[Study on Leaching Characteristic of Heavy Metal in the Manure-Amended Soil Using ICP-MASS].

Based on an 11-year fertilizer field trial (located at the lower liaohe river plain), the effects of different organic manure application rates on the accumulations of heavy metals (Cu, Zn, Cd and Cr) in surface soil (0-20 cm), and the leaching characteristic and vertical migration pattern of heavy metal have been investigated in this rainfed agro-ecosystem using undisturbed soil columns. The result showed that the content of heavy metal in surface soil was elevated with the increase of manure application. The increasing magnitude was in the order of Cd>Cu>Zn>Cr. According to the Chinese soil quality standard (GB15618-1995), the application of manure (not exceeding 50 t · ha⁻¹) did not result in serious heavy metal pollution in the surface soil. Chromium met the Grade I , and Cu and Zn met the Grade II; whereas, Cd was almost exceeded the threshold of Grade III. The potential risk of Cd in soil should be paid more attentions in future research. According to the National water quality standard (GB/T14848-93), the Cu and Cd concentrations in leachate samples were up to the Grade II except only a few samples that fell in Grade III. Furthermore, Cr in the leachate all matched Grade I water quality standard. These results indicated long-term application of manure (not exceeding 50 t · ha⁻¹) in our site had not induced contaminant risks of heavy metals in underground water. In addition, the Cu, Zn and Cd (except Cr) in leachate all declined with the increase of soil depth, indicating the low capacity of vertical migration of heavy metal. Among the four heavy metals, Zn and Cr tended to be leached into deep soil, whereas Cu and Cd were more prone to be accumulated in surface soil.

[Study on the main influencing factors of black soil spectral characteristics].

To develop soil properties quick measuring methods, promote the development of quantitatively remote sensing studies relating to terrestrial ecosystem, and deepen the application of remote sensing in agriculture, the hyperspectral reflectance of black soil in Songnen Plain, northeast China, was analyzed with spectral analysis methods (continuum removal, spectral angle match and spectral feature fitting) and statistic methods to discover the reflectance spectral characteristics and its influencing factors. The results are as follows: the soil parent material determines the basic characteristics of reflectance of the black soil, which is the mixture of montmorillonite and illite, and consistent with mineral analysis result. Organic matter is the main factor determining the curve shape of black soil reflectance in the region shorter than 1 000 nm, and indirectly influencing the reflectance in the region longer than 1 000 nm because of the correlation with soil moisture and mechanical composition. The varying process of soil reflectance with changing soil moisture can be quantitatively described with cubic equation, and moisture mainly changes the reflectance value but not the curve shape. Black soil reflectance is not influenced significantly by Fe, which is different from soils of south China. Roughness mainly impacts on the soil reflectance value but not the shape feature. The spectral feature of straw reflectance is remarkably different to that of black soil, and impacts on both the value and curve shape of black soil reflectance. Different soil tillage measurements result in different moisture holding ability and the amount of straw for different farm fields, and influence the reflectance further, with the order of soil reflectance from high to low is: no tillage, moldboard tillage, combination tillage, reduced tillage, and rotary tillage.

[K fertility and K deficit index of aquic brown soil under different fertilization systems].

A 15-year fertilization experiment was conducted on an aquic brown soil to study the variations of its K fertility and the index of K deficit under different fertilization systems. The results indicated that no K application accelerated the depletion of soil K, representing a certain decrease of soil available and slow-release K. Applying K alone could not keep soil K in balance, still having a decrease of soil available and slow-release K. The application of recycled compost combined with appropriate amount of fertilizer K could compensate soil K expenditure to a certain degree, and keep the concentrations of soil available and slow-release K somewhat constant. The statistic analysis on the past years test results showed that the critical values of soil available K in corn- and soybean fields obtained by crossing method were all 73 mg x kg(-1).

[Effects of land use type on soil organic carbon storage in aquic brown soil].

The profile distribution of soil organic carbon (SOC), its storage, and carbon/nitrogen (C/N) ratio at the depth of 0-100 cm under different land use types were investigated in this paper. The results showed that the profile distribution of SOC varied significantly with land use type. The SOC contents in each soil layer in forestland, mowing land and wasteland were all higher than that in agricultural land. In all land use types, SOC was significantly correlated with soil total N. Soil C/N ratio generally decreased with depth, which was higher in forestland than in mowing land, wasteland and bare land, and was the lowest in agricultural land. At the depth of 0-100 cm, the annual sequestration of SOC in wasteland was 4.52, 4.25, 4.46 and 3.58 t x hm(-2) more than that in farmland with no fertilization, farmland with recycled manure application, farmland with N, P and K fertilization, and farmland with the application of both recycled manure and N, P and K, respectively, suggesting that wasteland had a great potential in increasing SOC storage.