Zhenjie XIAO, Jianbin MA, Hanzeng XU, Dashuang LIU, Shengfeng WANG, Qianxi LUO,Shengxing WANG, Chengjiang LONG, Wenlong WANG, Yuping JIANG, Zhanghai LI

1. China Tobacco Hebei Industrial Limited Company, Shijiazhuang 050051, China;

2. University of Science and Technology of China, Hefei 230052, China;

3. Qiannan Company of Guizhou Tobacco Corporation, Duyun 558000, China

Materials and Methods

Soil samples collection

GPS fixed position was used to collect the soil samples in the tobacco planting soil in Fuquan City, and one mixed soil sample was collected in each 20 hm2area. The specific collection method referred to NY/1221.1-2006.

Method for the determination of soil nutrients

Organic matter was collected by using potassium dichromate method;available nitrogen was collected by reducing alkali diffusion method; phosphorus leaching by sodium bicarbonate(pH8.5) extraction-Mo-Sb-Vc colorimetry (Olsen) method; available potassium by using ammonium acetate extraction (pH7.0)-atomic absorption spectrophotometric method.The value of pH was determined by potentiometric method (water extraction,soil to water ratio was 1:2.5).

Grading indicator for the nutrient state and pH value of the soil

The indicators determined by the project of balanced fertilization to tobacco in Guizhou Province[16]were adopted to determine the level of soil organic matter, available nitrogen,available phosphorus and available potassium contents and pH value.The content of soil organic matter was divided into 4 levels, namely low (＜15 g/kg), moderate (15-30 g/kg), abundant (30-50 g/kg) and excessive (＞50 g/kg). The available nitrogen content was divided into 4 levels, namely low(＜80 mg/kg),moderate(80-120 mg/kg),abundant (120-150 mg/kg) and excessive (＞150 mg/kg). Available phosphorus(P2O5)content was divided into 5 levels, namely absent (＜5 mg/kg),low (5-10 mg/kg),moderate (10-20 mg/kg),abundant (20-40 mg/kg)and excessive (＞40 mg/kg).The available potassium (K2O) content was divided into 5 levels, namely absent (＜80 mg/kg), low (80-150 mg/kg), moderate(150-220 mg/kg),abundant (220-350 mg/kg) and excessive (＞350 mg/kg). The value of pH was divided into 4 levels, namely low (＜5.5), best(5.5-6.5), good (6.5-7.5) and high(7.5-8.5).

Results and Analysis

Organic matter content in the tobacco planting soil of Fuquan City

Soil organic matter is one of the most important sources of mineral nutrients for plants, the material basis of soil fertility, and the main indicator to measure the level of soil fertility. Soil organic matter should not be too low or too high for the growth of flue cured tobacco. If the soil organic matter is too low,it is not conducive to the growth of tobacco plant, and tobacco leaves are weak, resulting in low yield and poor quality; however, if the soil organic matter content is too high,it will lead to leaf remaining green when it is due to become yellow and ripe, thick tobacco leaf with rough main vein,high content of nitrogen substances like nicotine and protein, discordant chemical compositions, resulting in poor quality.Generally, the soil organic matter content in the range of 10-30 g/kg is easy to produce high quality tobacco.

Levels of soil organic matter contents The organic matter content in the tobacco planting soil of Fuquan City belonged to the level of moderate to abundant with the average of 26.8 g/kg,ranging from 11.5-56.2 g/kg,and the coefficient of variation was 25.8%.Among all the soil samples, soil organic matter content of less than 15 g/kg accounted for 2.8% of the total,15-30 g/kg accounted for 68.9%, 30-50 g/kg accounted for 27.8% , and more than 50 kg/kg accounted for 0.5%. Thus, the soil containing moderateorganic matter was in large proportion,accounting for nearly 70%.

