Forest soil nutrient classification method based on spatial analysis

In order to provide scientific basis for precise fertilizing for fast-growing trees, and exploring a suitable forest soil nutrient classification method, a grid soil sample method was used in Guangxi Leli Forest Farm. The soil available phosphorus in each grid was calculated and interpolated. Based on forest resources planning data, the average soil available phosphorus in fast-growing Chinese fir unit was extracted. Then we calculated average annual growth and relative annual growth where in medium available nitrogen and available potassium. The relationship between the relative annual growth and soil available phosphorus was fitted with “logarithmic” type. Soil phosphorus contents corresponding to the average annual growth of 50%, 75%, 90% and 95% were calculated. Then the area of soil available potassium critical value is divided into: 2.6, 4.0, 5.7 and 6.3, respectively, according to the results of classification.