| In order to improve the soil environment and the quality of tobacco leaves,in this paper,In 2016,we studied the effects of irrigation and biochar application before transplanting on soil moisture contents,soil available nutrients and soil microbes in the 0-60 cm tobacco-planting soil layer as well as the effects of it on flue-cured tobacco growth and the quality of tobacco leaves after flue-curing,which provided technical supports and theoretical guidance for exploring reasonable methods of combined application of irrigation and biochar in high quality tobacco production.The main results were as follows:1 Effects of irrigation at different times before transplanting on tobacco-planting soil water contentIrrigation before transplanting significantly improved soil moisture content in the 0 ~ 60 cm soil layer.Effects of irrigation at three different times before transplanting(T1: Irrigation on January 28;T2: Irrigation on March 4;T3: Irrigation on April 10;CK: No irrigation)on soil water content in the 0 ~ 60 cm soil layer were significantly different.The last irrigation on April 10 before transplanting had most great effects on soil water content.Water contents of soil treated with irrigation was higher than that of CK in the whole flue-cured tobacco growth period.For irrigation at three different times,change rules of soil moisture content in different soil layers throughout the reproductive period of flue-cured tobacco were basically the same.2 Effects of irrigation at different times before transplanting on available nutrient contents in tobacco-planting soil.Irrigation before transplanting made soil available P content increasing with soil depth.Effects of irrigation at different times before transplanting on soil available P in the 0 ~ 40 cm soil layer were significant.The irrigation treatment significantly increased the content of available potassium in each soil layer,especially in the surface soil.The irrigation made the soil alkali-hydrolysable nitrogen content decreasing with the increase of soil depth.3 Effects of the interaction of irrigation at different times and biochar application on the flue-cured tobacco growth and nutrient absorptionIrrigation at different times and biochar application both increased the maximum leaf area,plant height,stem circumference,effective leaf number and dry matter accumulation of tobacco plant.At 30 d after transplanting the combined application of irrigation on March 4 and biochar had the best effects.Within 60-90 d after transplanting,the combined application of irrigation on April 10 and biochar had best effects on the growth,that is,that treatment promoted the growth of flue-cured tobacco very well.The interaction of water and biochar improved the content of the available nitrogen,phosphorus and potassium in the soil and plant absorption of these nutrients,and reduced leaching loss of soil fertilizer,and improved the soil fertility,ensuring nutrients needed by the flue-cured tobacco growth.4 Effects of irrigation and biochar application before transplanting on soil microbesIrrigation and biochar application before transplanting effectively increased the content of soil microbes,especially in the 0 ~ 20 cm soil layer.Microbes in the 0 ~ 20 cm soil layer of CK1 and F3 treatment respectively accounted for 63.04% and 66.34% of that in the 0 ~ 60 cm soil layer;total microbes in the 0 ~ 60 cm soil layer of F3 treatment were 11.05% more than that of CK1.For three kinds of microbes in the soil,moisture and biochar had smaller effect on bacteria and fungi,and had more significant effects on actinomycetes.5 Effects of irrigation and biochar application before transplanting on soil moisture content of different soil layer and soil moisture dynamic change with timeThe soil moisture content was determined 30,60 and 90 days after transplanting.At 30 d after transplanting,the soil moisture content in the 0 ~ 60 cm soil layer was relatively high,and the moisture content of soil treated with the last irrigation and biochar application before transplanting was the highest,5.3% more than that of CK.At 60 d after transplanting,soil moisture content in deep soil layer was 2.6% ~ 2.6% more than that in surface soil.At 90 d after transplanting,moisture contents of soil with application of biochar was obviously increased,maybe due to the effect of water retention of the biochar.The moisture contents of different soil layers of all treatments increased first and then decreased with time.6 Effects of irrigation and biochar application before transplanting on dry matter accumulation of tobacco plantAccording to the data of dry matter accumulation of tobacco plant,we established the dynamic model of dry matter accumulation of tobacco plant by using Logistic equation.The dry matter accumulation of every treatment changed by the "S" shaped curve with time,and it can be divided into the slow growth phase linear growth phase,and residual phase.The leaf dry matter accumulation in mature period of tobacco plant treated with irrigation at three periods was 4453.02 kg·hm-2,4577.1 kg·hm-2 and 5180.84 kg·hm-2 respectively,while that of tobacco plant treated with biochar application was 5112.20 kg·hm-2,5397.32 kg·hm-2 and 5866.91 kg·hm-2,and all are higher that of CK.Promotion effects of application of biochar were more obvious.On the basis of irrigation,fertilizing biochar could improve the soil nutrient and moisture,meeting the needs of the growth of tobacco plant,which was beneficial to dry matter accumulation of tobacco plant.From the point of leaf dry matter accumulation rate,with the same irrigation amount,the accumulation rate of the treatment of the last irrigation before transplanting was the largest;with the same amount of biochar,combined application of irrigation and biochar significantly increased the maximum accumulation rate of leaf dry matter so as to increase dry matter accumulation.Meanwhile,application of biochar significantly increased the proportion of root and leaf dry matter accumulation of tobacco plant,and decreased the proportion of stem dry matter accumulation,optimizing the dry matter distribution in the organization of tobacco plant.7 Effects of irrigation and biochar application on mineral elements content of cured tobacco leaves and tobacco planting soilIrrigation at different times all increased K,Mg,Mn,Zn and B content of tobacco leaves.Ca,Cu,Fe content of tobacco leaves decreased with the increase of irrigation amount.K,Mg,Mn,Zn,Cu,Mo content of the biochar-applying treatment were higher than that of CK1,and B,Cu,Fe content decreased with the increasing of application rate of biochar.Irrigation before transplanting is conducive to the accumulation of tobacco leaf mineral elements,and there were interaction effects of irrigation and biochar-application on the accumulation of mineral elements.We made a statistical analysis of variation of soil mineral element contents in different treatments,and variation coefficient of soil mineral elements in different layers was from small to large followed by Ca,Mg,Mo,Cu,B,Mn,Fe and Zn,and Zn variation coefficient was more than 40% which was the largest,while Ca variation coefficient is only more than 3% which was the smallest,with large differences among various layers.8 Effects of irrigation and biochar application on chemical components in flue-cured tobacco leavesThe total sugar content of each treatment was higher than that of CK,and the total sugar of tobacco leaves would affect the degree of alcohol content;reducing sugar,affecting the acid-base balance of flue gas,was higher in treatments than in CK;in each treatment,the nicotine content was generally low,which could lead to the lack of smoke flavor and small momentum;irrigation and biochar application could also increase the content of potassium in tobacco leaves,and the potassium would affect the combustibility and hygroscopicity of tobacco leaves;chlorine had a great influence on the color,moisture content and storage time of tobacco,and the chlorine content of each treatment was in appropriate range.9 The effect of water and biochar on the aroma components of flue-cured tobaccoThe irrigation and biochar application at different times increased the carotenoid,phenylalanine and maillard reaction products,the content of tobacco carotenoid is higher than the control group in the different period of irrigation treatment,the irrigation effect of the last time before transplantation is the best,under the condition of the fertilization of biochar,the content of tobacco carotenoid is increasing little by little with the advance of the irrigation period;As for the phenylalanine aroma components,the interaction between water and biochar is beneficial to improving its content in tobacco;So we can see that the fertilization of biochar and the irrigation period are essential to the accumulation of the total aroma components. |
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