Regional distribution of soil organic matter Only 0.5% of the soil samples contained excessive organic matter,which were distributed in Yunwu Village, Guwang County. And 27.8% of the soil samples contained abundant organic matters, which were distributed in Shuiyuan Village,Duolangping Village, Huilong Vilalge,Shuanglong Village, Panjiaba Village,Guihua Village and Northwestern Street Village of Niuchang Town,Huangjiawan Village and Gaopingsi Village of Huangshi County, Malongjing Village, Sanjiang Village and Yunwu Village of Guwang County,Xianqiao Village and Dahua Village of Xianqiao County, Changchong Village and Longchang Village of Longchang County, Chahe Village of Chahe County, Pingshan Village and the Suburb of Chengxiang Town, Dongtian Village, Songjiang Village and Longping Village of Disong Town,Fuxing Village, Fenghuang Village,Wengyang Village and Langbohe Village of Luping Town, Luoao, Xinqiaoying Village of Lishan County,Yuyou Village of Huangsi Town,Liangshui Village and Gedong Village of Xinglong County. Finally, 2.8% of the soil samples had low organic matter content, which were collected from Bolanghe Village and Wengyang Village of Luping Town, Longchang Village of Longchang Town, Dongtian Village of Dichi Town.

Available nitrogen content in the tobacco planting soil in Fuquan City

Soil available nitrogen content is closely related with the yield and quality of flue-cured tobacco, and it is the main basis to determine the appropriate application amount of nitrogen fertilizer.

Levels of soil available nitrogen content The available nitrogen content in the tobacco planting soil of Fuquan City was moderateto excessive with the average of 134.1mg/kg,ranging from 65-215.1 mg/kg,and the coefficient of variation was 21.4% .Among all the soil samples,those with the content of less than 80 mg/kg accounted for 2.8% of the total, 80-120 mg/kg accounted for 28.9%, 120-150 mg/kg accounted for 41.7%, and with more than 150 mg/kg accounted for 26.6% of the total. The samples with moderateand excessive available nitrogen content were in the majority.

由仿射几何可知，空间直线可由Plücker坐标(L,M,N,P,Q,R)表示，其中(L,M,N)和(P,Q,R)分别表示直线的方向向量和直线相对于原点的矩。设图4中f1和f2上任意一点的坐标分别为σf1(x1,y1,z1)和σf2(x2,y2,z2)，则有z1=l/2，z2=-l/2，建立基于Plücker坐标的交点轴线方程：

Regional distribution of soil available nitrogen There were 26.6% of soil samples containing excessive available nitrogen, which were mainly distributed in northern and central Niuchang Town,including Shuiyuan Village, Shuanglong Village, Panjiaba Village, Huilong Village, Guihua Village and Duolangping Village, in Gaoping Village of Gaoping Town, in Malongjing Village, Sanjiang Village and Yunwu Village of Guwang County,in Huangjiawan Village of Gaoshi County, in Changchong Village,Fengxiangshu Village,Longjing Village and Longchang Village of Longchang Town. About 41.7% of the soil samples had abundant available nitrogen content,which were distributed in wide regions, including Gaoping Village of Gaoping Town, Shuiyuan Village,Shuanglong Village, Panjiaba Village,Guihua Village and Northwestern Street Village of Niuchang Town,Huangjiawan Village of Huangshi County, Malongjing Village, Sanjiang Village and Yunwu Village of Guwang County, Xianqiao Village and Dahua Village of Cianqiao County, Changchong Village, Fengxiangshu Village,Longjing Village and Longchang Village of Longchang Town, Chahe Village of Chahe County,Huangsi Village and Yuyou Village of Huangsi Town,Dongtian Village, Songjinag Villagg and Xiangpingying Village of Chisong Town, Fuxing Village, Wengyang Village and Langbohe Village of LupingTown, Xinqiaoying Village and Luoao Village of Lishan County, pingshan Village and Chengjiao Village of Chengxiang Town. And 28.95% of the soil samples had moderateavailable nitrogen content, which were mainly distributed in the northern part of the tobacco planting area, including Dongtian Village, Songjiang Village and Xiangpingying Village of Chisong Town, Fuxing Village, Fenghuang Village, Wengyang Village and Langbohe Village of Luping Town, Xinqiaoying Village and Luoao Village of Lishan County, Liangshan Village of Xinglong County,Longchang Village of Longchang Town, Huangjiawan Village of Huangshi County, Chahe Village of Chahe County, Gaoping Village of Gaoping County. And there were 2.8% of soil samples contained low available nitrogen, which were mainly collected from Longchang Village of Longchang Town, Langbohe Village of Luping Town, Dongting Village of Chisong Town, Shuiyuan Village of Niuchang Town.

