XIAO Qin-zhi, ZHANG Shuang-shuang, WANG Gui, DENG Bin, WANG Xi-chun, JIN Zhi-li, LI Jia-yin, GAN Zai-de, YU Jie, LIU Feng, YI Ke

1. Yongzhou Branch of Hunan Tobacco Company, Yongzhou 42500, PRC;

2. Raw Material Department of China Tobacco Hunan Industrial Co. Ltd, Changsha 410014, PRC

Abstract In order to explore the optimal phosphorus application rate of tobacco in Yongzhou area and provide scientific basis for the rational application of phosphorus fertilizer in tobacco production, field plot experiments with 4 phosphorus application rates were conducted to study the effects of different phosphorus application rate on the growth period, agronomic characters and economic characters of tobacco. The results showed that when the nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer was 135, 135 and 418.5 kg/hm2, respectively, namely the ratio of 1 ∶1 ∶3.1, the field growth period was the shortest, only 107 d; the agronomic characters and physical indexes showed good results in their performance; the ratio of superior tobacco leaves, average price and output value were 49.36%、26.04 yuan/kg and 56 064.12 yuan/hm2 respectively, significantly higher than that of other treatments. Therefore, the suitable phosphorus application in Yongzhou tobacco area was 135 kg/hm2. In conclusion, rational phosphorus application rate was conducive to accelerating the growth and development of tobacco plant and early harvest; it could also effectively increase the output value and yield of tobacco leaves and was more conducive to the formation of high-quality tobacco leaves.

Key words Tobacco; Phosphorus fertilizer; Growth and development; Agronomic characters

1. Introduction

Phosphorus is one of the three essential nutrient elements for crop growth and development[1]. When the crop lacks phosphorus, it grows slowly, short and thin, erect, branching little, and leaves are easy to fall off, ordinary in color, dark green or greyish-green, purple red leaf margin and petiole, stunted roots, delay of maturation, low yield and quality[2-6]. Rational application of phosphate fertilizer can increase crop yield and improve crop quality[7-10]. Phosphorus is an important life element of flue-cured tobacco and an composition of organic compounds in tobacco leaves. Phosphorus participates in the transmitting of biogenetic information and energy utilization in various ways in tobacco plant and plays a very important role in promoting the growth, development and metabolism of flue-cured tobacco. The nutrient status of phosphorus directly affects the yield and quality of flue-cured tobacco[11-15].

Yongzhou is an important tobacco production area in Hunan Province and Jiunijinye is famous for its high maturity and sweet fragrance. At present, phosphorus nutrition of parent material has become an important factor affecting the quality of local fluecured tobacco in Yongzhou tobacco area. In order to explore appropriate phosphate fertilizer application amount of tobacco rice crop rotation tobacco fields and provide theoretical basis for the most appropriate phosphorus fertilizer application amount in the tobacco fields and other tobacco rice crop rotation tobacco fields in Hunan Province.

2. Materials and Methods

2.1. Test site and materials

Experiment was conducted in the experiment base of Institute of Tobacco Science of Hunan Yongzhou Tobacco Company. Clay from tobacco rice crop rotation with 150.7 mg/kg of available nitrogen, 26.3 mg/kg available phosphorus and 80.0 mg/kg available potassium was used as test soil. K326 was used as test variety. Special tobacco fertilizer, ammon- ium bicarbonate and calcium magnesium phosphate (fertilizer) purchased from market were used as chemical fertilizer.

2.2. Experiment design and treatment

Based on the same amount of nitrogen (N 135 kg/hm2) and potassium (K2O 418.5 kg/hm2), four diffenrent treatments were set, which were: treatment A: N ∶P2O ∶K2O=1 ∶0 ∶3.1; treatment B: N ∶P2O ∶K2O= 1 ∶1 ∶3.1; treatment C ∶N ∶P2O ∶K2O= 1 ∶2 ∶3.1; treatment D: N ∶P2O ∶K2O= 1 ∶3 ∶3.1. In the experiment, random block design was adopted, each treatment had three replicates. The plot area was 60 m2, and the row spacing was 1.2 m×0.5 m. Floating seedling system, membrane transplanting, field management, picking and roasting tobacco were conducted according to production technology for local high quality tobacco.

2.3. Determination items and methods

2.3.1. Growth period investigation

Observe and record the dates, such as transplan- ting date, rosette stage, strengtrly growing stage, flower budding stage, topping stage, first-picking dateetc., according to the standard of Record of Flue-cured Tobacco Production in Hunan Province.

2.3.2. Agronomic characters investigation

At 30, 50 and 70 d after planting, select 5 tobacco plants with similar growth from each plot. Record their plant height, stem girth, knot distance, number of leaf, the maximum leaf length and width, and calculate leaf area (Length×Width×0.634 5).

2.3.3. Economic character investigation and determination of physical index

Single-picking and single flule-cruing[5]was adopted, and grade was carried out according to the National Classification Standards for Flue-cured Tobacco GB2635-1992. The quality and yield per unit area of each grade tobacco were calculated, and the output value was calculated according to the local purchasing price. 10 tobacco leaves were taken from each grade to determine its weight and thickness, and the average value was calculated.

2.4. Data analysis and processing

SPSS19.0 was used for statistical analysis of the data.

