Assessing on-farm efficiency and economics of fertilizer N, P and K in rice wheat systems of India

On-farm experiments were conducted in the Indian districts of Ludhiana (Punjab province), Karnal (Haryana province), Rampur, Faizabad, and Banda (Uttar Pradesh province), Ranchi (Jharkhand province) and Raipur (Chattisgarh province) to (i) measure grain output per unit of fertilizer-use through agronomic efficiency (AE) and partial factor productivity (PFP), and (ii) elucidate the economics of N, P and K applications in rice-wheat systems through marginal analysis. Five treatments of fertilizer N-P-K, i.e. un-fertilized control (0-0-0), N (N-0-0), NP (N-P-0), NK (N-0-K) and NPK (N-P-K) were tested on 81 farmers' fields during 1999 and 2000. The levels of N-P-K used were as per locally recommended rates. The AE of applied nutrients, in rice varied from 4.3 kg grain kg(-1) in Ranchi to 14.7 kg grain kg(-1) in Faizabad for N, from 12.8 kg grain kg(-1) in Rampur to 51.7 kg grain kg(-1) in Raipur for P, and from 7.7 kg grain kg(-1) in Ludhiana to 42.6 kg grain kg(-1) in Ranchi for K. In wheat, AE for N varied from 5.0 kg grain kg(-1) in Banda to 13.1 kg grain kg(-1) in Kamal, for P from 15.2 kg grain kg(-1) in Karnal to 61.3 kg grain kg(-1) in Ranchi, and for K from 4.9 kg grain kg(-1) in Kamal to 22.8 kg grain kg(-1) in Faizabad. The marginal profits earned per rupee invested on fertilizer application varied from Rs. 1.63 in Ranchi to Rs. 8.04 in Samastipur for N alone, from Rs. 4.00 in Ranchi to Rs. 9.48 in Samastipur for NP, from Rs. 3.94 in Raipur to Rs. 7.60 in Ranchi for NK and from Rs. 4.96 in Raipur to Rs. 9.69 in Samastipur for NPK. Grain yield in control plots (i.e. Y-0) exhibited a positive correlation with soil organic C (SOC) (r = 0.34, 0.42 in rice and wheat, respectively), available N (r = 0.53, 0.49 in rice and wheat, respectively), P (r = 0.66, 0.56 in rice and wheat, respectively), and K (r = 0.55, 0.50 in rice and wheat, respectively) contents. Both rice and wheat responded to applied NPK. However, the magnitude of the response to applied NPK decreased as Y-0 increased. Native nutrient supplying capacity of the soil for N was positive at all the locations, but for P and K, it was either negative or very small. (C) 2002 Elsevier Science B.V. All rights reserved.