Effect of long-term use of chemical fertilizers with and without organics on forms of soil acidity, phosphorus adsorption and crop yields in an acid soil

The effect of continuous application of chemical fertilizers with and without farmyard manure (FYM) and lime on different forms of soil acidity, phosphorus adsorption and crop yields was studied in a long-term field experiment initiated during rabi 1972–73. The imbalanced use of inorganic fertilizers continuously for 29 cropping years led to the deterioration of soil health that rendered the present soil unproductive for further cultivation. Continuous addition of 100% N alone (urea) caused maximum damage and not even a single grain of maize or wheat could be harvested in this treatment. It was due to the increased exchangeable acidity and exchangeable aluminium in the soil. Continuous omission of K in fertilizer schedule for 29 years resulted in about 50 and 32% reduction in maize and wheat grain yield, respectively, over 100% NPK treatment. Addition of lime or FYM, along with recommended doses of chemical fertilizers, significantly improved the soil productivity. Application of lime increased soil pH and significantly reduced all type of soil acidity with most conspicuous effect observed on exchangeable acidity. The use of FYM, on the other hand, had a moderate effect on exchangeable acidity as compared to that in the treatment of NPK application alone. Both these treatments maintained better nutrient availability and sustained higher grain yields over the soils where only chemical fertilizers were applied. Addition of 100% N alone resulted in maximum phosphorus adsorption (98%) and soils with 100% NPK + lime resulted in lowest P adsorption.