Farm Ireland
Independent.ie

Saturday 23 September 2017

Now is time to clean off paddocks

Liam Fitzgerald

Looking at grassland today is like going back 30 or 40 years when a lot of stock was out-wintered and fields were bare at this time of the year.

The period between mid-March and mid-April was known as the hungry gap when winter feed began to run out and spring grass was still not in plentiful supply.

We would expect to have growth of about 15kg DM/ha in March but so far it has been nil, apart from in the more climatically favoured areas. More significantly, the grass covers coming through the winter have been devastated by severe frost. Good ryegrass swards that were closed from late-October/early November have covers of 1,000-1,400kg DM/ha consisting of a mixture of green and decayed leaves in almost equal proportions. The feeding value of this material is still quite good.

Winds

Analysis indicates a digestibility of 70-80pc, depending on the ratio of green leaf to withered material, and the dry matter is up to 30pc as a result of the dry, easterly winds. Old pasture swards have very little cover and little sign of growth.

Current forecasts, at the time of writing, are that the weather will become unsettled, with temperatures hitting normal March levels. Increasing cloud will help reduce the incidence of frost, which will result in soil temperatures reaching normal values of 6-8°C.

Grass that has accumulated since last autumn should be grazed off. This will allow fresh growth to start that will respond to nitrogen.

Silage fields might have to be split up and block-grazed to get cattle to remove all the herbage. If given a choice they will selectively graze out the leafier material. While conditions are good, the heavier land could be grazed first. Unless you are short of feed, aim to close for silage in the first week of April. This will entail grazing off the silage ground by early April. The whole farm (silage and grazing areas) should have been grazed once by about the third week of April but this will vary depending on location and soil type. Achieving this target involves putting out the right amount of cattle in relation to the amount of grass available. A weekly grass budget will give a good guide to the appropriate stocking rate.

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If you delay turnout date or put out too few stock it could be well into May before the last paddocks in the rotation are grazed and by that time the grass has got too strong, and recovery for the next rotation is slower.

The opposite might be more likely this year. Current growth levels are a few weeks behind the average and with winter feed running out, there will not be any surplus grass. The point I am stressing is that even if grass looks scarce, it is better to get out some stock to graze off mature grass and get nitrogen on it to provide new growth.

Deluge

You can also spread nitrogen ahead of grazing for about a week, so as not to be out too frequently with the fertiliser spreader. I just hope that when the weather changes we don't get a deluge, which will prevent fertiliser application for weeks.

As temperatures improve there will be an increasing response to nitrogen. The grazing areas should get the equivalent of 0.75 bags urea/ac (35 units/ac). If soil phosphorus is low, use a high nitrogen compound.

Phosphorus helps grass growth when temperatures are low. Repeat the nitrogen application after the first grazing where grass is scarce. Silage ground that is being grazed at present and then closed up should get its nitrogen for silage by the end of the month. If you anticipate a grass shortage and intend to graze some of the silage ground in April, it could get about 0.5 bags urea/ac now and then get its silage application when being closed up. Apply about 125kg N/ha (100 units/ac) or the equivalent of two bags urea/ac for first-cut silage. Light soils need more nitrogen than heavy clay soils. On the heavy clay soils, you may not get a response in silage yields above 80 units of N/ac.

Slurry can be spread on silage ground that has been grazed at up to 33,000 litres/ha (3,000ga/ac). This will supply enough P and K for one cut of silage. If the slurry is applied in damp conditions the nitrogen losses are minimised, so 3,000ga/ac should supply about 25 units of nitrogen, thus allowing the chemical nitrogen to be reduced to about 70 units/ac.

Irish Independent