Utilization of liquid pig manure for resource cycling agriculture in rice-green manure crop rotation in South Korea.

A 2-year field experiment was carried out on rice (Oryza sativa, Japonica type) cultivation in South Korea. The objective of this study was to investigate the effect of application of liquid pig manure on biomass production and nutrient supply of green barley (Hordeum vulgare L.) and hairy vetch (Vicia villosa Roth) green manure crops and to evaluate the effect of nutrients supplied from these sources on rice yield and soil quality in a rice-green manure crop rotation system. Over the 2-year study period, application of liquid pig manure increased biomass production of green manure crops of barley and hairy vetch by more than 216% and 135%, respectively, compared with without liquid pig manure. Moreover, the results showed that the application of liquid pig manure significantly increased the nutrient supply levels in green barley- and hairy vetch-treated areas. Positive effects related to nutrient supply in green barley and hairy vetch treated with liquid pig manure were observed on rice yield, soil chemical characteristics, and microbial biomass C and N contents. In conclusion, the addition of liquid pig manure systems using green manure crops of green barley and hairy vetch improved rice productivity and soil quality. It is suggested that these combinations can be effective in developing resource cycling agriculture in a rice-green manure crop rotation system as it reduces the need for inorganic fertilizer.