The resistance to deformation of seedling trays under high-temperature environments is a key indicator for ensuring seedling quality and efficiency. Its stability directly affects root growth, water absorption, and subsequent transplant survival rate. Deformation caused by high temperatures not only damages the structural integrity of the seedling tray but can also lead to uneven substrate distribution, root exposure, or excessive water evaporation, thus affecting seedling development. Therefore, understanding the core factors influencing the deformation resistance of seedling trays requires a systematic analysis from the dimensions of material properties, structural design, manufacturing process, usage environment, maintenance methods, specification matching, and material aging.
Material properties are the material basis for determining deformation resistance. Seedling trays made of different materials exhibit significant differences in performance at high temperatures: polyvinyl chloride (PVC) has a stable molecular structure and strong heat resistance, making it less prone to softening and deformation in high-temperature environments; polystyrene (PS) has good flexibility, is not easily broken in winter, and also exhibits outstanding high-temperature resistance in summer; while polypropylene (PP), although high in hardness, is prone to deformation at high temperatures due to the relaxation of its molecular chains. Furthermore, seedling trays made of foam, with their closed-cell structure, effectively block heat transfer and reduce deformation caused by localized overheating. However, it is crucial to ensure that their density and thickness meet standards; excessively low density may lead to insufficient compressive strength.
Structural design enhances resistance to deformation by optimizing mechanical distribution. The cavity layout, edge reinforcement, and bottom support structure of the seedling tray directly affect its load-bearing and heat dissipation performance. For example, seedling trays with a mesh or reinforcing rib design at the bottom can reduce localized stress concentration by dispersing pressure, thus lowering the risk of deformation; rounded corners at the cavity edges prevent stress concentration and edge cracking at high temperatures; and the drainage channel design not only accelerates drainage but also reduces the tray surface temperature through air circulation, indirectly reducing thermal deformation. In addition, the thickness of the seedling tray is also a critical factor; excessively thin trays are prone to bending due to thermal expansion and contraction at high temperatures, while appropriate thickness enhances structural rigidity.
Manufacturing processes improve material stability through meticulous control. Heat treatment processes can eliminate internal stress in materials and reduce the tendency to deform at high temperatures. Temperature and pressure control during injection molding directly affect molecular density; higher density results in stronger resistance to deformation. Surface coatings can form an insulating layer, blocking external heat conduction and enhancing the tray's wear resistance, thus extending its service life. For example, galvanized metal seedling tray frames can reflect some heat through the metal coating, slowing the rate of internal temperature rise.
Temperature fluctuations and light intensity in the usage environment are external factors. During hot seasons, if seedling trays are exposed to direct sunlight for extended periods, the surface temperature may far exceed the ambient temperature, accelerating material aging and deformation. Poor ventilation can lead to heat accumulation, forming localized high-temperature zones, further weakening resistance to deformation. Therefore, during summer seedling cultivation, it is necessary to regulate the ambient temperature using shade nets, evaporative cooling systems, or ventilation equipment, while avoiding close contact between seedling trays and heat sources (such as heating equipment).
Maintenance methods include reducing human-caused damage through standardized operation. If reused seedling trays are not thoroughly cleaned, residual substrate or fertilizer may corrode the tray, reducing its structural strength. Rough handling during transport (such as throwing or squeezing) can cause the tray to crack or deform. When stacked for extended periods, without partitions between trays, the weight of the upper trays may crush the lower ones, causing irreversible deformation. Therefore, after use, trays should be cleaned and dried promptly, handled gently during transport, and stored in well-ventilated areas, avoiding excessive pressure.
The appropriate size should be selected based on the crop's needs. While seedling trays with excessively large holes can hold more substrate, rapid evaporation of moisture at high temperatures can cause the tray to shrink and deform due to water loss. Conversely, trays with excessively small holes may swell due to restricted root growth. For example, when cultivating leafy vegetable seedlings, seedling trays with a hole diameter of 2-3 cm are suitable for root growth while maintaining tray stability; however, when cultivating larger cucurbit seedlings, thicker seedling trays with a hole diameter of 5 cm or more are required. Material aging is an inevitable result of long-term use. With increased use, seedling trays gradually lose elasticity and resistance to deformation due to UV exposure, oxidation, and frequent temperature fluctuations. For example, PVC seedling trays may become brittle at the edges after 3-5 years of use, while polystyrene seedling trays may harden and crack easily due to the volatilization of plasticizers. Therefore, it is necessary to regularly check the condition of seedling trays and replace aging trays promptly to avoid affecting seedling quality due to tray deformation.
