Effect Of Fertilization On Soil Biochemical Activity And Quality Of Tobacco

Tobacco is a kind of staple cash crop, it plays an important role in national production and economic development.Recently, continuous cropping and abusing chemical fertilizer leads to the decrease in tobacco quality and soil fertility. So it is important for tobacco production to have study on the effect of fertilization on soil biochemical activity and quality of tobacco. So that we can select the optimum fertilization model and have knowledge of relationships between fertilizer, soil characteristic (chemical and biology) and quality of tobacco.There has been many reports about fertilizing in tobacco field. However, tobacco has obvious regional characteristic and there are few reports about the study of fertilizing of tobacco field from the view of soil biology and biochemical activity, especially there is no report about the effect of fertilizer on soil enzymatic kinetics. So it is necessary to discuss this issue.We studied the effect of different fertilizations(ck,chemical fertilizer, tobacco- specific fertilizer, organic manure, organic manure and chemical fertilizer) on quality of soil and tobacco in longxian baoji city Shaanxi province. We also selected the optimum fertilization model in order to provide evidences to flue-cured tobacco production in Weibei dryland of Shaanxi province. The results were as follows:1.Fertilizers improved soil fertility. Compared with other treatments, in organic manure and chemical fertilizer treatment, Alkali N, Available P, Available K in soil increased significantly. This indicated that organic matter combined with chemical fertilizer can increase the soil nutrient.2.Agronomical character of tobacco and tobacco quality were improved by appling fertilizers.There were significant or remarkably significant positive correlations between organic, Alkali N, Available P of soils and agronomical characters of tobaccos(e.g. plant height, leaf numbers, stem girth, knot length,maximum leaf length and width).And there were the same relations between the Available K in soil and Nicotine, Nitrogen and Potassi in tobacco. This indicated that fertilizer improved quality of soil, encouraged growth of tobacco and harmonized chemical composition of tobacco, improved tobacco quality finally. The model of organic matter combined with chemical fertilizer had the best effect, it can be the best one among fertilizers.3.Fertilizers improved soil enzyme activity, especially organic matter combined with chemical fertilizer. It remarkly increased activities of urease, invertase, alkaline-phosphatase, dehydrogenase, catalase. Organic matter model was following. The positive or apparent positive correlation was found between the activities of urease, invertase, alkaline- phosphatase, catalase and organic, Alkali N, Available P. So we concluded that the four enzymes could evaluate the soil fertility.4.Total enzymatic activity constructed by ourselves could more accurately reflect the levels of soil biochemical activity and fertility of different fertilizations. From the view of soil enzyme, it was also concluded that organic matter combined with chemical fertilizer was a better one.5.The effect of fertilizers on soil micro-organism was different. In general, bacteria increased significantly by appling fertilizers, there was no regular changes in the actinomyces but big varies in fungi. Only tobacco-specific fertilizer had more significant effect than ck. The two models of organic manure, organic manure and chemical fertilizer increased microbe number. And the McIntosh index was the highest in this two models .From the view of micro-organism, organic matter and organic matter combined with chemical fertilizer were better fertilizers.6.Accoring to urease,invertase and alkaline-phosphatase enzymatic kinetics, we concluded that K_m changed in the same rank quantitatively, but K_m of urease and alkaline-phosphatase of fertilizers were lower than ck. V_max, V_max/K_m and k increased after appling fertilizers increased significantly, especially in organic matter combined with chemical fertilizer treatment. It indicated that fertilizers not only increased content of enzyme, but also speeded the combination of enzyme and substrate and separation of production and enzyme and increased the speed of reaction.7.There were significant or remarkably significant positive correlations between V_max,V_max/K_m, k and Organic matter, Alkali N, Available P. So the three enzymatic kinetics could be indexes to evaluate fertilizer effect.