| The study area is located in Ning County of southeastern Gansu province. We collected data from the second soil survey report conducted in the early 1980s and soil sampling measurement data in 2007, respectively. Based on the above data source, we analysed spatio-temporal variation of topsoil nutrients in croplands and evaluated the cropland fertility of Ning County.The results showed that:(1) Both topsoil SOM and TN increased significantly in those soils such as Alluvial soil, Huangshan soil, Loessal soil and Heilu soil. These were mainly attributed to rapid increasing organic matter return resulted from increasing fertilizer application and crop biomass. However, the mean topsoil SOM and TN concentration in croplands of Grey-cinnamon soil, Huishan Soil and Huimian Soil in 2007 showed a significant decrease trend compared with that in 1984.All of the topsoil SOM, AK and AP displayed moderate spatial heterogeneity, with the value in C/(CO+C) of 0.500,0.500 and 0.516, respectively.(2) The total cultivated land area of Ning County is 86251.3 ha which can be divided into six grades. The area of grade one to grade two is 27295.4 ha, grade three 14732.7 ha, grade four 22037.0 ha, grade five to grade six 22186.1 ha, amounting to 31.6%,17.1%,25.6%,25.7%, respectively.The study will play a positive role in promoting the rational allocation of cultivated land, optimizing farming production structure in Ning County.
|
PDF Full Text Request