Potassium leaching in soil as affected by potassium fertilizer rates applied over pearl millet straw

The presence of straw on soil surface affects K cycling in the production system and can affect soil chemistry by modifying K leaching rate and intensity. An experiment was conducted to evaluate K leaching as affected by 30 mm of simulated rain over pearl millet straw receiving several broadcasted K rates. Pearl millet was grown for 55 days in a green house and then cut at soil level intopieces of 3 to 5 cm. Then it was distributed over the soil surface of 20 cm diameter PVC tubes at a rate of 8 t ha(-1). Rates of 0, 40, 80, 120, and 160 kg ha(-1) of K2O were applied over the straw and a 30 mm rain simulated. The straw was collected and analyzed for K contents. The soil was sampled at depths of 0-2, 2-4, 4-8, 812, and 12-20 cm and analyzed for exchangeable K contents. The 30 mm rain was necessary and sufficient to wash the K fertilizer applied over the straw down to the soil surface. K leaching intensity in the soil profile increased with K rates to a depth of 8-12 cm when there was no pearl millet straw on the soil surface. More K reached the soil in pots with straw on the surface, while K leaching decreased.