Jun GAO, Xinjie LI, Caiyou LU

1. College of Tea, Yunnan Agricultural University, Kunming 650201, China; 2. Jiangcheng County Tea and Characteristic Biological Industry Development Center, Jiangcheng 665900, China; 3. Cultivation Research Laboratory of the Modern Agricultural Tea Industry Technology System in Yunnan Province, Kunming 650201, China

Abstract The present study introduced the concept and characteristics of preserved tea plantation, and analyzed application and benefit of stereoscopic trimming and pruning technology in the cultivation of tea tree canopy in preserved tea plantations. The results show that the stereoscopic trimming and pruning technology of tea trees has more advantages in production efficiency than other trimming and pruning techniques in terms of yield and output value, and can better exert the regeneration ability of tea branches. The grade of branching is increased from grade 3-4 before unpruning to grade 9-13 (3-4 times higher), the length of internode is increased from 1-2 cm to 3-7 cm (increased 3-4 times), the picking area is increased from 0.9 m×1.1 m to 2.8 m×4.2 m (an increase of nearly 10 times), accordingly achieving the best production and economic benefits required in tea production.

Key words Preserved tea plantation, Canopy cultivation, Technology, Benefits

1 Introduction

Tea tree (Camelliasinensis), as a perennial woody and leafy economic plant, can grow for decades at a time of planting and can even last for hundreds of years under suitable natural conditions. So far, there are still many productive ancient tea trees and ancient tea plantations in Yunnan tea areas. Obtaining a certain quantity and quality of fresh tea leaves from the canopy of tea trees is the core of developing tea plantation production. Therefore, tea tree canopy cultivation is a main measure of tea plantation management, which directly affects the success of high quality and high yield in tea production, and also influences the sustainability of production capacity[1]. In the practice of tea plantation production, according to the characteristics of the cultivated tea tree varieties and the rules of growth and development and the actual environmental conditions, it is the principle that must be followed to carry out reasonable canopy cultivation technical measures and obtain high technical benefits. In recent years, as the tea products made from the fresh leaves of large tea trees and ancient tea trees in Yunnan Province have been favored by the market, "preserved tea plantation" similar to the growth of large tea trees and ancient tea trees has continued to appear in the tea areas of Yunnan Province. The most common one is the tea plantation formed by "transforming" the existing Yunnan big-leaf tea plantation that has been pruned, dwarfed and densely planted. In other words, it is to select and keep the tea trees with good characters in the tea plantation according to a certain row spacing, let them gradually restore the tree vigor and tree posture of their own trees and small trees, and excavate the rest of the tea trees one by one. Obviously, such "preserved tea plantation" is different from preserved tea plantation in the traditional sense. It is not a tea plantation that takes the form of "picking with leaves keeping", "preserving branches", "stop picking in a certain season", and not a moderate picking method that needs restoring original tree vigor and tree posture, as well as picking crown surface after pruning to different degrees, but rather a tea plantation formed by removing part of the tea trees from the existing tea plantation, preserving the required tea trees and restoring the original tree vigor and posture[2-3].

Through surveying the preserved tea plantations in different tea areas, we found that it has the following three characteristics. (i) The preserved tea plantation has significantly fewer tea plants per unit area and low fresh leaf yield, only 1 500-3 000 tea plants/ha, and the fresh leaf yield is lower than that of dwarf dense tea plantation. (ii) Some preserved tea plantations just leave the preserved tea trees naturally grow, but the picking area is limited, which affects the yield of fresh leaves; in addition, with the continuous picking of fresh leaves, the tree crown width of the preserved tea tree becomes narrower, the branches in the middle are dense, and the buds are small, resulting in a decline in the quality of fresh leaves. (iii) The fresh leaf price of preserved tea plantations is more than 30% higher than that of dwarf dense tea plantations, chemical inputs such as fertilizers and pesticides have been greatly reduced, and many preserved tea plantations have prohibited chemical fertilizers and pesticides, achieving zero input of chemical fertilizers and pesticides. From the fact that the tea market has been in a situation of "oversupply" for a long time, preserved tea plantation has and embodied a certain effect of "improving quality and increasing efficiency". These indicate that taking scientific and reasonable technical measures to meet the healthy growth of preserved tea trees and achieve continuous output of fresh leaves of preserved tea trees has become an urgent problem to be solved in the management of preserved tea plantations. As it is known to all, Yunnan big-leaf tea trees are arbor and small tree types with their own growth characteristics. In view of this, according to the characteristics of Yunnan big-leaf tea trees and the local environmental conditions, we carried out a research on the application and benefit analysis of "stereoscopic trimming and pruning technology" in tea tree canopy cultivation of preserved tea plantations, to provide a certain reference for the production of preserved tea plantations.

2 Materials and methods

2.1 Experimental time and placeFrom November 2017 to November 2020, we carried out experiments at Aka Luoduo high-density preserved tea plantation in Tianfang Village in Guoqing Township, and Gaoshan Laozhai high-density preserved tea plantation in Gaoshan Village, Qushui Town in Jiangcheng County of Pu’er City, Yunnan Province.

