Soil mapping can cut costs and boost yields

Farming is changing. Input costs are soaring, environmental restrictions are increasing, land prices are rising and the world population is growing ever larger.

The need to make the most of every inch of the land is becoming more pertinent, and one key way to do this is to understand your soils, according to industry experts.

Starting out

Chris Ascroft is at the beginning of his soil-mapping journey, which he hopes will enable him to vary his inputs and apply them exactly where they are needed on his 1,000ha of arable land at Wilbraham Farms near Cambridge.

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“I thought I had a fairly good understanding of what sort of soils I had. However, until you begin to map them out using the sort of technology that is now on offer, I don’t think you can have a full idea,” he says.

Using Agrii’s SoilQuest service, which maps out the soil profile across the field, Mr Ascroft is hoping to target each input, from cultivations to seed and fertiliser.

“Part of my thinking is I want to adjust the seed rate to get an even crop for better nitrogen benefits and, hopefully, get fungicides to work better,” he adds.

Precision farming is not new to Mr Ascroft, who has been heavily involved in the RTK network of local farmers (see right) employing guidance systems to improve efficiency.

What is RTK farming?

A real-time kinematic (RTK) network uses a local base station to guide a tractor or vehicle accurately in a field and add to GPS accuracy, down to +/- 2cm.

The RTK Farming Network is a collaboration project involving five farmers/farm managers to benefit from the efficiencies and cost savings of precision farming without the large individual capital spend of separate RTK base stations.

Costs and savings

SoilQuest costs

  • Scanning, testing and mapping £28.50/ha
  • Four-year package, including nutrient and seed maps online management software: £11/ha a year

Savings on Mr White’s farm

  • Seeds, sprays, fertiliser, 2-3% across the farm
  • Cultivations 10-17% using average 14% saving
  • Pressing £27.28 – saving £3.82ha
  • Power harrowing £46.19 – saving £6.46ha
  • Subsoiling £53.12 – saving £7.44ha

Using a Trimble box on his tractors in unison with the RTK network, Mr Ascroft is cutting costs for cultivations and applications by increasing accuracy.

“We are quite capable of spending £50-70/ha on base fertiliser. If you cut your spend by 50% by targeting it correctly, you can soon make back the money you have invested,” he says.

“At the minute we are making small percentage savings, but even if you are saving 2-3% on your inputs the investment is vindicated and, hopefully, it will continue to improve as you become more integrated into the system,” Mr Ascroft adds.

The importance of understanding soils is vital, according to Stuart Alexander of Agrii, which is among a number of advisers supplying precision farming services such as SoilQuest.

“You can go from one extreme to another on one farm, so gaining an understanding of how soil characteristics effect nutrient retention is essential, and needs to be measured.

“Soil mapping helps create management zones according to soil type ready for sampling or variable rate planning,” he says.

Two years on

Grower David White is slightly further down the road of mapping his soils at Hawk Mill Farm, Little Wilbraham, where he been using the system for two years on his 400ha of sandy loam over chalk soils.

“I know the variability of the soil on the farm, but [mapping] quantifies it in such a way that we can work with the differences accurately,” he explains.

Across Mr White’s farm, clay soils range from 19% to 61% and silt soils from 7% to 54%.

Mapping soil zones, with each tested for its P and K indices, allows Mr White to apply nutrients exactly where they are required. P and K indices range from -1 to 3+, while pH levels are from 7.2 to 8.6.

“Savings in nutrient and liming costs have had an immediate financial benefit, as well as an environmental one,” he says.

Mr White adds that the wide variety of precision-farming equipment makes investing wisely important.

“With the Trimble equipment, we get away from having to buy the machine with the box that the manufacturer sends, he says.

With soil mapping, a farmer can…

Nutrient analysis

Ensure samples are only taken in optimum locations, reducing cost and providing accurate information


Vary seed rates to achieve optimum plant counts


Understand variations in soil type and adapt applications accordingly

Yield potential

Manage soil zones differently to reduce variation and ensure the best gross margin is achieved


Target seed rates and slug pellet applications to improve plant stands and avoid leaching


Detailed zone maps enable cultivations to be varied for optimum establishment


Better targeting helps you comply with increasing legislative requirements

Quick rollout

Farm director at Thurlow Estate, Andrew Crossley, dived straight into soil mapping, rolling it out across the whole arable area in one go. “It was a huge benefit being able to see all the land and how it varied immediately rather than over a few years,” he says.

Investing in the equipment in such a short period of time and for such a large-scale operation meant Mr Crossley needed to see benefits early.

“Mapping your soils means anything can be variably applied. P and K savings were seen straight away, and then we will probably see variable seed rate benefits over two or three years,” he adds.

“In our second year we are radically increasing the seed rate in blackgrass hotspots – doubling it,” he says.

Lime applications used to be a “needle in the haystack” job according to Mr Crossley but now every field can be targeted appropriately.

“It’s getting this attention to detail back, which I think has been missing for a long time and is part of the reason for the wheat yield plateau,” he says.

Mr Crossley believes choosing the right equipment is something of a minefield. “Growers need to know how much they want to get out of it because if they invest and can only go so far it’s not money well spent,” he says.

Trial work

Mark Leaman, who manages 250ha for consultant group NIAB, has invested in both the RTK and SoilQuest systems to help establish consistent and reliable trial plots.

Variable rate application has been used alongside the soil maps but, rather than reducing fertiliser bills, the focus has been on more uniform trial plots.

“The process has removed variables from our trials work, meaning we can accurately assess the crop character or trait being tested,” he says.