ABSTRACT
Aim: The study aimed to identify the optimum tillage and source of nitrogen for refining yields, yield sustainability and rainwater-use efficiency, and to develop predictive models explaining the relationship between crop yield and monthly rainfall with main goal of reduced cost of cultivation and increased profitability for long-term sustainability of maize-wheat system. Methodology: A long-term field experiment on maize-wheat system was conducted from 2000 to 2012 at Regional Research Station, Ballowal Saunkhri, Punjab Agricultural University, Ludhiana in split plot design with three replications. The treatment included three tillage practices, viz., conventional tillage (CT), reduced tillage (RT1) and RT1 + herbicide (RT2) in the main plots and three nitrogen (N) management practices, viz., 100% N from organic source (F1), 50% N from organic + 50% N from inorganic source (F2) and 100% N from inorganic source (F3) in the sub-plots. The parameters included maize and wheat yield, rainwater use efficiency, economics, sustainability yield index to develop predictive models. Results: Prediction models expressing relation between yield and monthly rainfall showed beneficial effect of rainfall in June, July and September months on maize and January and February in wheat on crop productivity. RT2 gave highest mean maize grain yield (2264 kg ha−1) with 13.8 and 1.8% yield superiority over RT1 and CT, respectively. However, in wheat, CT recorded highest grain yield (2110 kg ha−1) with 7.9 and 1.7% higher yield than RT1 and RT2, respectively. The RT2F3 gave highest net returns of US$ 222.60 ha−1 with benefit-cost ratio (B:C) of 1.88, rain water use efficiency (RWUE) of 4.78 kg ha−1 mm−1 and a sustainable yield index (SYI) of 60.7% in maize, whereas in wheat it provided net returns of US$315.45 ha−1 with B:C of 2.28, RWUE of 23.0 kg ha−1 mm−1 and SYI of 47.4%. Interpretation: The efficient rainwater use and optimum yields of rainfed maize-wheat system can be realised with reduced tillage + herbicide based weed management along with application of recommended nitrogen. The study suggests the shift from conventional tillage practices to reduced/conservation tillage practices.