What is a disadvantage of using mat watering (capillary mats) in greenhouse irrigation?

Using mat watering, or capillary mats, in greenhouse irrigation indeed has size limitations based on pot size, and this can be a significant disadvantage. Capillary mats work by allowing water to be absorbed through the bottom of pots that are placed on the mats. This method is effective for smaller pots that can adequately draw moisture through their drainage holes. However, when dealing with larger pots, the ability of the capillary mat to deliver sufficient water consistently becomes less effective, as the larger volume of substrate requires a greater amount of water.

In larger pots, the distance from the mat to the center of the pot can hinder the movement of water through the growing medium, leading to uneven moisture levels. This could pose a challenge for plants that require consistent and adequate watering, making it difficult to maintain optimal growing conditions.

While other disadvantages like high initial costs, potential disease spread, and the need for constant water flow can be concerns, the sizing issue directly affects the effectiveness of the system in delivering adequate hydration tailored to plant needs based on pot size. This limitation can limit the versatility of mat watering in diverse greenhouse operations, especially where varying pot sizes are utilized.