Switching nitrogen applications on winter wheat to later in the spring could be key to boosting yields for three top growers striving to break world records in what so far is proving to be an extremely wet and frustrating season.

Most farmers will be keen to apply early nitrogen fertiliser to encourage backward wheat crops struggling to establish after heavy rains, and when that is completed they may be better off aiming to shift the timing of their nitrogen spreading slightly later than usual.

The three growers, along with fertiliser group Yara, are using two years of experience to tailor their nitrogen applications and so try to challenge the world record winter wheat yield of 15.6t/ha, achieved by New Zealand grower Mike Solari in March 2010.

Mr Solari’s brother, Richard, farms in Shropshire and clocked up a yield of 14.1t/ha in 2011 with the variety Oakley, and together with Colin McGregor in the Scottish borders and Will Osgerby in Humberside, he will be working to try to beat current top yields of 13t-14t/ha achieved in previous seasons.

“Getting the balance right will be difficult, with many growers itching to get an early nitrogen dressing on to encourage backward crops, but we would suggest being careful with the middle application and push more to a third or even fourth split,” Yara’s head agronomist Mark Tucker told Farmers Weekly.

After such a difficult season last year, Mr Tucker believes that filling the wheat ear in terms of grains per ear and grain size may be more important than targeting high ear numbers per square metre, and so a focus on later nitrogen timings may be the way forward to help fill the established ears.

“What we are looking for is to achieve the optimum size of the crop canopy to get top yields, and we suspect we should be looking at filling the ear and individual grains rather than producing too thick a crop,” he says.

Berwickshire grower and 2011 Farmers Weekly Arable Farmer of the Year Colin McGregor achieved his farm’s record wheat yield of 13.17t/ha at harvest 2011, growing the variety Grafton, with a population of 758 ears a square metre. However, yields fell dramatically to 6.31t/ha on one field, with an ear population of 725 at harvest 2012, in one of the wettest seasons on record.

Mr Tucker said the 2012 harvest crop showed tremendous potential, but the lack of sunshine and fusarium ear disease hit the yield potential. Therefore, he is considering to opt for a slightly lower ear population of 600-650 a square metre this season, but will be focusing on filling the ears. This is why he will be applying nitrogen later.

Many growers may tailor their nitrogen applications towards a three-way split of 25%/50%/25%, applied in late February/early March, late March/early April and late April/early May, but Mr Tucker points out that Shropshire’s Mr Solari, in his record 14.1t/ha harvest of 2011, split his nitrogen in four equal applications, with the final dressing being made in late May.

Mr Tucker acknowledges this might seem a lot of late of nitrogen, with 160kg applied in the last two applications, but he believes this could be the way forward to make sure the wheat ears are full and the grain plump.

New Zealand grower Mr Solari used a hefty 453kg/ha nitrogen on his record-breaking crop, suggesting nitrogen rates could go higher than the 320kg/ha used by his brother Richard. But perhaps equally important is when the dressings are made and how it is split.

Results from the 2012 harvest were largely a washout, with Mr McGregor blaming his poor 2012 harvest on the weather after his wheat yields fell sharply from a previous five-year average of almost 10t/ha. Humberside grower Will Osgerby’s yields from Oakley also dropped because of the rain, while Richard Solari did not take part in 2012.

Mr McGregor adds: “It started raining on 3 April last year and then we had 200% of our average rainfall for April, May, June and July, which, together with a lack of sunshine, hit yields”.

Arable land at his Coldstream Mains farm is currently very wet and he believes wheat yields have already been affected for this season. However, he believes feeding nitrogen to the crop through the season is key, with his preference being a four-way spring split of nitrogen fertiliser.

“Generally, we look to applying late nitrogen and favour a little-and-often approach,” he says.