Submitted to: Geoderma
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/15/2010
Publication Date: 3/11/2010
Publication URL: DOI:10.1016/j.geoderma.2010.02.019
Citation: Pavinato, P.S., Dao, T.H., Rosolem, C.A. 2010. Tillage and phosphorus management effects on enzyme-labile bioactive phosphorus availability in brazilian cerrado oxisols and temperature zone typic hapludults. Geoderma. 156(3-4):207-215. Interpretive Summary: Phosphorus is an essential element which can limit crop growth if it is provided in inadequate amounts or an environmental contaminant, if present in excess. Soil management system has a direct effect on the behavior of phosphorus in soils. In no-till crop production systems, plant residues and residue-derived organic matter accumulate at the surface and in the near-surface zone. Therefore, no-tillage can change the availability of P in soil, mainly because of residue-P accumulation in the near-surface soil layer, and as plant residues decompose and release the P contained within. In addition, organic compounds are produced during the decomposition of crop residues, which can compete for sites in soil that bind with phosphate, resulting in more phosphate being in solution for plants and microbial to use. In a conventional crop production system, tillage incorporates and redistributes the organic residues and residue-borne nutrients throughout the tilled soil layer. The intimate soil-residues contact enhances rapid microbial decomposition of the organic matter and loss of C from the soil and crop residue-P and organic anions are more dispersed throughout the tilled layer by the tillage operation. Tillage method altered soil P retention characteristics in the near surface zone; reduced sorption and increases in enzyme-labile organic P forms were related to organic matter sequestered in soils under no-tillage management. Estimates of bioactive P fractions using a phytases assay showed it to be an effective method to determine P availability in soil, particularly in soils that are low in organic matter while having an extensive P-fixing capacity. Improved organic matter storage and reduced tillage would improve the availability and the efficacy of phosphorus that was added as inorganic fertilizer P or as organic P in animal manure.
Technical Abstract: Tillage management practices have a direct effect on the behavior and availability of soil nutrients. Phosphorus (P) is an essential element in crop growth which can be growth-limiting or an environmental contaminant, if present in excess. Sorption and availability of various soil P forms were evaluated in an incubation and fractionation study of three soils with distinct biogeochemical characteristics and land management history. Ortho-phosphate and inositol hexa-kis-phosphate were strongly sorbed by all soils and the process was well described by the Langmuir sorption model. Soil maximum P adsorption capacity was 200, 800, and 1200 mg kg-1 for the Typic Hapludults and the Oxisols (i.e., Latossolo Vermelho-Amarelo and Latossolo Vermelho) soils, respectively. Tillage method altered soil P retention characteristics in the near surface zone; reduced sorption and increased in ligand-exchangeable and enzyme-labile organic P forms were related to organic matter sequestered in Oxisols under no-tillage management. Estimates of bioactive P fractions using a ligand-based phytases hydrolysis assay showed it to be an effective method to determine P availability in soil, particularly in Cerrado Oxisols that were low in organic matter while having an extensive P-fixing capacity.