Long Term Effects of Continuous Rotational Cropping and Fertilization on Crop Yields and Soil Properties — I. Effects on Crop Yields and Nutrient Uptake

The long term effects of fertilizers, manure and other agrochemicals on the yields of rice-wheat-cowpea in a rotation and nutrients uptake by them are studied at Pantnagar since 1971. The data on yields show that it will be beneficial to reduce the doses of NPK up to 50 per cent in rice and apply full doses to wheat if the fertilizers are in short supply. Nitrogen application alone remarkably increased the yields of rice and wheat. Application of FYM once in a year increased the yields of crops. The general decreasing trends over the years in the yields of rice (3.2 q ha⁻¹a⁻¹) and wheat (1.1 q ha⁻¹ a⁻¹) were noticed. Increase in the minimum temperature during maturity and maximum temperature during flowering reduced the yields of riCe (r = 0.813) and wheat (r = 0.789), respectively. Significant positive correlation coefficients were obtained with available Fe and Mn for riceand with organic matter per cent and available N, P, K, Fe and Mn with wheat yields. The uptake of N, P, K, Fe, Mn and Cu generally, increased with the increase in crop yields.