Evaluation and research on chestnut quality under different soil conditions

Abstract：【Objective】To analyze the relationship between chestnut quality and soil nutrients of different soil types, the key soil factors for chestnut quality formation were screened, and the comprehensive quality of chestnut under different soil conditions was evaluated by the principal component analysis. 【Methods】Six soil types included brown soil, cinnamon soil, yellow cinnamon soil, yellow brown soil, yellow soil and red soil. The organic matter, pH value, total nitrogen, total phosphorus, total potassium, hydrolytic nitrogen, available phosphorus, available potassium, available iron, available zinc and available manganese contents in different soil types were determined. The differences in soil nutrients and chestnut quality under different soil conditions were analyzed by single factor analysis of variance. Correlation analysis was used to explore the effects of these soil nutrient factors on the chestnut quality (water content, single grain weight, amylopectin/total starch, soluble sugar, protein, fat and total phenol contents). The comprehensive quality of chestnut was evaluated based on the principal component analysis. 【Results】(1)The nutrient contents of different types of soil varied greatly and the coefficient of variation of pH value, organic matter and mineral elements content ranged from 8.60% (pH) to 48.35% (totalphosphorus), and the contents of organic matter, total potassium, alkali- hydrolytic nitrogen and available phosphorus of brown soil were the largest. The pH and contents of total nitrogen and available potassium of cinnamon soil were the largest. The total phosphorus content of yellow cinnamon soil was the largest; The contents of available zinc and available manganese of yellow soil were the largest; The available iron content of red soil was the largest. Organic matter content was positively correlated with total nitrogen and potassium (p＜0.01) and available potassium (p＜0.05). There was a significant positive correlation between pH and available potassium (p＜0.05). Total nitrogen content was positively correlated with total potassium (p＜0.05) and negatively correlated with available iron (p＜0.05). Available zinc content was negatively correlated with available phosphorus and available potassium (p＜ 0.05). (2) Under different soil conditions, the variation coefficient of each chestnut quality index ranged from 5.99% (water content) to 26.32% (soluble sugar). The single grain weight on yellow soil (10.73 g) was significantly higher than that on other soils. The water content was the highest on yellow soil (47.31%), which was significantly higher than that on other soils. Soluble sugar content was the highest on brown soil (19.52%) and significantly higher than that on other soils. The ratio of amylopectin to total starch ranged from 0.44 to 0.60, and there was no significant difference between brown soil and cinnamon soil, and there was no significant difference among other soil types. The protein content was the highest on yellow soil (8.50%), the fat content on cinnamon soil was the largest and significantly higher than that on other soil types (2.22% ), the total phenol content was the highest on cinnamon soil (2.21 mg · g^-1 ). The single grain weight was positively correlated with the available manganese content. Available potassium content was positively correlated with soluble sugar content and amylopectin/total starch content. pH value was positively correlated with fat content and negatively correlated with protein content, and total phenol content was positively correlated with total nitrogen content. (3) Principal component analysis showed that the eigenvalues of the first three principal components were all greater than 1, and the cumulative variance contribution rate reached 96.70%, which can reflect most of the information of chestnut quality indicators. Among them, the variance contribution rate of first principal component was 46.94%, the soluble sugar (0.96) and amylopectin/total starch contents (0.91) with larger eigenvectors were classified as sweet and waxy quality of chestnut, and the second principal component eigenvector was protein (0.86) and fat (0.96), and it belonged to the storage quality of chestnut. The third principal component feature vectors, which were classified as the nutritional quality of chestnut. The sweet glutinous and storable quality of chestnut on brown soil was the best, while that on yellow soil was the worst. The nutritional quality of chestnut on brown soil was the best and that on red soil was the worst. Protein (0.86) and fat (0.96) were the third principal component feature vectors, which were classified as the nutritional quality of chestnut. The evaluation results showed that the comprehensive quality of chestnut on brown soil was the best, followed by brown soil, yellow cinnamon soil, red soil, yellow brown soil and yellow soil.【Conclusion】The sweet and waxy quality of chestnut nuts was the best on brown soil and the worst on yellow soil. The storage quality of chestnut nuts was the best on brown soil and the worst on yellow soil. The nutritional quality of chestnut was the best on cinnamon soil, but the worst on red soil. The comprehensive score ranking results showed that the comprehensive quality of chestnut was the best on brown soil, followed by cinnamon soil, yellow cinnamon soil, red soil, yellow brown soil and yellow soil. Soluble sugar, amylopectin/total starch, single grain weight, water content, fat and protein content can be used as the indexes of principal component analysis to evaluate the comprehensive quality of chestnut.