Farm visit: precision technology drives profitability on this NZ farm

Photo credit: David Wall

Craige Mackenzie is a grower at the top of his game, producing a wide range of combinable seed crops near Methven, at the foot of the Southern Alps in Canterbury.

And since 2008 – inspired by a Nuffield study of the carbon footprint of farming – he has been deploying precision techniques to reduce variability and his effect on the environment while raising returns off every hectare of his 200ha arable farm and, more recently, the neighbouring 330ha dairy unit.

Photo credit: Andrew Swallow

Greenvale Pastures farm facts

• 200ha arable plus adjoining 330ha, 1,100-cow dairy unit
• Undulating silt loam and stoney silt loam soils
• Wheat (seed, feed, milling), grass, forage and vegetable seeds grown
• 900mm/year rain plus up to 220mm irrigation
• 315m above sea level

“If you wanted to reduce your carbon footprint, the quickest way to do that was with precision ag – that became pretty clear as I travelled around the world,” he recalls.

With daughter Jemma, he has also built a business, Agri Optics, providing precision services proven on his own Greenvale Pastures farm to farmers throughout New Zealand.

Profit maps

Often, the starting point for precision farming, as it was for him, is turning combine-generated yield maps into “profit maps”. “That’s when you realise there are areas in fields that are losing you money. That makes you focus pretty quickly.”

Causes will vary from farm to farm, but soil structure and/or fertility issues are frequently the first place to look, with zonal or grid soil sampling a good way to identify nutrient or pH problems, which in turn can be relatively simply solved these days with variable-rate lime, potash and/or phosphate application.

Chicory for seed. Photo credit: Andrew Swallow

With such “low-hanging fruit” addressed, his next step was electromagnetic (EM) mapping of soil texture and equipping his centre-pivot irrigators with solenoids on every sprinkler so water could be variably applied.

“In Canterbury, there is hardly a farm that doesn’t have enough variation in the soil to justify variable-rate irrigation [VRI],” says Mr Mackenzie.

Environmental case

While that justification has to be financial first, environmentally the case is compelling too, as the risk of nutrient leaching or run-off is slashed and nearly all water abstracted for irrigation goes into production.

Aqua Check capacitance probes, installed after sowing each year and removed before cultivation, provide a continuous log of soil moisture in 35 zones across the 200ha.

Aqua Check. Photo credit: Andrew Swallow

“We have data to show that no water has gone past the root zone in the past three years… and if you haven’t had water leave the root zone, you haven’t lost nitrates or phosphates as leachate either. Some of our neighbours [without VRI] use twice the water we do.”

Even if soils were uniform, for cropping farms with square fields and pivots that travel in circles, VRI technology means irrigation volume can be regulated at each sprinkler as the pivot gradually crosses a field boundary running at an angle to it, tuning application rates to different crops.

Variable seeding

EM maps may also pick up soil compaction issues, allowing targeted remedial action and perhaps revision of traffic management. Mr Mackenzie also uses EM maps to vary seed rates.

“On the light soils we are lowering the seeding rate and on the heavier soils we are increasing it,” he explains. That reflects light soil’s generally poor nutrient and water retention, so crops come under stress sooner. If plant and tiller counts are reduced, then there is enough water and fertility to fill grain properly and yields are increased, rather than reduced.

“If you can maintain grain size and actually put less fertiliser on, you have ticked a lot of boxes. You have saved money on fertiliser and reduced your environmental footprint. And by reducing seeding rate, you will have actually increased your yield as well.”

Global issue

Mr Mackenzie, who has travelled widely looking at farming systems, says there are very few places globally where he has not seen enough variability in fields or farmed zones to justify adjusting inputs on the go.

Rolling farmland, for example – which thereis lots of in the UK, he points out – almost always has differences in soil texture and fertility on the hills and hollows.

Lowering seed rates on lighter soil zones where weeds such as blackgrass are a problem might create difficulties, he acknowledges, but with precision techniques, patches of such weeds might be mapped and seed rates raised on the problem areas. Similarly spray rates could be tuned to anticipated weed burden.

Smart imaging

On his own farm, he variably applies plant growth regulators, trace elements and, to a lesser extent, fungicides, by automated adjustment of spray volume on his locally built 24m trailed sprayer.

