Effect of Straw Return on Diffusion, Translocation and Transformation of Zinc in Calcareous Soil
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Supported by the National Natural Science Foundation of China (Nos. 41371288 and 31662233)and the National Key Technology Research and Development Program of China (No. 2012BAD14B11)

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    Abstract:

    【Objective】 Zinc (Zn) deficiency in humans caused by inadequate dietary intake is a nutritional problem, which affects approximately two billion people all over the world. It is well known that low zinc (Zn) availability in soil is an important reason for low Zn content of cereal grain, consequently resulting in Zn malnutrition in humans who rely mainly on cereals as staple food. Organic carbon in soil, especially its labile fraction, plays a decisive role in Zn translocation and transformation through changing soil chemical properties (i.e. pH and carbonate) and complexing and chelating Zn, of which the latter is one of the most important factors controlling solubility and mobility of Zn in the plant-soil system. Nowadays in China, the major approach to improvement of quantity and quality of soil organic carbon in cereal cropland is to incorporate crop straw, instead of the traditional organic manure and compost. When straw is incorporated, changing soil labile organic fractions, soil Zn responds correspondingly in diffusive translocation and transformation, of which the mechanism is still unclear in calcareous soils. 【Method】 In view of the above-mentioned scientific issue, an incubation experiment was carried out in greenhouse, using the half-cell device to evaluate effect of crop straw return on Zn availability (diethylenetriamine penta–acetic extractable Zn, i.e. DTPA-Zn) Zn diffusion and Zn transformation in calcareous soil. The soil treated with ground maize straw (0, 15 g kg-1 soil) and/or ZnSO4?7H2O (0, 20 mg Zn kg-1 soil) was placed in the 10-mm central compartment of the device, leaving the lateral compartments packed with untreated soil. After 45 days of incubation, the soils in the central cell and lateral compartments were collected with a frozen microtome for analysis of soil DTPA-Zn, total Zn, Zn fractions, soil organic carbon and its fractions (i.e. dissolved organic carbon and its SUVA254, humic substances, and fulvic and humic acids). 【Result】 Straw return alone significantly increased the concentrations of soil organic carbon and fractions of labile organic carbon (i.e. dissolved organic carbon and fluvic acids), but didn’t have much impact on diffusion of DTPA-Zn due to the weak response of soil DTPA-Zn in concentration in both central cell and lateral compartments. Additionally, straw return alone did not change proportions of Zn fractions in total Zn and it is because most Zn in the soil was strongly fixed in the fraction of residue (Res-Zn) that the response of Zn in transformation to the increased labile organic carbon was weakened in the soil. Zn addition alone significantly increased the fraction of Zn loosely bound to organic matter (Lom-Zn) and its distribution in total Zn; and greatly increased concentration of soil DTPA-Zn and its diffusive translocation in the central cell. However, diffusion of DTPA-Zn was only detected within the radius of 15 mm of the fertilized point after 45 days of incubation, which was attributed to immobilization of the added Zn. DTPA-Zn concentration in the central soil applied with straw and Zn was similar to that in the soil treated with Zn addition alone, but diffusion of DTPA-Zn was detected within the radius of 20 mm of the fertilized point after 45 days of incubation. Furthermore, the former was much higher than the latter in both cumulated diffusion and diffusion rate. The return of straw in addition to Zn application increased the fractions of labile organic carbon, such as dissolved organic carbon and fluvic acids, which inhibited transformation of added Zn into immobilized Zn (i.e. Res-Zn), thus increasing of DTPA-Zn concentration and its diffusion. 【Conclusion】 Consequently, in the case of straw return, Zn addition is a promising practice to increase concertation and diffusion of DTPA-Zn simultaneously in the calcareous soil.

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CHEN Yanlong, JIA Zhou, SHI Jianglan, LIU Ke, WANG Shaoxia, TIAN Xiaohong. Effect of Straw Return on Diffusion, Translocation and Transformation of Zinc in Calcareous Soil[J]. Acta Pedologica Sinica,2018,55(3):721-733.

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History
  • Received:July 26,2017
  • Revised:January 27,2018
  • Adopted:February 07,2018
  • Online: March 01,2018
  • Published: