不同耕作制度对土壤中锰赋存形态及其有效性的影响

以花岗岩母质发育的旱地红壤和水稻土为研究对象，探讨了不同耕作制度下土壤中锰的赋存形态及其生物有效性。结果表明：在水旱轮作条件下，土壤中的锰更多地以代换态和晶形铁结合态存在；旱作土壤中的锰则较多地以有机态和无定形铁结合态存在．然而，单位有机质络合的锰量却是水稻土大于红壤。水旱轮作措施具有活化锰的作用，使得土壤中锰有效性更大并且主要以代换态存在。旱作土壤则不同，土壤活性锰除来自代换衣外，尚有大约４５％以有机态或无定形铁结合态存在。

Effects of Cropping System on Morphology and Availability of Manganese in Soils

The paper explores the effect of different cropping systems oil the morphology and availability of manganese in acid soils in South China by using a sequential extraction procedure. Results show that manganese in paddy soil which is under alternation of culture of rice and upland plants such as wheat, soybean exists more exchangeable fraction and crystalline Fe oxide fraction and less organic fractioll and amorphous Fe oxide fraction than in upland field (red soil), and however per unit of organic matter in paddy soil could combine more manganese than that in red soil. The rotation of rice and upland plants can activate manganese and enable soil manganese to be more available,and so active manganese in paddy soil mainly comes from exchangeable fraction, but in red soil only about 45 %, in other words, nearly, 45 % of active manganese from organic fraction and amorphous Fe oxide fraction.