Response of Crops to Applied Potassium and Estimation of Critical Limits in Vertisols

摘要

Field experiments were conducted to study the response of crops to applied potassium(K)and estimate the critical limit of available K for Vertisols with different cropping systems,namely,soybean-wheat and rice-wheat at Bhopal,rice-wheat at Raipur,rice-rice at Jagtial,and soybean-wheat at Jabalpur with graded doses of K.Nitrogen(N)and phosphorus(P)were supplied as per the requirement of crops.Results revealed that rice responded to applied K in the farmers’fields at different centers.Increase in yield was significant up to 40 kg ha-1 at Raipur and rabi rice of Jagtial;however,in case of Bhopal all the crops and kharif rice at Jagtial responded up to 80 kg ha”1 of applied K.In rabi season,wheat responded up to 40 kg K ha”1 at Jabalpur,whereas at Bhopal response was noted at 80 kg K ha”1.Crop response to applied K during kharif was larger than during rabi season on the same field.Decline in available status of K occurring due to wetting is probably the reason for larger response of crop during wet season(kharif).Critical level of K deficiency in Vertisols computed using Cate and Nelson's graphical procedure for IN neutral ammonium acetate(IN NH4OAc,pH 7.0)was 335 kg K ha”1 which was closer to 337 kg K ha”1 using statistical procedure of the same authors.Higher critical level vis-a-vis the current value of 280 kg K ha”1 suggests for a reworking of 4Rs of K fertilization as current inadequate K could pose a threat to sustainability of the cropping systems in Vertisols.