By Joe Sheehy
Fertilisers are expensive, and must be used as efficiently as possible.
New reseeds and pastures that are high in ryegrass content will give at least a 25% better response to nitrogen, if that they have adequate lime, P and K.
More than 50% of our fairly good grassland areas contain too little ryegrass.
More than 50% of soil samples, many of which are taken from fairly high ryegrass areas, are too low in lime, P or K.
Therefore it can be concluded that farmers are wasting a lot of money on nitrogen fertilisers.
Many studies of this problem indicate that the average output from Irish pastures is only about 65% of its potential.
There are many situations where nitrogen can be cut back without loss of production, such as with proper use of slurry (applied in the spring), and clover.
Most of our slurry is still applied after first cut silage or during the summer.
If more of it could be applied in the spring, it would supply a lot of extra nitrogen.
Despite the proven value of clover, it was largely ignored by the majority of farmers until recently.
Bloat, which is often quoted as a reason for not using clover, is not a problem with clover pastures, if managed properly.
There was a traditional bias against clover among some farmers, advisers, and researchers.
However, research headed up by Moorepark researchers during the 19990s created new interest in clover, which is now bearing fruit.
In recent years, Teagasc trials at Moorepark and Clonakilty College indicated that including white clover in grass swards, receiving 200 units of nitrogen per acre, can increase production by 2.5 tonnes of dry matter per hectare (worth over €500).
Trials indicated that at moderate stocking rates of about 2.2 cows per hectare, €7,000 can potentially be saved off the nitrogen fertiliser bill on a 50-hectare dairy farm with a very high clover based pasture. For several years, this was achieved on the Teagasc Solohead farm, producing over 2,800 gallons milk per hectare, using only 72 units N per acre, with moderate levels of concentrate feed.
Even if part of a farm was converted into a high clover based sward with very low fertiliser N, it would give a significant saving.
Management of clover based swards is different to high-N swards, but not necessarily more difficult.
The best time to lay down a clover based sward is in the spring, or after a heavy crop of first cut silage by surface seeding into bare, clean ryegrass stubble.
A most urgent grassland job for every farmer right now is to carry out a proper soil test and eliminate soil deficiencies. Providing adequate lime and P can double the value of applied N and soil N.
In the peak growing season, on good quality ryegrass pastures that have adequate P, K, and lime, one bag of CAN can grow an extra 340 kg of feed dry matter, which is equivalent to over two tonnes of fresh grass or silage.
That is a financial return of around four to one.
As the season progresses, the response will gradually reduce.
As a result of soil tests, many farmers are applying straight K this autumn, thus reduce the dangers of grass tetany from spring applications.