That is equipped with six Normalised Difference in Vegetative Index (NDVI) sensors, known as GreenSeekers – one for each control section – and a Trimble GPS system.

Irrigator control. Photo credit: Andrew Swallow

“Every time we spray a crop, we are taking an image,” says Mr Mackenzie. Those images are used to inform variable-rate plant growth regulator (PGR) applications, notably in ryegrass seed crops, where Moddus (trinexapac-ethyl) rates go from as little as a 1 litre/ha split between two passes on less-dense areas, up to 2.5 litres/ha on dense areas.

Similarly, in cereals the NDVI data is used to tweak PGR rates, though with lower rates used, the chemical savings are less.

Yield hike

The combination of addressing variation in fertility and water availability, tuning seed rates to soil types and adjusting sprays on the move has boosted wheat yields in the lightest areas from 7t/ha to 10-12t/ha, for little, if any, extra annual input, while the high-yielding bits have edged up as well.

Photo credit: Andrew Swallow

Ryegrass seed yields have similarly soared, from near zero in some areas to 2.5t/ha consistently across whole fields. “It has made a massive difference. Our crops are so even now compared with what they were and, more importantly, they are profitable in every zone.”

And profitability is what it’s all about, stresses Mr Mackenzie. “You don’t always have to hit the highest yields in every zone to make the maximum profit in every zone.”

Record breakers

That said, when aboard his John Deere 9650STS header during the interview for this article, the yield monitor data for the previous paddock showed a world record wheat output, at 18.45t/ha.

“But we won’t talk about that because we didn’t do it officially,” says Mr Mackenzie, who has had a shot at the world record in the past, but never in a year that’s turned out to be a top one for wheat in their area.

Ensuring yield monitors are correctly set at the start of paddocks, and data recorded at the end, is an essential discipline with precision farming, he adds.

Individual sprinkler. Photo credit: Andrew Swallow

John Deere’s StarFire 2 GPS Autosteer on the header ensures the table is always full and a constant width is taken, which not only improves combine output, but means yield maps are more accurate.

With many of his crops grown for seed, such data, and the consistency and reliability of production his precision techniques bring, are key to getting the best contract offers.

“Your overall gross income goes up because you have some of these high-value crops,” he adds.

What next?

So where to from here with precision farming for Mr Mackenzie? Drones are about to have their day, he believes, as their price has tumbled to a point where they will become an everyday tool for agronomists and farmers alike.

The challenge is interpreting the imagery produced from multi- and hyperspectral cameras and turning it into management prescriptions for variable-rate-equipped machines, which is where firms such as Agri Optics will come in, he believes.

The firm’s just bought a drone, which will be tested on the farm, as they have done with everything Agri Optics has offered. “We don’t want to be pushing anything we don’t believe works and we want to have some case study data behind it.”

However, whatever precision farming’s future brings, for many farmers simply using the proven precision tools and techniques that are already available would be a leap forward, financially and environmentally, says Mr Mackenzie.

No great expertise in computer use or electronics is required these days either.

“You shouldn’t be afraid of the technology. Neither of us on this farm have had a tertiary education, but we understand this stuff inside out because we use it every day.”

Counting cost of precision technology

The perception that precision technology means pricey kit also needs to go, as many systems are now a fraction of the cost of the farm hardware they control, and the investment is often repaid within a year or two.

For example, to equip his sprayer with GreenSeekers cost about NZ$20,000 (£11,300). To repay that would only take 10ha of ryegrass to produce 800kg more yield, at NZ$2.50/kg (£1.40/kg), which varying PGRs has done time and time again.

Sprayer with GreenSeekers. Photo credit: Andrew Swallow

As for moisture probes, Mr Mackenzie has known farms to spend NZ$300,000 (£170,000) upgrading a pivot irrigator, then baulk at spending NZ$10,000 (£5,646) on five soil moisture probes to inform management decisions on its use.

However, regulation of water use and nutrient management is rapidly making such monitoring mandatory in Canterbury, so even if some farms continue to ignore the carrot of precision techniques, in some instances the stick of compliance will force adoption.