How does your fertiliser spreader’s CV stack up?

A CV is vital for employers to select the best candidate for a job as it showcases a potential employee’s experience, qualifications and skills.

But did you take a look at your fertiliser spreader’s CV before splashing out the cash on a new machine?

At a recent Fertiliser Association of Ireland conference, Teagasc’s Dermot Forristal explained why a fertiliser spreader’s CV or Coefficient of Variation is so important.

The Coefficient of Variation is a measure of how evenly the machine spreads the fertiliser, the researcher on crops and mechanisation at Teagasc Oak Park said.

The spread pattern can be measured in terms of the Coefficient of Variation. That’s when we try to put numbers on the evenness of spread. It isn’t perfect, but it is at least a single number.

The lower the value of the CV, the more evenly the fertiliser is spread. Once the CV rises above 20%, it can result in both yield and financial losses, which is why “a good CV is a low CV”.

“There is a relationship between the Coefficient of Variation and the financial loss you are going to have in terms of producing the crop, because you are not optimising your yield,” Forristal said.

CV values of up to 15% are acceptable, but Forristal warned that some of the values generated by manufacturers may not tell the entire story.

“Manufacturers have invested hugely in their test halls and they do a lot of work. The test hall, good and all as it is, provides perfect conditions that are never replicated in the field,” he said.

Manufacturers can get a CV of less than 5% at spread widths of 24-30m in a test hall – that’s never achievable in the field.

He warned that the difference in test hall-generated CV values and field-generated values are probably bigger today than they were in the past.

“If you were using a test hall in the past checking a 12m spreader, the less-than-perfect [field] conditions ‘impact’ probably didn’t have as big an effect.

“It is having a much bigger effect today and that is a real challenge,” he said.