Dissertation
Dissertation > Agricultural Sciences > Agriculture as the foundation of science > Soil > Soil chemistry, soil physical and chemical

Effect of Straw Decomposition on Zinc Supply Capacity of Soil

Author YangFang
Tutor TianXiaoHong
School Northwest University of Science and Technology
Course Plant Nutrition
Keywords soil microbial biomass Zn Zn fractions soil capability of supplying Zn straw decomposition
CLC S153
Type Master's thesis
Year 2011
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Zn is an essential micronutrient for plant and animal, it enters into the food chain through plant, and it enters the diets of human being directly or through animal indirectly, so the balance of nutrition and the health of human being are affected by zinc. Soil in central Shaanxi area is potentially Zn-deficiency, yield and quality of field crop and animal products are affected because of under supplying of soil zinc and low zinc supply capacity of soil. The most effective approach to solve zinc deficiency in soil is to increase the content of soil available Zn and soil Zn supply capacity.Wheat-maize rotation system is the main cropping pattern in central Shaanxi area. There is quite a lot of wheat and maize straw produced every year, and most of them are not effective used, which caused waste of resources. Nowadays, organic fertilizer input into soil is gradually decreased and straw return back to soil is gradually concerned, straw will be the main organic fertilizer put into soil. It is of great significance for straw returning to soil that it not only solves the resources waste problem, but also protects eco-environment. As we all know, straw contains substantial quantity of secondary and micro-nutrients, such as Zn. These nutrients can return back to soil as the crop straw return to field, and the soil fertility is increased.Two incubation experiments were carried out separately, and through the determination of soil total Zn, available Zn, Zn fractions etc. to study the effects of straw (wheat or maize straw) decomposition on Zn released from straw, the changes of forms of Zn fractions and the content of soil microbial biomass Zn (Mic-Zn). The primary results are as follows:(1) It is of vital significance to evaluate the contribution of straw returning to farmland to keep Zn nutrient balance in soils. In order to study the effects of straw decomposition on Zn released from straw, the changes of forms of Zn fractions and the content of soil microbial biomass Zn (Mic-Zn), an incubation experiment was carried out in dynamic microcosms for 42 days. The results showed that, the cumulative amount of CO2-C evolution and the content of soil microbial biomass C (Mic-C) were significantly increased as the straw added to soil increased, but they were unrelated to Zn concentration in straw and whether Zn fertilization was conducted or not. Whether the straw was added in soil or not, the contents of soil Mic-Zn, DTPA-Zn, exchange Zn (Ex-Zn) and loosely organic bound Zn (Wbo-Zn) were significantly increased when Zn fertilizer was added, and these four Zn fractions were also increased to some extent when high Zn concentration straw added to soil compared to low Zn concentration straw.(2) An incubation experiment was carried out in dynamic microcosms for 42 days to study the effects of straw decomposition on Zn released from straw, the changes of forms of Zn fractions and the content of soil Mic-Zn. The results showed that, the cumulative amount of CO2-C evolution was significantly increased by 38.69% on average as the straw added to soil increased, the content of soil Mic-C was also increased, but they were unrelated to Zn concentration in straw and whether Zn fertilization was conducted or not. Whether the straw was added in soil or not, the contents of soil Mic-Zn and DTPA-Zn were increased by 228.42% and 131.51% when Zn fertilizer was added compared to the control, Ex-Zn and Wbo-Zn were also significantly increased. The contents of soil DTPA-Zn was increased by 25.06% when high Zn concentration straw added to soil compared to low Zn concentration straw. The contents of soil Ex-Zn and Wbo-Zn were also increased to some extent.(3) Two incubation experiments were carried out separately under the same conditions in dynamic microcosms for 42 days to study the effects of straw decomposition on soil Zn supply capacity. The results showed that, the amount of CO2 evolution was significantly increased as the wheat or maize straw added to soil increased, the content of soil Mic-C and soil microbial biomass N(Mic-N) were also increased, but they were unrelated to Zn concentration in straw and whether Zn fertilization was conducted or not. Wheat straw decomposition was accelerated in soil, while maize straw decomposition was unrelated to the incubation medium. Whether the straw was added in soil or not, the contents of soil Mic-Zn and DTPA-Zn were increased when Zn fertilizer was added, and the content of both were also increased when high Zn concentration straw added to soil. The content of Ex-Zn was increased whether the straw decomposited in soil or in quartz sand, and the content of soil total Zn and other fractions of Zn were significantly increased when straw was added in soil, especially the Wbo-Zn.In conclusion, the cumulative amount of CO2-C evolution and soil Mic-C and Mic-N were increased as the straw added to soil increased, and they were unrelated to Zn concentration in straw and whether Zn fertilization was conducted or not; Whether the straw was added to soil or not, the contents of soil Mic-Zn, soil total Zn, DTPA-Zn and the fractions of Zn were increased when Zn fertilizer was added. The content of DTPA-Zn was significantly increased because of straw decomposition, and so did soil Wbo-Zn, therefore soil Zn supply capacity was increased.

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