Available phosphorus content in the tobacco planting soil of Fuquan City

The main source of phosphorus for tobacco growth comes from the soil.The content of phosphorous in the soil has obvious influence on the quality of tobacco. If the phosphorous content is too low, it will slow down the growth of tobacco plant, making the plant short and small, the leaves long and narrow and straight, which would grow in the shape of fasciation and with dark green color,and if the lake of phosphorous is very serious, the leaves in the lower part will present small spots, and if the phosphorous is not enough in the late part of the growth, the cured-leaves would present dark brown or cyan, which is lack of luster,resulting in poor quality.If the phosphorous content is too high, the tobacco plant will flower earlier, and make the leaves thicker and tougher,the tissue more coarse, which is lack of flexibility and oil and easy to break.

Levels of soil available phosphorus content The available phosphorous content in the tobacco planting soil of Fuquan City was moderatewith the average of 35.9 mg/kg, ranging from 6.1-163.7 mg/kg, and the coefficient of variation was 72.1%. Among all the soil samples, those with the content of 5-10 mg/kg accounted for 5.6%of the total, 10 -20 mg/kg accounted for 22.8%, 20-40 mg/kg accounted for 40.0%, and those with more than 40 mg/kg accounted for 31.6% of the total. The samples with moderateand excessive available nitrogen content accounted for 71.6%, while the soil samples lacking in phosphorous was only in the minority.

Regional distribution of soil available phosphorus There were 31.6% of soil samples containing excessive available phosphorous, which were distributed in wide area, mainly including Langbohe Village of Luping Town, Shuanglong Village, Duolangping Village, Panjiaba Village, Northwestern Street Village,Huilong Village,Guihua Village of Niuchang Town,Yuwu Village, Sanjiang Village and Malong Village of Guxiang County,Longchang Village, Fengxiangshu Village and Longjiang Village of Longchang Town, Huangjiawan Vilalge,Chahe Village,of Chahe County,Pingshan Village and Chengjiao Village of Chengxiang Town, Xiangping Village and Songjiang Village of Disong Town,Gaoping Village of Gaoping County, Xinqiaoying Village of Lishan County, Yuyou Village of Huangsi Town, Gedong Village of Xinglong County. About 40.0% of the soil samples had abundant available nitrogen content, which were also distributed in wide regions, including Shuiyuan Village, Shuanglong Village, Panjiaba Village and Northwestern Street Village of Niuchang Town, Huangjiawan Village of Gaoshi County, Dongtian Village of Disong Town, Fuxing Village,Wengyang Village and Langbohe Village of Luping Town, Malongjing Village, Sanjiang Village and Yunwu Village of Guwang County, Xinqiaoying Village and Luoao Village of Lishan County, Longchang Village of Longchang County, Chahe Village of Chahe County,Xianqiao Village of XIanqiao County, Gaoping Village of Gaoping Town, Huangsi Village and Luoao Village of Lishan County,Longchang Village of Longchang Town, Chahe Village of Chahe County,Xianqiao Village of Xianqiao County, Gaoping Village of Gaoping Town,Huangsi Village and Yuyou Village of Huangsi Town, Pingshan Village and Chengjiao Village of Chengxiang Town, Liangshuijing Village of Xinglong County. And 22.8% of the soil samples had moderateavailable phosphorous content, which were loosely distributed in Dongtian Village,Songjiang Village and Xiangpingying Vilalge of Chisong Town, Fuxing Village, Fenghuang Village, Wengyang Village and Langbohe Village of Luping Town, Xinqiaoying Village and Luoao Village of Lishan County,Pingshan Village of Chengxiang Town,Longjing village, Fengxiangshu Village, Changchong Village and Longchang Village of Longchang Town, Yuwu Village of Guwang County, Xianqiao Village and Dahua Village of Xianqiao County, Chahe Village of Chahe County, SHuiyuan Village of Niuchang Town,and Liangshui Village of Xinglong County. And there were 5.6 % of soil samples lacking available phosphorous, which were mainly distributed in Longchang Village and Changchong Village of Longchang Town, Langbohe Village and Fenghuang Village of Luping Town, Dongtian Village of Disong Town, Shuiyuan Village of Niuchang town, Yunwu Village of Guwang County, Luoao Village of Lishan County.

