Five years of conservation tillage and weed management in a rice-chickpea rotation of northern Gangetic Plains of India: Weed growth, yield benefits and economic profitability

Abstract

Cropping system diversification of cereal-cereal systems with alternative systems preferably with pulses/legumes is demand of time across the globe for sustenance of natural resources and climate resilience. Rice-chickpea has been advocated as a futuristic cropping system in rice ecologies of South Asia for diversification of dominating rice-wheat system. However, the long-term sustainability of this system with respect to weed severity/growth, crop/system productivity, profitability, and yield stability under variable tillage, crop residues, and weed management practices has not been studied elaborately. Hence, present study was undertaken for five consecutive years in split-plot design with four tillage and residue management practices in main plot (conventional and zero tillage with and without residues), and three weed control practices (pre + post emergence herbicides and manual weeding) in sub-plot. Conservation tillage system comprising zero-tilled (ZT) direct seeded rice (ZTDSR) - ZT chickpea with rice residue retention (ZTDSR-ZTC+RR) led to the lower weed density in chickpea (by 10 %) and system (by 7 %) than conventional-tilled (CT) puddled transplanted rice - CT chickpea without residues (PTR-CTC-R; farmer practice). Among weed management practices, pendimethalin 1 kg a.i. ha−1 – metsulfuron-methyl + chlorimuron ethyl (ready-mix) 4 g a.i. ha−1 in rice and oxyfluorfen 150 g a.i. ha−1 – propaquizafop 100 g a.i. ha−1 in chickpea decreased the weed density in system by 14–22 % (p < 0.05) than pendimethalin + one hand weeding. The best weed management practice (pendimethalin – metsulfuron-methyl + chlorimuron ethyl) had significantly total weed density rice (by 7 %) and system (by 10 %) than current recommendation of the Indo-Gangetic Plains region (pendimethalin - bispyribac-sodium). It suggested that rotation of bispyribac-sodium with metsulfuron-methyl+chlorimuron ethyl (mixture herbicide) could reduce weed density and increase yield over time. Mean of five years indicated a non-significant yield difference among conservation and conventional tillage systems in rice. However, conservation tillage practice (ZTDSR-ZTC+RR) had 10 % higher chickpea yield and 4 % higher system yield (five years mean) over the PTR-CTC-R (p < 0.05). Further, conservation tillage comprising ZT in both crops in system with added residues (ZTDSR-ZTC+RR) resulted in an economic benefit of INR 22,000 than the conventional tillage in both crops without residues (PTR-CTC-R). Moreover, five years sustainable yield index was 16 % higher in ZTDSR-ZTC+RR system than conventional-tilled rice-chickpea system. Thus, conservation tillage with suitable pre- + post- emergence herbicides such as pendimethalin – metsulfuron-methyl + chlorimuron ethyl in rice and oxyfluorfen – propaquizafop in chickpea can reduce the weed density and enhance the crop and system productivity over time than conventional tillage. This system can also sustain the yields of component crops and system in long-run with higher yield stability over conventional tillage without residues. This system can be adopted in the cereal-cereal based cropping system of rice ecologies to diversify the system and to reverse the weed infestation and yield decline.