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土壤中微生物固氮作用是含氮物质的根本来源,据估计地球上生物固定的氮素一年中约有17500万吨,也就是说地球上70％的氮素由生物固定的,而豆科植物固氮效能最高,平均每亩豆科植物固氮3～12公斤。在农业生产中氮素和水分是常遇到的限制产量提高的主要因子,所以提供植物所利用形式的氮素并使它在土壤中维持一定的数量是保证作物增产的前提。土壤中的氮素虽然在作物成熟后人为的移去一部分,但是通过施肥和种植豆科作物是它补充不足的主要来源。从古代至今的农
Nitrogen fixation by microorganisms in soil is the fundamental source of nitrogenous matter. It is estimated that about 175 million tons of nitrogen are immobilized on Earth on a yearly basis. That is to say, 70% of the nitrogen in the soil is biologically immobilized, while legumes The highest nitrogen fixation efficiency, the average nitrogen per acre legumes 3 to 12 kg. Nitrogen and water are the main limiting factors in agricultural production to limit the increase of production. Therefore, providing nitrogen in the form used by plants and maintaining a certain amount of nitrogen in the soil is a prerequisite for increasing the yield of crops. Although nitrogen in the soil is artificially removed after crop maturation, the main source of inadequate replenishment is fertilization and the cultivation of leguminous crops. Farmers since ancient times