Top up nitrogen and sulphur when conditions allow

Growers are being advised to apply key nutrients to cereal and oilseed rape crops as soon as soil conditions allow tractors to travel.

Many winter crops have established well this season and have taken up available soil nitrogen.

However, the wettest January on record for much of southern England and high rainfall across the UK has washed out reserves of soluble nutrients such as nitrogen and sulphur.

ADAS crop nutrition expert Brian Chambers says that when crops start growing again in earnest they could soon find themselves short of both elements.

“For cereal crops, growers should aim to get 40kg/ha of nitrogen applied when they can get on the land, but that is going to be the problem for many,” says Prof Chambers.

However, fertiliser producer Yara’s agronomic co-ordinator Ian Matts urges caution and says that growers should keep an eye on the weather forecast in case cold weather arrives.

“There is no point in rushing out applying nitrogen if the temperature plummets soon afterwards for two weeks and crops stops growing,” says Mr Matts.

“Despite that, some nitrogen will be required when you can get on the land, particularly in late-drilled wheat crops that aren’t as forward and have a poorer root system.”

Sulphur is a vital nutrient for oilseed rape growth, but has become increasingly important in cereals, as atmospheric sulphur levels have dropped in recent years.

Prof Chambers says that is likely to be a year when crops will respond well to sulphur applications, with good responses often seen after wet winters.

“You’ll have to have a damn good excuse not to be applying any and even if you have applied manures in the autumn, much of that sulphur would have been lost,” he adds.

He also suggests putting a third of oilseed rape crops’ nitrogen requirements on when possible and two-thirds later on.

“The most important thing for rape crops will be getting around the whole area with something, so a smaller split will help with timeliness,” says Prof Chambers.

Avon agronomist Stephen Harrison says ground conditions in his area are very squelchy, with the south west of the country bearing the brunt of recent rainfall.

He is also concerned that cereal crops will not have enough nitrogen to drive early growth and will be advising to get 30kg/ha N on in mid- to late-February, but stresses that growers should not make a mess unnecessarily.

“When run-off ceases and it dries out growers should get a dressing on, but there is no point in making ruts everywhere and damaging soil structure.

“Winter barley will be more pressing as shoot survival dictates final yield, so a nitrogen application will help ensure shoot numbers are maintained,” says Mr Harrison.

Manganese is also something that growers should take care of, adds Mr Harrison, but he not concerned about other micronutrients yet and is adopting a “wait and see” policy.

Phosphate and potash should not be forgotten and Prof Chambers recommends that where soil indices are between 0-1, a top-up application will be required.

“Where indices are 2, a maintenance application of phosphate would be useful, but potash is not so important,” he explains.


See also Potash needed for better nitrogen efficiency