Effects of Different Plant Residues and Manures on Potassium Pools Distribution of Two Clayey Soils under Different Moisture Conditions

Addition of organic residues to soil in organic farming may change soil K status and subsequently its availability and cycling. For this purpose, an experiment was done as factorial in completely randomized design with application of 11 organic materials (alfalfa, barley, pea and broad bean residues and sheep, cow, camel, poultry, pigeon and quail manures and vermicompost) in two clayey soils of Darab and Sepidan (Fars province) under two moisture conditions (field capacity and saturation) with three replicates. First, 2 g of organic materials was added to 100 g of soil samples and incubated for two months under field capacity and saturation conditions and laboratory condition (22±2˚C) and then the contents of soluble, exchangeable and non-exchangeable K were determined. Results indicated that all organic materials, except for vermicompost, alfalfa residue and camel manure increased soluble K and the highest increase was related to sheep manure up to 228 mg kg-1. The content of exchangeable K was increased with all organic residues application from 70 to 730 mg kg-1. The content of non-exchangeable K was also increased with organic residues application and the highest and lowest increases were found for poultry manure and camel manure, respectively. Generally, the contents of soluble and exchangeable K of Darab soil and non-exchangeable K of Sepidan soil were more affected by organic materials application. The saturation condition increased exchangeable K and decreased soluble and non-exchangeable K. Increase in the content of soluble K and soil salinity should be considered for organic amendments application to soils with high leaching potential and for salt sensitive plants.