Polkinghorne family of Kingara Farms in South Australia maximises crop yields

Maximising crop yields — and profits — using the best technology is the aim of this switched-on South Australian farming family.

South Australian grain grower Tim Polkinghorne in his crop at Lock on the Eyre Peninsula last week. Picture: Rob Lang

A range of country in one mixed-farming operation on South Australia’s Eyre Peninsula requires an equally extensive range of management.

The 7000-hectare family-run Kingara Farms business is not a one size fits all system, more a balancing act of rotations, seeding rates and a host of other factors to allow the Polkinghorne family to maximise yields.

Tim Polkinghorne, his partner Ellen Hardy, and Tim’s parents Andrew and Jenny Polkinghorne, run the business on a number of properties near Lock.

Their country varies – from lighter sandy soils to heavier clay loam soils – and each area is treated quite differently to maximise performance.

And while some might prefer a uniform soil type or to have all their properties close by – their farms extend over about 40km – Tim can see the benefits of farming across a more diverse portfolio.

“There are years where the lighter country will do better and years where our heavier country performs best,” Tim said.

In some ways, the Polkinghornes growth has allowed them to hedge their bets regardless of what the season brings in their 330-360mm country.

Despite what rain falls or doesn’t fall, at least some of the country should produce profitable yields as long as it is managed to its potential.

To that end, the family has invested in precision agriculture and a matrix of rotations to best fit each property.

That’s not to say they have gone out and bought all the latest precision agriculture technology, a trap Tim said some farmers fell into, rather than buy specific equipment or applications which had the potential to boost returns.

TECH SAVVY
Their first move into technology was to use variable rate seeding in 1997 with an air seeder which could sow with variable rates for both seed and fertiliser.

This allowed them to deal with the varying soil types and to increase sowing and fertiliser rates on their lighter country, where there was potential for crops to have lower germination rates.

“We can get a good growing season and then have hot north winds in spring that can cut the crop yields off,” Tim said.

“On our less fragile country, we don’t vary the seeding or fertiliser rate and give the crops the same amount of nitrogen but on the lighter soils, we need to make sure that there is cover, especially on the hills.”

In 2018, they installed a protein meter on their header to allow them to blend their grains to produce an even line for delivery.

But typical of their approach to precision agriculture – only use things which are important to their business – they did not rush to use the information they collected to produce maps that would sit in the drawer unused.

“We have a few examples we know we could do better with and maximise the investment we have made in precision agriculture, and the protein meter on the header is a good one,” Tim said.

“We can see what protein we have where, and we can blend it as we load trucks, but we are looking at the next step where we can analyse the data and through site navigation.

“We are now going to use the protein meter maps to determine our nitrogen application, decreasing the amount we apply on high protein areas and increasing the amount on low protein areas.

“Our aim is to bring the weaker areas up to get uniformity in production and to increase yield overall.”

Tim Polkinghorne in the driver’s seat at harvest. Pictures: Rob Lang

IN THE MIX
The rotations used on each of their properties are designed to maximise yields but also maintain ground cover.

Sheep fit into the mix with a mob of Merinos grazing the pasture phase on some of their country, and also using stubbles on less fragile areas.

Their most profitable rotation is wheat-lentils-wheat-lentils, but they vary this on some of their land to do a wheat-wheat-lentils, follow with a canola crop if there are weed issues and to use up the nitrogen after the pulse crop, and then followed with wheat.

Pastures are not sown with natural medic coming up if allowed, and its ability to re-emerge in a pasture phase has been seen even on country that had been continuously cropped for 20 years.

And while stock prices have come up and the pasture phase is useful in the rotations, Tim said there would be some properties where sheep would never be run.

“Even with rising stock prices, lentils are hard to beat that gross margin especially when price are $1000 a tonne and even more so when we were getting $1200-plus a tonne,” Tim said.

Another use of technology has been to study NDVI (normalised difference vegetation index) maps which show crop biomass, and are accessed through the Agworld app.

Tim said their use was “novice” but allowed them to ground truth decisions they had made in terms of crop management.

“We look at the NDVI to identify the good parts of the crop and those that are not performing as well and we might vary some nitrogen application accordingly,” he said.

“We also look at it to see what we did in terms of seeding rates or fertiliser strips and make some decisions after seeing how our management has impacted the crop.

“This year, there was a dry start and staggered germinations, so we looked back at the NDVI and saw that a certain spot came up first with minimal moisture and that’s an area that has been ahead all year, or we can look at where we have done deep ripping and see where germination was poor but a month later had thickened up due to that ripping.”

This year’s harvest has been described by the Polkinghornes as good.

WEATHER THE STORM
The Polkinghornes are currently finishing a good harvest, albeit with some weather damage to wheat. Wheat crops have yielded up to four tonnes/ha, against the long-term average of three tonnes/ha on their country west of Lock, while their lighter country crops have produced 2-2.5 tonnes/ha compared to the long-term average of 1.8 tonnes/hectare. Lentil and canola yields have also been above the long-term average.

But balanced against their profits this year is the prospect of high input costs next year.

The Polkinghornes have locked in their fertiliser and chemical supplies and have even bought a self-propelled sprayer fitted with weed seeker technology at an additional cost of $200,000 to maximise efficiency.

They won’t back off on applications but will draw on every piece of technology they have to make sure their spend on inputs is targeted.

Their move away from applying most of their phosphorus as liquid P and back to MAP will go ahead, but the cost savings Tim had planned might not be as big as he hoped for.

“We have obviously come off a big year, so a lot of nutrients have gone out in crop growth,” Tim said.

“We can’t treat it like a poor year and think there should be some left over – if we do that, our yields will start declining pretty quickly

“So, I think our strategy is that we have ordered what we decided we needed before the prices came out and we will be conservative where we can, but it will be business as usual.”