Effects Of Maize Straw Decomposition On Soil Enzymes And The Relationship Of Phosphorus, Zinc And Cadmium In Cinnamon Soils

The paper studied on the effects of application of (returning) maize straw on soil enzymes and the interaction of phosphorus with zinc and cadmium in calcareous soils, and also studied the effect-mechanism of the three elements. The effects of application of smashed maize straw into field with and without phosphorus on catalase, alkaline phosphatase, soil organic matter, active organic matter and available P were studied by indoor-experiments. The influence of phosphorus on adsorption-desorption of zinc and cadmium, and the influence of soil on adsorption-desorption of zinc and cadmium were studied respectively. The main results were as follows:1. Applying maize straw and phosphorus into soil, the activity of catalase was generally decreased with the culture time and the amount of corn stalk increased. The activity of catalase was the highest with low P. The activity of alkaline phosphatase was gradually increased with the culture time extrend, and reached the highest at high P content treatment. Maize straw promoted the increase of the content of soil available phosphorus, but there was no significant influence on active organic matter.2. Maize straw was placed in nylon bags and buried in soil. The speed of straw decomposition was faster in early stage and then became slow. The activity of catalase was first increased and then decreased with the culture time extrend. The activity of catalase was increased with the amount of straw increased. That is to say, the process of straw decomposition is conducive to improve the activity of alkaline phosphatase. The contents of soil organic matter, active organic matter and available P were all slowly increased with culture time increased, and also increased with the amount of straw increased.3. The influence of soils with different P contents on adsorption-desorption of Zn with different concentrations: under Zn10 treatment, Zn adsorption amount in soil was gradually decreased; under the same P content condition, Zn adsorption amount in soil was in the order of Cd0>Cd1>Cd2; with the concentrations of P increased, Zn desorption amount was first increased then decreased. Under Zn80 treatment, Zn desorption amount was gradually increased with P concentrations increased. The influence of soils with different maize straw contents on adsorption-desorption of Zn with different concentrations: with added maize straw content increased, Zn adsorption amount in soil was first increased then decreased; under the same P concentration, Zn adsorption was in the order of: without straw(C0) > constant straw(C1) > double straw(C2). Zn desorption amount was first increased then decreased with added maize straw content increased. Under the same P concentration, Zn desorption was in the order of: double straw(C2) > constant straw(C1) > without straw(C0).4. The cadmium absorption amount was increased at first and then decreased with P content increased, and the desorption amount was increased at first and then decreased, and at last increased when the Cd concentration was very low (Cd3 treatment). And when the Cd concentration was very high (Cd30 treatment), the Cd absorption amount was increased gradually with P content increased, under the same P level, the Cd absorption amount was significantly decreased with P content increased, but the desortption amount was increased. In different straw added amount to adsorption & desorption cadmium, the Cd adsorption amount was increased at first and then decreased, and under the same P level, the adsorption was decreased gradually in Cd treatment, and the Cd desorption amount was reached minimum when the P content was 120 mg·kg-1(P2), and then was increased with P content increased. Under the same P level, the Cd desorption amount was increased gradually with straw added amounts increased. But in Cd30 treatment, the Cd adsorption amount was increased gradually, And under the same P level, the sequence of Cd adsorption was C1 > C2, the Cd adsorption was reached max, and then decreased when no added straw when in 240 mg·kg-1(P3) level. The Cd desorption amounts was increased with P content increased, and under the same P level, the Cd desorption was increased gradually with straw added amount increased.