There are a number of key steps that must be taken in order to ensure a successful reseed.
These include building soil fertility, correcting soil pH, incorporating best practice in line with your method of reseeding and choosing the highest performing grass varieties from the current Department of Agriculture, Food and the Marine Recommended List or the new Teagasc Pasture Profit Index (PPI) list, to name a few.
Method of reseeding
According to Germinal Ireland’s managing director, Dermot Campion, failing to select the most suitable method when reseeding can lead to disappointing results, and therefore it is important to understand what the differences are.
“Farmers and contractors have a range of machines and methods to choose from for grassland reseeding, but farmers need to know which are suited to their own individual situation,” explained Dermot.
Ploughing is probably the most ‘fail-safe’ method and provides an opportunity to level the field or improve land drainage. Ploughing allows for the establishment of a fine firm seedbed, greater soil to seed contact and more available moisture for seed germination.
Minimum cultivation is an ideal method where ground contains a lot of stone or where rock is near the surface. As there is minimum ground disturbance, a quicker return to grazing is possible, which is important on highly stocked farms.
Minimum cultivation is generally cheaper than ploughing and the most fertile soil remains at the surface where nutrients are needed. Advice as always is to minimise the amount of surface thrash by grazing or cutting as tightly as possible.
Dermot highlights that there are a few options for farmers where minimum cultivation is an option:
Discing and one-pass
Ideally spray off the old sward about three weeks before cultivating to allow full breakdown of the old grass. Sods can be an issue if the ground is disced too soon post spraying, as the spray hasn’t fully worked down to the root, so it still binds soil.
These sods can be pulled by crows and can result in new seedlings struggling to be anchored in the ground, so when the field is grazed for the first time, animals will pull grass out at the roots.
Direct-drilling
In this instance there is no tilling of the ground; the seed is directly drilled into the sprayed off sward. Again, minimal surface thrash and liming are important.
Sowing in two directions can reduce the appearance of “lines” in the new sward. It is very important to monitor closely for slugs as they can enter the drills and attack the grass in rows.
This method is not suitable in dry conditions as there will be sufficient moisture in the soil for the seedling to germinate, but if moisture doesn’t come from above (i.e. rain) then the grass can shrivel and die.
Regardless of the method of reseeding, Dermot states that the following points are worth noting:
Minimise surface thrash
Surface thrash from the old sward can have a hugely negative effect on the germination and establishment of the new sward. It is always recommended to minimise the surface thrash by grazing or cutting and removing as much of it as possible.
This can be done about 7-10 days post spraying. As the thrash decays, it releases acids which create very difficult conditions for the new grass seeds as they start to germinate.
Liming
Liming is a vital part of reseeding. Using lime at reseeding is critical to the establishment of the new sward as it will help create a better environment for the germinating grass seed, while it will also neutralise and break down the thrash and dying grass from the old sward.
Lime should be applied as soon as possible after the thrash has been removed. The longer it is there the more effective it will be to break down the old sward.
Fine-firm seedbed
A fine and firm seedbed is essential to ensuring the seed makes good soil contact and doesn’t end up buried too deep following rolling. As a rule of thumb, before seed is sown you should be able to ride a bicycle across the seedbed.
Soil-seed contact
This is crucial, as once the seed germinates it needs to access nutrients from the soil. If it isn’t in contact with the soil the seedling will struggle to get the moisture and nutrients it requires, and quickly die.
Soil testing
Soil testing is essential to know the fertility status of your soil and allow you to create a fertiliser plan to meet the needs of the sward into the future.
If pH, phosphorous (P) and potassium (K) is low you need to put a plan in place to rectify the problem; possibly over a number of years. If you only address pH, P and K at sowing and neglect it down the road the new sward will struggle to maintain yield and its persistency will be affected.
Correcting deficiencies where they occur will help ensure a long and productive life from your sward.
Post-emergence spray
Application of post-emergence spray is often overlooked and in reality is an important part of any reseeding programme, as it will provide you with the best opportunity for weed control in the new sward.
Poor results are often reported with post-emergence spray, in particular clover-safe sprays, and more often than not the reason for this is it was applied too late and weeds had already established.
Depending on growth rate, post-emergence spray should be applied 4-6 weeks post sowing, so monitor your new reseed closely. Ideally, spray docks when they are the size of a €2 coin. Dermot recommends seeking advice sooner rather than later from your merchant, rep or advisor if you are unsure.
When it comes to choosing the right mixture, Dermot highlights how variety choice has a big impact on the quality of the sward.
He concludes that there are huge differences in grass quality between varieties on the Recommended List and the Teagasc PPI and farmers should be considering the highest performing grass varieties from the current Department of Agriculture, Food and the Marine Recommended List or the new PPI.
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