Tea plants are a type of cash crop that prefers warmth, moisture, and diffused light. Intercropping summer green manure in tea gardens can shield part of the direct sunlight, increase diffused light, and create a suitable growth environment for tea plants' biological characteristics. It also improves soil physical properties and enriches the soil. This not only benefits the survival and growth of tea plants and controls weeds but also increases surface vegetation coverage, inhibits soil moisture evaporation, and reduces rainwater runoff, achieving water retention and preventing loss of water, soil, and nutrients. This supports green, ecological, and sustainable development in the tea industry.

I. Characteristics of Suitable Summer Green Manure Varieties for Tea Gardens

Through years of experimentation, it has been found that varieties such as Tea Fertilizer No. 1, cowpea, Sesbania rostrata, and others have strong adaptability and can be effectively used in tea gardens.

1. Tea Fertilizer No. 1

Tea Fertilizer No. 1 belongs to the genus Cassia in the legume family and is an annual sub-shrub. It is tolerant to acidic aluminum, drought, high temperatures, and has strong adaptability, capable of growing in sandy, loamy, and clay soils. The initial growth of Tea Fertilizer No. 1 is slow with a distinct seedling hardening period lasting around 40 days. As a tall green manure plant, its height can reach over 2 meters; it has strong regrowth capacity and can be cut 2-3 times a year. Under proper management, the fresh biomass yield of Tea Fertilizer No. 1 can exceed 225 tons per hectare, making it an excellent green manure for tea gardens. Its nutrient content is high, with a total nitrogen content of about 4% in the dry matter, a total phosphorus content of around 0.3%, and a total potassium content of over 1%. Tea Fertilizer No. 1 can also serve as a pioneer crop in newly cultivated land, promoting soil maturation and increasing organic matter.

Flowering period of Tea Fertilizer No. 1

Tea Fertilizer No. 1 after two cuts

2. Cowpea

Cowpea belongs to the genus cowpea in the legume family and is an annual herbaceous plant that prefers warmth and tolerates high temperatures. Seeds begin germinating at 15°C, with the optimal germination temperature around 20°C and the optimal growth temperature between 25-35°C. When the daily average temperature rises above 25°C, growth accelerates. Cowpea seedlings initially grow slowly with a distinct seedling hardening period. Cowpea has strong adaptability to various soils, including sandy, clay, and loamy soils, with good drought, acid, and poor soil tolerance. It grows well in soils with pH values ranging from 4.0 to 7.5. Cowpea has strong regrowth capacity and can be cut 2-3 times a year.

3. Sesbania rostrata

Sesbania rostrata, also known as soybean hemp or sun hemp, is an annual herbaceous plant in the legume family. It has a straight stem reaching 1.5-2.0 meters in height with few branches at the base and more at the top. Sesbania rostrata has a taproot system with shallow penetration, a thickened conical main root, and weak lateral roots primarily distributed within the top 20 cm of soil, along with nodulating bacteria. Sesbania rostrata is a fast-growing variety without a seedling hardening period, germinating and growing rapidly. The optimal temperature range for germination and emergence is 20-30°C. The daily growth rate of the plant is less than 10 cm in the first 15-25 days after emergence, with faster growth thereafter. During the flowering stage, the plant height increases rapidly, reaching 5-7 cm per day from the onset of flowering to the initial flowering stage.

Sesbania rostrata has broad adaptability and can grow well in soils with pH values ranging from 4.5 to 9.0. It prefers sunlight and is drought-tolerant and tolerant of poor soil conditions. It has strong regrowth capacity and can be cut multiple times a year. From flowering to pod maturity takes 70-90 days, with a full growth cycle of 120-150 days. With timely sowing, adequate phosphorus fertilization, and proper management, good yields can be achieved, making it a valuable organic fertilizer source in tea gardens.

4. Sesbania sesban

Sesbania sesban belongs to the genus Sesbania in the legume family and is a tall, one-year-old herbaceous plant. It has a thick main root and a well-developed root system with roots extending 1.5-2.0 meters deep and a root spread of 50-70 cm. It forms many nodules and has strong nitrogen fixation ability. The optimal germination temperature for seeds is 20-30°C. Initial growth is slow with a distinct seedling hardening period lasting around 40 days. Sesbania sesban is widely adaptable, highly resilient, and can tolerate acidic and poor soils, thriving in different terrains, slopes, and soil types in tea gardens. It is a short-day plant, sensitive to light, preferring high temperatures and humidity, with an optimal growth temperature of 20-30°C. It has strong regrowth capacity and high yields, capable of being cut 2-3 times a year, and can serve as a pioneer crop on newly cultivated land.

5. Sicklepod

Sicklepod belongs to the genus Cassia in the legume family and is a semi-upright one-year-old herbaceous plant with a taproot system and relatively developed lateral roots, primarily distributed in the top 0-20 cm of soil. Sicklepod is highly resilient and broadly adaptable, characterized by its preference for high temperatures, drought tolerance, tolerance of poor soils, acid tolerance, low incidence of pests and diseases, and strong nitrogen fixation ability.

II. Key Points for Planting Summer Green Manure

1. Selection and Combination of Green Manure Varieties

The primary purpose of planting green manure is as a fertilizer. In tea gardens, summer green manure is mainly planted using intercropping or in vacant areas around the Tea Garden (green manure base). Since the growth period of summer green manure overlaps with the growth of tea plants, tea picking, and agricultural operations in the tea garden, the choice of intercropped summer green manure in tea gardens should consider the size of the space between rows. Generally, young tea gardens, heavily pruned tea gardens, and plucked tea gardens have larger spaces between rows, and summer green manure is suitable for intercropping. For mature tea gardens with closed rows where the space between rows is smaller, intercropping summer green manure is not recommended, but summer green manure can be planted in the surrounding vacant areas to provide an organic fertilizer source for the tea garden.

The selection of summer green manure varieties for intercropping in tea gardens generally follows the principle of benefiting the growth of tea plants and facilitating farm management, while also considering the size of the space between rows. For young tea gardens, especially those up to 2 years old, with large spaces between rows and small tea plants with weak resistance to high temperatures and drought, high-yielding tall green manure varieties are suitable. After intercropping tall green manure in young tea gardens and covering the row space with cut green manure, it can provide shade, mulch, and nutrients, effectively avoiding exposure to strong sunlight and ground heat during summer and autumn, promoting the growth of tea plants. For tea gardens with relatively smaller spaces between rows, to reduce excessive shading by tall green manure or avoid interference with agricultural operations in the tea garden due to green manure planting, tall green manure can be planted in combination with short or creeping green manure varieties at a ratio of 1: (2-3), or a “plant one row (green manure), leave one row (no green manure)” method can be adopted.