Friday, March 29, 2024

Converting white from gold

Avatar photo
Converting 200ha of a 1400ha family farming enterprise to dairying probably wouldn’t have been possible if it wasn’t for some very smart irrigation technology. Anne Lee talked to Nick Webster and Peter Mitchell in north Otago to find out how precise application is making their water go further.
Reading Time: 7 minutes

Around Oamaru, the Mitchell and Webster families are known for their expansive golden fields of sunflowers and grain crops, grown on the rolling downlands mostly for their specialist bird seed business.

But two years ago they decided to venture into white gold territory and convert 200ha of the 1400ha enterprise to dairy.

In hindsight, timing wasn’t great as the payout tumbled from a breathtaking high, but they have no regrets about taking the plunge into the industry and a long-term view about the benefits of spreading income risk.

Jock Webster and his son Nick along with Peter Mitchell, son of Jock’s original partner Ross are now at the helm of the business. 

Nick and Peter take charge of the day-to-day running of farming operations and say the foray into dairying allowed them to put land, unsuitable for cropping into a higher-returning land use – albeit on a long-term basis, given the current state of returns.

But they had to employ some smart technology to make it happen.

As with their other land, the dairy farm is located within the North Otago Irrigation Company (NOIC) command area.

Jock was founding chairman of the scheme that’s been running since 2006. It draws water from the Waitaki River and irrigators are required to own shares and pay an annual fixed charge as well as a variable charge for their water use.

The annual fixed charge is close to $600/ha and the variable water use charge averages about 9cents/cubic metre or about $1/mm applied.

Peter says they had enough shares to provide about 85% of the water the dairy farm would require. 

Buying more shares wasn’t an option but, given the experience they’d had with their cropping land using variable rate irrigation (VRI) technology to reduce water use, they decided to look at employing the same technology to make the water they had go further.

The farm is broken into two distinctive north-west facing blocks – one with a gently sloping gradient, the other much steeper with rocky outcrops.

By putting two pivots – one 500m and one 460m – on the flat-to-gently sloping area they were able to water 100ha effectively at a low rate.

By adding VRI they could add to that efficiency and make quick water savings as the technology could switch sprinklers off altogether over 1.8km of tracks, around gateways, troughs, over waterways and where natural springs create wetter areas.

These are designated as avoid areas and in total cover close to 13ha.

But VRI allows them to go even further and make additional water savings by applying irrigation across the paddock, in the same pivot pass, at varying application depths depending on soil type.

“There’s significant variability across the farm when it comes to soil types – there’s all sorts – and we’ve got some lower-lying areas that can get pretty wet. By altering the amount of water going on and shutting off over the avoid areas we could actually save enough water to irrigate another 15ha,” Peter says.

That additional area was included in the 100ha of steeper, rockier land they’re watering with K-line irrigation pods.

The VRI works in conjunction with GPS and electromagnetic (EM) survey (see page 36) technologies as well as telemetred soil-moisture probes.

An EM survey was carried out for the area under the two pivots to identify areas with specific soil characteristics including water-holding capacity. 

Using FieldMAP software combined with the EM survey information and the VRI technology, Peter and Nick can set up different irrigation plans that can be activated at the click of a mouse or tap of a screen.

They’re not restricted to a set plan and, if they wanted to, could adjust irrigation rates as often as they like.

The irrigator is fitted with solenoids and GPS technology so that when it passes over preset areas, based on the mapping inputs, the associated sprinklers can be pulsed on and off to deliver a variable rate of application along the length of the pivot.

Peter says the software is simple and fairly intuitive with the bulk of time spent in the initial setting up of blocks and plans.

The cost of setting up the VRI without the probes was about $100/m length of the pivot and with EM surveying costing about $60/ha the added expense of the precision technology was less than buying more shares and the annual costs of additional water. 

A rough calculation on the benefit of irrigating an additional 15ha in the milking platform to produce an extra six tonnes drymatter (DM)/ha grown shows an increase in revenue of $40,000/year at a $6/kg milksolids (MS) long-term average payout of $33,550/year at $5/kg MS. 

That’s a return on investment (ROI) of 40% at the $6/kg MS figure.

“There’s benefit in being able to put the effluent out safely through the pivots too,” Nick says.

The VRI allows them to turn nozzles off over tracks and troughs, but more importantly, keeps effluent 50m away from waterways or boundaries and any other hazard where there’s a risk effluent could make its way to water such as the low-lying areas of paddocks.

In a similar fashion to the irrigation water, application depths of effluent can be varied too, depending on soil type and soil moisture levels, ensuring the valuable nutrients can be more efficiently applied to optimise pasture growth.

The farm has 90-day storage and uses two clay-lined first stage ponds connected via a weeping wall to a 2700m3 polyethylene-lined storage pond.

The liquid effluent is pumped directly from that pond to both pivots and, to date, they haven’t had any major issues with sprinklers on the pivots blocking up.

Putting effluent out via the pivots means it can be applied to about 80ha of the farm – making great use of the nutrients across a big area.

