全球变化知识资源中心

Identifying cropping systems with small global warming potential (GWP) per unit of productivity is important to ensure food security while minimizing environmental footprint. During recent decades, double-season rice (DR) systems in central China have progressively shifted into single-crop, middle-season rice (MR) due to high costs and labor requirements of double-season rice. Ratoon rice (RR) has been proposed as an alternative system that reconciliates both high annual productivity and relatively low costs and labor requirements. Here we used on farm data collected from 240 farmer fields planted with rice in 2016 to evaluate annual energy balance, environmental impact, and net profit of MR, DR, and RR cropping systems in central China. Energy factors, emission values, and commodity prices obtained from literature and official statistics were used to estimate energy balance, GWP, and economic profit. Average annual yield was 7.7, 15.3. and 13.2 Mg ha(-1) for MR, DR, and RR systems, respectively. Average total annual energy input (36 GJ ha(-1)), GWP (9783 kg ha(-1)), and production cost (3057 $ha(-1)) of RR were 35-48% higher than those of MR. However, RR achieved 72-129% higher annual grain yield (13.2 Mg ha(-1)), net energy yield (159 GJ ha(-1)), and net economic return (2330 $ha(-1)) than MR. Compared with DR, RR produced statistically similar net energy yield while doubling the net economic return, with 32-42% lower energy input, production costs, and GWP. Consequently, RR exhibited significantly higher net energy ratio and benefit-to-cost ratio, and substantially lower yield-scaled GWP than the other two cropping systems. In the context of DR being replaced by MR, our analysis indicated that RR can be a viable option to achieve both high annual productivity and large positive energy balance and profit, while reducing the environmental impact.