石灰性土壤环境中缺锌机理的探讨

作者认为石灰性土壤中锌活性较低的原因,是由于碳酸盐导致土壤pH上升,在较高pH条件下氧化铁对锌的强烈固定,造成了大量专性吸附状态的氧化铁结合态锌及部份碳酸盐结合态锌,使交换态的有效锌含量很低,同时还证明:自然的石灰性土壤中,松结有机态锌与碳酸盐结合态是活性锌的直接给源,外源加入的锌仅为松结右机态锌。此外,石灰性土壤中各主要土壤的化学组份对外源锌的固定量高伛顺序为:氧化铁>有机质>粘土矿物>碳酸盐>氧化锰:对土壤中原有锌的固定作用大小依次为:粘土矿物>氧化铁>有机质>氧化锰>碳酸盐。

STUDY ON MECHANISM OF ZINC DEFFICIENCY IN CALCAREOUS SOILS

Fractionation of native and added zinc and their availability in calcareous soils were studeid, demostrating machanism of zinc deficiency in calcareous soils. The sequential fraction used includes exchangeable Zn (EXC-Zn), Zn weakly bound to organic matter (WBO-Zn),Zn bound to carbonate(CARB-Zn),Zn bound to manganese oxide(OXMn-Zn),Zn strongly bound to organic matter (SBO-Zn), Zn bound to amorphorous iron oxide (AMORFe-Zn), Zn bound to crystalline iron oxide(COXFe-Zn),and residue Zn(RES-Zn).Results show that distribution of native zinc in calcareous soils is as follows:RES-Zn(71.3%)>COXFe-Zn(20.5%)>AMORFe-Zn (3.53%)>SBO-Zn(2.1%)>WBO-Zn(1,4%)>OXMn-Zn(1.1%) >CARB-Zn(0.8%)>EXC-Zn,and EXC-Zn is all bellow analysis limit for calca-rous soils. The redistribution of adding zinc in calcareous soil is that Zn bound iron oxide, residue,weakly bound to organic matter accounted for 37.7, 24.3,and 24.6% but carbonate only for 6.4% of adding zinc, respectively, and exchangeable zinc is almost about 0,05 ppm after adding zinc.There is more amount of iron oxide in acid-neutral soils than that in calcareous soil,but Zn bound to iron oxide is much more in calcareous soil than that in acid-neutral soil. This is larger immobilization capacity of iron oxide in the higher pH soil environment. And this causes much less amount of exchangeable zinc in calcareous soils comparing with acid-neutral soils.Iron oxide played an more important role in immobilization of adding zinc than that of native zinc,and also more than carbonate did.Optimum regression analysis predicts that exchangeable zinc and carbonate zinc, and exchangeable zinc and zinc weakly bound to organic matter are the main sources of available zinc for native and addeing zinc in calcareos soils, respectively.