旱改水对砂姜黑土中锌含量的影响研究

EFFECT OF CROPPING SYSTEM ON ZINC CONTENT IN SHAJIANG BLACK SOILS

本文用连续分级浸提法，研究了早改水对砂姜黑土中锌的含量、赋存形态和有效性的影响。砂姜黑土中的锌绝大部分以残留态存在，晶形铁结合态约占１０％，其余形态锌一般小于３％。这些形态锌可以分为三类：一类为土壤锌的强度因子，即代换态锌；另一类是土壤锌的容量因子，即有机态、无定形铁结合态和晶形铁结合态锌；第三类为残留态锌。土壤中有效态锌主要来自代换态。旱改水后，晶形铁结合态锌向有机态和无定形铁结合态锌转化，使得土壤中锌的活动性提高，增加了土壤中锌遭受淋溶损失的机率，从而导致土壤中全锌和有效态锌含量降低。

Summary The paper deals with the influence of changes of cropping system from upland ferming to rotation of rice and upland farming on the total content form and availability of zinc in Shajiang black soils studied by using the sequential-extraction method in combining with the mathematical analysis methods of principal component analysis and linear regression. The residual, crystalline iron oxide--bound, amorphous iron oxide--bound, organically bound and exchangeable Zn of soils accounted for 75.60%~ 78.13%, 16.47%~ 20.00%, 2.19%~ 3.27%, 0.82%~ 2.86% and 0.56% 0.97% of the total Zn, respectively. These forms could be divided into bee groups. The first group was exchangeable Zn, which the available Zn mainly came from, being the intensity factor of available Zn in soils. Organically bound Zn, amorphous iron oxide-bound Zn and crystalline iron oxide-bound Zn belonged to the second group which was the capacity factor of available Zn. in soils. The third group was the residual Zn, which was unavailable to Plants but could be activated under artificial cultivation. Under the rotation of rice and upland crops, the ratios of exchangeable Zn and crystalline iron oxide-bound Zn to total Zn decreased, but those of organically bound Zn and amorphous iron oxide-bound Zn to total Zn increased, which enabled Zn in soils to be activated and be more movable, and thus reduced the contents of total Zn and available Zn in cultivated layer of soils.