Some suggestions on choosing seedling containers

1. Number of holes and hole volume

The number and volume of the holes in the plug tray directly affect the quality of seedling growth. Too few holes in the plug tray can lead to waste of production resources; conversely, too many holes result in inadequate space for healthy growth, making the seedlings weak and prone to disease. The holes should have a square inverted trapezoid or inverted cone shape, which encourages downward root growth. Additionally, drainage and air permeability holes at the bottom of the plug tray enhance drainage and ventilation for the substrate. In general, smaller planting holes in the plug tray lead to seedlings being more sensitive to shifts in humidity, nutrients, oxygen, pH levels, and EC value in the substrate. In contrast, larger holes provide greater substrate content and stronger buffering capacity, aiding root system growth. Choose the number and volume of holes based on the seedling variety and final size to optimize substrate use, improve space efficiency, and reduce production costs.

The plug tray's color affects both root temperature and plant light transmittance. Typically, black plug trays are preferred during winter and spring for their light-absorbing properties that raise root temperature. In contrast, silver-gray trays are optimal in summer or early autumn because they reflect more light, preventing overheating. White trays have higher light transmittance, adversely affecting root growth, which is why they are rarely used—except for white foam trays. In large-scale nurseries, black or dark gray plug trays are generally the standard choice.

Table 1: Specifications of plug trays for common varieties

When reusing the plug tray, the used equipment may carry residual pathogens and pests and must therefore be cleaned and disinfected. The seeding tray can only be reused after thorough cleaning and disinfection. Nowadays, many large and medium-sized nurseries utilize plug tray cleaning machines to streamline this process, significantly reducing labor costs.