Weeds are a valuable source of information for Co Tyrone suckler beef and sheep farmer Bronagh O’Kane.
Since taking over the running of her family farm in late 2019, Bronagh has been implementing management practices based around the principles of regenerative agriculture.
Soil health is a major factor, although it involves going beyond a basic chemical soil analysis, which tests for the likes of phosphorus, potassium and pH.
Instead of just knowing the soil’s chemical status, Bronagh wants to understand the physical structure of her soil and the biology that lives in it.
Visitors to her farm near Cookstown last week were told that weeds can shed a lot of light on what is happening below the ground.
All soils have a natural seed bank, so a spadeful of soil on any farm is likely to contain a huge quantity of seeds that can potentially grow weeds.
Bronagh said each type of weed will germinate when conditions in the soil are right for them and this is often nature’s way of addressing an underlying issue in the soil.
“If there is a compaction problem, then there is a lack of oxygen in the soil, so docks will grow because they have a massive tap root which helps break up the soil,” she explained.
Other weeds that are indicative of soil compaction or surface crusting include buttercup and thistles.
Rushes grow when soils are waterlogged and depleted of oxygen because the rush plant is capable of transferring oxygen to its roots.
The likes of catsear and hawkweed, which are closely related to dandelions, are a sign of low organic matter in soils.
“I had a lot of chickweed which is a sign of excess nitrogen from slurry or fertiliser, as well as low calcium and high potassium levels,” Bronagh said.
Asides from analysing weeds, a lot can be learned about soil by simply digging a hole in different fields.
Bronagh’s soils have a high clay content and could be described as heavy, although she has found other structural issues that can be addressed with better management.
“When I started digging holes, I knew something wasn’t right. I found there were no soil aggregates, there were very few worms, grass roots were shallow and there was poor water infiltration,” she said. A lot of these issues were put down to a history of set stocking, where livestock graze the same ground almost continuously, with no opportunity for grass to grow and soils to rest.
A paddock grazing system has now been set up, where cattle are moved on to fresh grass either daily or every two days.
“I try to never let them back over grazed ground to eat the new leaf in the re-growth. I need to let grass rest after each grazing to let the roots get down deeper into the soil,” Bronagh said.
Chemical inputs have been cut back on the O’Kane farm and no artificial fertiliser was applied this year at all. Livestock numbers have also reduced, as the farm moves to a lower input-lower output system.
Visitors were told that in 2019, there were around 80 cattle on the farm and current numbers stand at around 50 head (including cows, calves, and store cattle).
Bronagh’s father kept a pedigree Charolais herd, as well as commercial cattle. However, she is moving away from continental breeds and has bought an Aberdeen Angus bull.
The aim is to breed cattle that are easier calving, have lower maintenance requirements and are lighter on the ground.
She has diversified into sheep with a small flock of pedigree Charollais: “I want to get high value from low numbers. I also tup a batch of [commercial] ewes each September and sell them in the spring as ewes with lambs at foot.”
Bronagh O’Kane has started growing multi-species swards in some fields and baled silage was made from a herbal ley this year.
“I made the contractor mow it off high at the height of your hand. I didn’t want to cut it off too low, to avoid damaging the growing points on the plants,” she said.
The six-acre field grew back well and was grazed by cattle in the late summer. At that time, there was a heavy sward cover, but wet weather meant utilisation was not as good as hoped.
“I had to have faith and kept telling myself what was being tramped down was not lost forage. It is feeding the soil and stops weeds by covering bare soil,” Bronagh said.
Clover is also being incorporated into swards as a way of fixing nitrogen in the soil, although Bronagh maintains that having good soil health is essential for this process to work.
“If the nodules on the roots of the clover are not pink, then it is not fixing nitrogen. If you haven’t got the soil biology working with the clover, then it won’t fix nitrogen,” she said.
Bronagh O’Kane has been focussing on addressing imbalances in soil biology on her farm near Cookstown. This goes beyond visible earthworms and includes microscopic bacteria and fungi.
Visitors were told that soils on the farm are high in bacteria and low in fungi. This causes soil structure issues as fungi produce chemicals that bind soil particles together into large aggregates or clumps.
In a bid to stimulate soil biology and increase fungi levels, Bronagh has started producing an organic fertiliser known as vermicast, which is effectively made from the castings of earthworms.
There is an “earthworm farm” in a shed in the yard where vermicast is produced. Several large tubs contain worms and a compost mix, which is covered with roofing underlay.
The mix is made up of farmyard manure, straw and woodchips. The worms are fed regularly by sprinkling a mixture of pig meal and coffee grinds across the top of the mix.
Vermicast is harvested by putting the mix through a sieve. The worms and any large material are put back into a new mix. The finer particles that fall through the sieve are vermicast. This material is then put into a 400-micron pond filter bag and is dropped into a 1,000-litre cube of water in a process that is similar to making tea.
Bronagh uses a pond pump to help stir the mixture and then other additives, such as molasses, can be added too. The liquid is then applied to fields through a tractor mounted sprayer.