Yude NIU,Zhaojun NIE,Jinfeng LI,Zhijian HAN,Hongxing YANG,Guoliang WANG,Yunpeng MEI,Xianfeng LI,Jianhua TANG,Xiefeng YE,Hongen LIU*

1.Hanzhong Tobacco Company of Shanxi Tobacco Company,Hanzhong 723000,China;2.Resources and Environment College,Henan Agricultural University,Zhengzhou 450002,China;3.Shangqiu Quality and Technical Supervision and Testing Center,Shangqiu 476000;4.Tobacco College of Henan Agricultural University,Physiology and Biochemistry Research Center of National Tobacco Cultivation,Zhengzhou 450002,China

Tobacco is one of the important economic crops in our country.The economic benefit of tobacco production mainly depends on the quality,yield and production cost of tobacco[1].Biochar is a solid byproduct obtained from the low-temperature thermal conversion of biomass under anaerobic or micro-aerobic conditions,and it is a kind of biomass material with high organic carbon content,strong porosity,alkalinity and adsorp tion capacity[2].There were reports indicating that biochar contained mineral elements including Na,K,Mg and Ca which could promote cycling of soil nutrients and plant growth[3],and the application of biochar could obviously improve soil quality and raise crop yield[4-11].Currently,studies have focused on the effects of biochar on growth of ryegrass,spinach,soybean,rice and corn[12-15],and those on eftects of biochar on tobacco develop-ment and quality and soil physical and chemical properties were few.This study conducted field experiment at Laolongchi Village,Xiaonanhai Town,Nanzheng County,Hanzhong City,to test the effects of different biochar typesanddosagesonagronomic traits,the incidence of mosaic disease and yield and output value in tobacco so as to obtain the optimal biochar type and dosage for tobacco-growing area in Hanzhong and provide certain technique basis for improving tobacco quality.

Materials and Methods

Test site conditions

This experiment was carried out in from May to September of 2013,at Laolongchi Village,Xiaonanhai Town,NanzhengCounty,HanzhongCity.Hanzhong has an altitude of 1 000-1 500 m,belonging to the subtropical climatic region,having a moderate and moist climate due to the Qinling Mountains in its north direction which prevent the invasion ofcold current.Hanzhong is located in a middle latitude of the Northern Hemisphere and provided with warm and wet air due to precipitation all year round,and owing to the warm and wet airflow from southwest and southeast obstructed by the Ba Mountain and Qinling Mountains,the amount of precipitation in this region is sufficient.The soil is mountain yellow brown soil,belonging to loam,with such physical and chemical properties as organic matter 9.49 g/kg,pH 6.73,rapid available phosphorus 49.98 mg/kg,rapid available potassium 331.73 mg/kg,and available nitrogen 72.32 mg/kg.

Material

The tobacco cultivar used in this experiment was Yunyan 97.

Experiment design

Six treatments were designed,i.e.CK(conventional fertilization),T1(conventional fertilization+peanut shell char 300 kg/hm2),T2(conventional fertilization+peanut shell char600 kg/hm2),T3(conventional fertilization+peanut shell char 900 kg/hm2),T4(conventional fertilization+rice husk char 600 kg/hm2),and T5(conventional fertilization+wheat straw char 600kg/hm2).Each treatment was provided with three replications,randomized block design was adopted,and there were 18 plots in total,each having an area of 50 m2.The biochar was applied in the hole fertilization before transplanting.

