Improving irrigation efficiency
Reduced costs and more efficient water use for farmers are a step closer with progress in the development of a specialised irrigation system.
Three two-year-long trials undertaken by Landcare Research staff led by Dr Carolyn Hedley (and supported by HydroServices, Streats Instruments and Waterforce) found that farmers who used variable rate irrigation (VRI) achieved up to 36% water savings with no negative impact on yield and a current return on investment of between one and five years.
VRI was developed by one of our partners, Precision Irrigation-Lindsay Corporation, who modified sprinkler systems so that individual nozzles can be programmed to switch on and off, thus enabling VRI to be matched to soil management zones within a paddock. These zones are defined using sensor mapping that provides high resolution quantification of soil variability.
Meanwhile, our prototype web-enabled wireless sensor networks (WSNs), developed by Dr Jagath Ekanayake of Landcare Research, continuously monitor soil moisture within each zone under the irrigator. The WSNs use mesh networking technology to transmit data along the most efficient pathway between nodes to a base station. If one node fails, the other nodes simply re-route along any other available pathway. The soil moisture data can be accessed remotely and used to assist variable placement and timing of irrigation to soil management zones.
Water saved at a Fairlie dairy farm was diverted to otherwise unirrigated parts of the farm to increase pasture production, which enabled the cost of converting three systems to VRI to be paid back within one year. This year, a 36% water saving was achieved at the Manawatu Sand Country VRI trial site, because lower lying areas, where the water table is relatively high, required no irrigation at all due to a wet season. The VRI system on an Ashburton arable farm, where soils vary from very stony to silt loams under one irrigator, achieved 20% water saving in both years.
The ultimate goal is complete automation of the VRI system using real-time soil moisture monitoring of soil zones for precision irrigation scheduling.