Composition Characters of Soil Humus and Their Relationships with Routine Chemical Components in Tobacco Leaves in Middle Henan Tobacco Growing Areas

Twenty-two cultivated soil samples and corresponding tobacco leaf samples were collected from tobacco growing areas in the middle of Henan Province.The composition characters of soil humus and their relationships with the routine chemical components in tobacco leaves were investigated.The results indicated that:1) The average carbon content in humus(humus-C) was 8.44 g/kg,and the relative contents of humic acid(HA),fulvic acid(FA) and humin(HM) accounted for 20.53%,23.21%,56.26% of total humus content,respectively.Most of HA/FA ratios ranged from 0.7 to 1.0,and the humification degree of humus was relatively lower.2) Humus-C content extremely significantly positively correlated with alkali-hydrolyzable nitrogen and available phosphorus in soil;HA-C,FA-C,HM-C significantly or extremely significantly positively correlated with available phosphorus in soil.HA/FA ratio presented little relation to nutrient content in soil,however,it raised with the increase of humus-C content.3) Humus-C had little effect on tobacco routine chemical components,the potassium content in tobacco leaves tended to decrease with the increase of HA ratio and FA ratio and with the decrease of HM ratio,while it was on the contrary for starch content.