3. Results and Analysis

3.1. Effects of the different treatments on the growth period

As shown in Table 1, after transplanting, the return seedling stage in different treatments was consistent. The field growth period in the treatment B, C and D was shorter than that in the treatment A. Of which, Treatment B had the shortest field growth period, only 107 d. It indicated that under the conditon of the unch- anged application amount of nitrogen and potassium fertilizer, increasing the application amount of phosphorus was conducive to accelerating the growth and development of tobacco plant and early harvest.

3.2. Effects of the different treatments on the main agronomic characters of tobacco leaves

As shown in Table 2, the agronomic characters in the treatment B, C and D were significantly different from those in the treatment A, and were all superior to those in the treatment A. Nevertheless there were no significant differences in the agronomic characters between treatment B, C and D. In terms of plant height, the plant height of tobacco with phosphate fertilizer was higher than that without phosphate fertilizer, and treatment B showed the highest plant height. This indicated that the application of phosphorus fertilizer was beneficial to the growth and development of tobacco plants with the unchanged amount of nitrogen and potassium fertilizer.

3.3. Effects of the different treatments on physical indexes of cured tobacco leaves

The weight of single leaf is also an important index to measure the quality of tobacco leaves, and directly reflects the development and nutritional conditions of tobacco plants. As shown in Table 3, there was no significant difference in the weight of single leaf among treatments for B2F grade tobacco, however it still showed a trend of D>C>B>A. For C3F grade tobacco, the weight of single leaf in the different treatments showed a trend of C>D>B>A, and the weight of single leaf in the treatment C and D was significantly different from that in the treatment A and B, whereas there was no significant difference in the weight of single leaf between the treatment C and D, as well as the treatment A and B. For X2F grade tobacco, the weight of single leaf in the different treatments showed a trend of D=C>B>A, and the weight of single leaf in the treatment C and D was significantly different from that in the treatment A and B. This indicated that the application of phosphorus fertilizer was beneficial to increase the weight of single leaf with the unchanged amount of nitrogen and potassium fertilizer.

As shown in Table 4, for B2F grade tobacco, the leaf thickness in the different treatments showed a trendof A=B>C>D; while for C3F grade tobacco, the leaf thickness in the different treatments showed a trend of A=B>D=C. And for X2F grade tobacco, the leaf thickness in the different treatments was the same. This indicated that the leaf thickness of B2F and C3F grade tobacco was decreased with the increase of phos- phate fertilizer amount under the condition of unchanged amount of nitrogen and potassium fertilizer.

Table 1 Growth period in the different treatments Month-day

Table 2 The main agronomic characters in different treatments

Table 3 The weight of single leaf in the different treatments g

Table 4 The leaf thickness in the different treatments

3.4. Effects of the different treatments on economic characters of flue-cured tobacco

As shown in Table 5, the application of phosphorus fertilizer can significantly increase the proportion of superior tobacco leaves, yield, average price and output value with the unchanged amount of nitrogen and potassium fertilizer. Of which, treatment B showed the best effect, followed by C and D. The proportion of superior tobacco leaves in the treatment B increased by 10.95%, compared with treatment A, and that in the treatment C and D were all higher than that in the treatment A. The average price in the treatment B increased by 2.32, 0.56 and 3.20 yuan/kg respectively, compared with treatment A, C and D. The output value in the treatment B increased by 12 371.88, 415.80 and 8 888.10 yuan/hm2respectively, compared with the treatment A, C and D. This indicated that rational application of phosphate fertilizer was beneficial to improve the yield, output value and the formation of high-quality tobacco leaves.

4. Summary and Discussion

Table 5 Effects of the different treatments on economic characters of flue-cured tobacco

Phosphorus is an essential element in the growth and metabolism of tobacco plant. The amount of phosphorus applied directly affects the growth and development of tobacco plants, and then affects the yield and quality of tobacco leaves[1,16-18]. The results showed that when the ratio of N ∶P2O ∶K2O was 1 ∶1 ∶3.1, namely 135 kg/hm2nitrogen fertilizer, 135 kg/hm2phosphorus fertilizer and 418.5 kg/hm2potassium fertilizer, flue-cured tobacco had better performance in growth period, agronomic characters, revenue, yield and quality,etc. Comprehensive consideration, the suitable phosphorus application in Yongzhou tobacco area was 135 kg/hm2.

Phosphorus plays an important role in the early formation and growth of root system[2,18-20], and is a key nutrient element that promotes the growth of tobacco seedlings and increases the absorption and utilization of other nutrients in the early stage of the field of flue-cured tobacco. Generally, phosphorus fertilizer was applied early as base fertilizer in the production, and suitable for one-off application[2,21]. This study showed that increasing the application amount of phosphorus fertilizer with the unchanged amount of nitrogen and potassium fertilizer, namely changing the proportion of nitrogen, phosphorus and potassium fertilizers, could promote the growth and development of tobacco and early harvest. Compared with other treatments, treatment B could significantly increase the ratio of superior tobacco leaves, effectively improve the output value, yield and quality, and was more conducive to the formation of high-quality tobacco leaves. Therefore, the suitable phosphorus application in Yongzhou tobacco area was 135 kg/hm2, which could provide a reference for the application of phosphate fertilizer in flue-cured tobacco production in similar tobacco areas.