Continuous application of fertilizer over four decades on yield, physical and chemical properties of swell - shrink soil under finger millet – maize cropping sequence

Long term fertilizer applications and continuous cropping system of Maize - Finger millet (44 years of cropping sequence) has a significant impact on yield and nutrient balance on a soil system. The investigation assessed the effect of long term fertilizer usage on yield and nutrient balance through different treatments such as different doses of NPK (50%, 100% and 150%), NPK along with organic manure, omission of K, PK, addition of Zn along with NPK and omission of S from major nutrients. Application of inorganic NPK fertilizers at graded levels from 50 to 150% NPK increased the grain and straw yield of finger millet and maize. Under the integrated nutrient management practice (100% NPK+FYM),the percent increased grain yield was 17.08 in finger millet and 12.62 in maize over 100 % NPK indicating that INM is the best way of maximize the yield continuously in intensive cropping systems. Under this treatment, the soil available nutrient status was observed high. In INM treatment, possibly the added FYM, might have contributed directly in appreciable amounts of major and micronutrients to the soil and enhanced yields. The status of available N was highest under 100% NPK + FYM, followed by 100% NPK. Continuous addition of N alone did not influence available N, instead reduced available N when compared to NPK treatments. Addition of fertilizer P in progressive levels such as 50, 100 and 150% NPK levels has increased the soil available P (22.62 % in finger millet and 26.35 % in maize) over 100 per cent NPK. Also, addition of different levels of K has improved the soil available K (18.32 % in finger millet and 14.41 % in maize) when compared to 100 % NPK.