Gill, Roopinder SinghManinderdeep Singh2020-02-102020-02-102019http://krishikosh.egranth.ac.in/handle/1/5810142741The effect of long-term fertilizer application on potassium bearing minerals was studied under maize-wheat cropping system. The treatments consisted of control, 100% Nitrogen(N), 100% Nitrogen and Phosphorus(P), 50% Nitrogen, Phosphorus and Potassium(K), 100% NPK, 100% NPK+ farmyard manure (FYM) and 150% NPK. The physico-chemical properties, minerals and potassium fractions were analyzed from the surface soil samples (0-15 cm). The dominant minerals in sand and silt fraction of soil were quartz followed by feldspar and mica, while illite was the major mineral in clay fraction. The weathering of mica and feldspar in sand and silt fraction of soil was more intense in the treatments where potassium was not applied (100% N, 100% NP and control). Similarly, in clay fraction of soil, weathering of illite to vermiculite and smectite due to removal of interlayer potassium resulted in loss of illite in treatments without K application. The available (135.5 kg ha-1), water soluble (56.0 kg ha-1), exchangeable (79.5 kg ha-1), non-exchangeable (2151.1 kg ha-1), fixed (2286.7 kg ha-1) and total potassium (14362.6 kg ha-1) in soils was highest in 100% NPK+FYM treatment and increased with increasing dose of fertilizers. The results further indicated that illite was positively and significantly correlated with non-exchangeable, fixed K and total K in soils. Grain yield of both maize (60.7 q ha-1) and wheat (59.5 q ha -1) was highest in 100% NPK+FYM treatment followed by 150% NPK and 100% NPK treatment. Wheat and maize yield was positively and highly correlated with available, water soluble and exchangeable potassium in soils, indicating the importance of these fractions as plant available forms.enThesis