从我国实际出发,多积多施用农家肥,充分利用生物固氮资源,是提高地力的有效途径。1980年全国豆类作物(包括大豆、花生、蚕豆、豌豆、小杂豆等)的面积2.07亿亩,绿肥面积近1亿亩,每亩耕地平均5年可以轮种一次豆科作物。据测定,我国19种主要绿肥鲜草含氮量0.33—1.32％,一般亩 Starting from the reality of our country, applying more manure together and making full use of biological nitrogen fixation resources is an effective way to improve soil fertility. In 1980, the total area of ​​the country’s leguminous crops (including soybean, peanut, broad bean, pea, small beans and so on) was 207 million mu and the green manure area was nearly 100 million mu. On average, the leguminous crops could be rotated for 5 years per mu of cultivated land. According to the determination, 19 kinds of main green fresh grass in our country nitrogen content of 0.33-1.32%, the general mu