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First-cut silage yields can be increased by nearly 30% simply by applying the first nitrogen of the season as two splits in relatively short... How better fertiliser timings boost first-cut silage yields

First-cut silage yields can be increased by nearly 30% simply by applying the first nitrogen of the season as two splits in relatively short succession, suggest trials.

The type of nitrogen source – including sulphur and using true granular compounds rather than blends – can also boost Nitrogen fertiliser Use Efficiency (NfUE), according to findings from CF Fertiliser.

“It has to be the focal point for grassland producers moving forward,” says the company’s Mark Garrett.

“Maximising NfUE ensures as much vital nitrogen goes into plants to stimulate growth – rather than leaving the system where it could cause environmental concerns and economic loss to the farmer.”

The recommendations on application timings are the culmination of four years’ work. As well as timings, the study examined various intervals between splits to see if these had any major effect on efficiency.

Fertiliser Manual RB209 says farmers should consider split applications if applying more than 80kg N/ha for first-cut silage. Doing so reduces the chance of losing nitrogen when a single large application is made.

“The traditional RB209 view is that this second application should be made four weeks after the first one and this is something we have followed in the trials,” says Mr Garrett.

“But whenever we have carried this out, we have seen a significant drop off in yield of first cut silage compared to when all the nitrogen is applied as a single application.”

The trial examined the effects of applying 120kg N/ha as a single application; the same amount but with 80kg applied first followed by 40kg four weeks later; and the same split but with only one week between applications.

When cut eight weeks after the first application, the all-in-one approach delivered a yield of 6.83t/ha DM, the four-week interval produced 6.10t/ha and the one week interval yielded 7.86t/ha.

Splitting applications with a four week gap reduced yields gave the lowest yield, says Mr Garrett. But the same split with one week between applications produced 29% more than the four week interval and 15% more than the single application.

“The results suggest that you would be far better off applying your first cut nitrogen as two splits with one week between them than either as a single application or two splits with four weeks interval.

“What is really impressive is that simply applying the second application at one week rather than the traditional four weeks added 1.76t/ha DM to first cut yields for the same overall amount of nitrogen applied.”