Overseeding adds flexibility to grassland renewal

Monday 12.08.2019 , news

Continual improvement of grazing and silage leys is an integral part of Northern Ireland dairy farmer Kevin McGrade’s strategy of maximising milk production from forage.

He’s currently reseeding around 15% of his grassland each year, ideally following a full cultivation, but over-seeding – or stitching-in – is also proving invaluable as a way to maintain productivity.

“We’ve been going through a phase of expansion, taking on additional land that has needed improvement,” explains Kevin. “With the new land, and keeping the quality up on our existing land, we’re quite heavily focused on reseeding.

“Stitching in provides a lower cost option, but it’s mainly beneficial because it avoids taking land out of production. It’s also a very flexible way to reseed, which is particularly important in our situation where a combination of heavy land and high rainfall mean you need to take the opportunities when they come.”

Farming at Dromore, Co Tyrone, Kevin is now milking 180 autumn calving Holstein Friesians. He operates a grass-based system, with high quality silage and well-managed grazing underpinning production. In his quest to maximise production from forage, he is currently at around 3,000 litres from a herd average just under 7,000 litres.

Kevin McGrade typically makes two passes with an Einbock tine drill when over-seeding, with either the first or second pass delivering the seed and the other creating the right conditions for soil-to-seed contact.


Opportunistic improvements

Over-seeding is carried out to improve fields where necessary, at any point from the spring through to mid-summer.

“We use the AgriNet grazing management programme, so have figures from this on which to base our decisions on reseeding priorities, but we’re also mindful of the fact fields vary in their potential. In reality, its often a judgement call based on what we expect and then other factors such as the percentage of perennial ryegrass in the sward and the degree of poaching.”

Kevin has found that trying to set specific times for over-seeding rarely works, so the policy is to work it into the grazing rotation, taking opportunities when the conditions are just right.

The first step is to graze the field down tightly, to remove the cover, and then he’ll make two passes with the Einbock tine drill. Seed is drilled at half the usual rate, either on the first pass or the second pass, and a decision whether to roll or not after drilling is made depending upon conditions.

“We take soil samples ahead of any reseeding, and will then apply a compound fertiliser, typically at around 250kg/ha, to ensure that the right amount of phosphate and potash is available for the new seedlings,” adds Kevin. “We may use watery slurry, applied with a tanker or through an umbilical system, as an alternative to some of the bagged fertiliser.

“After over-seeding, it’s important to continually remove the regrowth from the old sward, to minimise the competition for the new seedlings. We’ll graze the cows on the over-seeded ley from ten days after drilling, and then repeat every two to three weeks until the new seedlings are established.

“This means that we are not actually taking the ground out of production but are improving the productivity very cost-effectively.”

The discipline of renewing leys in good time, whether through over-seeding or following a full cultivation, is ensuring high levels of grass dry matter production, which reached an enviable 12.46 tonnes DM/ha in 2018. Routine reseeding is also allowing Kevin to continually incorporate the best grass genetics into his system.

“We’re selecting grass varieties on the basis of their performance on the Irish Pasture Profit Index,” he says. “We are also moving towards having specialist leys for either cutting or grazing, so we have fields that are fit for purpose.”

He works closely with David Little of Germinal, who recommends bespoke mixtures to suit the method of establishment and the purpose of the ley. Currently, silage leys are based on the late heading perennials AberGain, a tetraploid, and the diploid AberChoice, both Aber High Sugar Grasses that are highly ranked on both the Irish PPI and the Recommended Grass and Clover List. The proportion for these silage leys is typically 30% tetraploid and 70% diploid, though Kevin uses closer to a 50:50 mix on his drier fields. He also uses a higher proportion of tetraploids for over-seeding, as he believes the larger seed has a better chance of establishing in the conditions.

Kevin (left) usually favours mixtures comprising just two varieties, with these being tailor-made by Germinal on the advice of David Little (right). 


Grazing leys are also dominated by Aber High Sugar Grass varieties, with intermediate diploids including AberGreen and AberWolf typically included. Kevin finds these diploids provide the higher sward density that is required in a grazing situation, particularly on his heavy ground.

None of the leys include clover, as Kevin’s priority is to maintain clean swards, and dock control, in particular, would be compromised if he was including clover. 

Attention to detail around grazing management and silage making is exemplary, ensuring the right raw material is converted into grazed grass or winter forage of the highest quality.

Flexible grazing management

Given his circumstances on a heavy land site in Northern Ireland, Kevin’s approach to grazing management is pragmatic. He’s installed cow tracks to improve access to fields and takes every opportunity to turn out early in the spring, but he accepts that they may have to come back in if conditions turn against him. Over the past three seasons, available grazing days has varied by as much as 30 days over a season, so flexibility is paramount.

Cows are strip grazed behind a single wire, this being preferable to paddocks, which Kevin finds too rigid for his situation.

Grass measurement is the key to the ongoing management, with Kevin cutting and weighing representative samples within a quadrat and calculating production based on a judgement of dry matter content. He’ll take measurements as frequently as every five days during peak growth periods, with figures being entered into his AgriNet programme to provide a farm-scale overview of grass production.

During the heaviest periods of growth, surplus grass is cut and round-baled for silage, ideally before it loses quality. Where fields do go beyond the optimum, bales are allocated for dry cows.

Ensuring quality silage

The current policy is for the first two cuts to go into the pit with third and fourth cuts going into bales. “We’re confident of the quality of the grass that we’re starting with, due to regular reseeding and good weed control, so we’re aiming to cut grass before it goes to head – to ensure we are maintaining that quality.

“We’re using a local contractor for most of the work, though we do some of the mowing and the tedding ourselves as required. It’s important to have a good relationship with your contractor, so that you can rely on them to work with you when needed.”

Grass production increasing

Year                Average production (t DM/ha)

2016                10.58

2017                11.45

2018                12.46


First cut silage (2018)

Dry matter (%)            28.1

Protein (% DM)           11.5

ME (MJ/kg DM)           11.4

D-value (% DM)           71.3


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