Farm Ireland

Saturday 25 November 2017

Hold off nitrogen use until prospect of milder weather

Liam Fitzgerald

About four weeks ago in this column, when discussing the timing of first nitrogen application, I said that the threshold temperature for grass growth, of 6°C, does not occur throughout most of the country until the start of this month.

Therefore, the response to nitrogen in February is likely to be low and may not cover its cost in terms of feed produced.

In a normal year -- where you have soil temperatures of 4-5°C in mid-February, a moderate cover of fresh grass and where ground conditions are good - it is sensible to begin spreading nitrogen at a rate of about 30kg/ha (25 units/ac).

Late last week, the 10cm soil temperature varied from 1-3°C, which is 2-3°C below normal.

We need a change in windflow from the polar north to the southwest to get adequate temperature for growth at this time of the year.


In addition to the absence of growth, existing covers have gone back due to the severe frost. Looking on the bright side, the year is moving on and, when milder conditions come, there will be good growth due to longer days and the increasing intensity of sunlight, so we would be expecting a degree of compensation.

In the meantime, it is better to hold off from spreading nitrogen until there is a prospect of milder weather.

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As ground conditions are good, a lot of slurry has been spread during the past three weeks. At 28,000l/ha (2,500ga/ac), undiluted cattle slurry supplies are the equivalent of 0.5 bags urea/ac or 2.5 bags of 0:7:30.

Due to the cold, there is an equally poor response to the nitrogen in slurry, but at least the P and K will not be lost.

Much of the cattle slurry gets diluted from leaking drinkers and the addition of water for agitation, so the fertiliser value is correspondingly diluted.

There is less loss of nitrogen with such 'watery' slurry and less contamination of pasture, but the spreading cost is higher. Graze off heavy grass covers before applying slurry. There is a good deal of semi-decayed and withered grass on fields, due to the severe night frosts. Fields with the higher covers have the most withered leaves. These will not trap sunlight to produce growth.

The recent cold spell seems to have done more damage than the snow in early January. Where there is a reasonable cover (more than 6cm), pastures with dead material will benefit from being grazed off. Removing this old grass will encourage fresh growth and better tillering, which will give a better response to nitrogen and provide a higher-quality sward in the next grazing.

In planning the first grazing, do a grass budget to find out how many cattle the available ground can carry for three to four weeks, assuming there will be little or no growth in that period. If growth picks up, more stock can be turned out.

By using the Teagasc grass-budgeting programme, you can measure the rate of growth between recordings, which will give you a guide to the appropriate stocking rate as you go through the month.

Throughout this month there will be early grass farm walks in every county or Teagasc area unit, which will deal with the best practices for getting the most from early grass and managing pastures for the following months. You may ask how we can have early grass demonstrations when there is no growth and possibly inadequate grass on some of the farms. Well, most farmers will be in the same position. It is when conditions are difficult that we need to discuss the problems and find solutions.

There was an estimated shortage of 10-15pc in winter feed stocks. This was manageable by sensible rationing and feeding extra concentrates. The delayed spring growth will add to the fodder shortage.


If your fodder stocks are running out, do a feed budget immediately so you can ration scarce forage until turnout to grass and decide on the options that best suit you.

These will be among the following: purchase of additional concentrates; application of extra nitrogen when conditions are suitable; purchase of minimum roughage; sale of stock; and later closing of part of the silage area. Those with finishing cattle should put them on all-concentrates with minimum roughage if they are not on this already.

These issues can be debated at the upcoming farm walks. Look out for the one in your area or contact your local Teagasc office for details.

Irish Independent