There is a lot of interest in irrigation scheduling at present, with a vast array of new irrigation scheduling equipment coming onto the market. This new technology offers great opportunities for improved irrigation management. Without a good understanding of soils and irrigation systems however, this new equipment can be of little or no practical use. It can in fact provide potentially misleading information, which may lead to under or over irrigation of parts of a property and significant losses in crop production and/or quality.

The integrated approach to irrigation is based on the integration of three factors:

• the soil being irrigated
• the irrigation system which applies the irrigation water
• the tools and methods used to schedule irrigation

The integrated approach to irrigation management ensures that the outputs from irrigation scheduling tools are correctly interpreted and that the management of irrigation enterprises is optimised.

Soils
Information from a soil survey can be used to select the most suitable crop varieties and rootstocks. Specific soil improvement requirements are often identified by a soil survey. Soil information is used to tailor irrigation system design and management to suit soil type and crop variety in achieving market requirements. Knowing the soil types present on the property and understanding the implications on management are the foundation for making appropriate management decisions. The aim is to improve profitability and sustainability. Understanding soil survey results and soil plans is a key step in this process. Key soil information for irrigation management includes assessing limitations for crop root-zone depth; management strategies to overcome the limitations; and determining the Readily Available Water holding capacity (RAW) of the potential or existing root-zone. Expressed as millimetres of water stored between full and refill points, RAW becomes the basis for irrigation system design and irrigation management

Irrigation systems
The type of irrigation system will often be selected according to personal preference, but soil types, crop types and environmental conditions should be taken into account also.

• Irrigation systems should be designed according to accepted hydraulic principles, taking contours into account.
• Incorrectly designed systems will result in uneven outputs from emitters across the irrigation system.
• In the case of sprinkler systems, the uniformity of distribution of water between emitters is also important and should be thoroughly investigated before installation.
• Selecting an appropriate application rate for the irrigation system is also important. Evaporation can rob a significant proportion of the water before it hits the ground if the application rate is too low. Runoff will result if application rates are too high and exceed the capacity of the soil to absorb water (infiltration rate). Application rate can be immediately compared with the RAW of the root-zone, to determine the approximate irrigation run time required to refill the soil moisture store. It is recommended however, that soil moisture monitoring equipment be used to fine tune irrigation management, including the appropriate irrigation depth for each irrigation unit.

Scheduling
Determining when to irrigate and how long to run the irrigation system for, are the key aspects of irrigation scheduling. Scheduling equipment, especially soil moisture monitoring devices, are well designed to assist the irrigator in determining when to irrigate. They can also provide information about how effective an irrigation was, providing valuable feedback to enable continuous improvement in irrigation management. Some form of scheduling equipment is vital to good irrigation management.

Integration
The integrated approach brings together the three critical aspects of an irrigation enterprise and facilitates informed decision making, leading to better irrigation management.

ICMS at PIRSA's Loxton Centre provide a range of services to assist in incorporating the integrated approach into irrigation management. ICMS conduct soil surveys and provide advice on appropriate plantings for the soils on the property and the appropriate division of the property into irrigation units. ICMS also provide assistance in designing irrigation systems. This is done by providing an independent design checking service to assess the hydraulic performance of the system design and whether it is matched to soil types. Distribution uniformity of sprinklers and spacing suggested by the designer are also assessed. ICMS can provide assistance in selecting appropriate irrigation scheduling equipment, by assessing the combinations of soils and plantings on the property. This determines the optimal number of monitoring sites, and explores the implications this has for the various systems being considered. The aim of this approach is to optimise irrigation management to give the greatest economic return on water with the least ongoing input of time, effort and money. By matching soils, plantings and irrigation systems, management of the system is simplified. Irrigation scheduling equipment becomes much more useful in the day to day management of irrigation, reducing time and effort, improving management accuracy and profitability of the enterprise.

Irrigated Crop Management Service (ICMS), PIRSA Rural Solutions

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