N still proving a popular chemical fertiliser

RESEARCH carried out by James Humphreys and colleagues in Teagasc in the late 1990s indicated that 200 to 220 units of N per acre were sufficient to support one cow per acre, without clover.

Many farmers were using 25% more than what was required, but there has been a huge cutback in N fertiliser since then without loss of production. The cutback was due to the rapid rise in fertiliser prices and nitrate restrictions. Figures indicate a reduction of 38% in fertiliser N usage since 2003.

With good quality clover swards such as at the Teagasc Solohead farm, 70 units of fertiliser N (including N for silage) are sufficient to support a stocking rate of at least 2.2 cows per hectare. This is higher than the rate that exists on most dairy farms depending on the chemical.