Introduction
Water is a limited asset and very few orchardists have surplus supply to their requirement. Water is also often expensive to source (either via bores or dams) and apply (pumping costs) and as such needs to be used efficiently.
The base aim of efficient irrigation is to maintain the soil moisture of your effective root zone within your chosen stress parameters, with minimal water lost to gravity or evaporation. There are other factors that can also impact on your decision making, such as critical irrigation periods, water quality, soil borne diseases and frost mitigation.
Efficient irrigation has three parts:
- ensure you have sufficient supplies of suitable quality water for your mature orchard in a dry season
- ensure you have a well-designed irrigation system that delivers the volumes required in an efficient and uniform manner
- ensure you supply irrigation at volumes and frequencies that maintain suitable plant water relations to produce the desired yields and quality without wasting water.
Ensure you have sufficient water at the start
The starting block for efficient irrigation is ensuring sufficient supply of suitable water. Water quality will be discussed later. Sourcing water in Western Australia is either via under-ground supplies (via a bore or a soak), surface catchment storage (dams, tanks), year round water course or an irrigation supply scheme. Nearly all sources (except storage tanks) require some form of licence or planning permission — contact your local shire and regional office of the Department of Water.
The volumes of water required annually to supplement rainfall will vary from season to season and is affected by orchard size, tree size, irrigation delivery methods, management practices, water quality and water source/storage system. As a rough guide, the volumes of water resources required annually varies from 5 megalitre per ha (Pemberton) to 21ML/ha (Carnarvon). More details on calculating your annual requirements can be found in ‘Growing avocados – annual water requirements’.