The water footprint of irrigation systems can be reduced significantly by combining data from Electromagnetic (EM) soil survey with variable rate technology on irrigators. Variable Rate Irrigation (VRI) is providing annual irrigation water savings of between 25 -50% on farms throughout NZ.  Flow-on benefits include reduced pumping costs, improved crop yields and soil health along with reduced nutrients leaching to groundwater.

The greatest water savings are on the shoulders of the irrigation season. At this time, with the use of VRI, the farmer is able to mine the soil moisture from high water-holding capacity zones, as identified by an EM soil survey, applying irrigation to the lighter soils as they start to come under stress. In this instance irrigators fitted with VRI are often only operating with 20% of the machine applying water. With VRI the farmer is able to control irrigation application by each individual nozzle along the length of the Irrigator. This allows the farmer to manage each soil zone separately as well as avoiding areas like water ways, laneways and water troughs.

The placement of soil moisture probes in zones determined by EM soil survey means that it is possible to accurately monitor and maintain optimal soil moisture levels. Irrigation water is applied to match the water holding capacity of each specific zone and match the use of the crops that are being grown in the individual zones. When soil moisture levels are maintained at a level between the crop stress point and the soil full point it allows the farmer to capture every rainfall event throughout the growing season. If the farmer can do this without soils reaching the full point they will eliminate any possible drainage.

Improved water quality is an immediate benefit of VRI. Through accurate irrigation water placement the farmer is able to maintain  nutrients with in the root zone of the plants giving optimal nutrient uptake while avoiding any leaching into the groundwater. When the use of multiple EM survey information layers including data on slope, aspect and drainage is combined with the use of VRI application systems runoff of nutrients, such as Phosphate, into waterways is also able to be avoided

The benefits of VRI are not limited to the environment. There are also significant potential savings in the amount of energy required to irrigate a field or farm. In times of low or restricted availability of irrigation water the use of VRI means that the crops or pastures requirements will be more likely to be met resulting in the most profitable outcome for the farmer.

Water is the biggest issue that will effect food production throughout the world both from a productive and environmental perspective. Agriculture uses 70 % of the world’s fresh water. With a growing population and need for increased food production the demand for water will only increase. Agriculture needs to get smarter about the way it uses water. This is now happening with the use of EM soil surveys and VRI.