Much of the early nitrogen applied to cereal and oilseed rape crops across the country during the mild late-February spell could go to waste unless steps are taken to keep it in the rooting zone long enough for crops to make use of it.

Agrovista technical manager Chris Martin says: “A lot of growers have been busy spreading bagged nitrogen, but most crops don’t need a lot this early, and probably won’t need much for a while yet. In some cases, up to half that applied so far could be wasted.”

The same is true for organic sources such as digestate and slurries on grass as well as arable crops, says Mr Martin. “It may well be the case that the maximum permitted dose of 250kg/ha of organic N could be applied in one go.

“Up to 80% of that can be readily available in digestate, which equates to 200kg N. Generally speaking arable crops will take up no more than 3-5kg/N/ha/day, so the problem is obvious, even at lower application levels.”

To counter the problem, Mr Martin recommends applying N-Lock Max to keep as much nitrogen as possible in the root zone, so it is readily available to crops when they really need it.


N-Lock Max is a new, more concentrated formulation of N-Lock that also works out cheaper than its predecessor. It contains 300g/litre of nytrapyrin, a nitrogen stabiliser. This inhibits Nitrosomonas bacteria which are responsible for converting ammonium to nitrite within the soil, keeping nitrogen in the ammonium form for longer.

“Ammonium is positively charged and is much more stable, so is less likely to be lost to the environment through leaching or de-nitrification,” says Mr Martin.

The product should be applied ideally within a week either side of the fertiliser being spread, as it need to be in the soil before rapid nitrification occurs. The rate is 1.7 litres/ha, in 100-200 litres/ha of water. It works best if applied in damp conditions such as heavy dews or showers, or 12mm of rain falls within 10 days of application.

It can be applied with liquid fertiliser, slurry and digestate, and can be tank-mixed with most T0 sprays.

Applying N-Lock early in the season will also help protect against N losses from the main dressing and beyond, as it provides activity for up to 12 weeks. This also helps farmers to manage fertiliser applications and reduce the number of splits to ease workloads.

“The usual timing is T0, close to the first main fertiliser application, and many growers will be planning to use it at this timing, particularly on leaky soils or high-potential crops,” Mr Martin adds.

N-Lock, a lower-concentrate formulation which was applied at a higher rate to put down the same amount of active ingredient, produced some impressive results in when trialled across 11 sites in in 2013 and 2014, increasing wheat yields by an average of 5%.

In the field, average yield increases of 10% are regularly recorded, says Mr Martin.

“Applying N-Lock Max ahead of the fertiliser is preferred. So, in a season like this, going earlier to help preserve some of the early-applied N makes good sense.”