The Effects Of Irrigation And Polyethylene Mulch On Tobacco Leaves-enlarging In Southwest Of Hubei Province

The experiment on the basis of collecting massive ecological environment data in southwestern Hubei,it was proposed that the drought stress in the middle and late growth of flue-cured tobacco in southwestern Hubei caused that the flue-cured tobacco leaf didn't expand in the producing area.The field identification experiment was conducted in hazelnut village of Xingshan county of Yichang City and JiaoYuan town and ZhuShan town of Xuan'en County in EnShi Tujia and Miao Autonomous Prefecture in 2005 and 2006,with native major variety as material.It was studied that the effects of exposing Polyethylene Mulch and irrigation on the roots growth and development,leaves-enlarging and internal chemical components of flue-cured tobacco and on its physical properties,output and product value after being baked. Besides the major factor influencing tobacco expanding in the tobacco product area of southwestern Hubei was testified with experiment and the exposing polyethylene mulch time and irrigation times were confirmed.The experiment conclusion as follows:1.The tobacco plant roots treated with exposing polyethylene mulch and irrigation developed better than that of CK.Indexes such as main root length, branches.and fibrous root number and root fresh weight all showed that that in treatment of exposing polyethylene mulch and no irrigation for 35 days(b)and 45 days(c)was better than that of CK(a).In exposing polyethylene mulch treatment at different time,the dynamic increase of roots fresh weight indicated that the roots grow fast in a period after exposing polyethylene mulch and the sooner,the more obvious.The roots fresh weight increased along with irrigation times increasing in the irrigation treatment in maturing stage.2.The middle and upper leaves treated with exposing polyethylene mulch and irrigation after being baked,their single leaf weight,equilibrium moisture content and leaf strength increased,their stalk rate and filling value reduced and their leaf thickness was moderate.The physical machinability of irrigation and exposing polyethylene mulch after 35 days in the experiment with different exposing polyethylene mulch and irrigation time was best.The physical machinability of exposing polyethylene mulch after 25 days in the experiment with different exposing polyethylene mulch time was best.It was best of irrigating at topping,doming and ripening stages once respectively in maturing irrigation experiment.3.The growth and development condition of middle and upper leaves treated with exposing polyethylene mulch and irrigation were better than that of CK,the leaf length and width and upper leaf area increased.The tobacco plant was treated with irrigation after being exposing polyethylene mulch and its leaf length and width were bigger than that of only treated by exposing polyethylene mulch.The effects of exposing polyethylene mulch and irrigation on upper leaves were more obvious than on middle leaves and irrigation was superior to exposing polyethylene mulch for the expanding of middle and upper leaves.4.The chemical components in flue-cured tobacco treated with exposing polyethylene mulch and irrigation was more coordinative that that in CK and the contents of N compounds,sugar,K~+ and Cl~- all increased along with advancing exposing polyethylene mulch and irrigation time.TN/nicotine ratio was less than 1, between 0.8 and 1.Total sugar/nicotine ratio increased along with advancing exposing polyethylene mulch time,the sugar content increment exceeded that of N compounds, total sugar/nicotine ratio becoming more coordinative and that of irrigation was the case.Exposing polyethylene mulch time advance and irrigation both increased K~+/Cl~-ratio obviously.5.Exposing polyethylene mulch and irrigation could increase tobacco output and product value.The economic benefit of irrigation and exposing polyethylene mulch after 35 days in the experiment with different exposing polyethylene mulch and irrigation time was best.The comprehensive benefit of exposing polyethylene mulch after 25 days in the experiment with different exposing polyethylene mulch time was best.The economic benefit of irrigating at topping,doming and ripening stages once respectively in maturing irrigation experiment was best.In summary,the leaves-enlarging difficulty of tobacco in southwestern Hubei was mainly caused by the season unbalance distribution of rainfall and the draught in fast-growing anaphase and maturing stages.The hill-slope distribution of tobacco field,the poor water holding capacity and the thin soil layer aggravated draught and then caused expanding difficulty of middle and upper leaves.Irrigation in fast-growing anaphase and maturing stages was the main measure to promote leaves-enlarging in the area.Exposing polyethylene mulch earlier while rain was positive to promote leaves-enlarging and enhance output and quality to some extent. Tobacco exposed polyethylene mulch after 25 days in the product area with altitude at 1200m in southwestern Hubei had strong roots,better leaves-enlarging,internal quality,physical machinability,output and product value performances.