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前 言 随同研究径流和农地侵蚀而产生的有关水质的问题,要强调改进径流期间田块产沙量和化学物质的预测方法。径流和侵蚀的作用有两方面。首先,自农地带走的泥沙和化学物质形成了非点源污染;其次,土壤流失及由侵蚀而产生的植物养分损失明显地影响土地产量。这些影响土地产量的因素虽然明确存在,但还没有研究清楚。为了研究维持国内农田持久的生产力的综合措施,很有必要了解影响生产力的因素。 农地土壤侵蚀有两种物理过程即土壤的剥蚀与输移。一般有两种侵蚀类型:一种是发生在渠道或细沟中;另一种发生在沟之间近乎水平的地面上。侵蚀的类型影响了泥沙的物理特性和侵蚀土壤颗粒的剥离和输移。 产沙的过程明显地与养分流失、泥沙输移率及土壤生产力的持续降低有关。被侵蚀的土壤颗粒不管是来自细沟里的耕作层还是沟间地表,对估算
Preface Along with the study of water quality related to runoff and agricultural land erosion, emphasis should be placed on improving the prediction of field sediment yield and chemical substances during runoff. The role of runoff and erosion is twofold. First of all, the sediment and chemicals carried away from the farmland form non-point source pollution. Secondly, soil erosion and the loss of plant nutrients caused by erosion significantly affect the land yield. Although these factors that affect the output of land clearly exist, they have not been studied clearly. In order to study comprehensive measures to maintain the long-lasting productivity of farmland in the country, it is necessary to understand the factors that affect productivity. Soil erosion in agricultural land there are two physical processes that soil erosion and transport. There are generally two types of erosion: one occurs in channels or narrow channels; the other occurs in nearly horizontal ground between channels. The type of erosion affects the physical properties of the sediment and the stripping and transport of the eroded soil particles. The process of sediment production is obviously related to nutrient loss, sediment transport and the continuous decrease of soil productivity. Eroded soil particles, either from the tilling layer in the gutter or from the ditch surface,