In early spring the best of Mayo’s patient acres have been used to a pattering of 10-10-20 granules — a routine grooming with nitrogen, phosphorus and potassium.
This year, with fertiliser prices quadrupled to some €1,000 a tonne, many silage meadows must have received the barest dusting of fertiliser. A Government subsidy of up to €1,000 was offered late to restore the bagstuff.
A fodder crisis happens to match a peak in Irish grassland research. Farm science took decades to challenge cheap chemical nitrogen as the optimum path to growth. As meadows were turned to its use, most Irish fields turned the same brilliant but lifeless, pollen-bare shade of green.
Basic botany teaches that some plants produce fertility of their own. Legumes (peas, vetches, clovers, beans) grow nodules on their roots that work with soil bacteria to “fix” nitrogen from the air.
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Mixed swards with white clover, as now urged by Teagasc, can reduce nitrogen fertiliser by up to a quarter. But creating them needs reseeding of meadows and paddocks, a change in grassland happening at less than 2 per cent a year. As fuel costs soar, such use of a tractor is even less appealing.
Multispecies swards can grow a good weight of silage without chemical nitrogen. A mix of plants sends roots to different depths, reaching more nutrients and moisture.
Trials by Teagasc and UCD since 2012 have ended in promising “huge potential”. A blend of red clover with timothy, ryegrass, ribwort plantain and chicory grew as much herbage, with little or no fertiliser, as a ryegrass plot with the usual chemicals.
This spring UCD research also brought arresting and relevant results from a study of earthworm activity in the soil.
It was known that earthworms helped crop yields in the long run by their burrowing and feeding, creating good soil structure and releasing nitrogen locked away in the soil’s organic matter. The discovery by Prof Olaf Schmidt and a research team at UCD’s School of Agriculture and Food Science is that nitrogen released by worms and other soil animals “is going into crops really fast”.
In a shortcut not previously known, earthworms enrich soil and plants through nitrogen excreted through their mucus. Researchers “were astonished” at just how fast it moved through soil, to roots, into plants and into aphids feeding on their sap.
All this — many different plants, lots of earthworms — makes a soil much closer to the natural world than most farmland can offer.
Earthworm activity also has a role, however, in the soil’s release of two greenhouse gases, carbon dioxide and nitrous oxide. In laboratory experiments by Dr Schmidt’s research team a newly developed material with ancient origins was used to see how far it might lock up the carbon.
The material is biochar, a carbon-rich charcoal made from superheating plant waste with little or no oxygen (pyrolysis). With origins in terra preta, a layer produced in soils after ancient Amazon fires, it is now promoted for a plethora of farming, gardening and industrial uses.
The earthworm experiment showed that biochar can check release of the soil’s greenhouse gases and lock away more carbon. This is one of many benefits advanced by the Irish BioEnergy Association (IrBEA).
Highly porous and absorbing, biochar can bind with nutrients and moisture and shelter the soil’s myriad micro-organisms. Mixing with slurry or poultry litter makes a fertiliser and cuts down its smell. Mixed with cattle feed, as trialled on a farm in Co Kildare, it captures methane produced in the gut.
Used in building materials such as bricks and plaster, it insulates walls and turns houses into permanent stores of carbon.
Its properties can vary with what’s burned to make the charcoal, and the manner of production. In 2019 the Farmers’ Journal reported that rushes from Irish farms have been converted into biochar “worth €1,750 per tonne on world markets”.
Bracken, scrub, wood waste and various manures are other choices for feeding a biochar heating machine, an operation that warrants farmer training. Properly done, some research suggests, the final biochar stores more than half the carbon of the original biomass, perhaps for thousands of years.
As a way of turning waste into a versatile and useful material, biochar seems a gift to the circular economy demanded for a sustainable world. The first Irish suppliers have websites and the IrBEA urges wider production.
“Great progress” in understanding biochar is acknowledged by the Ithaka Institute, a leading carbon research foundation, in framing a voluntary European Biochar Certificate to govern biochar production and uses. It predicts a continuing surge in the use of a material that most people have never heard of, but is advanced as a key technology in the future of the planet.