The Contrasting Effects of Alum‐Treated Chicken Manures and KH2PO4 on Phosphorus Behavior in Soils

• Published in: Journal of environmental quality Vol. 47; no. 2; pp. 345 - 352
• Main Authors: Huang, Lidong, Yang, Junming, Xu, Yuting, Lei, Jiayan, Luo, Xiaoshan, Cade‐Menun, Barbara J.
• Format: Journal Article
• Language: English
• Published: United States The American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc 01.03.2018
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2017.08.0314

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 free‐ranging 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 alum‐organic P complexes may reduce P solubility. By comparing alum‐treated KH2PO4 and manures, it appears that organic matter in manure could interfere with the formation of Al‐PO4 complexes. Core Ideas Alum reduced WSP from soils amended with manure more effectively than KH2PO4. Alum treatment increased P in the Al‐P fraction only in soils with KH2PO4. Alum could stabilize alum‐organic P complexes in chicken manure to resist degradation.