One of the key messages emanating from the recent Drummonds grassland reseeding event was the need for farmers to think 12 months ahead, from a planning point of view.
Driving this mindset are two key messages.
The first reflects the fact that adding clover into a reseed varieties mix ticks all the boxes; the second reality is centred on the fact that that clover-friendly herbicides are as rare as hens’ teeth.
So what does this entail from a practical point of view?
In essence, it means that farmers should act to remove problem weeds, including ragwort, nettles and chickweed, from an existing sward some months before the actual reseeding process takes place.
If this is not done, the use of a broadleaf herbicide, post-establishment, may well kill-out most of the clover that was in the new sward.
Under these circumstances, the farmer is then forced to look at stitching-in fresh clover seed at some future stage.
Reseeding
According to Drummonds agronomists, grass reseeding will deliver a full repayment on the investment made within two years.
Making this happen is a combination of factors – the higher growth rates achieved by new and improved grass varieties, the higher sugar contents within these forages and the role of legumes in fixing atmospheric nitrogen.
Drummonds’ Wesley Martin explained: “New and improved swards also hold out the prospect of grazing seasons being extended in both the early spring and at the back end.
“New grass varieties are also more drought resistant.
“Grazed grass remains the cheapest source of feed for ruminant livestock. The average production cost is 8c/kg of dry matter. The comparable cost for spring barley is 32c.”
According to Martin, new and improved grass leys can quickly generate an enhanced return of €160/ha.
Soil testing
Soil testing is the all-important starting point to any grass reseeding project.
“The results of a soil test will deliver critically important information where three key criteria are concerned – soil pH values plus soil phosphate and potash indices,” Martin continued.
“The optimal pH value for a grassland soil will be in the range 6.0 to 6.5. When this is achieved, soil phosphate and potash availability will be at their optimal levels.
“Adding lime, as required, allows farmers to meet this target.”
Managing a new sward is as important a requirement for livestock farmers as is establishing it in the first place.
Getting it grazed down – preferably with young calves or weanlings – is critically important.
New swards should not be grazed before the emerging grasses have reached the three-leaf stage.
One very practical way of establishing a new sward’s suitability is through the use of the ‘pull test’. If young grass plants can be easily pulled from the ground by hand, then they should not be grazed.
If young plants resist hand pulling, then they can be grazed carefully using young stock at the outset.
When asked about the possibility of new swards being easily poached, Wesley Martin said: “Yes, old swards have a high root mass that can help, from a stock carrying capacity.
“This is why it is so important to encourage active root growth within a new sward. Ensuring that available soil phosphate is at the required level is key in this regard.”
Soil structure
Courtesy of his presentation, Grassland Agro’s John O’Loughlin highlighted the role that soil structure plays when establishing a new crop of any kind.
Where soils containing a high level of organic matter are concerned (black soils), he indicated that pH values should be maintained at a value of 5.8.
He defined those soils containing 20% organic matter or more as falling into this category.
According to O’Loughlin, soil compaction is a major challenge on many Irish grassland farms.
This refers to the physical degradation of the soil, leading to a reduction in biological activity, porosity and permeability. As a consequence, soil structure is partly destroyed.
Compacted soils impede root development which can reduce yields. Along with reduced plant growth, poor aeration induces the loss of soil nitrogen (N) and produces greenhouse gases [GHGs] through denitrification in anaerobic sites.
The Grassland Agro representative encouraged farmers to dig inspection holes in their fields, using a spade, to check for the presence of compaction.
“Following the recent rains, it’s very probable that compaction problems will increase on many farms over the coming weeks,” he said.
“This will be a direct result of silage machinery and other items of heavy equipment trafficking fields.”
O’Loughlin then demonstrated the use of the ‘GrassVESS’ app as a means of quickly assessing soil structure on a visual basis.
He compared soil to a three-legged stool, with biological, physical and chemical attributes. And all three criteria must be assessed by farmers, if they wish to maximise their grassland and crop outputs.
“The physical health of every soil is extremely important,” O’Loughlin added.
