| Land fertility evaluation is one of the fundamental tasks in soil science. Take Zhejiang Songyang County as an example: the result of its land fertility evaluation based on the evaluation model which is recommended by Zhejiang's authority consists with its actual land situation moderately. However, this official model has taken all aspects of the whole province into consideration. So, inevitably, some of its evaluation criteria are unnecessary for Songyang. To avoid needless evaluating cost, 1017 sample points are grouped herein by topography (Takaoka, hill and basin plain), and the correlation analysis is performed to filter the evaluation factors in each group. Then a new land fertility evaluation model is established through scaling up the weight of these factors in proportion referring to the official one. The evaluation result matches well with that comes from the official recommended one.Inverse Distance Weighted (abbr. IDW) and Ordinary Kriging (abbr. OK) are applied to compare the land's Integrated Fertility Index (abbr. IFI) as well as its content of soil organic matter, phosphorus, potassium and total nitrogen. The result demonstrates that Inverse Distance Weighted (abbr. IDW) performs more precise.According to the Spatial Interpolation for both grouped and ungrouped data, data-grouped can effectively reduce the interpolation error of the land's Integrated Fertility Index (abbr. IFI) as well as its content of soil organic matter, phosphorus, potassium and total nitrogen. So interpolating after the data-grouped is a good choice. However, the data of total nitrogen content doesn't show any big difference in this spatial analysis. It means that data-grouped doesn't make any sense for this data. Therefore, the ungrouped data should be used instead.With the selective method, the distribution maps of Songyang's land fertility and soil nutrients come out according to the results of spatial interpolation for the sample points (Takaoka, hill and basin plain). And meanwhile, the characteristics of spatial variability of land soil nutrients are studied in detail. |
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