Soil fertility and its spatial distribution for Carya cathayensis stands in Lin'an, Zhejiang Province

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To identify soil fertility quality and its spatial distribution differences in Carya cathayensis stands and to guide farmers with fertilizer application, the main plantation area in Lin'an was selected for this study. In this study, differential GPS was used to locate and navigate in the field and a soil sample was collected within a radius of 10 m and a total of 189 soil samples were collected from 7 townships in Lin'an. Soil pH and status of nutrients (organic matter, available N, available P, and available K) were evaluated and their spatial distribution characteristics were revealed by geostatistics and Kriging interpolation. Results indicated that the average soil pH was 5.23 with 87% of the soil pH values in the range of 4-6 meaning soil was seriously acidic. The average organic matter content in the soil was 31.6 g·kg-1 with average available N of 155.40 mg·kg-1, available P of 14.04 mg·kg-1, and available K of 85.73 mg·kg-1. Soil organic matter, available N, and available K were abundant. According to the standard fertility grading for Zhejiang Soil (with first representing low content and fourth representing high content), soil organic matter was mainly in the third or fourth grades accounting for 54% of the soils and soil available N was in the third grade for 76% of the soils. Soil available K was more than 50 mg·kg-1 for 80% of the soils. Soil available P, however, was insufficient for 63% of the soils at less than 10 mg·kg-1 which meant the first or second grades. Coefficients of variation for soil nutrients were between 27.15% and 141.03% indicating that soil nutrients in the study area had different degrees of variability. Yield of C. cathayensis varied from town to town and had a spatial correspondence to soil nutrients. This study showed that stands were seriously acidic with soil organic matter, available N, and available K sufficient, but in most areas available P was insufficient to meet the growing needs of C. cathayensis.