This system is often used for bedding plants. It consists of a water absorbing fiber mat that is covered with a perforated plastic covering. The plants draw up the water from the mat by capillary action through he drainage holes in the pots. This system is easy to install, it allows for the use of non-uniform sized pots, and is flexible to accommodate plant growth. Because greenhouse crops are planted in soil-less media or material that does not have an endless supply of nutrients, it is important to apply fertilizers throughout the growth of the crop.
Liquid fertilizer is the most common and easiest way to apply nutrients to a large number of plants.
This simulates a slow release fertilizer and promotes even growth. Nutrient supply is not as constant and decreases between appications. This often causes growth to fluuctuate. Both methods can be directly added to an automatic irrigation system. Carbon dioxide in a greenhouse can actually increase the rate of photosynthesis in some plants such as carnations and roses.