Effects of winter green manure cultivation on rice yield and soil fertility in paddy field

Green manure has been important as a complete source of high-quality nutrients, bio-fertilizers and organic fertilizers. Generally, paddy fields in southern China have been laid fallow in winter. This has generally amounted to waste of land resources for a significant portion of the year. Agricultural non-point source pollution caused by overuse of chemical pesticides with low-use efficiencies has had serious environmental pollution. Hence the large-scale promotion of winter green manure was crucial in achieving sustainable agricultural development. To explore the ecological role of winter green manure in improving soil nutrients, an experimental study was conducted where green plants (milk-vetch, ryegras, rapeseed) were planted during winter and plowed into rice fields 15 days before early rice planting for eight consecutive years. A continuous winter fallow was used as the control experiment. The results showed that average rice yield in fields with winter green manure was higher than in winter fallow fields. The most obvious increase was in the milk-vetch treatment (10.48%), followed by the rapeseed treatment (7.31%) and then the ryegrass treatment (5.76%). pH and alkaline hydrolysis nitrogen in the milk-vetch treatment was highest. pH and alkaline hydrolysis nitrogen increased by 0.58% 1.37% and 6.59% 35.35%, respectively. Organic matter, available P, available K and C/N ratio in soils with ryegrasse treatment were highest. Soil organic matter in ryegrass treatment was higher than that in other treatments by 2.99% 4.98%. Alao available P increased by 19.25% 31.05%, available K by 16.97% 22.15% and C/N ratio by 0.97% 6.61%. Rice yield highly significantly correlated (P < 0.01) with per-panicle spikelets, seed setting rate, grain weight, alkaline hydrolysis nitrogen and available P; and was significantly correlated (P < 0.05) with per-panicle grains, organic matter, available K and organic carbon; while it had no significant correlation with panicle length, effective panicle, soil pH and C/N ratio. The study showed extremely close correlation among the respective rice yield varibles and soil nutrients. On the whole, the study showed that winter green manure improved soil fertility and enhanced rice yield. Milk-vetch, ryegrass and rapeseed used in the experiment respectively belong to Leguminosae, Gramineae and Brassicaceae. These crops constituted the traditionally common winter green manure species in the study area. The study was critical for increased agricultural productivity, improved soil quality and increased farmer income. The paper provided the theoretical basis for improving soil fertility and land utilization for sustainable agricultural development in China.