Gill, Roopinder SinghHarpreet Kaur2019-10-102019-10-102019http://krishikosh.egranth.ac.in/handle/1/5810130569The field and pot experiments were conducted to study the effect of potassium (K) application on availability of K to wheat and contribution of exchangeable and non exchangeable K towards wheat nutrition. In pot experiment, twenty bulk soil samples having a range in available K were used and K was applied @ 0, 15, 20, 25 and 30 kg K ha-1soil. Wheat (cv PBW 725) was grown as a test crop. The different potassium fractions i.e. water soluble, exchangeable, available and non exchangeable K were determined. The amount of corresponding forms ranged between 8.86 to 23.7, 66.1 to 379.8, 75.1 to 403.1 and 898.4 to 1861.3 mg kg-1 soil in these soils. The mean grain yield varied from 8.43 to 20.58 g pot-1. All the forms of K showed positive and significant correlation with grain & straw yield, K content and K uptake. The highest positive and significant correlation of wheat grain yield was found to be with water soluble K (r = 0.905*) followed by available K (r = 0.836*), exchangeable K (r = 0.831*) and non exchangeable K (0.815*). In K deficient oils, grain yield of wheat increased significantly with graded levels of applied K. However, in K sufficient soils, grain yield increased significantly up to application of 25 kg K ha-1. In both K deficient and sufficient soils, K concentration and uptake by grain and straw of wheat increased significantly with incremental levels of applied K. About 83.6 per cent variation in grain yield of wheat was due to the combined influence of water soluble and exchangeable potassium while available and non exchangeable form of potassium explained only 2.3 per cent variation in grain yield of wheat. However, in K deficient soils, contribution of non exchangeable K towards grain yield was higher as compared to K sufficient soils. The critical limit of available and non exchangeable potassium for wheat as determined by graphical method was 168 and 1338 kg K ha-1, respectively. The field experiment was conducted at two sites, at the Research Farm of Department of Soil Science, Punjab Agricultural University (PAU), Ludhiana (medium in available potassium i.e. 228.9 kg ha-1) and at Regional Research Station, Gurdaspur (low in available potassium i.e. 125.6 kg ha-1). The K was applied @ 0, 10, 15, 20, 25, 30, 35 and 40 kg K ha-1 soil and wheat (cv PBW 725) was grown as test crop. The mean grain yield in PAU, Ludhiana and RRS, Gurdaspur soil was found 47.5 and 42.5 q ha-1, respectively. In PAU, Ludhiana soil, the significant response of wheat to applied potassium was recorded up to 25 kg K ha-1 soil, however, in RRS, Gurdaspur soil response was recorded up to 40 kg K ha-1. The water soluble, exchangeable, available and non exchangeable K were found to be 13.8, 75.9, 84.5 and 1053.6 mg kg-1 soil, respectively in PAU, Ludhiana soil and 10.1, 61.1, 70.5 and 969.7 mg kg-1 soil, respectively, in RRS, Gurdaspur soil. The kinetics of non-exchangeable K release from ten bulk soil samples having a range in available K was investigated using 0.01 M oxalic acid. The cumulative amount of K released in 200 h ranged between 86 and 253 cmol kg-1 x 10-2. The highest amount of non exchangeable K release (253 cmol kg-1 x 10-2) was found in Mansa soil (sufficient in K) and lowest amount (86 cmol kg-1 x 10-2) was recorded in Gurdaspur soil (deficient in K). Kinetics of non exchangeable K release from soils were adequately described by Elovich, first order, power function and parabolic diffusion models while zero order model was not suitable to describe K release.ennullThesis