Effect Of Mulch Ways And Transplant Depths On Root Growth And Leaf Quality In Flue-cured Tobacco

This study was focused on tobacco roots formation, agronomic traits and dry matter accumulation, tobacco quality, yield and economic traits, with different treatments of mulch ways and transplant depths treatment, and the relationship between roots development and over-ground growth were analyzed. This study shows that mulch and Deep planting have a great influence of root growth and distribution. We can regulate the root to achieve our goal of High-quality fitness products through the treatment of mulching and deep planting. The main conclusions are as follows:(1) Tobacco roots are composed of main root, lateral roots and adventitious roots, the growth of root biomass showed two peaks, appeared at 50-70 days and 70-90 days after transplanting respectively, the second peak is significantly larger than the first peak. There are different trends showed in the horizontal and vertical distribution of Tobacco Root length density in soil:vertical, changes by "S" type curve in the 0-10cm soil layer; and its grow with a bimodal curve in 10-20cm,20-30cm and 30-40cm soil layer; horizontal,0-10cm away from the main root axis, showed two peaks which appeared at 30-50 days and 70-90 days after transplanting; 10-20cm away from the main root axis was a linear growth trend in 90 days after transplanting,,20-40cm away from the main root axis showed a back extension single-peak curve. the vertical distribution of root biomass in the soil showed "干" structure. Most of the root distribute in 0-24cm soil layer, only a very small biomass distributed under 30cm soil layer.(2) Straw mulching treatment significantly promoted the development of tobacco roots and root length density compared with the film coverage treatment and CK. the final total dry weight of root is 101.08g which was increased by 42.19% than CK. Mulching treatment increased root activity in the early growth stage, among it, activity of the roots were the highest 0.567 mg/g-1.h-1和0.942 mg/g-1.h-1 with A2B2 in topping and vigorous growth stage, it increased nutrients and water absorption. the other way around the late growth stage, the root activity dropped to0.104 mg/g-1.h-1, so beneficial to leaf maturity.(3) Deep planting make root distribute deeper and wider, the root volume is greater, and promote the increase in adventitious root dry weight, lateral root dry weight and total root dry weight, improve root activity significantly in fast grow stage and topping stage,and they were reach to 0.494mg/g-1h-1 and 0.683mg/g-1h-1 respectively, but will not affect the normal leaf yellowing.(4) Mulching treatment was more effective than deep transplanting treatment in increasing total sugar content, reducing sugar content and decreasing nicotine content of flue-cured tobacco leaves. Both mulching and deep transplanting could significantly decreased the starch content in tobacco leaves and its decreased 3.66%and9.68% compared with CK. Mulching significantly reduced the total nitrogen content of middle leaves, membrane covering is better than straw mulching, deep transplanting can significantly reduce the total nitrogen content, both mulching and deep transp;anting increase the potassium content in different parts of tobacco. and its increased 16.94% by straw mulching significantly which is more effective than film coverage about the 5.40% in increasing the potassium content. the quantity of potassium increased also raise up to 14.52% by deep planting. There was no obvious effect on chlorine content of tobacco under different treatments, but chlorine contents of different treatments were in an acceptable range.(5) Mulching remarkably decreased the ratio of difference of two sugar/total sugar in flue-cured leaf. Within it, straw mulching is better than plastic film covering, but the effect of deep planting was not significant. Mulching and deep planting significantly improved the ratio of potassium chloride in all parts of tobacco leaves. The ratio of potassium/chloride in lower and middle leaves was highest in the treatment of film covering, and it is highest in straw mulching treatment for upper leaves; The ratio of nitrogen to nicotine of A2B1 is 0.95 and 0.96 to A2B2, its more fit to the standard of quality tobacco. Straw mulching was more effective than film coverage in increase tobacco yield, straw mulching> film covering>CK, deep planting plus straw mulching treatment was significantly better than other treatments.(6) There existed significant correlativity between tobacco root parameters, agronomic traits, leaf chemical quality and economic benefit, so by regulating the root growth to achieve high quality production is of momentous significance.