Effect Of Mung Bean Intercropping And Returning As Green Manure On Sugarcane Growth And Field Soil

Sugarcane has large biomass and long growing duration.Long-term of continuous cropping easily results in soil nutrient imbalance.At present,the input of fertilizers in sugarcane production is large.It is important to explore measures to reduce application of chemical fertilizers in sugarcane production.Three pot experiments were conducted to study the effects of nitrogen,phosphorus and potassium supplies on mung bean/sugarcane interaction under greenhouse conditions.A field experiment was carry out to study the best sowing time for mung bean intercropped with sugarcane.Another field experiment was carry out for 2 years to study the effect of mung bean intercropping with sugarcane and green-returning on growth of sugarcane and soil fertility of sugarcane field.The main results are as follows.1.At the nitrogen supply rate 50 mg/kg,the advantage of sugarcane/mung bean intercropping was significant.Under the four nitrogen supply levels,the sugarcane biomass,and nitrogen,phosphorus and potassium uptakes by sugarcane increased by 2.33%-20.41%,4.68%-19.93%,5.05%-12.22%and 1.98%-20.82%,respectively,compared with the monoculture of sugarcane.2.At the phosphorus supply rates 0 mg/kg and 50 mg/kg,the advantage of sugarcane/mung bean intercropping was significant and more significant for the rate 50 mg/kg.Under the four phosphorus supply levels,the sugarcane biomass,and nitrogen,phosphorus and potassium uptakes by sugarcane increased by 6.75%-25.56%,3.97%-22.48%,6.21%-22.75%and 7.39%-23.61%,respectively,compared with the monoculture of sugarcane.3.At potassium supply rates 100 mg/kg and 200 mg/kg,the advantage of sugarcane/mung bean intercropping was significant,and more significant for the rate 200 mg/kg.At the four potassium levels,the sugarcane biomass,and nitrogen,phosphorus,and potassium uptakes by sugarcane increased by 4.25%-14.40%,3.11%-14.04%,3.42%-10.14%,and 4.95%-22.40%,respectively,compared with the monoculture of sugarcane.4.The emergence rate and the tillering rate were significantly reduced when mung bean was sown at the time of sugarcane planting and 10 days after sugarcane planting,while the tillering rate and seedling rate of the sugarcane were not affected if mung bean was sown after sugarcane emergence rate reached 20%.After the intercropped straw of mung bean returned to the field,the nutrients released by decomposition can be used by sugarcane plants,which produced a compensation effect for sugarcane at later growth stage.As the result,the intercropping improved the cane yield as compared with the single cropping of sugarcane.It is suitable to sow mung beans when planting sugarcane and return the mung bean straw to the field at its podging stage combining with the earth up for sugarcane.5.The nutrient accumulation characteristics of the intercropping mung bean plant were potassium>nitrogen>phosphorus,and the nutrient content for different growth stages of the plant was early flowering stage>flowering and podding stage>green pod stage?seedling stage.The mung bean straw returning could provide the soil with 80.52-113.14 kg N/ha,54.28-70.25 kg P2O5/ha and 299.55-392.77 kg K20/ha.6.The releasing rate during mung bean straw decay was potassium>nitrogen>phosphorus>dry matter.During sugarcane growth,the decomposition rates of potassium,nitrogen,phosphorus,and dry matter were 89.31-93.5%,58.59-67.45%,50.58-56.98%,and 40.36-55.11%,respectively.7.Under the condition of mung bean intercropping and straw returning,sugarcane growth and siol nutritrent content were not affected when nitrogen or potassium application was reduced by 30%.8.Mung bean intercropping and straw returning improved the plant height,stalk diameter,juice Brix,and cane yield of sugarcane,and significantly improved the accumulation of dry matter,nitrogen,phosphorus,and potassium in the aboveground part of sugarcane.9.Compared with sugarcane monoculture,consecutive two years of mung bean intercropping and green straw returning to the field improved the available nitrogen,available phosphorus,available potassium,organic matter,total nitrogen,total phosphorus,and total potassium by 8.84%-29.47%,1.25%-35.63%,17.05%-37.05%,14.01%-23.22%,7.53%-15.27%,5.73%-15.27%,and 3.57%-19.82%,respectively.10.Compared with sugarcane monoculture,consecutive two years of mung bean intercropping and green straw returning to the field improved the contents of 1-2 mm and 0.5-1 mm mechanically stable aggregates in soil,and the contents of 0.25-1 mm,1-2 mm and 2-5 mm water stable aggregates in soil,but reduced the content of<0.25 mm mechanically and water stable aggregates,and the percentage of aggregate damage.11.Compared with sugarcane monoculture,consecutive two years of mung bean intercropping and green straw returning to the field reduced the soil bulk density by 2.86%-10.88%,while increased the total soil porosity by 3.65%-13.45%,increased the soil capillary porosity by 26.47%-41.75%,and increased the ratio of capillary porosity/total porosity by 20.44%-32.62%.