Technical Specifications for Tomato Seedling Management in Summer Nursery Stage

During the summer nursery period, due to the climate characteristics of high temperatures, intense sunlight, frequent rainfall, and high humidity, tomato seedlings face four major risks: sunburn, rain damage, high temperatures, and excessive elongation. To ensure robust seedling growth, improve transplant survival rate, and enhance future yield, systematic and comprehensive management measures should be taken as follows:

I. Seedbed Site Selection and Construction

1. Seedbed Site Selection

   • Select vegetable plots that are elevated, well-drained, well-ventilated, and far from disease sources for seedbed establishment.
   • Control seedbed width at approximately 1 meter for easy management and ventilation.

2. Shade and Rain Protection Facilities

   • Build a double-layer protective shelter above the seedbed. The first layer is a rainproof plastic film to effectively prevent rainfall from directly entering the seedbed and reduce humidity fluctuations; the second layer is a shade net with good light transmittance and strong shading ability (40%-50% shading rate) to reduce light intensity, prevent seedling scorch, and ensure sufficient photosynthesis.
   • During continuous heavy rainfall or at noon under intense sunlight, promptly cover with additional shade curtains or thicker shade nets to control temperature and light intensity inside the seedbed, preventing damage to the photosynthetic system and physiological wilting caused by heat stress.

II. Nursery Method and Seedling Age Control

1. Shortening the Nursery Period

   • Adopt direct seeding nursery technology to avoid root damage and disease infection caused by transplanting.
   • Control seedling age within 30-35 days, aiming to cultivate “appropriately aged, strong seedlings” and prevent the formation of excessively elongated or aging seedlings.

2. Substrate Management

   • The nursery substrate should be loose, well-aerated, rich in organic matter, with pH maintained between 6.0-6.5. Disinfect the substrate in advance (e.g., high-temperature steaming or chemical disinfection) to reduce disease pressure.

III. Integrated Disease Prevention and Control

1. Disease Control During High-Risk Seasons

   • During the hot and rainy summer season, tomato seedlings are susceptible to diseases such as damping-off, root rot, and leaf mold. Apply preventive broad-spectrum fungicides during the nursery period:

     • Apply 75% wettable powder of chlorothalonil at 500 times dilution;
     • Or apply 500 times dilution of thiram wettable powder;
     • Spray every 7-10 days, 1-2 consecutive applications, combined with foliar spraying of trace element nutrient solutions to enhance plant resistance and vigor.

2. Environmental Regulation for Disease Prevention

   • Maintain good ventilation in the seedbed, reduce air humidity, and prevent prolonged moisture on leaf surfaces to avoid conditions favorable for pathogen spore infection.

IV. Water Management and Elongation Control

1. Water Regulation

   • Follow the principle of “watering when dry” during the seedling stage to avoid flooding or prolonged wet conditions, which may lead to excessive elongation and disease.
   • During rainfall, ensure that rainwater does not directly flow into the seedbed; if necessary, set up temporary drainage ditches.

2. Excessive Elongation Control

   • If excessive elongation occurs in the later seedling stage, apply growth regulators such as chlormequat chloride (or paclobutrazol as a substitute) for chemical control:

     • Use 0.1%-0.15% chlormequat chloride solution;
     • Evenly spray on seedling foliage once every 7 days, apply continuously for 2 times;
     • Apply on windless sunny mornings before 10 a.m. or in the evening to avoid phytotoxicity caused by high-temperature application;
     • Control internode elongation, promote sturdy stems and thick leaves, forming compact and robust seedlings.

V. Comprehensive Technical Objectives

Through the above systematic measures, the summer tomato nursery can effectively achieve the “four preventions and one control” objectives (protection against sunburn, rain, high temperatures, diseases, and control of excessive elongation), ensuring transplant survival rate, vigorous growth, and stable high yield in the later production stage.