The effluent programme is pre-set in the software that drives the pivots and VRI so a simple click and the system is set to go.

It won’t go, though, unless the valves that allow the effluent to flow into the irrigation system at the central pivot tower have been opened manually. Non-return valves are set up, too, to ensure no effluent can flow back into the water supplying the pivot.

Records associated with the software mean proof of placement and compliance with resource consents and NOIC’s farm environment plans is not just simple to prove, it’s also much simpler to achieve.

Peter says the NOIC farm environment plans are stringently audited, as they should be, but no one wants to spend a lot of time finding the information to prove they’ve done what they should.

The software and data that’s stored does all that for you whether it’s effluent placement and timing or irrigation scheduling and soil-moisture monitoring, he says.

They have two soil moisture probes on the dairy farm but aim to put in more relative to soil type variations.

They’re using AquaCheck probes that measure soil moisture at varying depths and automatically send that information back to web-based software via telemetry.

The data is presented graphically so Peter and Nick can see what soil moisture levels are within the root zone and deeper in the soil profile along with the trends. 

Field capacity and refill point are also shown on the graph with the aim always to keep soil moisture levels in the root zone above refill point but below about 80% of field capacity to make enough “room” for rainfall.

The lower soil profile soil moisture levels, set at about a 400mm depth, should remain steady as an increase in those levels shows drainage down through the profile – which in turn means wasted water and possible nutrient losses.

The annual rainfall in north Otago is relatively low, averaging 560mm/year over the past 10 years. 

That’s a little lower than Canterbury, but Peter says evapotranspiration rates are not as high in north Otago.

Last summer and autumn was particularly dry, though, and the farm used about 300mm/ha to top up rainfall.

At $1/mm as well as the annual fixed charge there’s an incentive to keep that irrigation water in the root zone. 

On the steeper country, watered by K-lines, making best use of water also requires some precision technology.

This time the biggest gains are to be made in accurate placement of the pods at each shift, making GPS and farm-mapping technology of critical importance.

With painstaking accuracy, Peter has drawn where pod lines should be laid onto the computer-based FieldMAP of the area.

Each line is numbered so that the direction of the next move is clear to anyone charged with shifting the lines – which takes about three hours each day.

The computer map is loaded into the TracMap system on the four-wheeler. 

Whoever is moving the lines can then see where they are relative to the pod lines on the screen-fitted bike and can use that to guide them into exactly the right spot.

It’s a simple system that means different people can move the pods with extreme accuracy.

Just having them a couple of metres out on an ongoing basis can mean big inefficiencies in watering – either through overlapping spray patterns, wasting water or under-watering because of gaps.

Without the technology, the effects of those mistakes takes days to show up by which time the damage in lost production or wasted water has been done.

“The technology we can use onfarm now to be more precise with those inputs and measure conditions – it’s really quite exciting stuff.

“I think you do need to have a passion for this kind of information so you really make use of it,” Peter says.

It’s important new technologies can be used intuitively and don’t require farmers to be trained extensively to use them, he says.

“The more intuitive it is to use the faster the adoption is going to be. Developers have to remember farmers are good at farming – looking after crops and stock – and that’s what they want to be doing. They don’t want complicated systems.”

Both Peter and Nick say that while their initial motivation for the irrigation and mapping technologies was financial, the environmental wins are also important in terms of both better outcomes and compliance itself.

Technology take-over

The use of technology on the farm extends beyond irrigation for Peter Mitchell and Nick Webster.

They’ve set up their 54-bail rotary dairy with Protrack, automatic cup removers, auto-feeding and auto-drafting so milking can be a one-person job.

It’s allowing them to keep staff numbers down to three full-timers and a relief milker this season with one of the full-time staff – their farm manager, Sarah Smart.

Nick says the first port of call for supplements is the dairy as the aim is to minimise any wastage.

The whole farm was regrassed for the conversion in time for last season and across that first season they fed about 800kg drymatter (DM)/cow. 

About 75% of what was fed in the dairy was palm kernel and grain with silage fed in the paddock, mostly in autumn.

Back calculations suggest pasture intake was 13.5kg DM/cow last season.

Nick says the benefits of automation in the farm dairy are largely in labour savings but also in data collection and the ability to simplify work for the operator.

Protrack means he can externally load in a drafting list and link Minda information easily while the automated feeding system allows them to preferentially feed different groups within the herd simply and effectively.

 

By the numbers

Costs

Cost of VRI on pivot – $100/m

Cost EM survey – $60/ha

Approximate cost  = $96,600

Benefits

  • Additional 6t DM/ha pasture production over 15ha  =  90t DM
  • Assuming 15% wastage and 11.4kg DM eaten 
  • to produce 1kg MS 
  • @ $6/kg MS return, additional gross income  = $40,000 
  • @$ 5/kg MS return, additional gross income  = $33,550 
  • ROI @ $6/kg MS =  41%
  • ROI @ $5/kg MS =  35%
Total
0
Shares
People are also reading