Effects on Yield and Quality of Strobilurin applications to Spring Malting Barley

Abstract

The influence of strobilurin fungicide programmes on the response to increasing levels of nitrogen fertiliser was evaluated, in terms of yield and grain quality for malt production. Trials were conducted at four locations over three years. Fungicide sprays containing low dose mixtures of Opus (epoxiconazole) plus Corbel (fenpropimorph) were applied twice, at GS 30 and GS 45-49. This 'conventional' programme was evaluated alongside strobilurin programmes, where the spray mixtures in the conventional programme were supplemented by full and half recommended rates of Amistar (azoxystrobin) or Ensign (kresoxim methyl plus fenpropimorph), at each fungicide timing. Together with an untreated control, this gave six fungicide treatments, which were applied across each of four levels of applied nitrogen, 75, 100, 125 and 150 kg/ha.

The shape of the nitrogen response curve was not influenced by fungicide chemistry. However yields were consistently higher where strobilurin fungicides were used, whilst still increasing as nitrogen dose increased. Full rate strobilurins in each spray gave higher yields than half rates, but full rates were not cost-effective, whether compared to the half rate, or the conventional programmes. The higher yields achieved with strobilurin fungicides did not lead to an increase in grain nitrogen levels. Where the overall grain nitrogen levels in a trial were low, conventional and strobilurin programmes produced similar levels. Where they were high, the higher yields achieved with strobilurins diluted the grain N, resulting in lower levels with these programmes. Strobilurins therefore reduced grain N from excessively high levels, and have little or no influence when levels were inherently low. This allowed the use of higher levels of nitrogen fertiliser than have been traditionally associated with a malt spring barley crop, without the risk of producing excessively high grain nitrogen content. At all trial sites, over three years the most cost-effective treatments involved two sprays based on half rates of Amistar, with 150 kg/ha applied N. However, the requirement for grain nitrogen levels in a certain band, rather than as low as possible, for most of the UK market, means that excessively low grain nitrogen may not be acceptable for a malt quality sample. Where applied nitrogen levels were kept low, the use of strobilurins on occasion reduced the grain nitrogen below the minimum level assumed for this project (1.6%). Nitrogen level therefore needed to be kept reasonably high where strobilurins were used, in order to reach the required grain nitrogen level. Specific weights, and screenings, were improved by fungicide treatment, but only in some cases was there a greater improvement from strobilurins than from conventional fungicides.