Green manure is a clean organic Fertilizer free from heavy metals, antibiotics, hormones, and other residues. It is also an effective measure to reduce the application of chemical fertilizers and improve Soil fertility. Intercropping winter green manure in Tea gardens is an effective way to maintain and improve soil fertility, utilizing garden resources to nourish the garden and trees. This practice can maximize resource utilization, as green manure covering the soil surface reduces soil erosion by rainwater, absorbs and activates soil nutrients, and prevents nutrient loss. Since there is less competition between winter green manure and tea plants, it has good prospects for wider application in tea gardens. Based on years of experimental research, this article introduces suitable varieties of winter green manure for tea gardens and key points in their cultivation techniques.
Suitable Varieties of Winter Green Manure for Tea Gardens and Their Characteristics
Tea garden soils are typically acidic and rich in aluminum, so the green manure crops grown must be acid and aluminum tolerant. The main criteria for selecting suitable green manure crops are biomass yield and quality, which are important indicators of a variety's stress tolerance and productivity. Nitrogen content is one of the most critical factors influencing green manure quality. After several years of trials, we found that Vicia villosa, Vicia sativa, Raphanus raphanistrum, Xiangyepea No.1, and Astragalus sinicus have strong adaptability, high yields, and high nutrient contents, making them promising for wider application in tea gardens.
1. Vicia villosa (Field Vetch)
Field vetch is a one-year or biennial herb belonging to the legume family. There are three main types: hairy field vetch, smooth field vetch, and Blue flowered field vetch. Its growth cycle is about 230 to 250 days. It grows prostrate or semi-prostrate with tendrils, allowing it to climb around tea plants. Field vetch is highly adaptable, cold-resistant, and drought-tolerant but not flood-tolerant. It can grow in both sandy and clay soils. It is acid and poor-soil tolerant and grows well in newly cultivated, impoverished young, or low-fertility tea gardens (
).
Note: a – intercropped with hairy field vetch, b – intercropped with smooth field vetch.
Note: a – root system and nodules of hairy field vetch, b – root system and nodules of smooth field vetch.
Figure 2. Root system and nodule formation of intercropped field vetch in tea gardens.
2. Vicia sativa (Arrowleaf Clover)
Arrowleaf clover, also known as broad-leaved clover or wild pea, is a one-year or biennial semi-prostrate plant in the legume family with a growth cycle of 210 to 230 days. Its stems ascend obliquely or climb, reaching lengths of 100 to 250 cm. Arrowleaf clover prefers cool and humid climates. Its seeds germinate best at temperatures of 26 to 28°C and can germinate at temperatures as low as 2 to 3°C. It is cold and drought-tolerant, growing optimally at 14 to 18°C during the vegetative stage. Arrowleaf clover can withstand temperatures as low as -6°C and survive short-term exposure to -10°C. It is adaptable and grows well in acidic, low-fertility tea gardens, producing high yields (
).
3. Raphanus raphanistrum (Field Radish)
Field radish, commonly known as full-garden flower, is a one-year or biennial erect plant in the mustard family. It prefers warm and humid climates, with seeds capable of germinating and growing at temperatures as low as 4°C, and optimal germination occurring around 20°C. The optimal growth temperature for field radish is 15 to 20°C. Seedlings are tolerant of both cold and heat, growing normally at 25°C and remaining unaffected by 0°C temperatures. Field radish has a short growth cycle, is adaptable, and can tolerate acidic, drought-prone, and poor soils. It also has a strong ability to absorb insoluble phosphorus in the soil and is widely used in tea gardens (
).
4. Xiangyepea No.1
Xiangyepea No.1 belongs to the legume family and is a one-year or biennial prostrate plant. It has a growth cycle of about 210 days and can be sown from mid-September to mid-November in the Changsha tea region. In acidic soil environments, its root system is well-developed, and rhizobium develops well, giving it strong biological nitrogen fixation capabilities, significantly improving soil quality (
).
Note: a – nodules, b – seedling stage.
5. Astragalus sinicus (Purple Clover)
Purple clover, also known as red flower grass seed, is a one-year or biennial plant in the legume family. It prefers warm and humid conditions, with the optimal growth temperature being 15 to 20°C. It is intolerant of drought and waterlogging, with the optimal soil moisture content being 24% to 28%. When the soil moisture content is below 9% or above 36%, seedlings may wilt, die, or experience poor growth. Purple clover performs poorly in poor soils but grows well in loose, fertile sandy loam or clay loam soils.
Cultivation Techniques for Intercropping Winter Green Manure in Tea Gardens
1. Timely Sowing
The appropriate sowing period for winter green manure is generally from mid-September to late October. Within this period, sowing should be done as early as possible to ensure adequate ground coverage before winter. This promotes higher yields of green manure and helps insulate and retain moisture in the soil around tea plants, reducing daily fluctuations in soil temperature and promoting tea plant growth. Due to autumn and winter droughts and low temperatures, if green manure is sown too late, the seedlings will be small and provide inadequate ground cover, which does not help with insulation and moisture retention and can reduce green manure yields. Research has shown that the daily fluctuation in soil temperature at the surface and 5 cm depth in tea gardens intercropped with winter green manure was 2.5°C and 1.4°C, respectively, while in control plots (without green manure), these figures were 5.0°C and 4.2°C, respectively.
2. Appropriate Fertilization
When intercropping green manure in tea gardens, especially in newly cultivated or impoverished gardens, applying moderate amounts of fertilizer, particularly phosphate fertilizer, is necessary. Many tea gardens suffer from phosphorus deficiency, and leguminous and cruciferous green manures have a strong ability to absorb phosphorus. Applying appropriate amounts of phosphorus fertilizer promotes the growth of green manure, increasing its yield and quality. This achieves the effect of phosphorus-enhanced nitrogen fixation and using a small amount of fertilizer to produce a larger amount of fertilizer. Fertilizer should be applied before or after land preparation, or together with the application of base fertilizer for tea gardens, mainly using phosphate and potassium fertilizers with a small amount of nitrogen fertilizer. Typically, 10 to 20 kg of calcium magnesium phosphate or super