Nitrogen management in spring malting barley for optimum yield and quality

Abstract

A series of trials investigated the agronomy of spring malting barley grown with high levels of applied nitrogen (150-200 kg/ha N). Growth regulators, seed rates and number of nitrogen applications (splits), and their influence on nitrogen dose response, were examined in trials run at four sites in England and one in Scotland. The trials were conducted over three years, 2002-2004, with varieties Optic and Cellar.

In most trials the yield response to nitrogen rates between 150 kg/ha and 200 kg/ha was fairly flat. Higher rates frequently produced excessive grain nitrogen and the optimum rate was usually 150 kg/ha, particularly for Cellar. In the Hampshire trial in particular, Optic occasionally maintained grain N in the target range (1.65-1.85%) with 175 kg/ha.

Growth regulators were rarely required for lodging control, lodging being infrequent throughout the trial series. In 2002, fertile tiller numbers were unusually high at some of the trial sites, which led to a high proportion of small grains and hence high screening levels. A sequence of Moddus followed by Terpal prevented excessive tiller numbers, thereby reducing screenings. However, this effect was most consistent with higher rates of applied N (e.g. 175 and 200 kg/ha), which tended to produce excessive grain nitrogen, a parameter which was not influenced by growth regulators in this case. At the more appropriate 150 kg/ha level these growth regulator effects were less consistent. These effects were also not seen in 2003 and 2004, when excessive screenings were not a significant problem.

Despite this, small yield increases seen with a single Terpal treatment (rather than the Moddus/Terpal sequence) were sufficient to make this treatment cost-effective at two of three sites.

Seed rate studies looking at 200, 300 and 400 seeds/m2 indicated that occasionally 200, but more often 300 seeds were adequate, with either a low (100 kg/ha) or a high (175 kg/ha) rate of applied nitrogen. High grain nitrogen levels seen with the higher applied nitrogen rate were reduced with the higher seed rates, particularly where growth regulators were used, but these effects were small.

Splitting the applied nitrogen, i.e. applying it in more than one dose, was beneficial to yield and grain quality with the higher rates of N, but again 150 kg/ha was a safer rate in terms of optimum yield and reliability of keeping grain nitrogen in the required range. At this rate of applied N, there was no disadvantage in applying a single dose at early crop emergence.