How to measure soil health and vitality

A successful no-till system relies heavily on good soil condition, with factors like structure, water retention and organic matter levels all influencing crop performance.

The phrase “soil health” is increasingly cropping up in conversations between growers, agronomists and researchers and interest in the role that soils play in helping or hindering yields is flourishing.

However, one question that remains largely unanswered is how can you measure soil health?

See also: Why investing in soil organic matter can sustain future yields

Frontier soil microbical activity

Therefore, to fully understand the current and potential performance of arable land, some kind of test is needed to quantify the vital signs of soils.

Frontier’s national crop nutrition manager Mike Slater says although soil testing is nothing new, conventional analysis has only ever given a limited insight into soil vitality as a whole.

He says the big challenge is to decide on the key signs of healthy, fertile soil and develop a way of accurately measuring these parameters.

“You can measure soils in so many different ways and you can easily get yourself confused.

“There is an increasing demand for this type of work. Growers know their soil conditions but want to know how to improve them, not just for yield benefits,” he explains.

Over the past few years Mr Slater has been involved with a team at Frontier working to develop what they believe to be the UK’s first comprehensive soil testing service.

Frontier Soil vitality index

“This is a tool to help growers with decision making to enhance soil vitality. Other companies offer testing, but nobody else offers a service where it is all brought together in this way.

“We’ve selected a bunch of soil measurements that we think are most important and useful to allow growers to form an action plan of how to improve the vitality of their soils,” he explains.

At Cereals last summer, Mr Slater says there was a “steady chatter” about soils which encouraged the company to develop this new test.

Soil testing

The test analyses the physical, chemical and microbial properties of a soil sample, all of which is combined to give a “soil vitality index” score. This is calculated using a unique algorithm developed by Mr Slater himself.

Samples are tested throughly on a range of properties including bulk density, which affects crop rooting and access to nutrients and water, and soil porosity which determines how easily water can enter and move through the soil profile.

Frontier soil type

Soil pH, organic matter content and levels of 12 nutrients and trace elements are also evaluated.

A corer is used to take soil samples to a depth of 25cm rather than the 15cm usually taken for other soil tests. This allows both the topsoil and subsoil to be examined.

Between 16 and 20 samples will need to be taken at each location to get a reliable and representative set of numbers, Mr Slater explains.

“It is best to choose fields where there are big variations in yield or fields that are under performing or plateauing.

“We recommend taking between two and four location samples from each of these fields, using yield data to target key areas. This allows some comparison to take place.”

Soil vital signs check

  • Physical: Bulk density, organic matter content, porosity, signs of compaction and moisture levels
  • Chemical: soil nitrate, pH balance, extractable phosphorus and potassium, plant available nutrients and potential for N and P loss
  • Biological: earthworms, microbial biomass, soil enzymes and total organic carbon

Mr Slater says the full testing service, which will be available to growers from this spring, will cost £25 per location sample.

“If you’re testing for P and K you may as well be testing for all this at the same time and it isn’t something that you’ll need to do very often, perhaps once every 5-10 years,” he adds.

“I don’t think growers can afford not to have this testing done – I think it will pay dividends.”

Testing helps to make best decisions on farm

Patrick Tomlinson is farm manager at the Lockwood Estates in Scampton, just north of Lincoln.

In total 2,500ha of estate and contract farmed land sees cropping of 1,000ha wheat, 585ha oilseed rape and 300ha maise along with smaller areas spring barely, sugar beet and rye.

The farm company is keen to find ways of improving soil and already uses field mapping and variable rate applications for P and K.

When new land is taken on to contract farm, it is tested so that key soil properties like land type, pH and nutrient levels are known and understood.

Mr Tomlinson tells Farmers Weekly that testing like this will help growers continue to farm marginal land in the face of lower prices.

“I think we have certainly as an industry lost our focus on understanding soil mechanics and we’ve forgotten that it is the most valuable resource that we have. As growers we need to understand what is going on in our soils more.

“As prices and payments for growers drop there is less flexibility in the system and it is going to bring into question growing crops on marginal land.”

The farm was one of the first to trial Frontier’s new soil vitality test, with soil samples taken earlier this year. He says that at the test can help growers avoid yield hampering compaction or water logging problems.

“As growers, nobody knows the land better than us. We all know what we need to do but sometimes we need a push in the right direction.

“This sort of testing serves as a good reminder that as farms and machinery get bigger and bigger, we need to stop and think about the damage that is being done to the land.

The test results prompted Mr Tomlinson and his team to think about the type of machinery that is used and the tramlines.

“We all want to prevent and avoid the consequences of compaction,” he says.

“It is a very good way of looking at what you’ve got and asking how things can be improved. I think it will help with good decision making on farm when it comes to things like cover cropping, variety choice and also not falling foul of regulations.”