Published by Farmers Guide, September 2008

TerraGator gives class-leading
capacity and cost-effectiveness

DORSET-based contractor William Weld recently took delivery of his latest Challenger TerraGator and couldn’t be more pleased with its performance. Mr Weld, who uses the new 2244 model exclusively for injecting pig and cattle slurry, is already achieving workrates of up to 100 acres/day.

“I charge about the same per hectare as a contractor using conventional slurry spreaders, but the difference is that the TerraGator can do in a day what it would take a week for a splash-plate machine to achieve,” he told Farmers Guide.

While the speed of operation is important – Mr Weld said big arable operators, in particular, want to see all the operations on their land carried out at the same kind of workrates – there are even more important benefits of injecting slurry rather than leaving it on the surface.

“In the three years since I began injecting slurry, the advantages have become clear,” he said. “The crop gets much steadier access to nitrogen and you don’t appear to lose N to leaching and volatilisation. Defra suggests that 50% of available N is lost within the first six hrs after surface applications.

“Customers that have been injecting since I started now find the soil is releasing nitrogen all the time, which is useful here in the South-west where growth can continue all year round. There are now grass crops that get no inorganic N, yet they seem to get a much better start in the spring and there is no apparent yield penalty – in fact, there’s evidence that the discs on the slurry injector are cutting the grass root and encouraging tillering and a thicker crop.”

But it’s not just dairy farmers that have found the system ideal on grassland, arable crops have just as much to gain from the system.

“There’s no doubt that there are major savings to make by using slurry in place of inorganic N,” Mr Weld said. “A typical oilseed rape crop might get about 20 cubic metre/ha of cattle slurry, and that would provide 60kg/ha N, 30kg/ha of P and 70kg/ha of K, as well as 30kg/ha of sulphur.

“Unlike bagged N, however, the nitrogen from slurry lasts longer in the crop. About half of it is available to the immediately, while the other half will be released during a period of a few months. It used to be referred to as non-available N, but in fact it goes through the nitrogen cycle and becomes available to the crop in due course.”

In practice, nothing is spread these days before it has been fully analysed for nutrients and the application rates are, more often that not, decided by agronomists. It’s then down to Mr Weld and his TerraGator to make sure the correct amount goes on the field.

“This is where the TerraGator makes the job extremely straightforward,” he said. “The unit’s Falcon VT controller helps set the application rates, which are calculated from the injection width, the forward speed and the flow rate. As the TerraGator uses a displacement pump, it’s easy to work out exactly how much material is going into the ground.”

Mr Weld’s TerraGator, which is powered by a 330hp Sisu engine, carries a 15 cubic metre slurry tank and injects via an 8.4m Veenhuis unit that has 48 individual disc injector points across its width.

“In operation, the TerraGator is working at 14-15km/hr,” Mr Weld said. “The slurry is injected at 1.0-1.5 inches deep and, depending on the application rate, it can take less than two minutes to empty the tank.”

To keep the machine moving, a fleet of three nurse tankers bring slurry from the pit to the TerraGator.

“If we’re working just after harvest, conditions usually allow the tankers to run in the tramlines and come to wherever the last load was exhausted,” Mr Weld said, “but if we’re working after rain, we’ll often just reverse the nurse tanker through the gate and take the TerraGator there to reload.”

Naturally, the loading process is accomplished without either driver leaving the cab, and it’s as quick as emptying the tank. Loading is done via Challenger’s Superload system that uses two pumps to give the quickest filling times available. In independent tests, rates of up to 14 cubic metres/minute have been achieved.

“With a machine like this you have to keep it moving, so I ordered the largest pumps available,” Mr Weld said. “Its nine cubic metres/minute pump is substantially greater than those offered by its competitors, and at application rates of 20 cubic metres/ha I can apply 60-70 cubic metres an hour, while at 30 cubic metres/ha, 100 cubic metres/hr is possible.”

Admitting the capital cost of the TerraGator is substantial, Mr Weld said that nothing could beat the machine for output and reliability.

“I’m now on my third four-wheel Terragator and injector, while I’ve also run three-wheeled TerraGators with fertiliser spreaders fitted for the past 14 years,” he said. “These machines are built to do the job asked of them, rather than to a budget, so you know that quality has been built in – there is no scrimping on materials to save money.

“But, equally, Challenger knows the machines have to earn their keep, so the performance is there to ensure that if you have got the work to keep them going, you will make a return on your investment.”

At the moment, Mr Weld is able to keep the injecting TerraGator working almost year round, although he fears the latest NVZ rules may have some effect on this.

“As I see it, the rules are biased towards slurry application on grassland, which is a very different story from injecting it for arable crops,” he said. “It would be much better to follow the closed periods used on the Continent, where no slurry can be applied between the end of October and February 1st.

“This would allow time for autumn applications of slurry in arable crops, where it will be of some use, and means spreading won’t start again until you can get back onto the land without too much fear of slurry run-off.

“As far as I’m concerned, this would help Defra’s stated aim of encouraging more slurry injection, as more of it will go into growing crops that will use the nitrogen, rather than lying on bare land where it can run off into water courses.”