Effect Of Flue-cured Tobacco Continuous Cropping On Soil Chemical And Physical Properties And Tobacco Leaf Quality

Through the study of soil nutrient deficiency and its repair mechanisms on tobacco field continuous cropping obstacles in the city of Chongqing , this project mainly explored the way of mineral nutrition for the resumption in the tobacco fields and the releasing to nutrition disorders in continuous cropping obstacles of tobacco plant. The results showed that:1 Effect of tobacco continuous cropping on soil nutrient statusDue to the tobacco continuous cropping, the pH value decreased, average decrement of neighboring stubbles was 0.05 unit, leading to soil acidification; soil organic matter content would decrease year by year, average decrement of neighboring stubbles was 0.56 g/kg; the total nitrogen, total phosphorus and total potassium content of soil increased differently with the extension of cropping year: P(6%～31%)> K(6%～21%)> N(2%～12%); available phosphorus and potassium content lowered year after year, the level of reducing is P(6%～24%)> K(2%～10%), and available nitrogen content had a slight increase; The ratios of N/P, N/K, K/P increased significantly, which resulted in the imbalance of soil nutrient.2 Effect of tobacco continuous cropping on soil micro- ecosystemWith the increase of cropping years, catalase activity in soil continued to increase, invertase activity showed a declining trend, phosphatase activity rapidly reduced, following by a gradual increase, urease activity showed "N" word trend; the number of microflora lshowed that: bacteria> actinomycetes> fungi, the number of bacteria and actinomycetes fell with tobacco cropping, while the fungi rose.3 Effect of tobacco continuous cropping on tobacco available nutrientsPhosphorus and potassium content of tobacco lowered year after year , the level of reducing : P> K (phosphorus content dropped by about 16.7%～26.5%, potassium content about 10.4%～20.0%), and nitrogen had a slight increase in content(nitrogen increased by 2.2%～15.8%); in the three tobacco areas, tobacco sulfur and magnesium level was declined even with the increase of cropping years, and calcium content had first increasing and then decreasing trend. 4 The correlation analysis of the tobacco nutrients and the corresponding soil nutrientsThrough the correlation analysis of the tobacco nutrients and the corresponding soil nutrients in different stubbles, with the extension of cropping years, phosphorus, potassium, calcium, magnesium, sulfur content of tobacco and the corresponding element contents in the soil showed a strong positive correlation, while the total nitrogen of tobacco and soil available nitrogen was a weak positive correlation, the iron, molybdenum, zinc, boron and chlorine content and the corresponding element contents in soil were tested a strong positive correlation, in which tobacco chlorine and soil chlorine content achieved a significant positive correlation (P<0.05) in the third and multiple stubbles.5 Effect of tobacco continuous cropping on agronomic traits, yield and quality of tobaccoWith the increase of cropping years, trunk height, stem girth and internode of tobacco plant declined gradually, and the dome speed of upper leaves of tobacco plants had a downward trend; tobacco production, output value, the ratio of mid-high grade leaves declined in different extent;the nicotine, protein, and total nitrogen content in tobacco showed a marked increase trend, with total sugar and reducing sugar content in a clearly lowering trend; schmuck value, two sugar ratio and the ratio of sugar to nitrogen dropped significantly, the ratio of nitrogen to alkali and the ratio of potassium to chloride didn't change significantly. In the three tobacco areas, neophytadiene,solanone andβ-damascenone had a high content, and carotenoids had the most degradation products. With the extension of cropping years, total neutral aroma components of flue-cured tobacco decreased in the three areas, in which the highest was in Nanchuan followed by Fengjie and Shizhu. The neophytadiene, carotenoids and phenylalanine aroma components lowered year by year, and cembrane aroma and brown reaction products generally showed a decreased tendency, and differrent stubbles showed a similar laws, namely, the content in the first and second stubbles had no obvious changes, and the third and multiple stubbles changed markedly.6 Effect of soil remediation agent on soil micro- ecosystemThe soil enzymatic activity of different soil remediation agent treatment in different stubble changed,and had the respective pointedness: in the second stubbles, the XF3 treatment (mineral synergist, 25 g/plant+ (NH₄)₆Mo₇O₂₄·4H₂O, 0.7 g/plant) was beneficial to increase catalase, urease and phosphatase activity; in the third stubbles, XF2(mineral synergist, 25 g/plant + MgSO4, 10 g/plant) and XF4(mineral synergist, 25 g/plant+ MgSO₄, 10g / plant+(NH₄)₆Mo₇O₂₄·4H₂O, 0.7 g/plant) was beneficial to increase urease and phosphatase activity, XF1(mineral synergist, 25 g/plant) was in favor of the expression of catalase activity, XF3 treatment was more conducive to the expression of invertase activity; in the multiple stubbles, catalase and urease activity of XF2 and XF3were relatively high, XF4 was more conducive to the expression of invertase activity, XF1 more conducive to the expression of phosphatase activity. XF4, XF1 and XF3 treatments were advantageous to the growth of bacteria, fungi and actinomycetes respectively in the second stubbles; XF3, XF2 and XF3 treatments were beneficial to the reproduction of bacteria, fungi, actinomycetes respectively in the third stubbles; XF2 treatment was conducive to the propagation of the three microorganisms in the multiple stubbles.7 Effect of soil remediation agent on tobacco qualitySoil remediation agent treatment increased the number of tobacco leaves, trunk height and stem girth in three county of Shizhu, Nanchuan , Fengjie and so on, in which XF2 and XF4 treatment was most obvious, and helped to improve ratio of mid-high grade leaves, yield per mu, the average price, yield value per mu.