Farm Ireland

Wednesday 17 January 2018

Getting grass growing is not easy as the winter hangs on

Liam Fitzgerald

Grass remains scarce on all farms following the hammering grass swards took during the winter and the absence of any growth until mid-March.

By then, fields that were closed in late October and early November had a cover of over 1,000kg dry matter/ha of mixed quality green grass and withered/dead material.

This needs to be grazed off immediately as it is delaying the growth of new grass. It is important to get it off the silage fields before closing, otherwise the quality of first-cut silage will be reduced by 4-6 DMD units.

Analysis of this over-wintered herbage suggests it is in the range of 70pc-74pc DMD and considerably better than most of the silage that stock are eating at present. Fields that were grazed late into November remained bare and are only now starting to grow.

The most difficult situations are where silage has almost run out and grass is scarce. In that case, the priority now is to maximise grass production by applying nitrogen on rested fields.

Supplement scarce silage with meal. Every kilogramme of meal fed will save about 7kg silage, and feeding 3kg meal to a dry cow or heavy store will reduce the silage required by 50pc.

Calved cows indoors with calves at foot need about 5.5kg meal/day if silage is cut to 50pc of requirements. Even when you have plenty of silage, put out enough stock to graze off heavy covers before April 1 and then turn out additional animals as grass supply increases to maintain 12-14 days' grass supply ahead of stock.

Grass growth should now pick up with each passing day. Soil temperatures are now in the range of 7.5-10°C and should rise further unless there is a cold snap.

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Growth increases rapidly between seven and 12°C and more slowly up to 25°C. There is now plenty of moisture in the soil, the only danger is that we might get too much rain.

Apart from climate, growth is increased in two ways by management: (i) apply 0.5 bags urea or 1 bag CAN per acre after each grazing; (ii) have a large number of grazing divisions and a small number of grazing groups.

The greater the number of divisions you have, the shorter the time cattle will spend in each division and the longer the interval between each successive grazing within a 20-day rotation.

There is little growth in a paddock while it is being grazed down, so the faster you get it grazed and stock off the faster the recovery. Aim for six to eight divisions per grazing group and, if ground conditions are good and grass is scarce, divide these again with a temporary fence to allow you to ration grass more accurately while maximising growth on the paddocks that are recovering. By keeping the number of grazing groups as small as possible the number of paddocks is kept to a minimum.

Having a few cattle in most fields delays growth and response to nitrogen, especially when grass covers are low. This often happens on suckler farms with cows at different stages after calving all over the place.

From now on, when growth rates are increasing rapidly, you don't need high pre-grazing grass covers and you can graze tightly if conditions are good.

A 10 cm (4in) of pre-grazing grass height and a post grazing height of 3.5 cm (1.5in) is quite suitable. A height of 10cm represents a yield of about 1,000kg dry matter (DM) per ha.

From this we would subtract about 200kg DM for wastage, leaving 800kg available for animal intake. How long will a hectare of such grass last 25 suckler cows with calves?

Each cow needs about 15kg DM per day giving a total herd requirement of (25x15) 375 kg DM per day. Therefore, the 800kg will last 25 cows (800/375) approximately two days.

Grass measurement and grass budgeting is a very useful tool in herd management, especially when grass is scarce. It allows you to plan ahead and anticipate problems with shortage or surplus before they arise.

There are different levels of sophistication with budgeting, from simple calculations like the above to computer-calculated tables and graphs that crunch more figures and give you better predictions.

It best done as part of a beef discussion group where group members learn to do the measurements and budgeting and use the information at meetings.

For more information contact your Teagasc adviser.

Irish Independent