August is one of the most important target months of the year when it comes to the reseeding of old pastures.
Reseeding 10% of the farm each year is a target that farmers should aim to achieve to increase productivity from their grassland.
In order to determine if a reseed is required, farmers should first consider the objective of the field in question; is it to improve quality of the silage or grazing area, increase utilisation or simply to grow more grass?
If the answer to any of these questions is ’yes’, then reseeding will produce an improvement in the quality of the grass swards on your farm, leading to increased palatability and digestibility, enable higher stocking rates to be carried and enhance silage yields.
Cost benefits of reseeding
Grass is the cheapest form of feed for ruminant livestock at approximately a quarter of the cost of meal.
Reseeding will be a cost effective investment but only when carried out successfully. If this is achieved, it will increase the amount of grass grown in a new sward versus an old ley.
College of Agriculture, Food and Rural Enterprise (CAFRE) advisors in Northern Ireland have assessed the pros and cons of the various seed establishment options, when it comes to establishing a new ley.
Conventional ploughing will bury pest and weed problems, including rushes. It will also alleviate compaction issues.
However, the associated disadvantages relate to the fact that ploughing will disturb dormant weeds; it pushes nutrient rich soil below the surface. Cost may also be an issue.
Cultivation and drilling
Minimum cultivation, on the other hand, does not disturb the soil surface and is significantly cheaper than ploughing.
However, the time required to produce an even seed bed is considerable, while decaying trash can release organic acids into the soil.
Direct drilling was the third technique assessed by CAFRE. This system of establishment retains the existing sward and it is the cheapest option available.
The downside is the challenge of getting the new seed to germinate effectively. In addition, the technique is not suited to all ground types.
Where conditions suit, there is ample evidence to confirm that direct drilling, or over sowing, works well.
Reseeding grass varieties
Establishing new grass varieties using such techniques is dependent on reducing the competition from the existing sward, until the new grass seed has germinated and established.
Normally, this is achieved by tightly grazing or cutting a field for silage prior to reseeding. Alternatively, the existing sward can be sprayed with a specified herbicide at a reduced rate.
The grass seed is normally then sown at two thirds of the normal rate using a bespoke reseeder or direct drill.
Careful management of the reseed post sowing is vital for the establishment of a successful new sward.
Minerals
Adequate nutrients in terms of nitrogen (N), phosphorous (P) and potash (K) along with sufficient moisture will ensure good growth and once established, grazing with light cattle or sheep will encourage tillering of the grass to thicken the sward and give a good establishment.
In good reseeds, there can be up to 10,000 tillers/m2.
The threat from weeds needs to be carefully monitored with targeted spraying necessary if a specific problem arises.
However, precise fertiliser application and selective grazing should help the new grass compete with any weeds and reduce the need for herbicide treatment.