Effects Of NPK Ratio On Growth, Development, Yield And Quality Of Flue-cured Tobacco

Tobacco is a unique leaf-oriented cash crop whose growth and nutrient absorption are heavily affected by various nutrients; therefore, cultivation of good soil environment is essential to secure its quantity and quality as well as sufficient and timely supply of various nutrients for tobacco is an important technique to improve its yield and quality. With 47,000 hm² tobacco growing areas, Chongqing is one of our country's main tobacco growing areas. Tobacco industry is pillar industry for people in Wuling district and farmers in Three Gorges Dam Area to alleviate poverty and become prosperous and from which it also generates the primary income for financial taxation of poverty counties of national level such as Pengshui, Youyang. The current specialty fertilizer for tobacco in Chongqing used to make great contribution to tobacco growth and farmers' income; however, the effect of fertilizer will vary with soil nutrient whose contents are highly affected by cultivation, fostering, types of crops and agricultural activities. The methods of field experiment and indoor analysis are adopted in this paper to adjust a suitable dosage for tobacco fertilizer according to the changes of soil fertility. This paper aims at providing scientific basis for suitable dosage fertilizer of tobacco and excellent tobacco leaf manufacture in Chongqing bases on the researches has been done in Chongqing between 2006 and 2007 focusing on the effect that different proportion of N, P₂O₅ and K₂O has on the growth, nutrient absorption, economic character, quality and soil nutrients of tobacco. The main results of experiments are as follows:1. The effects of NPK ratio on growth and nutrient absorption of flue-cured tobaccoExperiment results showed that, compared with treatment CK, the NPK ratios were 1:1.3:2(treatment 2), 1:1.6:2.5(treatment 6) and 1:1.3:3(treatment 8) can increase height, stem diameter, leaf numbers and maximal leaf area of flue-cured tobacco. Under the different NPK ratios, with the advance of flue-cured tobacco growing period, the dry matter accumulation of flue-cured tobacco increased. In each period, the dry matter accumulation in different organs of flued-cured tobacco showed the order of leaf>stem>root. In mature period, the maximal dry weight of root, stem and leaf appeared in treatment 6. The maximal N content appeared in treatment 8. The maximal P₂O₅ content appeared in the treatments when the NP ratios were 1:1.3 and 1:1.6. The maximal K₂O content in different organs of flue-cured tobacco appeared in treatment 7 and treatment 8. Increasing the P and K levels contributes to increasing the absorptiong of P₂O₅ and K₂O of the flue-cured tobacco. Treatment 6 and treatment 8 made for the different organs of flue-cured tobacco accumulating N, P₂O₅ and K₂O.2. The effects of NPK ratio on soil nutrients Under the different NPK ratios, the variation tendency of 0-20cm and 20-40cm depth of soil are nearly the same. At the resettling stage, the NH₄⁺-N and NO₃^--N contents of 0-20cm depth of soil reached the max, as the flue-cured tobacco entered the boosting period, the N contents in the soil decreased obviously. In the mature period, some treatment of NH₄⁺-N and NO₃^-- N contents increased, others decreased. As the soil layer was deeper, the influences of NPK ratio to the NH₄⁺-N and NO₃^-- N contents were weaken. The NH₄⁺-N and NO₃^-- N contents of 20-40cm depth of soil were less than the NH₄⁺-N and NO₃^--N contents of 0-20cm depth of soil. Using P fertilizer caused the accumulation of the availabe P of 0-20cm depth of soil. At the resettling stage, the availabe P contents of 0-20 cm depth of soil were between 21.02mg/kg and 38.41mg/kg. As the boost of flue-cured tobacco continues, the availabe P contents of 0-20cm depth of soil were on downtrend as a whole. In each period, the availabe P contents of 20-40cm depth of soil differ during 9.79-17.33mg/kg, 14.81-27.19mg/kg and 8.22-10.30mg/kg。The availabe P downward migration can be found in the soil layer profile. The soil availabe K went up with the potassium fertilizer application. At the resettling stage, the availabe K contents of 0-20cm depth of soil were between 206.94mg/kg and 276.80mg/kg. It was important for promoting the nutrient uptake by tobacco plant to raise the potassium supply capability of soil through adding potassium application amount. The results showed that as improved P level and K level, the availabe P and availabe K increased in 0-20cm of soil profile.3. The effects of NPK ratio on the economic properties and quality of flue-cured tobaccoThe economic properties and quality of flue-cured tobacco leaves were influenced remarkably by different NPK ratios. Treatment 6 had the highest production and production value, treatment 7 had the lowest production. Treatment 6 took the first place in average price; treatment 5 had the lowest average price. Treatment 6 had the highest ratio of high grade leaves. When the NPK ratios were 1:0.5:3,1:1.6:2.5, 1:1.3:2 and 1:1.3:3, ratios of middle grade leaves were higher than treatment CK. As improved P and K levels, the total sugar, reductive sugar, the ratio of total sugar and protein, the ratio of reductive sugar and nicotine, the ratio of total sugar and total N in tobacco leaves increased. The results showed that as improved K level, the K₂O and the ratio of K₂O and Cl in the tobacco leaves increased. The harmonies of flue-cured tobacco leaves of T6,T7 and T8 treatment were the better of all treatments.Colligating economic character and quality of flue-cured tobacco, the optimum NPK ratios were 1:1.6:2.5 and 1:1.3:3 in Chongqing.According to the above all, the optimum NPK ratio was 1:1.6:2.5 in Chongqing. Secondly, the more suitable NPK ratio was 1:1.3:3.