The fore-rotating crop in the experiment field was tobacco having a yield of 2 490 kg/hm2,which was provided with special fertilizer for fluecured tobacco 900 kg/hm2+potassium nitrate 75 kg/hm2+potassium sulfate 262.5 kg/hm2+high-calcium phosphorous 150 kg/hm2+biological fertilizer 150 kg/hm2+oil residue 300 kg/hm2+diammonium phosphate 75 kg/hm2.The treatment with conventional fertilization was as follows:special fertilizer for flue-cured tobacco(12∶15∶18)1 050 kg/hm2, high-calcium phosphorous(44% )150 kg/hm2,potassium sulfate(＞51% )262.5 kg/hm2,biological fertilizer 150 kg/hm2and organic fertilizer 300 kg/hm2,and the fertilization was carried out after ridging in a manner of row placement.Aftertransplanting,topdressing was performed with potassium nitrate(9∶0∶35)75 kg/hm2.

The row spacing and plant spacing were of 110 and 55 cm.After ridging and fertilization on the experiment field,hole drilling,hole application and transplanting were conducted on May 11,and the management of each plot was performed according to the production technique regulations of local high-quality tobacco.The agronomic traits and the incidence of mosaic disease were recorded during each growth stage of tobacco;and after the tobacco was mature,harvest and traditional curing was conducted separately for each plot;the economic traits including yield,grade and output value of each plot were recorded;and X2F,C3F,B2F samples were collected respectively in an amount of 0.5 kg,which were pulverized,sieved and subjected to determination for ordinary chemical components.

Determination items and methods Tobacco plant agronomic traits and the incidence of mosaic diseaseThe agronomic traits including plant height,stem diameter,effective leaf number,maximum leaf length and leaf width were recorded during the resettling stage,vigorous growing stage,squaring stage and mature stage of tobacco,respectively,and graduation statistics was conducted on the incidence of tobacco mosaic disease according to the industrial standard by Hanzhong Tobacco Company.

Economic traitsGraduation was conducted according to the grading method in “flue-cured tobacco” of GB 2635-1992,and the economic traits including yield,output value,highgrade tobacco proportion,mid-high grade tobacco proportion,low-grade tobacco proportion of the flue-cured tobacco produced in each plot were investigated.

Data processing

The experiment data was subjected to statistic processing with Excel 2003.

Results and Analysis

Effects of different biochar types and dosages on tobacco agronomic traits during various growth stages

Effects of different biochar types and dosages on growth and development of tobacco in resettling stageAs shown in Table 1,compared with the treatment of conventional fertilization T0,each of the treatments from T1to T5showed increased plant height,stem diameter and maximum leaf area,i.e.,application of biochar effectively promoted the early and fast growth of tobacco.Among the agronomic traits, with increasing dosage of peanut shell char(T1-T3),the indexes including plant height,stem diameter,and maximum leaf length,leaf width and leaf area also increased gradually,and reached their peak values by applying peanut shell char 900 kg/hm2(treatment T3).

For biochar types,the resettling stage had the plant heights in order of T5＞T2＞T4,the stem diameters in order of T5＞T4＞T2,the maximum leaf lengths in order of T4＞T5＞T2,the maximum leaf widths in order of T5＞ T4＞T2and the maximum leaf areas in order of T5＞T4＞T2,indicating that different types of biochars caused no obvious difference in growth and development of resettling-stage tobacco.

Effects of different biochar types and dosages on growth and development of tobacco in vigorous growing stageFrom Table 2,it could be seen that during the vigorousgrowing stage of tobacco the plant heights and maximum leaf areas of various treatments showed obvious differences.In comparison with the treatment of conventional fertilization T0,the plant heights,stem diameters and maximum leaf areas increased after the application of certain amounts of biochars (T2-T5),indicating that the fast growth of tobacco in vigorous growing stage was promoted.Among the agronomic traits,the indexes including the stem diameter,maximum leaf length and width and the maximum leaf area also increased gradually,and their peak values appeared at the dosage of 900 kg/hm2(T3).As to the plant height and effective leaf number,with increasing dosage of peanut shell char(T1-T3),they show a trend of increasing first and decreasing then,and reached their peak value at the dosage of 600 kg/hm2(T2).The results showed that application of peanut shell char in the range of 600-900 kg/hm2could effectively promote the growth and development of tobacco plants in vigorous growing stage.

