Ritchie said the biggest wastage of water was irrigating the driest point to wet enough. The wetter areas get overwatered and that water goes down the drainage channels. The waste water could also flush nutrients and a badly run system could be very damaging.
The Ritchies have trialled electromagnetic mapping on the Wainui block and believe there is potential to water according to soil type and depth in the future, as well as identifying leaching rates. Using the irrigation technology system Growsmart Precision VRI, the Ritchies have been able to eliminate overlap in their irrigation system ensuring consistent application of water and a better return time. Ritchie said better return times meant they could get better crops out of their soil types.
With this technology they were able to put bigger nozzles in the pivot and control the water flow. Ritchie said under their consent water allocation was quite low so it was about working out how to make 20 litres a second go as far as possible.
For James Bowan of Heartland Chips fame precision ag technology is a means of maximising water efficiency and yield. The Bowans own 1200ha near Temuka and another 200ha near the Rangitata River. They also grow cereals and winter cows on their land.
Variation in the soil’s sand and silt content means a range of water- holding capacities across the farm. An electromagnetic survey was carried out by Agri Optics on 44ha to understand the effect of historic land development on soil patterns and crop growth.
Bowan also installed a Growsmart Precision VRI-equipped centre pivot at the start of the 2014-15 growing season. He developed an irrigation plan and installed two soil moisture sensors, one in the heavy soils and one in the light soils to allow him to monitor and adjust his variable-rate irrigation plans.
The expected yield increase of 5% on the 44ha, which produces 60 tonnes/ha at $200/t could lift profits by $26,400. At about $40,000 for the precision agriculture technology installed it would be a 65% return on investment.
Savings not chicken feed
Crop farmers need to invest in the latest technology if they want to see continued improvements onfarm, Peter Mitchell says. Mitchell is part of the Mitchell Webster Group, which has companies specialising in small animal feed and selling sunflower, barley and wheat grains.
Parts of their 1400ha farm in north Otago become stunning tourist attractions each year when the sunflowers bloom. In the dry climate water is one of the most valuable resources.
On the McCarthy block their centre-pivot is 500m long, irrigating 85ha of rolling, clay-rich soils. It is one of four that the group has invested in Growsmart Precision VRI technology and electromagnetic mapping.
Using this technology on the McCarthy block they reduced their water usage 23.5%, from 34 litres/sec to 26l/sec.
Savings have been the result of avoiding irrigation application over 7ha of springs and ditches as well as varying application rates based on soil texture groups. With high costs for irrigation shares and additional water usage charges, reduced flow requirements meant the group no longer needed $77,000 worth of irrigation shares.
The group estimated by using the latest technology there has been an average increase in production of 5%.
