Research On Prevention And Control To Non-point Source Pollution By Orchard Construction Model Of Soil And Water Conservation Type

Ecological environment is the premise and foundation of human survival and development. With the increasing of human economic activities, China’s ecological situation is becoming more and more serious. Ecological damage and environmental pollution have great effects on the sustainable development of the social economic system. The environmental issues have attracted wide attention by domestic and foreign disciplines. Jiangxi Province is one of the provinces with serious soil and water loss in south China, the comprehensive management of soil erosion is arduous and urgent now. Fruit industry as the development of soil erosion control is an important measure and developed rapidly in recent years. But in the process of hilly resources’utilization, nutrient loss, soil degradation and non-point source pollution happen in many sloping orchards, because of absence of effective soil and water conservation measures, and one-sided pursuit of short-term interests.In this study, based on southern soil erosion area, to solve such ecological problems as fertility decline, serious non-point source pollution of fruit industry in red soil sloping orchards, the field observation test data from2004to2006in Dean was used to analyze characteristics and rules to prevent and control non-point source pollution of four soil and water conservation(SWC) models, i.e. mound before and ditch behind+grass planting on the ridge(treatment Ⅰ), level terrace+grass planting on the ridge(treatment Ⅱ), contour cultivation+inter-cropping crops(treatment III), clean tillage model(treatment Ⅳ) comparing with the bared (CK). At the same time, different orchard construction models’ inferences on soil carbon, nutrient and non-point source were analyzed. The follow conclusions are received through the research:(1) Characteristics of sediment yield and runoff amount of different SWC orchards are as follows:①Monthly outputs of runoff and sediment were on the occasion of the basic trends in the bimodal distribution. Runoff and sediment outputs occur at basically the same as spatial and temporal distribution of rainfall, and the most serious period caused runoff and sediment was from May to September, expercially in May、June、August.Therefore, in these key months, it needs to take positive and effective prevention and control measures to control runoff and sediment.②Compared with CK, runoff reduction rates of SWC orchards was71.40%-95.52%; sediment reduction rates of SWC orchards was73.17%～99.84%。which indicates that the soil and water conservation measures had some benefits to control runoff and sediment output. But different treatments had different effects. The effect of three kinds of SWC orchard construction models on controlling sediment output stands ranked in the descendant order of Ⅱ>Ⅲ>Ⅰ.(2) Effects on non-point source pollution prevention of different SWC orchards are as follows:①Soil erosion and non-point source pollution is a pair of inseparable symbiosis. Pollutant volume carried by runoff divided that carried by sediment (ES/ER values) was between the range of1.83～16.00, which was all greater than1, indicating that whether SWC measures were implemented, pollution volume carried by sediment was greater than that carried by runoff. N and P migration was largely affected by the flow of sediment. The loss of N and P in soil was sediment-bound. The higher enrichment degree of pollutants in the soil was, the stronger control ability of non-point source pollution was.②Absolute volume of non-point source pollutants carried by runoff and sediment stood ranked in the descendant order of Ⅱ>Ⅲ> Ⅰ. The better effects of SWC measures had, the more obvious controlling effects of non-point pollutant were. SWC measures’ impacts on non-point source pollution loss were following as:first, it can reduce the absolute number of non-point source pollutants loss. Second, non-point source pollutants can be made in a single way, which make the surface runoff clean, thus prevent the migration of non-point source pollutants.③Different SWC measures on orchards had different way and process to control non-point source pollution loss. Runoff concentration containing pollutants in SWC measures were significantly less than that of CK. N concentration of SWC measures was higher in the beginning processing. Later, total N concentrations in runoff were stable at0.31g/m3,0.26g/m3,0.40g/m3or so. The total N and total P concentration were in the overall downward trend. In CK plot, total N and total P content of soil was the lowest, but the initial total N and total P in runoff was the highest, and this part of the N, P amount made the direct loss of available nutrient attenuation and easily to result in non-point source pollution in water.(3) Controlling effects on non-point source pollution of different SWC orchards are as follows:①SWC orchard construction models had obvious effects to control non-point source pollutants, which total nitrogen, ammonia nitrogen, total phosphorus regulation results were above98.5%,97.8%,96.6%or more, respectively. In each treatment plot, soil active organic carbon content and carbon pools rose over time. organic carbon content’s order was Ⅰ> Ⅱ> Ⅲ.②Since nutrients having different formation process, different treatments had different variation rules of soil organic matter, total N and total P. Total N content variation was similar to organic matter in each plot. The organic matter content was between10.17-16.28g/kg, with the order of Ⅰ>Ⅱ>Ⅲ, while the performance law of total P wasn’t consistent with the active organic carbon.③The relation results of soil nutrients elements show that organic matter and total N, available N had a significant positive correlation; and had a significant positive correlation with total P, the correlation coefficients were0.881,0.748,0.658respectively. This explains that the accumulation of soil nitrogen is closely related to organic matter input. The orchard management in the future, we must take full account of the interaction of a variety of nutrient factors to improve nutrient utilization and reduce excess fertilizer negative effects of pollution.