Abstract: In order to investigate the effect on crop yield and soil fertility of Vicia villosa as a green manure crop in tobacco growing, a field experiment comprising three treatments was set up: winter fallow without a green manure crop (CK), a winter green manure crop of V. villosa not inoculated with rhizobium (V), and a winter green manure crop of rhizobium-inoculated V. villosa (VR). Plants of V. villosa were harvested for measurement at the beginning of flowering (187 days after planting) to determine their yield and nutrient levels, and then ploughed under, with tobacco planting following 45 days later. For tobacco planting on V and VR plots, fertilizer was applied at 80% of the rates recommended by the Guangyuan Tobacco Company for the CK treatment. Before planting tobacco and after harvest, soil samples were collected and physicochemical traits, enzyme activity and microbial populations were determined. Key results were: 1) Rhizobium inoculation enhanced vigor of the V. villosa green manure crop. Plant biomass and nutrient content, fresh grass yield, hay yield, root yield, nodule numbers, and plant height were all increased by 1.3% to 50.7%; total N, total P, and total K were increased by 1.8% to 5.0%; N, P, and K accumulation increased by 14.3% to 21.5%. 2) In the soil tests taken before planting tobacco, the VR treatment had increased soil nutrient content and microbial populations, compared with the CK treatment. Specifically, total N, organic matter, and available N, P, and K increased by 2.5% to 126.6%. Meanwhile, the activities of sucrase, catalase, phosphatase and urease were increased by 14.6% to 82.5%, while populations of bacteria, actinomycetes and fungi were increased by 85.3% to 236.9%. In the soil tests taken after harvesting tobacco, it was found that the VR treatment increased soil nutrient content and microbial populations, even with the 20% reduction in chemical fertilizer application. Total N, organic matter, and available N, P, and K were increased by 12.3% to 64.1%, the activities of sucrose, catalase, phosphatase and urease increased by 5.4% to 67.0%, compared to CK, while populations of bacteria, actinomycetes and fungi were increased by 65.1% to 473.3%. This finding that use of rhizobium-inoculatedd V. villosa (i.e. the VR treatment) can improve soil fertility status even with a 20% reduction in inorganic fertilise application, is of great significance to development of more sustainable tobacco leaf production practices.

Key words: Vicia villosa, rhizobium, soil enzyme activities, number of microorganisms