A rethink of fertiliser nitrogen recommendations for winter barley crops could be on the horizon with GrowHow suggesting changes to the timings and amount applied, based on three years of trials.
Work carried out by ADAS at two sites on GrowHow’s behalf suggests that applying as much as half of the crop’s nitrogen requirement in late February increases both grain and straw yields, while reducing grain N levels.
Furthermore, the results indicate that high yielding crops could require more nitrogen than current Fertiliser Manual recommendations advise, with growers being urged to apply an additional 20kg/ha for every expected tonne above 7t/ha.
Six nitrogen rates, ranging from 0 to 300kg/ha of N, were applied at two different timings on two-row variety Saffron and six-row type Pelican. The early timing, which involved a 50:50 split in February and at GS30, was compared with the Fertiliser Manual approach of 40kg applied towards the end of February, with the remainder going on at early stem extension.
Early nitrogen delivered up to 0.4t/ha more grain and about 0.5t/ha additional straw, reports GrowHow’s Allison Grundy.
“It also reduced the grain N% by about 0.1%. So this approach could be used on both malting and feed varieties, as the reduction in grain N concentration offsets the higher N rate.”
However, early nitrogen also increases the height of the crop and the lodging risk, she acknowledges, making it important to get the PGR programme right. “Otherwise, you risk losing the benefit of early applications.”
Concerns about the lodging risk and the suitability of the proposals for malting varieties mean that agronomists are taking a more cautious approach.
Chris Bean of UAP says that higher rates of nitrogen are already being used in the field, reflecting the yield potential of modern varieties.
“The Fertiliser Manual rates are being exceeded. The wheat rates changed when the manual was revised, but the barley figures remained the same. Many feel that it’s time to re-consider, so these trials are of interest.”
But he adds that malting barley specifications have also changed, making it important that growers seek advice if they are intending to alter timings and rates. “And the critical factor is that you must keep crops standing. Don’t jeopardise that.”
Ben Freer, regional agronomist in the south and west with NIAB TAG is not convinced that timings should alter much. “We always aim to have all the nitrogen on by the end of March, especially on malting varieties.”
He usually advises an early application of one third of the total nitrogen, with the balance being put on before April. “We’re unlikely to exceed a total of 180kg on feed varieties, with malting types getting around 150kg/ha.”
Malting recommendations are led by the market, he stresses. “It’s important that you check their requirements for grain N. Timing is less important.”
He points out that lodging isn’t the only danger of applying too much nitrogen too soon. “If that application coincides with a wet period, it all gets washed down before the crop can use it.”
[web only last para] Dave Robinson of Frontier Agriculture says putting nitrogen on early encourages straw growth, he explains, which is why malting varieties have a reputation for being weak strawed. “You will have to be very diligent with PGRs if you go down this route.”