The Characteristics of Soil Humus in Growing Regions of Fresh-sweetness Type Tobacco

In order to understand characteristics of humus in clean aroma tobacco-growing regions(CATGR), the soil humus and its composition of 52 soil samples from Yunnan, Fujian, and Sichuan provinces with typical CATGR were analyzed. The results showed that humus and carbon contents of the soils in CATGR conformed to normal distribution. The carbon content of humus, humin, humic acid and fulvic acid were 16.3, 12.3,1.7 and 2.3 g/kg, and HA/FA was 0.75 on average. Humus and compositional carbon contents increased with soil development degree. The soil type from high to low as follows: Paddy soil > Red soil > Purple soil. The carbon content of humic acid in Fujian were the highest of paddy soil in CATGR, the soil HA/FA ratios in Fujian was the highest, and Sichuan was the lowest. There were significant differences of humus and compositional carbon contents on average among different regions. The averages of humus content and composition could be influenced by soil type of the samples, therefore, the assessment should consider the sample composition.