Available potassium content in the tobacco planting soil of Fuquan City

Potassium is of great function and influence on the growth and development, yield and quality of tobacco, as well as the security of tobacco product,and therefore, the content of potassium in tobacco leaves is often treated as on of the indicators to evaluate the quality of tobacco.

Levels of soil available potassium content The available potassium content in the tobacco planting soil of Fuquan City was relatively excessive with the average of 222.1 mg/kg,ranging from 33.8-585.2 mg/kg, and the coefficient of variation was 53.5% .Among all the soil samples,those with the content of less than 80 mg/kg accounted for 8.9% of the total, 80-150 mg/kg accounted for 26.7%, 150-220 mg/kg accounted for 20.0%, 220-350 mg/kg accounted for 28.3%,and thosewith more than 350 mg/kg accounted for 16.1% of the total. In general, the samples with moderateand excessive available nitrogen content were in the majority, and the soil lacking in or absent in potassium accounted for 1/3 of the total, which needed to add with potassium fertilization.

Regional distribution of soil available potassium There were 16.1%of soil samples containing excessive available potassium, which were mainly distributed in Haungsi and Yuyou Village of Huangsi Town,Gedong Village of Xinglong County,Longchang and Longjing Village of Longchang Town, Shuiyuan, Pajiaba,Huilong and Guihua Village of Niuchang Town, Pingshan and Chengjiao Village of Chengxiang Town, Xiangping, Dongtian and Songhua Village of Disong Town,Chahe Village of Chahe County,Gaoping Village of Gaoping County,Huangjiawan of Gaoshi County, Sanjiang and Malong Village of Guwang County, Luoao Village of Lishan County, Langbohe Village of Luping Town. About 28.3% of the soil samples had abundant available potassium content, which were distributed in Shuiyuan Village,Duolangping Village,Shuanglong Village, Panjiaba Village and Northwestern Street Village of Niuchang Town,Chahe Village of Chahe County, Pingshan Village and Chengjhiao Village of Chengxiang Town, Xiangping, Dongtian and Songjiang Village of Disong Town,Gaoping Village of Gaoping Town,Huangjiawan Village of Huangshi County, Malongjing Village, Sanjiang Village and Yunwu Village of Guwang County, Xinqiaoying Village of Lishan County, Longchang Village of Longchang Town, Langbohe Village and Wengyang Village of Luping Town, Xianqiao Village and Dahua Village of Xianqiao County,Liangshuijing Village of Xinglong County. And 20.0%of the soil samples had moderateavailable potassium content, which were mainly distributed in Yunwu Village, Sanjiang and Malong Village of Guwang County,Pingshan Village and Chengjiao Village of Chengxiang Town,Dongtian Village,Songjiang Village and Xiangpingying Village of Disong Town, Chahe Village of Chahe County, Fuxing Village, Fenghuang Village and Wengyang Village of Luping Town, Xinqiaoying Village of Lishan County, Huangjiaguang Village of Huangshi County, Yuyou Village of Huangsi Town, Longchang and Longjing Village of Longchang Town,Shuiyuan Village and Northwestern Street Village of Niuchang Town.About 26.7% of the soil samples showed the lack of soil available potassium, which were mainly distributed in Pingshan Village of Chengxiang County, Songjiang, Xiangping and Dongtian Village of Disong Town, Sanjiang and Yunwu Village of Guwang County, Xinqiaoying and Luoao Village of Lishan County,Longchang Village, Longjing and Fengxiangshu Village of Longchang Town, Wengyang, Fuxing, Langbohe Village and Fenghuang Village of Luping Town,Xianqiao Village of Xianqiao County. And there were 8.9% of soil samples was absent in available potassium, which were mainly collected from Yunwu and Sanjiang Village of Guwang County,Luoao Village of Lishan County, Longchang Village,Changchong and Fengxiangshu Village of Longchang Town, Fuxing,Langbohe Village and Fenghuang Village of Luping Town, Dahua Village of Xianqiao County.

pH levels of the tobacco planting soil of Fuquan City

Soil pH degree could reflect the proportion of H+concentration to OHConcentration in soil solution, and it also determines the amount of acidic ions(H+or Al3+)or alkaline ions(Na+)in the soil colloids as well as the existing kinds of acid salt and alkaline salt.It is generally believed that the most optimum pH value range is 5.5-7.5, and when the pH value is in the range of 5.8-6.5, it is more conducive to the production of high quality tobacco leaves. If the soil acidity is too high,that is the soil pH value is too low, it may make the aluminum and manganese elements reach toxic levels,and reduce the microbial activity, and also reduce the amount of soil cation exchange capacity and availability of phosphorus molybdenum and other nutrients, making the soil aggregation become low. If soil pH value is too high, although the tobacco can grow normally, the output quality of the leaves will decrease.

