Effects Of Planting Green Manure On Ecological Environment, Yield And Quality Of Citrus In Citrus Orchard At Three Gorges Reservoir

The growth of green manure crops and its effects soil properties, weed growth and soil nutrient loss in citrus orchard were studied under field experiments. The effects of green manure and its combining application with different amounts of chemical fertilizer on nutrient uptake in leaf and fruit, the quality and yield of citrus were researched through long-term experiment in citrus orchard. The above experiments aimed to provide technical support and theoretical guidance for the cultivation and application of green manure crops in citrus orchard at Three Gorges Reservoir. Main results are as follow.(1) 7 types of green manure crops could complete their life circle in citrus orchard at Three Gorges Reservoir. Vicia villosa Var., Vicia villosa Roth. and Vicia sativa L. were higher than the other four kinds of green manure in the biomass and nutrient accumulation among the entire growing period. Especially in the full-bloom stage, the biomass of Vicia villosa Var. was up to 26642 kg/hm2. The biomass and nutrient accumulation of Vicia villosa Var. were the highest among seven kinds of green manure.(2) Green manure could increase soil organic matter and available nutrient and improve soil physical properties in citrus orchard. Vicia villosa Var. and Vicia villosa Roth. could improve soil physical and chemical properties clearly. The majority of green manure could increase soil enzyme activity in citrus orchard at Three Gorges Reservoir.(3) The weed growth could be inhibited effectively by planting green manure in citrus orchard at Three Gorges Reservoir. Based on weed density and weed control rate in citrus orchard, Vicia villosa Var., Vicia villosa Roth. and Vicia sativa L. had the best influence on weed inhibitory control, the weed control rate>70.0%, following by Trifolium repens L and Vulpia mvuros(L.)C.C.Gmel., and then Trifolium pratense L. and Astragalus sinicus L(43.7% and 43.0%).(4) In the hot and rainy season, the surface runoff and nutrient loss were reduced by planting green manure in citrus orchard at Three Gorges Reservoir. The citrus orchard by planting Vicia villosa Var., Trifolium repens L. and Vulpia mvuros(L.)C.C.Gmel could decrease the amount of water loss by 11.0%, 11.4% and 24.0%, respectively. The amount of total nitrogen loss was decreased by 8.3%, 16.7% and 40.8%, respectively. The amount of total phosphorus was decreased by 7.5%, 25.3% and 58.0%, respectively. Compared with CK, the rest forms of nitrogen and phosphorus loss were decreased to some extent.(5) Vicia villosa Var. could replace part of fertilizer and optimize fruit quality in citrus orchard at Three Gorges Reservoir. 1/3 of fertilizer was reduced which could keep the yield of citrus steady under planting green manure in citrus orchard. The quality of citrus could be improved by planting Vicia villosa Var. with appropriate amount of fertilizer. Excessive fertilizer could lead to reduction of yield and quality deterioration.