| A field experiment was conducted at Shaoyang in Hunan province in 2007 and Yunyan 87 was chosen as material to study the effect of different covering treatments on soil physical and chemical properties, yield and quality of tobacco. Five different covering treatments were whole growth period straw covering (T1), whole growth period plastic film covering (T2), early growth stage plastic film covering (T3), straw and plastic film covering (T4) and growth without covering (T5). The main results are outlined as follow:(1) Soil temperature was regulated obviously by different covering treatments. Compare with T5, the surface soil temperature of T2, T3 and T4 were increased respectively by 2℃, 2.1℃and 1.3℃in 30 days after transplanting; Meanwhile, T1 was decreased by 5.5℃. Compare with T5, the temperature of 5cm, 10cm, 15cm and 20cm upper layer soil in 30 days after transplanting at T2, T3 and T4 were increased respectively by 0.9℃, 0.8℃and 0.6℃, and at T1 was decreased by 0.4℃.Soil moisture in different covering treatments decreased, then increased slowly in 70 days after transplanting. After more than 100 days, soil moisture decreased. In 30 days after transplanting, soil moisture of T2, T3, T4 and T1 were higher than T5, which were increased respectively by 8.61%, 7.82%, 8.37% and 1.88%. However, soil moisture in T2 was the lowest in all treatments in 50 days after transplanting. There wasn't significant different among different treatments in 70-100 days after transplanting.Thus, T4 had obvious effect of soil moisture conservation, which has warming effect in low temperature and cooling effect in high temperature.(2) Soil nutrient transformation, tobacco nutrient absorption and soil available nutrients content were affected by covering treatments. The results showed the content of soil alkali-hydrolysable nitrogen, rapidly available phosphorus, rapidly available potassium and organic matter were increased in T1 in early growth stage after transplanting, and were increased in T4 in late growth stage.(3) Tobacco agronomic characters, biomass and tobacco root activity were influenced by different covering treatments, which effected biomass yield and economic yield. According to comprehensive measure index of the agronomic characters, biomass and tobacco root activity, T1, T2, T3 and T4 could significantly promote tobacco growth. The effect of T1 was in middle and late growth stage of tobacco, and the effects of T2, T3, T4 were in early stage of tobacco. Compare with T5, the yield of tobacco leaves in T4, T3 and T2 were increased respectively by 499.5kg/ha, 411kg/ha and 316.5kg/ha, meanwhile the economic efficiency were increased respectively by 6051 yuan/ha, 4691 yuan/ha and 4292yuan/ha. T1 could not increase yield and output value of tobacco leaves. There was no significant difference in rate of high class leaves and average priced among different treatments.(4) Tobacco quality was affected by different covering treatments. Total soluble sugar and reducing sugar content of middle and upper leaves and starch content were increased, and nicotine content of middle and upper leaves and K content of upper leaves were decreased. Tobacco aroma quality in T1, T3 and T4 were better than T5. Flue-cured tobacco leaves of grade C3F was best in T1, and flue-cured tobacco leaves of grade B2F was best in T4. The result of smoking quality showed that T5 was the lowest. Flue-cured tobacco leaves of grade C3F was best in T1, and secondly for T4, and flue-cured tobacco leaves of grade B2F was best in T4, and secondly for T3. |
PDF Full Text Request