Up the N for max protein: higher rates of fertiliser N will be needed to secure a breadmaking premium on high yielding milling wheats

摘要

There's no escaping the annoying fact that high wheat yields equal grain protein dilution, with the threat of scuppering a milling premium. When you add the yield-boosting strob factor to the equation, the answer comes firmly in favour of adding extra nitrogen. The key question is by how much and when? If you're milling wheat consistently falls short of the milling protein target of 13 percent, the general rule of thumb to raise grain protein by 0.5 percent is to apply about 30kg/ha, according to DEFRA's RB209 fertiliser handbook, points out ADAS's David Parish. "A feed wheat needs about 180-220kg/ha to get the optimum yield, depending on the level of soil nitrogen fertility left by the previous crop. For low to medium yielding milling wheats an extra 40kg/ha may be necessary. But high yielding bread wheats Xi19 and Malacca, need much more--a further 80kg/ha," he says. So for high yielding bread wheats that's a total of 300kg/ha -- at least 50kg more than many growers might anticipate. The main nitrogen dressing should be split applied at early and late April. There is, of course, the option to use 40kg/ha of this amount a little earlier to boost tiller numbers, and many growers may have done just that this season, he points out. As for the 80kg/ha protein boost, he suggests: 20kg/ha of ammonium nitrate during late April with the main dressing 40kg of ammonium nitrate in the third week of May 20kg/ha foliar spray in late June/July, at milky ripe stage. When calculating fertiliser requirements,we tend to use the economic optima rather than the biological optima, he points out. So adding 20kg or even 30kg of that protein boost fertiliser during late April might also help to boost yields too. Growers worry needlessly about wasting N by applyingammonium nitrate in May, he says: "You only need 2mm of rain before grain filling at the end of June to utilise the fertiliser. And the dilution effect of greater yield will be balanced by the May nitrogen application."