In recent years, the area of tea gardens has grown annually in response to the increasing demand in the tea market. However, the expansion of tea garden areas has brought about a series of issues including soil erosion, acidification, and reduced fertility, which are detrimental to tea yield and quality. This article, based on the current distribution of tea gardens in our country, summarizes the more common problems in the tea garden soil environment. It also analyzes the remediation effects and mechanisms of applying biochar, microbial fertilizers, and compound conditioners, aiming to provide a theoretical foundation for future soil improvement work in tea gardens and the promotion of soil conditioners.
This article, based on the current distribution of tea gardens in our country, summarizes the more common problems in the tea garden soil environment. It also analyzes the remediation effects and mechanisms of applying biochar, microbial fertilizers, and compound conditioners, aiming to provide a theoretical foundation for future soil improvement work in tea gardens and the promotion of soil conditioners.
I. The Area and Distribution Characteristics of Tea Gardens in Our Country
As of 2022, the total area of tea gardens in our country has reached 3.3303 million hectares, ranking first in the world. Based on geographical location, ecological environment, tea plant varieties, and other factors, tea regions in our country are divided into four major areas: South China, Jiangnan (South of the Yangtze River), Southwest China, and North of the Huai River. In South China tea region, red and brick-red soils predominate, which tend to be acidic but relatively fertile; in the Jiangnan and Southwest China tea regions, red and yellow soils are common, with clayey textures and low organic matter content; while in the North of the Huai River tea region, yellow-brown soils predominate, containing a high proportion of clay particles, making them heavy and not very fertile.
II. The Impact of Different Soil Conditioners on the Tea Garden Soil Environment
Currently, the main issues in tea garden soils include loss of water and nutrients, soil acidification, and soil heavy metal pollution. To address these issues, measures such as adding organic manure, soil conditioners, and intercropping green manures in tea gardens can improve the soil environment and restore degraded soils, improving the growth conditions of tea plants.
1. Biochar Improvement: Biochar is a carbon-rich solid pyrolysis product obtained from biomass under anaerobic conditions at high temperatures. Its impact on the tea garden soil environment is specifically manifested in several aspects: ① Biochar has a large specific surface area and high porosity. Its porous structure can effectively reduce soil bulk density, increase soil porosity and water content, promoting the rapid utilization of nutrients by tea plants and achieving higher biomass production of tea leaves. ② Applying biochar can significantly increase the pH of acidified soils and increase the content of organic matter and nutrients. ③ Biochar can immobilize heavy metal elements in the soil, reducing their harm to the soil and plants. Utilizing tea waste (pruning litter/tea residue) converted into biochar through high-temperature pyrolysis and then applying it to tea gardens can effectively improve soil quality and should be a key research direction for resource utilization and soil improvement in tea gardens.
2. Microbial Fertilizer Improvement: Microbial fertilizers, also known as bacterial fertilizers, are a new type of environmentally friendly biological fertilizer processed using special techniques and rich in single or multiple types of beneficial soil microorganisms. Their specific effects are: ① Microorganisms are important drivers in the transformation of soil nutrients, capable of altering the active state of nutrient elements in the soil, increasing the availability of organic matter and soil nitrogen, phosphorus, potassium, and other nutrient substances, providing sufficient nutrients for the growth of tea plants. ② Microbial fertilizers have a positive regulatory effect on soil pH and nutrient content. ③ After microbial fertilizers are applied to the soil, they can directly increase the number and diversity of soil microorganisms.
3. Compound Conditioner Improvement: Traditional conditioners such as peat, dolomite powder, and biogas slurry can also be used to improve soil structure and fertility, but most are applied individually, resulting in single effects. If soil conditioners are combined with fertilizers, this can significantly enhance the efficiency and effectiveness of soil improvement, maximizing economic benefits in tea gardens. Research shows that the application of bioconditioners with Calcium phosphate effectively regulates soil pH, rapidly increases the content of available phosphorus and organic matter in the soil, and the effect becomes increasingly evident over time. Magnesium fertilizers can increase soil microbial biomass and bacterial community composition, enriching soil microbial activity and promoting the transformation of soil nutrients. In summary, biochar, microbial fertilizers, and compound conditioners all have certain effects on improving the quality of tea garden soils. However, different soil improvement methods have complex impacts on the tea garden soil environment, with various indicators responding differently to the conditioners, exhibiting complex pedological effects. Therefore, implementing targeted measures based on the different conditions and actual benefits of tea gardens is of significant importance.
III. The Impact of Different Soil Conditioners on the Growth and Development of Tea Plants
1. Biochar Improvement: The growth and development of tea plants improved with biochar is closely related to the degree of biochar application. Within an appropriate range, biochar can exhibit good improvement effects, improving the number of leaves on new shoots of tea plants, significantly increasing the mass of one hundred buds, and increasing the chlorophyll and soluble protein content in the leaves, enhancing photosynthesis in tea leaves, thereby increasing the fresh leaf area and yield of tea plants. However, excessive biochar can stimulate microbial reproduction and Metabolism, causing increased soil moisture, affecting the growth of tea plants and reducing yield.
2. Microbial Fertilizer Improvement: After microbial fertilizers are applied to the soil, they can quickly improve soil physical and chemical properties, providing sufficient available nutrients for tea plants, promoting the accumulation of substances within tea leaves, enabling earlier bud emergence of new shoots of tea plants, strengthening the growth of tea plants, advancing the harvesting period, and increasing the yield of fresh leaves. Using antibiotic fertilizers can accelerate the development of the root system of tea plants in acidified tea gardens, increasing the number and weight of roots, with a particularly beneficial effect on the growth of young tea plants.
3. Compound Conditioner Improvement: Compound conditioners have a significant impact on the growth of tea plants and the absorption of nutrients, specifically: ① Applying biochar and organic manure in tea gardens, where organic manure can directly supply nutrients to the soil environment and tea plants, rapidly increasing soil fertility, and biochar can play a role in the “temporary storage” and “natural controlled release” of available nutrients in the soil. This has good reference value for reducing fertilizer application and simplifying tea plant cultivation. ② Compound conditioners can promote the development of the root system of tea plants, enriching the nutrients in the organs of tea plants, promoting the development of the roots, stems, and leaves of tea plants. ③ Compound conditioners have a significant impact on the taste, color, and aroma of tea.
In summary, all the different conditioners have improvement effects, but there are differences (Table 2). Among them, biochar-based fertilizers show better performance in the improvement of acidified tea garden soils and in increasing tea yield and quality. They can be a key research direction in the exploration of excellent soil conditioners in the future.
IV. Outlook
Currently, soil conditioners have a certain effect on improving the quality of tea garden soils. However, in the context of the global emphasis on energy conservation, emission reduction, and low-carbon development, to improve the effectiveness and benefits of application, research and improvement are needed in the following areas:
First, many tea producers are unclear about the management models of Green Tea gardens, organic tea gardens, and non-polluting tea gardens, and there is an urgent need to develop and promote standardized tea garden management.
Second, promoting circular agriculture in tea gardens, recycling large amounts of tea plant waste and then returning them to tea gardens, can reduce costs while increasing nutrients, and is a key direction for future research on biochar conditioner technology.
Third, clarifying the mechanisms by which soil conditioners affect the growth of tea plants and the quality of tea can guide practice more scientifically.
Fourth,