Levels of soil pH value The pH values of the tobacco planting soil of Fuquan City was ranged from 4.4-7.9 with the average of 6.2. Among all the soil samples, those with the pH value of less than 5.5 accounted for 28.3%of the total, pH value of 5.5-6.5 accounted for 33.9%, pH value of 6.5-7.5 accounted for 21.7%, and those with the pH value of more than 7.5 accounted for 16.1%of the total.The soil samples with the best and good pH values accounted for the majority, but there were still some soil samples showing strong acid and strong alkali,which required some improvement to make it more conductive to produce more tobacco with high quality.

Regional distribution of soil pH value There were 28.3% of soil samples having low pH values,which were loosely distributed in Sanjiang Village,Yunwu Village and Malong Village of Guwang County, Northwestern Street Village of Niuchang Town, Longchang Village and Longjing Village of Longchang Town, Chahe Village of Chahe County, Pingshan Village of Chengxiang Town, Xiangping Village of Disong Town, Hunagjiagang Village of Huangshi County, Wengyang Village and Langbohe Village of Luping Town,Yuyou Village of Huangsi Town,Xinqiaoying Village and Laoao Village of Lishan County,Xianqiao Village and Dahua Village of Xianqiao County.Among all the soil samples with low pH values, the soil samples with pH values of lower than 5.0 accounted for 10.0%, which were mainly distributed in Sanjiang Village and Yunwu Village of Guwang County,Longchang Village of Longchang Town, Chahe Village of Chahe County, Pingshan Village of Chengxiang Town, Xiangping Village of Disong Town, Huangjiagang Village of Huangshi County, Wengyang Village of Luping Town, Yuyou Village of Huangsi Town, Xinqiaoying Village of Lishan County. And 33.9% of the soil samples had proper pH values, which were distributed in wide range of areas including Gaoping Village of Gaoping County, Duolangping Village, Northwestern Village, Shuanglong Village,Panjiaba Village and Huiylong Village of Niuchang Town, Sanjiang Village,Yunwu Village and Malong Village of Guwang County,Huangjiagang Village of Huangshi County, Xianqiao Village and Dahua Village of Xianqiao County,Longchang Village, Longjing Village and Changchong Village of Longchang Town, Chahe Village of Chahe County, Pingshan Village and Chengjiao Village of Chengxiang Town, Huangsi Village of Huangsi Town, Gedong Village of Xinglong County.And 21.7%of the soil samples had proper pH values, which were mainly distributed in the Panjiaba Village, Guihua Village and Shuiyuan Village of Niuchang Town, Huangjiawan Village of Huangshi County, Xiangping and Dongtian Village of Disong Town,Longchang,Fengxiang and Longjing Village of Longchang Town,Chengjiao and Pingshan Village of Chengxiang Town, Gedong and Liangshui Village of Xinglong County,Chahe Village of Chahe County,Yuyou Village of Huangsi Town, Laoao and Xinqiaoying Village of Lishan County, Fuxing and Langbohe Village of Luping Town. And there were 2.8%of soil samples showed high pH values, which were mainly distributed in Songjiang, DOngtian and Xiangping Village of Disong Town, Pingshan Village of Chengxiang Town, Chahe Village of Chahe County, Huangjiawan Village of Huangshi County, Sanjiang Village and Yunwu Village of Guwang County, Yuyou Village of Huangsi Town, Xinqiaoying Village of Lishan County, Langbohe Village and Wengyang Village of Luping Town,Shuiyuan Village of Niuchang Town.

