Determinants of spring barley yield in a high-yield potential environment

The literature suggests that grain number largely determines and as such limits yield in barley. Many of the reported studies were conducted in relatively low-yielding environments and it is unclear if grain number is also a limiting factor in high-yield potential climates. Nor is it known with certainty what physiological or morphological traits must be targeted in order to increase grain number. A detailed programme of assessments was carried out on replicated field plots of a two-row spring barley variety (Hordeum vulgare L. cvar Quench) at three sites (Carlow, Wexford and Cork) in Ireland from 2011 to 2013. Plots were managed for high yield potential as per current best farm practice. Destructive sampling and in-field assessments were carried out at approximately weekly intervals from emergence onwards to gather growth, development and yield component data. Across nine site/seasons, grand means of 8·52 t/ha for yield, 18 419 for grain number/m² and 46·41 mg for mean grain weight were achieved. Grain number/m² accounted for most of the variation in yield and ear number/m² accounted for most of the variation in grain number/m². Early-season maximum shoot number/m² had little influence on harvest ear number/m². The period over which final ear number was determined was more flexible than the literature suggests, where the phases of tiller production and senescence varied considerably. Significant post-anthesis re-tillering occurred following the initial phase of shoot mortality at two out of nine site/seasons, but this appeared to contribute little to yield. Yield was positively associated with the proportion of shoots surviving from an early season maximum to a mid-season minimum (R ² = 0·62). Shoot size and weight at the beginning of stem extension had the largest influence on shoot survival, indicating that crop condition and hence growth and development pre-stem extension may be more important for shoot survival than growth and development during the stem extension period. Achieving high shoot numbers of adequate size and weight at the beginning of stem extension may be an appropriate target for establishing a high-yield potential crop.