Farm Ireland

Friday 14 December 2018

Fertiliser plans need firm commitment from farmers for long lasting results


Soil testing and applying lime now is the best approach to dealing with low pH
Soil testing and applying lime now is the best approach to dealing with low pH
PJ Phelan

PJ Phelan

Over the years I'm sure you have read lots of articles on fertiliser use. Most are technically strong with plenty of well-researched information and advice for farmers how to get the best from fertiliser use/fertiliser plans based on recent soil samples, advice on slurry/organic fertiliser use and timing of fertiliser application.

Here, I will try to highlight what I see going wrong on farms and finish off with outlining some of the changes in the new nitrate regulations.

Nutrient Management Plans

Teagasc's new planning programme (NMP), which we are all obliged to use, is a great improvement on previous planning programmes.

However, it will only give results at farm level if there is an input at the planning stage from the farmer and if it is implemented.

Yield is determined by the most limiting factor.

If field features such as soil type, compaction, drainage, elevation etc are limiting yield potential, additional fertiliser will do very little for your pocket, apart from making it lighter. With our current grain prices, poorer fields should be reseeded with grass or maintained as fallow.

Fields which yielded highest last year, and expected to do the same this year, need more phosphorus (P) and potash (K) than lower-yielding fields.

Also Read

NMPs should include an additional nitrogen and phosphorus allowance on farmers where higher-than-national-average yields have been achieved in any of the previous three harvests.

The allowance of 20kg/ha P for cereals on P index 4 soils and high pH should be utilised. Most cereal crops need an application of 12 units of sulphur (S) /ac - 15 kg/ha.

You should do at least one soil sample for every soil type on your farm for trace elements as there is evidence there are a lot more trace elements applications taking place than can be justified. If applying trace elements this year, get one foliage sample analysed to find if future applications are justified.

Organic fertilisers

Imported cattle/pig slurry, poultry manure and mushroom compost are fantastic sources of N, P and K and provide a range of trace elements.

However, it is important to know their nutrient concentrations and of differing concentrations coming from different sources.

Don't assume it is the average concentration. Now is the time to go to farmers who were looking for you to take slurries last autumn.


Low pH is a problem on many farms, with recent soil tests showing over 50pc of tillage soils being under pH 6.5. Gran-lime is great to solve a problem during the growing season, but you are far better off soil testing now and applying ground limestone.

Lime, and if necessary for your budget, a reduced application of N P K will give a better response than N P K alone. Use magnesium limestone on soils with low magnesium levels.

Phosphorus (P) and Potash (K)

The cheapest way to bring up fertility is to use a combination of slurry and 10-10-20. Low soil P and /or K soils respond to combine drilling for spring crops. If broadcasting, hold back some of the P and K for topdressing six to eight weeks after sowing spring crops or six to eight weeks after the first spring application.

Nitrogen (N)

Nitrogen applications are largely determined by farm limits and how much we think the crop can take without lodging. In many situations, lower N applications will give optimum yields if other nutrients, including Sulphur, are managed better. The use of coated urea gives environmental benefits, but unfortunately have brought the price/unit N close to that of CAN. It would be great if coated urea could be subsidised to bring the price back to that of standard urea.

Trace Elements

Trace element deficiencies are normally managed with foliar applications early in spring. Good firm seedbeds improve contact between soil and roots and improve nutrient uptake.

Nitrate Regulations

The new nitrate regulations came into effect on January 1 this year and have brought some welcome improvements.

Nitrogen allowances have been increased for potatoes, phosphorus increased for oilseed rape and, most importantly, 20kg/ha of P may be incorporated prior to or during sowing winter crops up to October 31.

There is now a requirement for organic matter testing/certification by FAS advisors that the land will only be fertilised to that permitted by index 3 on land in areas with a large proportion of peatlands.

Bord Bia

For potato and vegetable growers who wish to be quality assured by Bord Bia, there is now a requirement for all soils to be analysed for organic matter - back to where all tillage farmers were prior to 2014.

PJ Phelan is a tillage advisor based in Tipperary and is a member of the ACA and ITCA.

For Stories Like This and More
Download the FarmIreland App

Indo Farming

Get the latest news from the FarmIreland team 3 times a week.

More in Tillage