Conclusion and Discussion

(1) The organic matter content in the tobacco plant soil of most areas of Fuquan City was suitable for planting flue-cured tobacco. The measured results showed that 96.7%of the regions in Fuquan City had moderateto abundant organic matter content in the tobacco planting soil, making it suitable for planting flue-cured tobacco. And only 2.8%of the regions had poor organic matter content, while 0.55 had excessive content, which was not suitable for planting flue-cured tobacco.As for the soil with abundant and excessive organic matter content, no or few organic fertilizer should be applied in a short-term range; as for the soil with suitable organic matter content,organic fertilizer could be applied to keep the balance of organic matter in the soil;as for the soil with low organic matter content, it needed to increase the application amount of organic fertilizer.

(2) The available nitrogen content in the tobacco plant soil of most areas of the areas of Fuquan City was suitable for planting flue-cured tobacco.The regions with medium and abundant content of soil available nitrogen accounted 70.6% of the total area of Fuquan City, making it suitable for planting flue-cured tobacco. And 2.8%of the total area had low available nitrogen content in the soil, while 26.6%had excessive available nitrogen in the soil. The content of available nitrogen could reflect the ability of nitrogen supplying. As for the soil with different nitrogen supplying abilities, the application amount and time of nitrogen fertilizer should be different. As for the soil with excessive available nitrogen,the application of nitrogen fertilizer should be controlled strictly; as for the soil with abundant available nitrogen content, the application amount of nitrogen fertilizer should be controlled,and the dressing time of nitrogen fertilizer should be strictly controlled to prevent the excessive available nitrogen amount in the soil for the absorption of tobacco after the tobacco ripe, which was not in favor of the formation of high quality tobacco; as for the solid with moderate available nitrogen content, the proper application amount and dressing time should be controlled;as for the fare with low nitrogen supplying ability, the amount of nitrogen fertilizer application should be increased.

(3)The available phosphorus content in the tobacco plant soil of most areas of the areas of Fuquan City was suitable for planting flue-cured tobacco.The results showed that the tobacco planting soil in Fuquan City had abundant content of available phosphorus, and there were few regions lacking phosphorus. To plant tobacco in the area abundant in phosphorus,the application amount of phosphorus fertilizer should be lowered accordingly,and the nitrogen to phosphorus ratio could be reduced to 1.0:(0.6-0.3),which was not only conductive for the production of high quality tobacco, but also could reduce the production cost,preventing the damage to environment caused by excessive phosphorus application.

(4) The available potassium content in the tobacco planting soil of Fuquan City showed great variation.In general, the available potassium content in the tobacco planting soil of Fuquan City was in the medium to abundant level with an average of 222.1 mg/kg,but it showed wide variation range from 33.8 mg/kg to 585.2 mg/kg. There were large amount of soil(35.6%of the total)lacked and absent in available potassium.Therefore,it should increase the application amount of potassium fertilizer to the soil lacking in available potassium. As for the soil with moderate available potassium content, attention should also be paid to the application of potassium fertilizer to ensure the proper potassium amount as well as scientific application of potassium fertilizer.

(5) Part of the tobacco planting soil in Fuquan City showed strong acidity or alkalinity, which required proper modification and fertilization.There were 10%of the tobacco planting areas in Fuquan City showed strong acidity (pH ＜5.0) and 16.1%showed strong soil alkalinity (pH ＞7.5),which needed to be modified,and selective application of fertilizer was in favor of the production of more high quality tobacco. As for the area with the pH ＜5.5, especially those with strong acidity of pH ＜5 and strongly acidic soil, calcareous material was needed to regulate the pH to make the soil pH gradually increase to around 6.0. During fertilizer selection,soil pH value should also be considered.If it was acid soil,it was better to select the calcium magnesium phosphate fertilizer which was weak acid soluble in nature, while the ordinary water-soluble superphosphate should be avoided.

(6)The regional distribution of soil pH,organic matter and available nutrients showed showing a certain regional feature and more obvious differ-ences. The regional distribution feature could provide referential basis for the selection of flue-cured tobacco planting soil with suitable and optimal pH value, application match of tobacco-used fertilizer and scientific application of organic fertilizer and nitrogen phosphorus and potassium fertilizer. As a whole, it needed to base on the measured contents and level distributions of major nutrients in the soil to adjust measures to local conditions with precise formula to balance fertilization.

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