NI Fertiliser Limits Calculator

Across the farm’s grassland, available nitrogen from chemical fertiliser and from organic manures other than livestock manure must not exceed 272 kg N/ha a year where more than half the livestock manure comes from dairy cattle, or 222 kg N/ha for other farms — and it must be in proportion to what the grass needs. Livestock manure counts separately against the 170 kg N/ha limit.

Winter wheat 220, spring wheat 180, winter barley 170, spring barley 140, winter oats 140 and spring oats 110 kg N/ha, covering available nitrogen from both manure and chemical fertiliser. You can add 20 kg N/ha for every tonne your expected yield exceeds the standard yield, if farm yields in one of the last three years show it.

Soil samples are analysed for Olsen phosphorus (mg P per litre of soil) and given an index: 0 (0–9), 1 (10–15), 2- (16–20), 2+ (21–25), 3 (26–45) and 4 (46–70). The higher the index, the less phosphate the crop needs — at index 3 and 4 most grassland uses have no allowance for chemical phosphate at all. The regulations treat sampling every fourth year as the basis for phosphate recommendations, with no more than 4 ha per sample.

Yes. Chemical phosphate is only allowed to make up the difference between the crop requirement and the available phosphate already supplied by slurry, manure and other organic materials. At soil P index 0 or 1 about half the phosphate in slurry (60% for solid manures) is counted as available; at index 2- and above, all of it is.

Any organic manure with more than 0.25 kg of total phosphorus per kg of total nitrogen — such as pig farmyard manure, layer manure, duck manure and broiler breeder litter. It can only be spread where you can show the phosphate is needed for the crop, and you must keep a fertilisation plan.

Yes, if you apply chemical phosphate to grassland, spread anaerobic digestate or use high-phosphorus manures, and every year if you have a derogation. A nutrient management plan covers all of these.