Curbing nitrates near trout-lakes and rivers

AnotherLife: In harsher winters it was the slow seep of green into the hollows of the hillside's grassed-over potato ridges that encouraged hopes of spring.

Now, warmer rain - and a lot of it - has kept the hill green(ish) since autumn and raised the lawn ankle-deep around the frogs' pond. Primroses have beaten the crocuses into bloom, but the frogs, at least, have stuck to the Old Calendar, conjuring glittering spawn as usual, just in time for my birthday.

A few years back, when declines among the world's frog species were pressing for explanation, the role of nitrate fertilizers in the animals' breeding waters was a hot suspect in North America. Tadpoles were vulnerable, it seemed, even at nitrate levels acceptable for human consumption. There are, no doubt, other causes at work - "synergy" is the popular word - but excess nitrates, whether from chemical fertiliser or slurry-spreading, are no good for life in general. The EU's current arm-twisting over Ireland's nitrate levels is not just to bully the farmers.

With the switch of farm payments away from production, many grassland farmers will be using much less artificial fertilizer anyway - even, as with many part-timers in sheep country, abandoning it altogether. But this is the month when many intensive dairy and livestock farmers are hovering impatiently over the land, waiting for it to be dry enough to take a tractor's weight. The marriage of nitrates to the eager genes of perennial ryegrass are the standard presciption for early grazing.

The supremacy of ryegrass in Irish agriculture, both for early pasture and silage, has seemed a "given" of the countryside, accepted as sound and necessary however much it might limit biodiversity or bore the eye. But at a time when so much else is changing - not least, the climate - the future of ryegrass monocultures is being called into question. As nitrate use diminishes over wide areas of the island, traditional mixed swards of grasses and wildflowers could return after half a century - and with them, no doubt, a much richer variety of insects and birds.

In his heavyweight (but very readable) tome, Farming in Ireland: History, Heritage and Environment, UCD's John Feehan described the the "ryegrass revolution" that enthroned Lolium perenne so exclusively in the 1960s. "It managed to get the edge," he wrote, "not because of any great advantage in productivity over other species such as Timothy and cock's foot, but because of its slightly greater digestibility and an ability to withstand treading and repeated defoliation better than most." It also lapped up nitrogen so greedily that, on good soils, it could come to dominate a sward, even without reseeding, in two or three years.

Feehan is also senior editor of Tearmann, the Irish journal of agri-environmental research, and this has now published a significant report by Helen Sheridan and colleagues on experiments at Teagasc's research centre at Johnstown Castle. They showed that dry-matter yields from unfertilised mixed swards were almost 17 per cent greater than ryegrass-dominated control swards that had received large applications of fertiliser. In the experimental reseedings, mineral-rich ribwort plantain, ox-eye daisy, bird's-foot trefoil and wild carrot, and grasses such as cock's foot, Yorkshire fog and red fescue together boosted the nutrient value to livestock. "Animals like variation in their diet; it enhances palatability," adds the report. This comes afters a decade of research showing that plant productivity increases in ratio with diversity of species (as Charles Darwin said 150 years ago), that the land shows an even more sustained fertility and recovers more quickly from stresses such as drought.

In his Tearmann editorial, John Feehan reminds us that agro-chemical farming did not lift agriculture out of some traditional dead-end, but succeeded an already sophisticated and productive use of multi-species seed mixtures. "It is time to blow the dust off the farming manuals that were relegated to the top shelf with the triumph of ryegrass," he writes, "and breathe into their pages the new life that our modern understanding of ecology makes possible . . ." Forecasts of the impact of climate change already suggest that, as the east of the country runs dry in summer, livestock farming on grass will move west. It is here, in a countryside rich in trout-lakes and rivers, that nature has most to gain from curbing the run-off of nitrates (humans, too).

At lower inputs and on soils which are naturally less fertile, ryegrass loses its aggressive edge and local grasses move back in to make up perhaps half the sward. All of this supports Feehan's call for "a new research agenda for grassland management" and a look back across a whole century to mixtures such Eliot's Clifton Park Method, with its chicory, clover and kidney vetch.