate well with P uptake from the composts. A P fractionation indicated that most of the compost P was associated with Fe and Al and only 2 to 5% was in organic forms. The Fe-bound P fraction of the amended soils increased with increasing P application from all sources. Two factors appeared to control the P uptake response of corn: the treatment of the wastewater to remove P at the sewage treatment plant, and the P fixing capcity of the soil.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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