Growing and utilising grass is one of the most important factors influencing profit on Northern Ireland farms, writes Dr Norman Weatherup, Senior Beef and Sheep Technologist, CAFRE.
Reseeding unproductive swards to improve grass quality, and putting in place a grazing system to match grass supply to stock demand are key to getting the most from grass.
Swards can be improved in several ways. The traditional method is by sward destruction using chemicals followed by ploughing, cultivation and sowing a completely new sward. This method is the most expensive, takes the field out of production for the longest time but is the most reliable.
Minimum tillage or min-till also involves destruction of the old sward but reduced cultivation (one or two passes with a power harrow) is used rather than ploughing. This reduces the cost of reseeding and unproductive time for the sward but will slightly reduce reliability.
Overseeding can be used where a sward has some productive grass present but the sward is thin or open. The old sward is not destroyed and a reduced rate of seed is stitched in. This method has the lowest cost and shortest unproductive time but also further reduces reliability.
Getting the balance between supply and demand
Grassland management is about having excellent stock performance by growing and utilising sufficient grass to meet requirements. Animals have to eat every day but grass growth varies significantly throughout the season, sometimes on a daily basis. The key is keeping supply and demand in balance.
If animals are set stocked, sward height will fluctuate during the season due to variations in supply and demand. This can often result in areas of rejection by stock leading to wasted grass and poor utilisation or areas which are overgrazed resulting in lower overall grass growth.
Paddock grazing systems
Moving from a poorly managed set stocking system to a well managed rotational grazing system (where there are 3-5 paddocks) can increase utilisable yield of grass by 56%. Increasing the number of paddocks to seven or more can increase utilisable yield by 92% over a set stocking system. In practice, this means five stores/ha could be grazed rather than only 2.6/ha.
It is important to graze swards at the correct stage. Having too much grass will result in dead leaves, stem and seed head production. In turn this will reduce the palatability and energy content of the sward, leading to sward deterioration over time and reduced stock performance. Stock should enter grazing swards at 10cm (3000 kg DM/ha) and exit at 4cm (1600 kg DM/ha). The easiest way to manage this is to maintain a grazing wedge.
The field that stock have just grazed will have the lowest cover and they should be entering the field with the highest cover with the other fields being intermediate. This is the easiest way to identify when a surplus or shortfall is likely to occur and allow remedial action to be taken, i.e., taking out surplus paddocks for silage or feeding additional concentrate. Good grazing management will result in more grass grown and better utilisation resulting in a significant increase in stocking rate.
Walk paddocks and assess quality regularly.
Measure grass covers regularly and manage the wedge for best utilisation of grass.
Act promptly when a surplus or shortfall of grass is identified.
Several computer programmes are available which can help with making grassland management decisions.