Seedling nutrient blocks are compressed substrate blocks used during the seedling stage.

A seedling nutrient block is a seedling-growing product made by compressing substrate, nutrients and water-retaining materials into a block, usually square in shape, which slowly expands and softens after contact with water. It combines the steps of filling soil and applying fertilizer in traditional seedling raising into one, so that when using it you simply sow the seeds directly into the block, saving the trouble of mixing nutrient soil.

The characteristics of nutrient blocks are relatively balanced nutrients and good air permeability and water retention, and during the seedling period the number of top dressings can generally be reduced. At transplanting, the block can be buried in the soil together with the seedling, causing less damage to the root system and usually a shorter recovery period, which is why it is welcomed by home vegetable gardens and large-scale seedling operations.

When using it, generally first lay the nutrient blocks flat in a seedling tray or shallow box, water them thoroughly so they fully absorb water and expand, then place seeds into the central hole of the block and cover with soil. During the seedling period, take care to keep the blocks moist but not waterlogged, and after emergence give appropriate light to avoid leggy seedlings. Sowing depth and temperature requirements differ among crops, so adjustments should be made flexibly according to the seed instructions.

When purchasing, pay attention to how firm or loose the block is; if too hard it absorbs water slowly, while if too loose it tends to crumble. If mold appears on the surface during use, it is mostly related to excessive humidity and poor ventilation, and humidity should be reduced and ventilation increased promptly. Nutrient blocks are suitable for raising seedlings of many vegetables such as leafy greens and melons and fruiting vegetables, but for crops with a long growing period and high fertilizer demand, appropriate nutrient supplementation may still be needed later.