Irrigation whets cropping appetite

Kim and Richard Dakins by the FAR weather station on their farm.

01-11-2009 | Not Specified

Richard and Kim Dakins picked the perfect time to irrigate their family farm at Takapau.

The central Hawke's Bay farmers began irrigating in January 2007, just in time to counteract three particularly dry years on the Ruataniwha Plains.

"It would have been a pretty tough three years without it," Richard says. "Timing-wise we couldn't have done the irrigation any better."

The couple farm in partnership with Richard's parents Paul and Denise, and have turned a 200ha dryland business into 105ha of irrigated cropping, with the livestock part of the business condensed. Richard also does some agricultural contracting.

The move to irrigation has enabled them to double the farm's income, which is important since the farm is now sustaining two families.

Land prices are astronomical in the district, and spending the same amount of money wouldn't have added much land, so investing in irrigation gave a much better return.

Richard and Kim met while travelling overseas, and came back to farm in 2000. Kim, from Arkansas, has a nursing background, and now they have two boys, five-year-old Jordan and two-year-old Zachary.

Richard, with an applied science degree in agriculture from Massey, worked in the irrigated Westerfield district of Ashburton, and at PGG before heading overseas.

"I had always been interested in irrigation, and came back here and realised the potential for it."

State Highway 50 splits the farm, with 65ha on the western side and 135ha on the eastern side. This eastern block, which is 2km long and just over 500m wide, was just the right shape for a lateral irrigator.

The first step, though, was to drill for water. "Nobody had drilled around here to any depth, and the drillers wanted to drill as far east as possible, closer to where other bores had been. However, because of the cost of power and the need to stay as far away from other bores as possible, we drilled closer to the road."

A test bore to 130m was promising, so they drilled a bore about 50m away from it, reaching 132m. Just drilling the bore was a big investment at $130,000.

The next step was to look at three options for irrigation - a towable pivot with four circles, a roto-rainer or a lateral.

The shape of the farm suited a lateral system, also minimising earthworks and the number of bridges required. The irrigator itself is 486m long, with two end guns, giving it coverage over 523m.

Now there are six bridges for the wheels of the irrigator to run across, and a major laneway culvert.

With a pivot, they would have needed 16 bridges.

They put in a new laneway down the centre of the farm, and took out some shelterbelts and a few fences. Shelter is possible beneath the irrigator, as long as it only grows up to 3m high.

All of the irrigated 105ha is devoted to cropping, with some grazing integrated.

In 2000 the farm carried 500 ewes, 150 to 200 rising two-year cattle and the same number of yearlings, and 650 calves reared. Usually they also had a few paddocks of feed barley and process peas.

Now 75% of the Datkins' farm income comes from cropping. A wider range is grown: maize for silage, process peas, malting barley (the largest crop), milling wheat, seed barley, and grass seeds.

Ewe numbers have halved, with a policy of buying in the replacement two-year ewes in January, with half going at weaning in November. This leaves the farm with few stock over summer. In spring, any yearling cattle left are sold store, and older beef animals are finished for slaughter. Then, when everyone else is dry, they buy back whatever cattle class is going.

Most years, dairy grazers are run for eight weeks from May through to July, feeding on oats and barley straw. They are a good fit with the cropping, leaving the farm when it's time for destocking before the cropping season begins.

Working out when and how often to irrigate is a precise business, with HydroServices having three sites in each crop to a metre deep where they measure soil moisture using a neutron probe. Soil moisture is measured each week, providing Richard with water schedules for the irrigator. He emails HydroServices the rainfall and the irrigation he has put on, and they send back recommendations for irrigation and the date by which it has to be applied.

About halfway down the irrigated part of the farm the soils change from Takapau silt loams over red metal which are free draining, to a Poporangi silt loam with a pan at 40cm.

The Poporangi soils are a constraint, with careful attention being paid to ensure they don't get too wet. They can't cope with heavy cattle in winter either.

Surprisingly, the water holding capacity of both soils is almost the same.

When the soils are full with water, there is 143mm in the soil profile. The stress point of the soil is at 96mm, so that leaves only 47mm of water to use for growing the crops.

If the water level in the soil falls below 96mm level, then yields are reduced. "Hitting the stress point will cost you yield. One year we did and it cost us a $900/h in lost yield. It was the worst-case scenario but it did happen. We lost 3t/ha in a 10ha paddock."

Another problem they face is that there's a lot still to understand about the layered underground aquifers in the Ruataniwha Basin. The Hawke's Bay Regional Council has tried to slow development as it learns more about the water supplies.

Richard and Kim's resource consent to take water works out at a rate of 3.6mm/day over the 105ha, while normally irrigators are designed for 4.6-5mm/day.

This 3.6mm restriction is the main limiting factor at peak times of the season.

"We haven't got enough allocated water to apply at the higher rate, so we are stretching the same amount of water further through crop rotations. Different crops require different amounts of water at different parts of the season."

Each crop usually takes about 200mm of irrigation, with around 10 or 11 applications of around 24mm each time. "It all depends whether it rains or not."

Richard is an avid weather watcher in summer, and for the past year has had the FAR Takapau weather station in the paddock closest to the house. "It's brilliant," he says.

The Met Service is his computer home page, and he uses FAR weather information to keep an eye on likely rainfall and evapotranspiration levels.

In the past three years annual rainfall has been right on the long-term average of 960mm/year, but there have been dry autumns, and larger falls at other times. Table 1 shows rainfall and evapotranspiration levels through this year, with low rainfalls from March to May.

  Printable View