29 March 1996

System is a slurry success

Slurry irrigation is a low compaction method of supplying nutrients to arable crops?

James de Havilland reports

NOW entering its fourth season, Ted Stamfords slurry irrigation system is adding weight to the old adage, "Where theres muck, theres brass." Corny, perhaps, but true.

Mr Stamfords East Yorkshire arable unit takes all the muck from his brothers 250-head pig fattening enterprise. That means a million gallons of slurry onto 190ha (470 acres) of arable crops.

"Before installing the irrigation system we used a tanker fitted with a Transpread boom. This enabled me to spread slurry onto growing crops," Mr Stamford explains.

"Although the tanker system worked well, the equipment was too heavy and caused too much damage."

The Stamford brothers looked into irrigation systems over a number of years, but initially they put the decision off.

"When I first looked at slurry irrigation I didnt like the in-field spreading systems," Ted Stamford says.

"The irrigator wheels were too close together, for example, and were not wide enough to run down the tramlines. I was also concerned about reliability."

As irrigation systems developed, the Stamfords doubts faded and they finally took the plunge in 1993, and invested in a system supplied by John Pett Irrigation.

At the time, a 50% grant was available for the fixed plant side of the scheme (see table for costings), the actual amount paid being substantially less than for a new slurry tanker and tractor.

"I also saved money by hiring in a small trencher to install the underground hydrant supply pipes," Mr Stamford says.

"Installation took about three weeks in all, four hydrants being sufficient to cover all the land we can spread on."

So how does the Stamford system work? In simple terms, slurry from the pig enterprise is fed to the arable units earth bank storage lagoons via an existing underground pipe system. The slurry is then treated with Fettle enzyme, and agitated.

"Originally we had problems with the agitator blocking, but a modification which pushes material away from the intake filter, and good weed control around the lagoon cured that," Mr Stamford says.

The 63mm (2in) diameter underground pipe, which supplies the field hydrants, is fed by a pump sited adjacent to the lagoons. The pump incorporates a number of safety features to prevent excessive pressure build-up.

"A pair of flashing beacons, fitted to a telegraph pole, tells me when the system is working," Mr Stamford explains.

"At first I was constantly checking the in-field irrigation unit because there was no way of knowing if it had stopped."

In practice, unforeseen stops are now rare, problems usually being traced to how the pipes are laid rather than an inherent weakness in the system itself.

The actual setting up of the unit in the field is straightforward enough, but took time to master. Four over-ground 50mm (2in) diameter feed pipes transfer the pumped slurry from the hydrants to the various fields, with the irrigation machine itself being supplied by a 35mm (1.5in) trailed flexible hose of 500m (1640ft).

Slurry is applied at a rate of around 37,500 litres/ha (3300gals/acre), equating to 105kg/ha of N (84 units/acre). Theoretical system range is 22,500-227,500 litres/ha (2000-20,000gals/acre).

"How much slurry you can apply in a day depends on the length of the tramlines and how often you need to move the irrigator," Mr Stamford explains.

"The pump has a 1200gal/hour output, and its not difficult to average a 20-hour spreading day. Although a tanker has a far higher potential output, the irrigator has two big advantages: It can work when a tractor and tanker cannot get on the ground, and it can work at night." &#42


COSTINGS (Feb to March 1993)

Fixed items qualifying for grant (pump system,underground piping, electrics etc.)£11,114

Less grant at 50%£5557

Non-grant items

In-field irrigator£4003*

Over-ground piping£548

Cost net of grant£10,108

Total ex-grant£15,665

*See current prices below.

Current prices to install a similar system, without grant, will vary according to piping requirements and existing lagoon facilities.

The cost of installing underground piping to in-field hydrants also needs to be considered. If undertaken by farm labour hiring in a trencher this can be carried out economically, with trencher hire costs being upwards of £60 a day.

Main component costs

Pett 1.5kW Floating Propeller Agitator£1000

Pett 4kW 1200 gal/hour pump unit£2700

Pett Slurrymatic 500 irrigator£4480

Ted Stamford uses an irrigation system to spread slurry over most of his 470 arable acres. Irrigation replaced a conventional tractor/tanker policy.