28 March 1997

Out of sight – and its out of mind…and nose

Its a technique that has been around for years without making a big impact. But contractor Tim Houghton is confident that injection will increasingly be the favoured method of applying farm slurry to grassland.

Peter Hill reports

LATER spring turn-out dates and hardening public opinion are two factors increasing the popularity of farm slurry injection, according to Berkshire contractor Tim Houghton of Mousefield Farm Contractors.

Based at Grange Farm, Hermitage, just a few miles north of Newbury, Mr Houghton is well aware of the angst that can be stirred up by the traditional smells of the countryside.

"If were surface spreading and the wind is in the wrong direction, the phone calls soon start," he says. "The fact is, people moving into the countryside are less and less tolerant of what they consider to be noxious smells and are quite prepared to tell us what they think about them."

Injection, he reckons, is the only way to combat such complaints. Also, he argues, it is the best method of making late spring applications of slurry to grazing or conservation ground.

"With cows being kept inside longer, slurry storage lagoons and stores have to be emptied late spring when maize ground is no longer available," he points out. "That means putting it on to grass, either after a first cut has been taken for silage, or on to grazing aftermaths. Injection allows that to be done without contamination or having any detrimental effect on grass regrowth."

Tim Houghton has plenty of experience of liquid application techniques, having provided a sewage sludge and non-toxic slurry waste disposal service which involved dribble bar and arable injector options. Having given it up, largely because of the difficulty of finding disposal sites year-round, enquiries about spring farm slurry injection led to the new service being rolled out this year.

"I evaluated the idea and equipment on the farm here last year and concluded it has potential," he says.

The service is based around a Greentrac grassland injector which can be either attached to an 11,360-litre (2500gal) slurry tanker, or carried directly on the tractor and used with lay-flat hose and a pump as part of an umbilical system.

Each injector unit on the 3m (10ft) rig uses a disc to cut a slot, a share to open it, and a rubber nozzle to deposit the slurry. Its designed to work shallow to minimise surface disturbance, and so cannot place huge quantities of slurry underground. But its enough to make the system viable, reckons Mr Houghton.

Slurry is fed to each injector unit via a distribution head containing an hydraulically driven (and therefore reversible) chopper designed to reduce any lumps to proportions that will not block the outlets.

"It works well enough," he says. "The discs wont penetrate hard, dry conditions in the way a tine injector will, but then most of its work should be at times when the ground is reasonably soft anyway. And weve had no problems with blockages."

Experience to date suggests the umbilical hose method of supplying the injector will be most popular and where the application site is too far from the slurry store – 2000m (610ft) maximum – a nurse tank previously used on sludge disposal can be brought into service.

"The slurry tanker is increasingly unpopular because of its weight and its also more expensive overall because of poorer work rate," says Tim Houghton. "You have to be careful to avoid tyre scuffing damage when dragging the hose – there is a lot of weight when its full – but there is only the weight of the tractor to worry about when it comes to concerns about soil compaction and weve got that on big, soft radials."

Better work rate

Work rate is better because its a more or less continuous operation, although the output achieved on any particular job can vary enormously with the distances and terrain involved. High frictional losses dampen pumping rate as distances increase and inclines also have a significant effect on pumping rate.

"Thats partly why we charge by the hour; you can make a rough estimate of how long the job will take but its not until you actually start that it becomes clear how things will work out," says Tim Houghton.

A home-built reeler carries the 100mm (4in) lay-flat hose; operational lessons learned include making sure that, once deployed, the pipe is kept full as it is dragged around corners or at headlands; otherwise it rolls and quickly becomes a wayward coil.

Lagoons and above-ground stores are "liquidised" 24 hours before emptying when necessary, using a tractor-operated Mix-It propeller-type stirrer. A tractor-powered Doda chopper pump then feeds the umbilical hose.

"We looked at using an engine-driven pump with remote control to make it a one-man operation," says Tim Houghton. "But it really needs two to set up and to move, so we settled for a simpler tractor-powered pump. Besides," he agrees, "you always get debris problems emptying lagoons so its as well to have someone on hand to deal with them."

Slurry is injected using a Greentrac geassland machine which employs discs to cut slots in the turf.

Tim Houghton: "Slurry injection is the only way of avoiding complaints from locals with sensitive noses."