Effects of soil texture and rates of K input on potassium balance in tropical soil

Abstract

The efficiency of potassium (K) fertilizer use is important in sustainable agriculture and is affected by losses related to soil texture. However, there is no information on how much K is lost by leaching in tropical soil. The effects of rates of fertilizer-K application on K dynamics and budget in a soil-plant system at depths up to 1m were studied in Botucatu, SAo Paulo, Brazil, from 2000 to 2012; soil types were a sandy clay loam (250gclaykg(-1)) and a clay soil (670gclaykg(-1)) under no-till management. The soils were fertilized annually with 0, 25, 50, 75, 100, 125 and 150kgKha(-1). Annual applications of 50-75kgKha(-1) to the sandy clay loam soil and 25-50kgKha(-1) to the clay soil were sufficient to achieve a large grain yield and maintain soil exchangeable K in the soil profile. An annual application of up to 150kgKha(-1) to clay soil does not result in a large amount of leaching below 1-m depth. Non-exchangeable K plays an important role in tropical cropping systems. The increase in rates of fertilizer-K application intensifies losses by leaching below 1m in sandy clay loam soil, which represents 16-52% of the K added as fertilizer. Therefore, because of the considerable leaching potential, splitting the applications of K is an important management strategy to minimize losses and improve the efficiency of K use in tropical soil with small clay contents. Highlights We investigated the effect of soil texture on K movement in the profile. Losses of K were estimated in a cropping system with cover crops. In tropical soil clay content plays an important role in the movement of K in the soil profile. In clay soil K losses are small, but can be up to 52% of the nutrient applied to sandy soil.