Abstract:
In order to clarify the soil nutrient characteristics and fertility abundance and deficiency of typical tobacco fields in Hengyang City, Hunan Province, the main planting area of strong flavor type tobacco leaves in China, this study selected 9 representative tobacco-growing towns to observe and sample the topsoil and profile (0~100 cm) soil of tobacco fields, and clarified the profile nutrient characteristics and fertility suitability of 8 soil fertility indicators (pH, organic matter, total nitrogen, alkali-hydrolyzed nitrogen, available phosphorus, available potassium, exchangeable calcium, exchangeable magnesium) in typical tobacco fields. The results showed that the topsoil of typical tobacco fields in Hengyang was generally suitable for acidity and alkalinity, the content of organic matter content was high, while the levels of total and alkali-hydrolyzable nitrogen were suitable. However, the available phosphorus was severely deficient, and the gap between the abundance and deficiency of available potassium was obvious. The content of exchangeable calcium was suitable or higher, whereas that of exchangeable magnesium was suitable or lower. On the whole, the content of each index was the highest in the plough layer (0~20 cm). With the increase of profile depth, pH and available potassium had no obvious regularity. The contents of organic matter, total nitrogen and alkali-hydrolyzed nitrogen showed a trend of ‘down-up-down’, and the rising inflection point generally appeared in the depth of 60-80 cm. The content of available phosphorus decreased slowly (except for Chashi Town, Guanshi Town and Banqiao Town). The content of exchangeable calcium in some tobacco fields 20-60 cm increased first and then decreased, while that in Chashi Town showed a downward-upward-downward trend, and the remaining tobacco fields did not change much. The content of exchangeable magnesium decreased slowly. The changes of available phosphorus, available potassium and exchangeable calcium in Chashi Town tobacco field were significantly different from those in other tobacco fields. The results of soil fertility suitability evaluation in Hengyang showed that the indexes of available phosphorus, alkali-hydrolyzable nitrogen and available potassium had significant restrictive effects on the soil fertility adaptability index (SFI) of typical tobacco fields in Hengyang. The fertility of typical tobacco fields reached medium and high levels as a whole, and only Hongshi Town had low fertility. In the future, soil nutrient conservation and fertilization optimization measures should be carried out to improve the content and effectiveness of phosphorus, potassium and magnesium in soil, so as to ensure the nutrient balance between tobacco fields and tobacco leaves in Hengyang.