Study On Screening Of Green Manure Crops For Citrus Orchard In Zigui, Hubei Province And Their Key Technique Of Production And Utilization

To improve the yield and quality of citrus and ecological environment of orchard, the growth, nutrient absorption and accumulation, effects on soil properties of different green manure crops were studied in citrus orchard in Zigui, Hubei Province under the condition of field experiments. The sowing date and rate of the green manure crops being appropriate for citrus orchard in Hubei Province were further determined. The decomposition dynamic of Vicia Villosa Var. was studed by the nylon-bag experiment. The techniques of green manure crops constructed according to this project were more appropriate for the citrus orchard in Hubei Province. Main results are as follow.(1) All of6types of green manure crops(Vicia villosa Var., Vicia villosa Roth., Vicia sativa L., Astragalus sinicus L., Trifoliurn repens L., Vulpia mvuros (L.) C. C. Gmel) might complete their life cycle in citrus orchard in Zigui Country, Hubei Province. At full flowering stage, the biomass of green manure crops reached1844～4044g/m2, which could provide fresh yield of11067～24264kg/hm2and N, P2O5, K2O, C of34.65～97.24kg/hm2,13.82～30.61kg/hm2,76.17～147.35kg/hm2and728.01～1729.92kg/hm2for the citrus orchard. Among those green crops, Vicia villosa Var. grew better, fixed more nitrogen and carbon, concentrated and activated more phosphorus and potassium from soil for citrus. The carbon accumulation of Vulpia mvuros (L.) C. C. Gmel was the highest, which could provide more carbon source than other green manure crops for the citrus orchard.(2) Interplanting green manure crops had a warming effect in winter and a cooling effect in summer in the citrus orchard. The coverage of green manure crops (Vicia villosa Var., Vicia villosa Roth., Vicia sativa L., Vulpia mvuros (L.) C. C. Gmel) reached a high level during overwintering stage and re-greening stage. During January to February, the temperature of soil layer in0～10cm could be increased. The temperature increase covered by Vicia Villosa Var. and Vicia Villosa Roth was higher. During July to Septemper, the coverage of green manure crops could decrease the temperature of soil layer in0～10cm, which was more significantly at high temperature period. The effect of Trifoliurn repens L. was the best. Vulpia mvuro (L.) C. C. Gmel and Vicia Villosa Var. took the second place. The coverage of green manure crops had not obvious effect on the temperature in the soil layer below15cm. Interplanting green manure crops in citrus orchard also decreased markedly the daily temperature range in soil.(3) In the vigorous growth period of green manure crops in citrus orchard, the moisture and available nutrients content in soil were not decreased. Compared with clean cultivation, the soil water content was promoted by4.36%-6.91%during drought and high temperature period. When citrus needed more nutrients, they could promote the content of available nitrogen and phosphorus in orchard soil. After one year planting green manure crops, the content of soil available nutrients had a certain promotion. Interplanting green manure crops declined pH in0-20cm soil layer, did not change it in20～40cm soil layer. In general, pH was in a fitting range for citrus growth.(4) The suitable seeding rate of Vicia villosa Var. was60kg/hm2in citrus orchard in Hubei Province. At the seeding rate of60～120kg/hm2, the fresh yield, dry matter and nutrients accumulation of Vicia villosa Var. were significantly higher than30kg/hm2, which reached a high level. It was appropriate to use Vicia Villosa Var. at the seeding rate of60kg/hm2with the consideration of economic effect. At the seeding rate of15kg/hm2, the fresh yield, dry matter and nutrients accumulation of Vulpia mvuros (L.) C. C. Gmel reached the maximum. To reduce or increase the seeding rate, the growth and nutrients accumulation of Vulpia mvuros (L.) C. C. Gmel were in bad condition.(5) The suitable seeding date of Vicia villosa Var. was September in citrus orchard in Hubei Province. With the sowing date delaying, the fresh yield and nutrients accumulation of Vicia villosa Var. were decreased. From the middle ten days to last ten days of October, sowing Vulpia mvuros (L.) C. C. Gmel showed a certain advantage in fresh yield of shoot and nutrients accumulation. Early and delayed sowing could not obtain high yield and nutrients accumulation.(6) At full flowering stage and after withering returning to field, compared with ground mulching, the accumulated decomposition rates of carbon, nitrogen and phosphorus were higher by soil burial. The accumulated decomposition rate of potassium was little difference. At the full flowering stage, the decomposition of returning to field was fast in the early stage, and then it became slow in the late. After withering, it was slow in the early stage, and then it became rapid, in the late it became slow. Before the next sowing of green manure crops, the accumulated decomposition rates of dry matter and nutrients were basic approximate between two different periods of returning to field. The choice of green manure crops’s period and way of returning to field could consider the production reality in citrus orchard.