Foliar nutrition diagnosis of Castanea mollissima by using Diagnosis and Recommendation Integrated System

Hebei province is one of the largest chestnut production areas in China, especially Qianxi County，and the production of chestnut is the main income for the local farmers. However, there are some problems in chestnut production such as unreasonable application of fertilizers. Nutrition and fertilization are important factors in determining the yield and quality of chestnut. With the aim of providing reference for nutrition diagnosis and balanced fertilization in chestnut production, foliar samples were collected from 23 representative orchards of Castanea mollissima cv. zaofeng, and foliar nutrition diagnosis was conducted by using diagnosis and recommendation integrated system (DRIS). The results show that the optimum concentrations of N, P, K, Ca, Mg, Fe, Mn, Cu and B in leaves of Castanea mollissima are (1.9970.169)%, (0.1300.012)%, (0.5710.059)%, (1.2950.112)%, (0.6790.075)%, 685.87576.159 mg/kg, 593.780131.690 mg/kg, 12.7261.507 mg/kg and 43.4187.889 mg/kg. The suitable ranges of DRIS indices for N, P, K, Ca, Mg, Fe, Mn, Cu and B are －2.267－1.894, －2.157－2.108, －2.080－2.450, －1.719－1.224, －3.960－2.962, －1.807－1.510, －3.002－4.079, －0.826－0.943 and －2.127－2.773. The chestnut orchards in different areas of Qianxi County have different orders of nutrition requirement, and the orchards in northwest and southwest parts of Qianxi County are in Mn nutrient deficiency. There is a significant negative correlation (P0.01) between nutrition imbalance index (NII) and the yield. The results of correlation analysis indicate that positive correlations or negative correlations between different mineral elements in leaves are not significant in the middle of July, which suggests that the middle of July is the ideal time for topdressing for avoiding the fertilizer loss due to the antagonism of the elements.