Traditional sports turf management entails largely sterile soils. By one estimate, the soil under a typical golf green will have less than one per cent of the bacteria and fungi found in wild grassland soil.
Yet microbes have an important role to play in helping grass to take up nutrients from the soil and, in their absence, artificial nutrients have to be added. But this results in weaker plants, which then have to be protected from attack by hostile fungi by applying fungicide, diminishing the beneficial soil flora still further.
One of the companies encouraging grounds managers to break this cycle and work more with natural processes is Surrey-based biotechnology firm Symbio.
"We started this whole (biological turf care) programme due to the requirements of schools," says the firm's co-founder and managing director Martin Ward. "We now have a 100 per cent organic programme for schools and local authorities, even though not all of it is Soil Association approved.
"It means there's no chemicals spray so it cuts down on training and no chemical residue so there's no danger to children or pets. Cost-wise, when you get organic products working well, you no longer take all nutrients out of the bag but convert what's in the soil - you are generating your own fertiliser."
If what is in the soil needs a boost, he advises: "Compost from green waste is about £25 a tonne - an active soil biology will help take that up."
Converting to the biological approach
One recent convert to the biological approach is John Lyon School in north-west London. In charge of its 5ha of sports pitches, and two grounds staff, is head groundsman Andrew Robinson, who has worked at the school for 24 years.
"The grounds are a nice flagship for the school," he says. "We have one of the best schools for sports pitches and, having doubled the grounds care budget over the past ten years, we can now host 30 senior football games on each pitch over the season."
Robinson aims to be 100 per cent organic and has taken on board expertise from suppliers and consultancies to guide him. "We want to get our NPK use down," he says. "Not just to be environmentally friendly - it increases the salt level in the soil and the agricultural products can be dusty and unpleasant, so not ideal on a school ground.
"Also, some day I may find that the plug gets pulled on my finances. By building up the soil biology, I hope to reduce my costs. Getting the friability back in the soil will let the roots develop better and I will have to spike less, so there's less wear and tear on the machinery."
In the machinery shed sits not only a tank in which the compost teas are brewed that will then provide the boost to the soil's biology, but also a microscope to analyse both the soil and the tea.
A "starter pack" from Symbio consists of protozoa, which reproduce in the tank, a fungal booster and compost with olive oil to neutralise the scum. To improve nutrient uptake, a humic acid is added at the end.
The brewing cycle takes 24 to 36 hours. "After 18 hours I take a sample and look at it under the microscope," says Robinson, who trained at the soil analysis laboratories of environmental consultancy Laverstoke Park. "Depending on the results, you might tweak the amount of feed or the temperature next time," he explains.
Tipping the bacteria-fungi balance
The process is far from being all muck and magic. During a recent presentation at Laverstoke Park, US-based soil researcher Dr Elaine Ingham made the point that if the aim is to tip the bacteria-fungi balance in favour of a particular plant, great care is needed in producing and applying the compost tea - both soil and tea need to be analysed for microbial content.
"Rye likes an equal balance between the fungal and bacterial content," Robinson advises. "You can find out what that balance is under the microscope, along with the nematodes and other microbes that eat the bacteria, producing natural ammonia.
"You also need an oxygen meter in the tank to prevent it becoming anaerobic, or you might over-stimulate it. I also keep a log of soil and air temperatures at each application. But I'm still a novice at this."
One goal for this season is to stop early establishment of Poa annua, though this may take more conventional measures, he admits. "As elsewhere in the world, Poa is the biggest bane of my life. But if you give it a 7:7:7 fertiliser, you give it everything it wants, and in spring it will out-compete other grasses," he adds.
So far Robinson deals with the problem by using 400ml per hectare of Primo Maxx growth retardant in the brew. "It should slow down the Poa and the rye and give the seed a chance to come through," he says.
Getting the right species mix also has an impact on water use, he adds. "In America they've done a lot of testing with fescues and bents and found they can use 30 per cent water, which can be a significant saving - we spent £6,000 last year on water and that's only using half the water that some agronomists recommend.
"Every two to three weeks, I take core samples - you don't know how dry it is unless you dig it up. But the grass has to be kept a bit thirsty, otherwise it becomes lazy - it just sits there."
Most sports turf is grown on sandy, free-draining soils that require regular watering. Robinson says: "I've used thousands of tonnes of sand on the pitches over the years, but this might mean we use a bit less."
He adds that healthier soil biology should reduce the incidence of turf diseases, such as red thread, which strike when nutrition levels are low. "Good biology crowds out the bad," he says. "But a slow-release fertiliser would also solve the problem for a few months."
Robinson first contacted Symbio to deal with a problem patch that retained water and had gone anaerobic. "We have different areas of turf performing differently," he says. "There's a missing key that will unlock the nutrients. A lot of people don't want you to go down this route. Symbio has things to sell too but is honest in saying that it doesn't know everything."
While it is still under development, the understanding of soil biology has made some strides recently. "There has been a lot of crossover from golf," Robinson points out. "They have worked out a lot in the past few years on how different nutrients affect each other - for example, too much sulphur and iron will lock up your potassium."
He and his team intend to make their own compost from mowings and woodchip. "But you have to turn it and mix it, which means getting a front-loader bucket - you don't want it to get hot," he says.
But there is no immediate prospect of a saving on labour, he admits. "At this time of year, I work 90-hour weeks, sometimes from seven in the morning until midnight."
The job of changing the pitches over from the football to the cricket season at the John Lyon School has not been helped this year by the previous tough winter, which left twin problems of snow mould and standing water.
"I made the mistake of feeding the pitch between the snow," head groundsman Andrew Robinson admits. "There were also a lot of undulations. We took the top off but probably went too deep."
He says of the square: "You plane it off until you have a table top, which lets you mow down to 1-4mm. But a cricket square is very difficult to grow grass on - it's clay based and with no drainage the water just sits on it."
Some authorities advise against creating "heave" on the surface of the square when aerating, but Robinson says it is useful in moderation.
"I put the VertiDrain on it with one-inch tines, which gives you cracks and fissures without disrupting the surface too much," he says. "You get a lot of feed down - 18 bags rather than eight. But if it's too wet, the VertiDrain will do more harm than good - the water will just sit in the holes."