2.2 Experimental methods(i) Features of preserved tea plantation: by transplanting or removing, a preserved tea plantation with plant spacing and row spacing of 4 m×4 m triangular-to-space distribution is formed. (ii) Suppressing or pruning off the main branches: prune the middle main branches for some upright tea trees, preserve 2-3 primary branches, and remove the apical dominance to keep the tree height below 2.5 m (once in November every year until the formation of 2-3 shaped backbone branches that favor the growth of the tea tree). (iii) Canopy culture of arbor stereoscopic tea trees: because there were too many branches in grade 2, few branches above grade 3, the picking area was small, and the yield and output value were low, we cut off the grade 2 branches that took up more than 60% of the space, or removed the tops where the grade 2 branches and grade 3 branches meet outwards. For branches above grade 3, we also carried out in sequence to stimulate the germination of more productive branches, and finally formed arbor stereoscopic tea trees (one time separately at the end of May and mid-November annually). (iv) Daily care and canopy protection: due to the improper early management of preserved tea plantation and the humid growth environment, it is easy to be infected by some parasitic (epiphytic) plants to breed diseases and insect pests. It is necessary to carefully scrape off the moss and lichen parasitic on the trunk with the cut bamboo tools, and at the same time clean the branches with weak growth potential and pests (these should be carried out at the same time of fresh leaf picking).

2.3 Data statisticsWe surveyed and measured the biological characteristics of preserved tea plantations, including tree type, tree posture, tree height, crown width, grade of branching, length of internode, spring tea germination period,etc.Besides, we also investigated the picking times, yield per plant, fresh leaf price, dry semifinished tea price, and yield per hectare of preserved tea plantation tea trees from 2016 to 2020 and analyzed the benefit.

3 Results and analysis

3.1 Biological characteristics analysis of preserved tea plantation tea tree canopy after cultivationFrom Table 1, it can be seen that the preserved tea plantation has solved the following problems after 3 years of stereoscopic tree pruning: the tree height was controlled and the tree posture was improved, forming sprawling stereoscopic tea trees with reasonable distribution, orderly branch levels, and orderly spatial branch structure; the picking area has been increased, and the picking area was increased from 0.9 m×1.1 m to 2.8 m×4.2 m (an increase of nearly 10 times); the tenderness-keeping ability of tea tree branches was strengthened, and the grade of branching was increased from grade 3-4 before pruning to grade 9-13 (3-4 times higher); the length of internode was increased from 1-2 cm to 3-7 cm (an increase of 3-4 times), which increased the yield of high-density preserved tea plantations; improved the cold resistance, drought resistance, and pest resistance of tea trees in tea plantations, and realized zero input of chemical pesticides. In preserved tea plantations, using the arbor stereoscopic pruning method had a wider growth space, and it is convenient for the pest control and water and fertilizer management of the tea plantations. The picking area of the tea trees after the standardized arbor stereoscopic pruning was significantly larger, the branches were more distinctly arranged, and the space utilization rate was higher.

3.2 Analysis of production and economic benefits of preserved tea plantations after tea tree canopy cultivationFrom Table 2, it can be seen that the stereoscopic tree pruning of the two tea plantations solved the problems of low tea plantation production and economic benefits. The picking times was reduced from picking in the whole year to 3-4 times a year, which effectively saves time and labor input and improves the production benefits. Although the yield of fresh leaves was decreased, the price of fresh leaf rose from 4.00-5.00 yuan/kg of the whole year picking to 35.00-40.00 yuan/kg, an increase of 5-6 times. The price of dry semifinished tea was increased from 23.00-28.00 yuan/kg to 220.00 yuan/kg, an increase of 8-9 times, and the total output value also increased by 5-6 times, which further increased the economic income of tea farmers.

4 Conclusions and discussion

The stereotyped pruning method described by many scholars has solved the problems of the low yield and output value of dwarf and dense tea plantations and problems in the protection, development and utilization of ancient tea plantations[4-7]. In the past three years, we surveyed trees in Aka Luoduo preserved tea plantation tea, Tianfang Village, Guoqing Township, Jiangcheng County, Pu’er City, and Gaoshan Laozhai preserved tea plantation tea, Gaoshan Village, Qushui Town, Jiangcheng County, Pu’er City and the results show that this method can expand the growth space of tea trees, enhance the effective use of light by tea trees and promote the photosynthesis of tea trees.

Table 1 Biological characteristics and planting benefits of Gaoshan Laozhai tea plantation

Table 2 Biological characteristics and planting benefits of Aka Luoduo tea plantation

Besides, it solves the unfavorable factors brought by the apical dominance, stimulates the germination of multi-level shoots, and increases the length of internode. Through stereoscopic trimming and pruning technology, the reserved tea trees can be formed into stereoscopic tea trees with hierarchical and spatial sense, and the space for branch germination can be increased. In addition, it reduces the loss of tea tree nutrients and prevents the tea tree from entering the aging period in advance; effectively saves time and labor input, and improves production and economic benefits. To a certain extent, it solves the contradictions and problems that need to be solved between the yield, quality and benefit in the current preserved tea plantations.

Through the above analysis, we believe that for the tea tree canopy of preserved tea plantations, adopting stereoscopic trimming and pruning technology is an effective method to solve the problems of extensive management, not distinct biological characteristics, weak enthusiasm of tea farmers, deficient labors, and low output value of tea plantations, and it conforms to the demands of production development of preserved tea plantations.