Irish weather conditions over the past 14 months have been challenging, and the recent warm spell has made grass management especially difficult.

A range of conditions have been thrown at Irish farmers this year, from high rainfall and flooding, to sub-zero temperatures and snow, and now Mediterranean temperatures and soil moisture deficit.

In the context of grassland management, each weather type creates its own problem and equally has its own solution. Some grass measurements are showing growth has dropped to sub 20 kgDM/ha. Those not already down to this level will soon drop until rain arrives.

Here are grassland management tips to deal with the current conditions…

  • Anticipate and be reactive: While your most recent grass measurement may show growth remaining relatively healthy, prolonged soil-moisture deficit will cause a drop in grass growth rate. Knowing that there is little to no rain forecast for another 7-10 days, be reactive and take action BEFORE growth drops. In all cases of demand (how much is eaten off the grazing area per ha per day) – dropping demand while growth is still high is a better strategy than waiting until growths hit the floor.
  •  How do I drop demand? – there are a number of options: Supplement milking cows – introduce or increase the amount of concentrate and/or silage in the diet. Keep conc input below 4kgs – response is questionable above this level. Feed good-quality bale silage before pit silage: Remove young stock from the grazing area – these animals are under least pressure and can be housed if necessary. Alternatively, identify a sacrifice area and stand them on it and feed with silage: Increase the total area for grazing – there is the option to re-graze some 2nd cut silage paddocks once the covers are not too high. Often the 2nd cut area is growing aftergrass from the first cut which is of excellent quality and cows will happily graze out cover up to 2000 kgDM/ha of such aftergrass.
  • Lengthen your rotation: Grass tillers need to have three leaves present before being grazed. If growth drops considerably then it will take longer for these three leaves to develop. Increasing the rotation length will allow more time for this to occur. Plan for target rotation length of circa 24/25 days depending on the severity of the drought.
  • Fertiliser application: The response to nitrogen is not immediate after application. It takes time for the nitrogen to move through the horizons of the soil to be available to the roots and moisture is needed for this process. In dry conditions the grass plant can not readily take in the nitrogen but night time dews will allow the nitrogen to move into the top horizon in the soil. Once rain finally does arrive, the response will be quicker. It is advisable to apply 50-60% of the normal rate after grazing. Only use an Ammonium Nitrate nitrogen fertiliser in these dry conditions. Also expect a luxury uptake of nitrogen when rain arrives – the grass will become sour and cows will not be happy to graze it – this is temporary and will correct itself within a couple of days.
  • Don’t be tempted to top paddocks: Drought conditions bring stress to the plant due to obvious lack of moisture and lack of nitrogen uptake. This causes the tillers to become reproductive and produce stem and seed heads. Graze out may suffer but don’t be tempted to “mow/top off” the residual as it will delay re-growth in an already low growth period.
  • Measure to manage: Even though growth is low, continue to do your weekly grass walks. Gather the information which will allow you to make the more informed management decisions.

Noel Gowen, consultant with Grasstec Dairy Solutions, specialists in establishment and management of grazing dairy systems in Ireland and UK. [email protected] / www.grasstec.ie