“In the first instance, farmers must define their targets in this regard and manage their soils accordingly.
“Aeration and sub-spoiling are techniques that can be used to improve the physical structure of a soil. But if carried out at the wrong time, they can be totally counterproductive, in terms of the outcomes generated.”
One very obvious consequence of soil compaction is the limitation on plant root growth below ground level.
“Evidence of this can be easily gauged, simply by using a spade to turnover a sod,” O’Loughlin explained.
“Where compaction has occurred, the root zone will be very thin.
“But where compaction is not an issue, roots will be seen travelling deep into the ground. Compaction limits plant access to the total nutrient pool within the soil.”
Clover
The use of clover in both grazing and silage swards was repeatedly highlighted at the event.
Specifically from a silage perspective, the benefits of including red clover in a varietal mix were heavily endorsed.
According to the Drummonds agronomy team, red clover is a cost-effective source of home-grown protein with the ability to fix atmospheric nitrogen.
Moreover, it performs well in severe weather with its long tap root increasing sward performance in both cold and drought conditions. Soil fertility and structure will be benefit accordingly.
Red clover can be included in a silage varietal mix at a weight ratio of 1:2. In order to achieve optimal dry matter yield, the other component of the mix should be a hybrid ryegrass variety.
If managed properly, red clover will remain viable within a sward for up to six years.
Representatives from Whelehan Crop Protection also attended the reseeding event. The issue of maintaining clover in a new sward, after the use of a broadleaf herbicide was discussed in detail.
Looking to the future, the company hopes to have access to a new herbicide brand ‘ProClova’ within the next 12 months.
The product has been specifically developed to enable farmers preserve white clover in new swards while still providing enhanced broadleaf weed control.
Multi-species swards
The potential for multi-species swards into the future was also discussed at the reseeding event.
They comprise a mix of at least two forage species. Perennial ryegrass and other grass varieties tend to make up the backbone of these mixtures, along with legumes and herbs.
Performance from these swards is delivered through the complementary activities of the various plant types.
A variety of leaf and root architecture combines to maximise the use of light, moisture and nutrients, both below and above ground level.
Deep rooting species, such as perennial chicory and plantain, allow nutrients to be taken up from different depths within the soil profile, relative to what is the case with a shallower rooting perennial ryegrass.
Having a range of different species within a sward will also mean multiple sources of protein, energy and minerals. The end result is a more complete nutritional profile for the grazing animal.
Successful reseeding?
So what are the key steps to ensure a successful reseed?
According to Drummonds agronomists, the process starts by identifying relevant fields, based on perennial ryegrass content and paddock performance.
Soil testing is critical. The pH objective for mineral soils is in the range 6.3–6.5. Farmers should target Index 3 or greater for both phosphorous and potash, while also ensuring that all nitrates regulations are adhered to.
Existing swards should be sprayed-off using glyphosate. Sufficient time will be needed to ensure that all existing plants are dead, prior to cultivation taking place.
Cultivation work can be carried conventionally by ploughing and tilling. This approach will help level the field. However, minimal cultivation can also work just as well; a fine, firm, seedbed is key.
Growers should apply lime as required.
A quality seed mixture should be selected to meet the required production targets.
Seed mixes should be sown out at a rate of 14kg/ac, under ideal conditions, and no deeper than 10-15mm.
Farms in derogation must include 1kg/ac of coated clover or 0.6kg/ac of naked clover seed.
Ground should then be rolled well to ensure good soil to seed contact – this is crucial.
Nitrogen, phosphate and potash should be applied to the seedbed, as per soil test recommendations.
It is important to be on the look-out for possible pest attack e.g., fruit flies, slugs, leatherjackets etc. Appropriate action should be taken, where needed.
A post-emergence herbicide spray should be used to control any weeds such as nettles and chickweed.
It is important to use a clover-safe spray when necessary. Re-seeds should be grazed lightly to promote tillering of new plants.
Farmers should ensure that young plants are not being ‘pulled up’ by grazing animals.