Nursery irrigation should be applied at a rate that matches the ability of the growing media to absorb and hold the water that is applied. The best designed irrigation layout operated at the correct pressure cannot deliver the required efficiency if a significant portion of the applied irrigation is quickly draining through the growing media without being absorbed and held in the container. Ensuring the application of water matches the absorption rate of the growing media will take full advantage of the water holding capacity of the growing media. This application of water is known as the Mean Application Rate (MAR) and the past results from a national survey of over 200 nurseries showed an average MAR of 20.2 mm/h. Production nurseries should be seeking to achieve a MAR of between 5 & 12mm/hr, but there are many variables that can have an impact on the absorption rate such as the makeup of the growing media, the physical components, the air-filled porosity, the addition of wetting agents and polymer gels and scheduling techniques. A well designed premium growing media can greatly improve irrigation efficiency.
