Organic Trust News

May 2022

Pasture in Context

When a grassland farmer converts to organic production, it doesn’t take long to realise that the favoured grass of the nitrogen fuelled “green revolution” - Perennial Ryegrass (PRG) - is no longer centre stage.
Modern varieties of PRG have been selected and bred to perform predictably in a high input system. It responds well to inorganic fertilisers, can produce a high volume of grass with artificially accelerated growth, and can tolerate repeated grazing in a short rotation. Grown like this, it is a protein-rich grass but often low in energy and fibre, and it can be desperately deficient in micronutrients and secondary metabolites. Ryegrass isn’t the best species in a longer rotation. Its palatability drops considerably when it is not kept vegetative and is prone to lodge if allowed to grow tall. In a vegetative state, it tends to “melt” away in adverse weather, both drought and frost, and its shallow roots don’t stand up to winter grazing.
There is a well-researched symbiosis in a sward with PRG and white clover, where the nitrogen-fixing clover supports the nitrogen hungry ryegrass. This simple combination can work quite well, but it is a single trick mechanism, and with all simplified systems in ecology, it is vulnerable. Although white clover and ryegrass are persistent perennial plants, clovers stay completely dormant until the last spring frosts have passed and only fulfil their nitrogen-fixing role when soil temperatures are consistently above 10 degrees Celsius.
White clover is a legume, and as with almost all legumes, they are light-loving early successional plants. Its pioneering role in nature is to restore fertility to soil in the early stages after a disturbance before the plant community builds complexity. We have halted that succession in agriculture and have harnessed clover because it is very palatable high-quality feed for livestock. To maintain clover dominance in a pasture, it needs to be grazed or mown short and frequently.
Our love of clover dominance is one of the main arguments against allowing pasture to become more complex and grow longer. In diverse natural pastures, by definition, no plant dominates. Nitrogen is cycled through pasture plants in a multitude of ways. Clovers may take advantage of the niche and access to light during the period after grazing. As the pasture height increases, different soil microbes in the soil process fresh organic matter – the leaves and roots of plants or the dung and urine of livestock and wildlife. There is a multitude of diverse and resident nutrient cycling processes at play.
In a mixed pasture and the rising popularity of mixed-species swards, the power of diversity is coming to the fore as a low input, high production method, which is also excellent for soil health and animal nutrition. Ecologically this complexity is a lot more stable, but it is essential to manage it in such a way as to preserve that variety of species. Sown multi-species-swards (MSS) are often criticised for their lack of persistence, and this is partly down to management. The grazing and mowing regime used to halt succession and preserve the simple ryegrass, and clover sward will also simplify a more complex sward. The later successional species in a multispecies sward often need a longer time to recover after a grazing event; observing and planning for this can maintain the diversity of a sward indefinitely. This recovery period after grazing will change throughout the year depending on the speed of growth. All the species in a purchased mix may not recover at the same rate; therefore, the timing of your grazing events will favour certain species on a particular rotation, so it is important not to be too systematic. A good rule, which is somewhat counterintuitive, is to rotate quickly when growth is fast and rotate slowly when growth is slow. This rule helps to ensure the recovery period is adequate and, in turn, allows dynamic diversity within the pasture.

To sow or not to sow
The rise of research into sowing multi-species-swards is undoubtedly a welcome trend. They are a fantastic option to fast track pasture succession when seeding arable ground back into pasture or pasture ground that has been routinely reseeded with ryegrass.
However, the grazing management required to maintain diversity will also create diversity, especially on older, more natural pastures with a good local adapted seed bank present in the soil. So it is worth asking the question of whether or not there is a need to go through the fashionable but costly procedure of sowing new seeds. It is worth practising the management required to maintain and encourage diversity first and observing what happens before breaking ground.

Dock Beetles -The Green Armoured Alli.

Generally, docks are regarded as a problematic weed, and farmers have a low tolerance for its presence, despite having a robust taproot that breaks up compaction and helps maintain soil structure. Although they can contribute a minor amount to the diet of grazing animals, especially with micro-nutrients such as zinc and tannins, docks are generally seen as a significant problem in pasture. Their impact on yield is best understood in grassland; it has been shown that 5-10 docks per m 2 reduced weight harvested grass by 30%, although herbage remained constant.

There is a solution - a natural balancer - the Dock Beetle or Mint Beetle, Gastrophysa viridula, is a native, iridescent beetle ranging from blue, through green, to almost bronze as an adult, although green is most common.

The adult beetle occasionally attacks rhubarb, but they can only complete their life cycle on plants in the Rumex family, sorrel and particularly R. obtusifolius or broadleaf dock. The adult beetles emerge from winter diapause in late spring, the timing depends on temperature, and are most often seen on warm sunny days of May. Its larvae can strip a dock plant like a white butterfly caterpillar can destroy a cabbage plant.

After mating, the females can lay 1,000 eggs on the underside of the leaves in batches of about 30 tiny pale yellow rugby balls that turn orange before they hatch approximately seven days later. The beetles emerge and start feeding on docks in April and develop through three larval stages, which can completely defoliate a plant before they drop to the soil to complete their development through a pupal stage. It potentially has three generations through the dock season and can continually attack the host plant.

When looking for hostplants, dock beetles only move a relatively small distance, around eight metres. This limited dispersal ability means if you have dock beetle on your farm, you should count yourself lucky because farms that lost them due to pest management are unlikely to quickly get them back in sufficient numbers.

By shredding dock leaves before the plant flowers, the beetles act as a form of biological control. Studies have shown that the beetle alone can remove 79% of leaf area between August and September and that herbivory has a severe effect on the regrowth capacity of plants, root and seed quality and quantity.

Organic Demonstration
Farm Walks

Teagasc, Department of Agriculture, Food & the Marine and organic organisations invite all farmers and members of the public to see organic farming in practice and to meet and speak with the producers and sector’s experts.
Click here is see the full lineup and to register.

Contributions
Thank you to Louis Ward for the inspiration and source material on the dock beetles
For contributions just email clivebright@gmail.com

Organic Marts

Drumshanbo
May 21st
11:30 am

Contact 0719641116

KILMALLOCK
May 14th
11:00 am

Contact 063 980 50

COOTEHILL
May 13th
6:30 pm
Cattle only

Contact 086 179 0929

1st - 31st May

The National Biodiversity Data Centre hosts a month-long (virtual) Festival of Farmland Biodiversity in May. The Festival aims to encourage a more positive engagement around biodiversity and farmland and highlight some of how farmers are working to support biodiversity on their farms. Click here to see the programme and use
#FarmlandBiodiversity on your social media posts.

Organic Trust News

May 2022

Organic Demonstration Farm Walks

Organic Demonstration
Farm Walks