Nitrogen: To spread or not to spread?

As we move nearer the closed period for spreading chemical fertiliser – which starts mid-September – attention must now turn to building grass covers for the autumn period.

Having said that, grass growth is good with supply greater than demand, which is leading to farmers baling surpluses in many cases.

Farmers may be inclined to hold off driving grass growth as a result of the favourable growing conditions. But, naturally, grass growth rates will dip in the coming weeks, so that’s where fertiliser spread now will be effective.

Although the growth response to N fertiliser in autumn is best described as modest, there is an opportunity to extend grass growth – especially when ground temperatures remain on the high side and conditions are favourable.

Teagasc estimates the average response to every 1kg of N applied – during early August, early September and early October – in the graph below. Approximately 30kg of N/ha (24 units of N/ac) was applied to test response levels.

The grass growth response to the nitrogen application in early August was 27kg of DM (dry matter) per kilogram of N. In September, 19kg of DM per 1kg of N was achieved.

Naturally, the lowest response was in October, when a growth response of 10kg of DM per 1kg of N was recorded.

So now is the time for farmers to put a plan in place when it comes to fertiliser. Teagasc recommends that farmers continue to spread N in the form of protected urea.

The amount of N spread will depend on the stocking rate on each individual farm an how much N has been applied so far. Farmers should adjust application rates as required.