SEWAGE SLUDGE AS A PHOSPHORUS AMENDMENT FOR SESQUIOXIC SOILS

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Abstract
The objective of this study was to evaluate the effectiveness of sludge P in comparison with inorganic P, as a fertilizer for P-deficient sesquioxic soils. Municipal sewage sludge and monocalcium phosphate (MCP) were applied to two soils—Griffin clay (Typic Haplorthox) and Clovelly sandy clay loam (Tropeptic Haplorthox)—at rates equivalent to 200, 500, and 1,000 kg ha−1 P. Italian ryegrass (Lolium multiflorum) was grown in the soils using a split pot technique, and tops were harvested at 14, 35, 63, 97, 125, 153, 181, and 209 d after commencement of root:soil contact. Yield and concentration of P, N, Ca, Mg, K, and Na in the plant tissue were determined. Both soils exhibited large responses to applied P, with P uptake from sludge treatments being significantly greater (P < 0.05) than MCP treatments in the Griffin soil, and significantly lower than MCP treatments in the Clovelly soil. Rates of P uptake declined rapidly with time in MCP-treated soils, and in sludge-treated soils rates of P uptake increased or declined only slowly. The relative efficiency of sludge P compared with MCP increased from 44 to 90% and 64 to over 100% with time in the Clovelly and Griffin soils, respectively. © Williams & Wilkins 1987. All Rights Reserved.