PHOTO: LINDSAY CORPORATION
PHOTO: LINDSAY CORPORATION
WATER TECHNOLOGY ▶▶▶
Profiting from precision irrigation
BY ANDREW SWALLOW N
ew Zealand, a country generally known for its ample annual rainfall and phenomenal natural crop growth, is an unlikely origin for a
precision irrigation development that’s gaining traction globally. However, light soils and spo- radic precipitation in some regions, plus readi- ly available water for irrigation, mean close to 800,000 ha or 6.5% of the country’s farmland is artificially watered. Originally, much of that was with flood irrigation using border-dykes but, in the drive for water use efficiency and environmental protection, spray irrigation has become the norm, mostly with centre-pivots.
Economic, environmental and social benefits are prompting a growing number of Australasian and US farmers to adopt precision variable rate irrigation systems.
Annual savings of NZ$18,000 (€10,536) An increasing number of centre-pivots are being fitted with controllers on every sprinkler that tailor the amount of irrigation applied on the move according to crop type, growth stage, soil hydrology, topography, weather and environmental risk. Farmers using it re- port improved yields and returns with re- duced run-off and other benefits. They include Peter and Sandra Mitchell, cropping farmers
from near Oamaru, in New Zealand’s South Is- land, who fitted VRI (Variable Rate Irrigation) on a 500 m pivot covering 85 ha in 2013. “We were growing all sorts of crops under it, with different soil-types, north and south facing slopes and flats and a spring-fed waterway: there was so much variability it was perfect for it,” recalls Peter Mitchell. As members of a new irrigation scheme, their water supply was also relatively expensive at NZ$612/ha/year (€358) before on-farm pump- ing and scheme share capital costs, so any wa- ter savings would be worth more to them than to farms with cheaper water supplies. Partici- pating in a research project to evaluate the in- stallation, also reduced set-up costs and pro- vided expert monitoring and advice in the first couple of years. “We bought all the hardware and they did all the soil tests etc.” Those soil tests revealed available water holding capacity to 1m deep ranged from 116 mm to 217 mm.
Lindsay has picked up the New Zealand-developed technology and is rolling it out in the US and other markets.
20 ▶ FUTURE FARMING | 25 May 2018
5% higher wheat yields with VRI Over the first two seasons, VRI reduced water use 27% which, based on an all-inclusive water cost of NZ$800/ha (€468) saved NZ$216/ha (€126), or NZ$18,000/year (€10,536) across the 85 ha pivot area. “So it was just over a four year payback on water savings alone,” Mitchell says reflecting on the $70,000 (€40,971) cost to put VRI on the 500 m pivot. The water sav- ing meant they could either reduce their shareholding in the scheme, releasing capital, or use the water elsewhere. They chose the lat- ter, as they did when they put VRI on another pivot two years later. That was a 750 m ma- chine covering a semi-circle of 85 ha. The
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