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The contrasting effects of alum-treated chicken manures and KH2PO4 on phosphorus behavior in soils

Huang, L., Yang, J., Xu, Y., Lei, Y., Luo, X., and Cade-Menun, B.J. 2018. The contrasting effects of alum-treated chicken manures and KH2PO4 on phosphorus behavior in soils. J. Environ. Qual. 47:345-352.

Abstract

© American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Alum [KAl(SO4)2×12H2O] is often added to chicken manure to limit P solubility after land application. This is generally ascribed to the formation of Al-PO4 complexes. However, Al-PO4 complex formation could be affected by the matrix of chicken manure, which varies with animal diet. Alum was added to KH2PO4 (as a reference material) and two manures from typical chicken farms in China, one from an intensive farm (CMIF) and another from freeranging chickens (CMFR). These were subsequently incubated with soils for 100 d to investigate P transformations. Alum reduced water-soluble colorimetrically reactive phosphorus (RP) from soils amended with manure more effectively than in soils amended with KH2PO4. Alum addition lowered Mehlich-3 RP in soils with CMFR but had no influence on Mehlich-3 RP in CMIF- or KH2PO4-amended soils. A comparison of P in digested Mehlich-3 extracts with RP in undigested samples showed significantly increased P in digests of alum-treated CMFR only. Fractionation data indicated that alum treatment increased P in the NH4F-RP (Al-P) fraction only in soils with KH2PO4, but not in soils with manure treatments. Furthermore, NaOH-extracted nonreactive P was markedly higher in soil with alum-treated CMFR relative to normal CMFR. The CMFR manure was assumed to contain higher concentrations of organic P because these chickens were fed grains only. These results suggest that the formation of alumorganic P complexes may reduce P solubility. By comparing alumtreated KH2PO4 and manures, it appears that organic matter in manure could interfere with the formation of Al-PO4 complexes.

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