在第一讲中谈到土壤含有一定数量的有机质,其重量一般不超过5％,容量不超过12％。土壤有机质含量虽然不高,但是作用却很大。所以人们常常把土壤有机质含量作为判断土壤生产力的重要指标之一。我国有几千年的耕种历史,能够保持地力常新而不枯竭,应归功于我国的农业有传统的施用有机肥的习惯。 In the first talk about the soil contains a certain amount of organic matter, its weight is generally not more than 5%, the capacity does not exceed 12%. Although soil organic matter content is not high, but the role is great. Therefore, soil organic matter content is often used as one of the important indicators to judge soil productivity. Our country has several thousand years of cultivation history, and can keep the new and inexhaustible land fertility, thanks to the traditional habit of using organic fertilizer in our country’s agriculture.