Atfarm's Variable N-Rate Application maps are intended for nitrogen.

Compound fertilisers

It's possible to use Atfarm's application maps for compound fertilisers such as N+S or NPK fertilisers with a high nitrogen content, but the recommendation is for nitrogen only. Therefore, please refer to your soil analysis and choose your fertiliser wisely.

Phosphorus and potassium fertilisers

Please don't use Atfarm's application maps for applying other nutrients. However, we're working on application maps for other nutrients such as phosphorus and potassium.

From a crop production point of view, Yara's agronomists recommend variable rate fertilisation for nutrients other than nitrogen. However, if all nutrients have been applied uniformly in recent years, for example organic fertilisers such as manure or slurry, there may have been a build-up of nutrients such as phosphorous and potassium as these nutrients haven't been leached out and, due to lower yields, less nutrients have been removed than have been applied. These areas of oversupply require special consideration when switching to variable rate fertilisation.

Slurry

Please don't use Atfarm's application maps for for slurry applications.

Variable Rate Application (VRA) of slurry is generally possible where technically feasible, considering nutrient availability and other factors. However, slurry is mainly used for initial applications, such as in cereals, where the Atfarm algorithm suggests that the area should be homogenised. This means that more slurry would be applied to less developed sub-areas and thus more phosphorus and potassium would be applied to these areas. A possible oversupply of phosphorus and potassium in these sub-areas is therefore more likely.