Leaching of Potassium in Illitic Soil Profiles under Different Crop Rotations

The correlation between sorption and mobility of K in illitic soils has been used to compare its leaching in profiles under eight different crop rotations. K saturation of the CEC was estimated in 15 cm soil layers up to a depth of 225 cm before and after rainy seasons. These data indicated that amount of fertilizer K applied after the rainy season determined K saturation status of the plough layer, while K application to the summer and rainy season crops determined K saturation of 30–180 cm layer. After the monsoon rains, a significant increase in the K saturation of only 180–225 cm layer was observed. However, K saturation values in this layer did not differ statistically under different crop rotations; thus providing an evidence that K released from illitic minerals during rainy season is leached up to 225 cm or beyond. Fertilization and cropping activities in the profile do not affect leaching of K up to this depth.