Nitrogen fertiliser dose cuts won’t trim fungicide costs

Disease pressure won’t be reduced enough by lower N rates to justify major cuts in fungicide costs.

Don’t react to higher input costs and lower grain prices by cutting wheat fungicide use dramatically next season, growers are being advised.

With growing costs increasing, the temptation for some growers already considering disease control plans will be to cut back on expenditure. “The first thing we growers think is can we trim fungicide costs,” admits Russell McKenzie, a Cambridgeshire grower with 130ha of wheat this season.

Growing a tonne of wheat this year will cost him in the region of £70-75/t, based on his five-year average yields of 10.7t/ha, an increase of £16-18/t from last season. Fertilisers are the key influence – programme costs have increased from £90-135/ha to an “astronomical” £170-320/ha, depending on whether P and K are used in addition to N. But diesel and parts have also increased.

It all means Mr McKenzie will, like many farmers, look to cut costs. Nitrogen dose, however, will be his first target rather than fungicides, he says. “Depending on what our soil samples say, we’ll probably cut back to 180kgN/ha on first wheats from 200-210kgN/ha, and to 210-215kgN/ha on second wheats from 240kgN/ha.”

David Nicholls, an AICC agronomist covering Cambridgeshire and Hertfordshire, agrees growers have the opportunity to cut N rates based on economic optimum calculations. “Growers who have bought N at the top end could cut by 40kgN/ha.”

But don’t assume that reducing N rates means there will be a lower disease risk, Bill Clark, Broom’s Barn director says.

“It sounds logical, but it is wrong. The amount of N you would have to drop before it has an effect on disease pressure is huge. Dropping 30-40kgN/ha will have no effect.”

In N response trials covering a range of rates from 50 to 300kgN/ha, a drop of 100kgN/ha was needed before there was a significant effect on disease, and then mainly on rusts, he says. “Nobody will drop by that amount.”

It is a message Mr Nicholls agrees with. “I’m not planning on disease development being any different.”

Fungicides will remain a very cost-effective input, Mr Clark stresses. “The average yield response to a fungicide programme costing £65-70/ha is around 2t/ha. Cutting back is virtually always self-fulfilling – yields will go down.”

Don’t forget last harvest, despite the horrendous conditions, was, for many growers, the best harvest in terms of yield for many years, James Taylor-Alford of Bayer CropScience says. Part of that, at least, could be down to the more robust fungicide programmes growers were confident to apply with higher grain prices.

“It’s another reason why I’m hesitant about cutting back on fungicides,” Mr Nicholls says.

While Mr Clark agrees higher fungicide use would result in higher yields – he still believes many growers are applying sub-optimal doses of fungicides – he says last year’s yields were down to the favourable climate rather than fungicides. “If you look across Europe, yields were high, even in Denmark, where they use lower inputs.”

Savings up to £8/ha – but don’t cut out early fungicide

A cut in fungicide budget of around £6-8/ha might be possible suggests, Mr McKenzie. “I don’t think we can get to £10/ha without compromising yields.”

The cuts won’t be through cutting out a spray, such as T0 or T3, altogether. “The strategy will remain the same with the cost savings coming from tweaking doses a little, depending on disease pressure.”

The backward nature of crops might encourage some growers to consider dropping the T0 spray, he suggests. “For us, it is a really useful management tool.” The danger of cutting that timing is losing the insurance it brings, Mr Nicholls says. “You can end up chasing disease for the rest of the year. You can end up spending more.”