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Soil organic carbon (SOC) in agricultural land is influenced greatly by indeterminate human activity, making it difficult to understand the spatial pattern of SOC. Soil pH and topographic conditions are key indices in the Chinese Soil Genetic Classification System (CSGCS) and manage some critical factors that control the dynamics of SOC either directly or indirectly. To identify the extent to which pH and topographic factors control SOC levels in dry farming cropland soils of the mountainous region of Southwest China, we compared the differences along topographic gradients, and analysed the contribution of different factors in determining SOC status using analysis of variance (ANOVA) and linear regression. Our results indicated the SOC levels ranged from 10.46 g•kg− 1 to 37.60 g•kg− 1 and were significantly correlated with soil pH, landscape position, slope and elevation (p

The properties of soils derived from carbonate rock, red residua, and sand-shale in Guizhou province, China are essentially different. However, the effects of parent material and anthropogenic activities on the concentration of trace elements when the soils are converted into paddy soils are unknown. A total of 319 paddy topsoil samples (0–20 cm) were collected in a typical region to determine their relative contribution to the concentrations of trace elements in the soil. The results indicated that the contents of trace elements were far beyond the uncultivated soil background and the input of organic fertilizers was presumably responsible for accumulation of trace elements. In addition, principal component analysis showed that the first component included Cd, Cr, and As, which strongly associated with anthropogenic activities. Pb and Hg formed the second component, which related to both parent materials and anthropogenic input. Furthermore, the Cr and Hg contents in paddy soil derived from carbonate rock have higher values than other types of soils partly because of the high background values as well as slightly alkaline condition. In the paddy soil derived from red residua, high physical clay content accounted for enrichment of Pb.

For establishing rational farming mechanism, it is essential to know the relative contribution of different geological background and anthropogenic activities to trace elements in agricultural soil. In this paper, 282 surface soil samples were collected based on the different geological background. Five harmful trace elements (As, Cd, Cr, Hg and Pb) were analyzed. The results indicated most of trace elements contents were far beyond the threshold of uncultivated soil background, which indicate anthropogenic input strongly influenced on trace elements in agricultural soil. In addition, correlation analysis showed trace element contents exhibited high relationships with soil pH, C/N and physical clay (

To research the influence of Pseudostellaria heterophylla planting patterns on soil nutrients.The root zone and non-root zone soil nutrient status were analyzed, which included the crop rotation, intercropping, relay cropping, 1-year planting, 3-year planting, 6-year planting and 10-year planting.The results showed that there were differences in the soil nutrient of root zone among different planting patterns. The soil nutrient of root zone in seven different planting patterns were all significantly higher than that of non-root zone soil. And the soil nutrients of root zone showed a significant enrichment. The enrichment ratio of total K and Olsen K in 6-year and 10-year planting were both negative value, which indicated that the soil potassium was deficiency. The average pH value of root zone was 0.32 lower than that of non-root zone. There was a significant positive correlation between the organic matter value and the total nitrogen content in root zone and non-root zone (P0.01). The soil nutrients were high in crop rotation and intercropping, it would he helpful to improve soil quality and absorption to nutrient.The reasonable application of nitrogen fertilizer ,organic fertilizer and potash fertilizer can significantly increase the organic matter content in soil ,and it will help to retain the fertilizer capacity of soil.

To determine the effects of parent material and land use on the concentration of trace elements in the agricultural topsoil of Guizhou Province, China, a total of 584 agricultural topsoil samples were collected in a typical region. The results indicate that the contents of trace elements (As, Cd, Cr, Hg, and Pb) in agricultural soils were greater than in the uncultivated soils, and the paddy fields exhibited higher contents of trace elements than dry lands. The enrichments of most trace elements in agricultural topsoil derived from carbonate rock were more serious. In paddy fields, Cd, Cr, and As showed positive relationships with soil organic matter (0.01) but were not affected by pH, carbon-to-nitrogen (C/N) ratio, and clay (0.05). Lead and Hg formed the second component in principal component analysis (PCA) and were closely related to pH and clay content. In dry lands, the trace elements were well correlated with pH, C/N, and clay (0.05). Analysis of PCA and correlation showed that Cd, Cr, and Hg were mainly derived from inorganic fertilizers, whereas Pb and As were primarily from organic manures. These results suggest that the effect of anthropogenic activities on paddy fields is more serious than on dry lands. Parent materials not only serve as sources of soil trace elements but also control the loss and accumulation of trace elements by affecting soil physicochemical properties, especially in dry lands.