Nursery management significantly influences the survival and Transplanting rates of Tea seedlings. Different ecological and physiological factors at various stages of development require distinct management approaches, depending on when the cuttings were taken.

I. Development Cycle of Tea Seedlings

When using short-shoot cuttings, the process from planting to developing a standard-compliant tea seedling can be divided into two phases: the pre-plant stage where the cutting is establishing itself, and the phase where a complete plant develops into a viable seedling. The survival rate during the first phase is critical in propagation techniques. Summer and early autumn cuttings have longer growth cycles and larger growth volumes, which often result in a significant number of weaker plants due to competition for nutrients and space, particularly in the second year of growth. To improve transplanting rates and seedling quality, the second phase is typically managed in two different periods: one when the seedling is less than 20 cm tall, focusing on promoting vigorous growth, and another once it surpasses 20 cm, implementing measures to control stronger plants while stimulating weaker ones.

II. Element Management

Nursery element management encompasses water, light, temperature, fertilization, pest and weed control, and plant regulation. Each of these elements has specific management priorities based on the time of cutting. Since these elements are interrelated and interdependent, management should consider their interactions.

(a) Water Management

1. Influence and Management Focus

Water supply must be moderate. In propagation, overwatering is more common than underwatering. Excessive watering can cause rotting and leaf drop, leading to death, especially in nurseries with micro-sprinkler irrigation systems. Insufficient water reduces survival rates of cuttings that have not yet formed complete plants and weakens seedlings, making them unable to reach transplant standards.

Excessive water causes rotting of the underground parts of cuttings and seedlings

The most critical period for water management in the nursery is from the time of planting until the end of the first flush's growth, except for nurseries planted in late autumn to early spring, which usually do not need watering during the winter-spring film-covered period. Special attention should be given to water management in the spring after removing the film before the flush matures and during high temperatures in summer and autumn.

2. Water Regulation Methods

Water supply can be provided through misting or irrigation. Regular or irregular watering can be applied based on the stage of propagation. Drainage to prevent waterlogging is necessary during rainy seasons.

Misting: For nurseries planted in May, summer, and autumn, misting should be done regularly after planting and after removing the film in winter and spring until root formation. Misting should maintain soil moisture and prevent leaf dehydration but should be done sparingly to avoid runoff. Typically, misting is performed once or twice a day in clear weather, once a day on cloudy days, and not at all on rainy days. After root formation, watering should be done only when the soil surface is dry, gradually transitioning to irregular watering.

Irrigation: Nurseries planted in late autumn, winter, and spring that are immediately covered with film, or those with established plants facing prolonged dry spells, can use irrigation through field ditches to increase soil moisture. However, for uneven nurseries, more misting water may be required to thoroughly moisten the seedbeds.

Flooding prevention: During continuous rainy weather, standing water in field ditches should be drained promptly. For low-lying areas, especially where the substrate is too clayey, water supply should be controlled. In nurseries using sprinkler systems, continuous irrigation should be avoided to prevent waterlogging damage to the seedlings.

(b) Light

1. Influence and Management Focus

During high-temperature seasons, shading to reduce light intensity is essential to prevent excessive exposure. In winter and on rainy days, excessive shading should be avoided. Apart from the season of cutting, key periods for shading include sustained high temperatures above 35°C in summer and autumn and sudden temperature rises above 25°C in clear weather following the Spring Tea harvest in the second year.

2. Light Regulation Methods

Summer cuttings use single-layer black nets with 70% shade or double-layer 50% black nets for shading. Other seasons use single-layer 50% black nets. From October onwards to the initial period of the next year's spring tea, a single layer of 50% net is added over the film. Shading structures can be low (70 cm above the seedbed) or high (around 1.6 m). Higher shading structures provide better shading effects but require additional arch-shaped covers for winter insulation, which can be cumbersome.

For winter nurseries, shading nets should be removed when the spring flush growth ceases and the seedlings have reached a certain height. When removing the nets, if there is consecutive hot weather, a hardening-off process should be implemented, alternating between half a day uncovered and half a day covered for about a week, to prevent leaf scorching, tip dieback, or plant death.

(c) Temperature

1. Influence and Management Focus

The primary concerns are frost damage below zero degrees Celsius in winter and spring and high temperatures above 35°C in summer. Frost damage occurs when the soil surface freezes and expands, causing changes in the microecology around the roots, which can hinder or kill the root system or callus tissue. Covering with film too early in early winter can trigger premature bud break, making the buds susceptible to subsequent winter frost damage or entering dormancy, inhibiting normal physiological activities and growth the following year. High summer temperatures often interact with water and light to impact seedling development.

Frozen sprouting buds due to low temperatures

2. Temperature Regulation Methods

Nurseries planted in summer and autumn generally begin covering with film when temperatures drop to freezing point. Nurseries planted in late autumn, winter, and spring should be covered immediately after planting. If temperatures are expected to drop below -5°C, additional small arch-shaped covers should be added inside steel pipe greenhouses. Adding a 50% shading net after covering with film can also prevent sudden temperature fluctuations and eliminate the need for ventilation. Film is typically removed in mid-April when temperatures stabilize above 10°C, retaining the shading net until late May or early June. Temperature regulation in summer primarily relies on water and shading.

(d) Fertilization

1. Influence and Management Focus

For cuttings taken before August, which have longer growth cycles and larger growth volumes, fertilizer and water control should begin after the spring flush growth ceases in the second year to prevent excessive growth. For cuttings taken in winter, spring, and May, aiming for transplanting in the same year, fertilizer and water supply must be increased to promote faster growth.

2. Fertilization Management Methods

One month after May cuttings and after removing the film for winter and spring cuttings, potassium dihydrogen phosphate foliar fertilizer (0.2%–0.5%) can be sprayed along with watering. Spraying should be done weekly until the new roots grow to over 5 cm and form the first root cluster or the first flush growth ceases. Then, urea (0.5%–1%) or compound fertilizer is applied by watering monthly until the flush growth stops.

(e) Pest and Weed Control

1. Influence and Management Focus

Common pests in the nursery include false eye green leafhoppers, mites, and black scale insects. Diseases include anthracnose, cercospora leaf spot, brown spot, and white root rot, as well as physiological disorders. Weeds include Arisaema, Alternanthera philoxeroides, Digitaria, and Setaria. Preventing diseases is most important before the seedlings develop into complete plants. Pest control and weeding are more labor-intensive in summer and autumn.

2. Pest and Weed Control Methods

Before covering with film in autumn, fungicides such as carbendazim and tolclofos-methyl can be sprayed as a preventative measure.