Changes of Enzyme Activities and Nutrient Contents in Continuous Cropping Tobacco Soil for Different Years

Abstract：In order to study the changes of main fertility levels of continuous cropping tobacco soil,the activity of main enzymes( invertase,urease,catalase and acid phosphatase) ,pH value,contents of organic matter,nitrogen,phosphorus and potassium were measured in typical flue-cured tobacco planting regions with continuous cropping tobacco for different years,mainly at five counties( district) of Henan( Jiaxian, Shaoling district, Fangcheng county, Xiangcheng county and Songxian ) . The results showed that the activities of invertase and urease were increased in the second year of the continuous planting,and there was a declining tendency with the increase of continuous planting year in the most of tobacco growing areas,and there was a directly reducing with the planting years increase in some areas. The catalase activity increased in the second year of continuous planting,then deceased,and then tended to be stable after continuous planting for 3 years. The acid phosphatase activity declined gradually with the increase of continuous planting year within 3 years of continuous planting,then tended to be stable. The soil pH value decreased with the increase of continuous planting years in most of places, except Fangcheng county, which were 5 . 6—6 . 6 . The contents of organic matter increased with the increase of continuous planting years in Jiaxian and Songxian,were not obviously changed in Fangcheng county and Xiangcheng county, and increased first and then decreased in Shaoling district. The contents of total nitrogen decreased in most of the areas ( such as Jiaxian, Xiangcheng county, and Songxian ) with the increase of continuous planting year,and increased in the early planting years then reduced in Shaoling district,and increased in Fangcheng county. The contents of available phosphorus decreased first and then increased in Shaoling district and Songxian,and on the contrary in Jiaxian,and were not obviously changed in Fangcheng county and Xiangcheng county. The contents of available potassium varied differently in different places. Overall, there were change rules for main enzymes activity and nutrient index in different planting tobacco regions with the increase of continuous planting years, but which were not completely consistent in different regions, which indicated that the tobacco planting conditions, farming activities influenced the main enzyme activities,pH value, contents of organic matter, nitrogen, phosphorus and potassium in the soil. Therefore,it requires different solution for different planting area to solve the tobacco continuous cropping obstacles.