Table 1 Effects of biochar on agronomic traits of tobacco in resettling stage

Table 2 Effects of biochar on agronomic traits of tobacco in vigorous growing stage

For biochar types,during the vigorous growing stage,the plant heights showed an order of T5＞T4＞T2,the stem diameters showed an order of T4＞T5＞T2,and all the maximum leaf lengths,leaf widths and leaf areas were in AN order of T4＞T5＞T2.The results indicated that the treatments of rice husk char and wheat straw char were obviously superior to the treatment of peanut shell char,and rice husk char was more beneficial to promoting the development of leaves of tobacco in vigorous growing stage,while wheat straw char was more favorable to the increases in plant height and effective leaf number.

Effects of different biochar types and dosages on growth and development of tobacco in squaring stageIn Table 3,In comparison with the treatment of conventional fertilization T0,the plant heights,stem diameters and maximum leaf areas increased after the application of certain amounts of biochars(T3-T5),indicating that the growth and development of tobacco in squaring stage were promoted.Among the agronomic traits,the plant height and effective leaf number of tobacco in squaring stage increased gradually,and their peak values appeared at the dosage of 900 kg/hm2(T3),and except the plant height,effective leaf number and stem diameter,the maximum leaf length and leaf width as well as the maximum leaf area were smaller than those of conventionalfertilization treatment T0when applying peanut shell char 300-600 kg/hm2(treatments T1-T2).The results indicated that peanut shell char was required in application in a sufficient amount above 900 kg/hm2which might be more beneficial to the growth and development of tobacco plants in squaring stage.

For biochar types,the squaringstage plantheights,effective leaf numbers and stem diameters showed an order of T4＞T5＞T2,and the maximum leaf lengths, maximum leaf widths and maximum leaf areas were in order of T5＞T4＞T2.The results indicated that the treatments of rice husk char and wheat straw char were obvious better than the treatment of peanut shell char,and the treatment of rice husk char was more favorable to the promotion of tobacco stem development during the squaring stage,while the wheat straw char was more beneficial to the leaf development of tobacco in squaring stage.

Table 3 Effects of biochar on agronomic traits of tobacco in squaring stage

Table 4 Effects of biochar on agronomic traits of tobacco in mature stage

Table 5 Effects of biochar on economic traits and yield and output value of flue-cured tobacco

Effects of different biochar types and dosages on growth and development of tobacco in mature stageAs shown in Table 4,compared with the treatment of conventional fertilization T0,each of the treatments from T1to T5showed increased plant height and effective leaf number during the mature stage,while there was no great effect on stem diameter,maximum leaf length and leaf width and maximum leaf area.Among the agronomic traits, with increasing dosage of peanut shell char(T1-T3),the indexes including plant height and effective leaf number increased gradually, and reached their peak values by applying peanut shell 900 kg/hm2(treatment T3).In comparison with the treatment of conventional fertilization T0,the treatment of peanut shell char 300 kg/hm2(treatment T1)had increased maximum leaf length,maximum leaf width and maximum leaf area,while the treatments of peanut shell char 600-900 kg/hm2showed no obvious increase.The results indicated that the application of peanut shell char still had certain effects on the longitudinal stem development(plant height)and effective leaf number of tobacco in mature stage,but weakened effects on transverse stem development(stem diameter)and leaf development of tobacco.

For biochar types,the mature stage showed the plant heights and effective leaf numbers in order of T5＞T4＞T2,stem diameters in order of T5＞T4=T2,the maximum leaf lengths in order of T2＞T5＞T4,the maximum leaf widths in order of T2=T4＞T5and the maximum leaf areas in order of T2＞T5＞T4.However,the peanut shell char,rice husk char and wheat straw char caused no obvious difference in growth and development of mature-stage tobacco.

