Department of Soils, Haryana Agricultural University, Hissar, 125004, Haryana
In a long-term field experiment to study the uptake and depletion pattern of added and native soil potassium in a wheat-pearl millet rotation, it was observed that the application of N and P alone and in combination with K enhanced the uptake of potassium. Contribution of the non-exchangeable form towards total potassium removal was about 90% which decreased to about 70% with the use of potassic fertilizer. The available K declined from 620 to 350 kg/ha after eleven crops (six wheat+five pearl millet). Results of a laboratory study carried out on soils from the experimental plots indicated that cumulative potassium release measured after five successive extractions was higher in potassium treated soils as compared to untreated ones. The difference was only in the first extraction representing the exchangeable K after which the release became independent of the available potassium of the soil.
Depletion of soil potassium, long-term cropping, release of non-exchangeable potassium
