ass日本风韵熟妇pics男人扒开女人屁屁桶到爽|扒开胸露出奶头亲吻视频|邻居少妇的诱惑|人人妻在线播放|日日摸夜夜摸狠狠摸婷婷|制服 丝袜 人妻|激情熟妇中文字幕|看黄色欧美特一级|日本av人妻系列|高潮对白av,丰满岳妇乱熟妇之荡,日本丰满熟妇乱又伦,日韩欧美一区二区三区在线

With the impact of rainfall, soil nutrient transported along soil particles and water into surface runoff. It decreased soil fertility, polluted water resources in surface and ground, and then induced a series of ecological environmental problems, which attracted more attentions of researchers at home and abroad. The objectives of the study mainly focused on the development of both the mechanism and controlling measures of soil nutrient transport proposed by researchers all over the world. For the mechanism, the impact of different factors on soil nutrient transport was mainly discussed, and the empirical models and physical based mathematical models were also discussed. Besides, all mentioned physical based models were based on the inner mechanism of nutrient transfer, including the theory of mixing depth, convection and dispersion, the impact of raindrop and water scouring. For the controlling measures, methods protecting soil and nutrients from erosion and runoff were proposed with consideration of serious erosion phenomenon in China. Meanwhile, the existed problem and further study work were also discussed.