Spatial variability of soil nutrients and GIS-based nutrient management in Yongji County, China
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Abstract:
Integrated nutrient management is important for sustainable agricultural production and protecting environment quality and has been widely investigated around the world. In this article the spatial variability of soil nutrients was investigated and a regionalized nutrient management system was developed using geostatistics and geographic information system technologies. A total of 511 GPS-referenced soil samples were taken in Yongji County, Shanxi province, China, and analysed for major soil nutrients: soil total nitrogen (TN), Olsen extractable phosphorus (OLSENP) and extractable potassium (EXTK). Low concentrations of nitrogen (N) and phosphorus (P) were found and they are likely to be the main limiting nutrients for crop growth in this county. Within the county moderate spatial dependence was found for all three soil variables, but at different spatial scales. The spatial distributions of TN, OLSENP and EXTK were estimated by using kriging interpolation. The cropped areas of the county were divided into fertilizer management categories consisting of four classes of TN, three classes of OLSENP and two classes of EXTK. For the targeted crop yields, regionalized fertilization maps of N, P and K in the county were produced using geographic information system. In 3-year field verification trials in two villages the crop yields of the wheat–maize rotation system increased by 10–20%, and farmers' cash income increased by 1550–2610 RMB ha−1 year−1 where regional fertilization recommendations were implemented, in comparison with traditional farmers' practices. The regionalized maps are a practical alternative to site-specific soil nutrient management approaches in areas where it is not practical, because of small farm size or other constraints, to use intensive soil sampling and chemical analyses.Keywords:
Nutrient Management
Geostatistics
Crop Rotation
A geostatistics method combined with GIS was applied to analyze the spatial variability of top-soil acidity in the typical area of Taihu Lake Region.The results showed that the spatial variability of soil pH was apparent in isotropy within the distance of 30km,beyond which the anisotropy of spatial variability was increasing due to the change of soil parent materials in the direction of NE34°.The semivariogram showed the soil pH had a relatively good spatial autocorrelation with the ratio of nugget to sill reaching 0.29,and the autocorrelative range extended to about 44km.The map of the soil pH interpolated through block Kriging depicted that the soil pH was higher in the northern part of the studied area than in the middle part,and the high spot of pH inlaid in the lower patch in the southern intervale.
Geostatistics
Variogram
Sill
Spatial Dependence
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