Non-Point Source Pollution Characteristic With Straw Mulching In Slope Cultivated Land In Mountain Area Based On Peach-Soybean Interplanting System

The losses of nitrogen and phosphorus of surface runoff is an important factor for non-point source pollution in Dianchi lake watershed.While the nitrogen and phosphorus losses is closely associated with straw mulches,precipitation strength,surface runoff and vegetation canopy.Field plot experiment at Dianchi lake watershed were conducted to plant soybean under peach trees in Caojiachong village,Kunming prefecture, Yunnan Province.The soil surface of peach-soybean interplanting system were treated with 36 kg straw mulches per plot,54 kg straw mulches perplot and 72 kg straw mulches per plot,and questionnaires were investigated to villagers. The effect of the synergistic reaction between straw mulches and agro-forestry on the reduction characteristic of the losses of CODcr,NH4+-N,NO3--N,TN,TP and surface runoff of the farmland were studied. The yield increasing effects of crops and fruits were discussed.Not only couldstraw mulching improve soil fertility and effectively reduce the export of total nitrogen and phosphorus loads,but also significantly increase the yield of crops and farmers’ income,even improve eco-environment in countryside and achieve the economic and ecological benefits.Peach(local variety)-soybean interplanting system was selected for the agro-forestry community. Strength,weakness,opportunity,threaten were analyzed and the relationshipsamong straw mulches,canopy configuration,vegetation cover,precipitation and the losses of nitrogen and phosphorus,surface runoff quantity,soil nutrient contents,cation exchange capacity,plant morphological characteristics,nitrogen and phosphorus contents were determinated from May2014 to October2015.The results showed that:(1) Under the heavy rain or storm(precipitation strength between 25mm/24 h and 100 mm/24 h) condition in the treatment of 36 kg/plot,54 kg/plot and 72 kg/plot straw mulching,the reduction rate of CODcrloss were 24.31%,50.50% and 65.19%, respectively. The reduction rate of NH4+-Nloss were 12.56%,49.38% and 58.60%, respectively. The reduction rate of NO3--Nloss were27.78%,39.55% and 58.61%, respectively. The reduction rate of TNloss were 3.85%,31.67% and 56.01%, respectively. The reduction rate of TPloss were 23.02%,0.19%and 42.65%, respectively.(2) After 30 days treatment,the reduction rate of surface runoff, NH4+-N,NO3--N,TN,TP losseswere5.40%,38.80%,29.03%,29.40% and 53.82% in the treatment of 36 kg/plot straw mulching and 0%,54.40%,50.10%,40.40% and 66.56%in the treatment of 54 kg/plot straw mulching, respectively. After 60 days treatment,the reduction rate of surface runoff, NH4+-N,NO3--N,TN,TP losses were11.50%,70.50%,70.98%,71.27% and 74.84%in the treatment of 36 kg/plot straw mulching, and 52.56%,90.10%,89.50%,90.37%,85.71%in the treatment of 54 kg/plot straw mulching, respectively.(3) Comparing control(0 kg/plot), the contents of soil available nitrogen in 36 kg/plot, 54 kg/plot and 72 kg/plot straw mulching increased by 3.68%, 33.12% and 47.11%, respectively.The contents of soil available phosphorus in 36 kg/plot, 54 kg/plot and 72 kg/plot straw mulching increased by 33.64%, 132.30% and 256.48%, respectively.The contents of soil organic matter in 36 kg/plot, 54 kg/plot and 72 kg/plot straw mulching increased by 8.31%, 49.76% and 76.22%, respectively.The soil CEC in 36 kg/plot, 54 kg/plot and 72 kg/plot straw mulching increased by 35.15%, 23.37% and 41.90%respectively.(4) Growth and morphogenesis of soybean were affected with straw mulching. In seeding, drum grain and mature stages, soybean’s comprehensive response index in 36 kg/plot and 54 kg/plot straw mulching, which depended on plant height, shoot weight, root length, root weight, the number of leaves and nodules, were 171 and 98;247 and 361;94 and 247. Straw mulching had time effects on promoting soybean’s growth.(5) With0 kg/plot,36 kg/plot and 54 kg/plot straw mulching, the contents of total nitrogen were 2.46%,2.63% and 2.95% in the root of soybean, and 3.98%,4.50% and 5.08% in shoot of soybean. The contents of total phosphorus were 1.50%,1.69% and 2.24%in the rootof soybean and 1.17%,1.35% and 1.50% in shoot of soybean.(6) With the treatments of 36 kg/plot, 54 kg/plot and 72 kg/plot straw mulching, the yield of soybean were 13.70 kg/plot,16.28 kg/plot and 21.40 kg/plot, which increased by 24.09%,47.46% and 93.84% comparing with control(0 kg/plot).(7) The ratio of maize and vegetables to total household incomewere 40%~60%,30%~90%.While the understanding of villagers for utilizing of straw mulch were less than 20%.The total yield of crops were about 17594.4 tons, vegetables were about 42430.6 tons, straws were 14683.3 tons in Dabanqiao town. Straw resources were abundant but underutilized.In general, peach-soybean interplanting+straw mulch synergistic effect was not only contribute to use straw mulch resources effectively, but also could decrease the loss of nitrogen and phosphorus and promote the absorption of nitrogen and phosphorus to soybean, increase the yield. Different straw mulches were show up time-delay effect with change of growth periods of soybean for reducing of NP load exports, while presented the similar sequence 72 kg/plot>54 kg/plot>36 kg/plot>control. The ecological benefits, economic benefits and social benefits should be achieved.