Analysis on economic traits of fluecured tobacco under different biochar types and dosages

In Table 5,compared with the treatment of conventional fertilization T0,the single leaf weight,yield,output value and mid-high grade leaf proportion increased after the application of certain amounts of biochars (T1-T5).Among them,the yield,output value and mid-high grade leaf proportion of tobacco increased obviously with increasing peanut shell char dosage(T1-T3),and their peak values appeared at the dosage of peanut shell char 900 kg/hm2(T3).For single leaf weight,the treatments of applying peanut shell char showed an order of T1＞T3＞T2,and the treatment of applying peanut shell char 600 kg/hm2presented an decrease compared with the treatment of conventional fertilization T0.The results indicated that applying peanut shell char could improve the yield,output value and mid-high grade leaf proportion of tobacco,but the specific dosage needed further discussion in the aspects of improving single leaf weight and promoting leaf development.

For biochar types,the yields were in order of T4＞T5＞T2,the output values showed an order of T4＞T2＞T5,and the single leaf weight performed as T5＞T4＞T2,while the three biochar types had no great difference in improving midhigh grade leaf proportion.The results showed that,in Hanzhong,application of rice husk char had the best effect in improving tobacco yield and output value,while wheat straw char and peanut shell char showed no great difference;and the application of all the three types of biochars could raise the mid-high grade leaf proportion,but showed no great difference with each other;and the application of wheat straw char had the better effect on increasing single leaf weight,while no great difference presented between application of rice husk char and wheat straw char.

Conclusions and Discussion

Biochar is loose and porous and has the advantage of good adsorption capability[16],and it is thus can adsorb fertilizer and nutrients and control the release thereof after being applied into soil to improve the utilization rate of fertilizer,to thereby promote growth and development of fertilizer and improve yield of flue-cured tobacco.This study obtained similar results.This study showed that during the early and middle growths stages of tobacco biochar can increase plantheight,stem diameter and leaf size,effectively promoting early and fast growth of tobacco,and raised yield,output value and mid-high leaf proportion,resulting in increased economic benefit.The tobacco-growing area in Hanzhong suffers serious fertilizer loss and low fertilizer utilization rate due to greater amount of precipitation caused by terrain and climate factors,and thus had decreased tobacco yield and quality.It is advised that the tobacco-growing area in Hanzhong adopts biochar to improve utilization rate of fertilizer,to thereby improve tobacco yield and output value and finally increase tobacco economic benefit.

In this study,with increasing dosage of peanut shell char,all agronomic traits during each growth stage increased significantly,and yield,output value and mid-high grade tobacco leaf proportion increased obviously,and reached their peak values at the dosage of 900 kg/hm2.It is advised thatthe tobacco-growing area in Hanzhong adopts biochar in a controlled dosage of about 600-900 kg/hm2.

For biochar types,from the agronomic traits of tobacco in each stage,the treatments using rice hisk char and wheat straw char were better than that using peanut shell char;and the treatment of rice husk char was more favorable to promotion of tobacco leaf development in vigorous growing stage and tobacco stem development in squaring stage,while wheat straw char was more beneficial to improvement of plant height and effective leaf number in vigorous growing stage and tobacco leaf development in squaring stage.Furthermore,application of rice husk char had the best effect in improving tobacco yield and output value,while wheat straw char and peanut shell char showed no great difference;and the application of all the three types of biochars could raise the mid-high grade leaf proportion,but showed no great difference with each other;and the application of wheat straw char had the better effect on increasing single leaf weight,while no great difference presented between application of rice husk char and wheat straw char.Consequently,a better effect can be achieved in the tobacco-growing area in Hanzhong by selecting rice husk char as the materials for improving soil.

To sum up,using biochar for improving soil and promoting tobacco growth and development is a good measure for the tobacco-growing area in Hanzhong,the dosage of biochar is suitable to be controlled at 600-900 kg/hm2by hole application,and for biochar type,rice husk char can be selected as the material for improving soil.

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