Abstract
AbstractFactorial experiments were carried out on spring- and winter-sown oat crops in Ireland in 2016–2019 to identify plant responses in yield formation and grain filling procedures. Two cultivars (Husky and Keely), three seed rates (250, 350 and 450 seeds/m2), six applied nitrogen (N) rates (40, 70, 100, 130, 160 and 190 kg N/ha) with a plant growth regulator (PGR) were examined in spring and winter sowings, using the same cultivars at five rates of applied N (80, 110, 140, 170 and 200 kg N/ha). The applied N rate and seed rate significantly (P < 0.05) modified the yield components determining grains/m2 in spring- and winter-sown crops with increases in panicle number of key importance. Increases were also observed in the proportion of primary grain by weight (0.9–1.6%) and number (0.7–1.4%) ratios in spring-sown crops in response to applied N rate, with winter-sown crops exhibiting a more consistent pattern of grain fill. Seed rate and PGR application had minor effects on yield components and panicle conformation. Grain fill procedures played an important role in the maximization of grain yield under seasonal conditions. Significant positive correlations were observed between the number of aborted grain sites and yield under drought conditions (0.22), with negative associations observed in near-optimal conditions (−0.22 to −0.41). Agronomic effects on grain site abortion were minimal in comparison with seasonal effects. In seasons characterized by cool, consistent conditions, grain yield was maximized by the utilization of all available grain sites. Where assimilate shortages were encountered during grain fill the abortion of grains sites was positively associated with grain yield.
Highlights
Grain yield in oats is predominantly determined by grain number (Peltonen-sainio et al, 2007; Finnan and Spink, 2017) with grain weight of lower importance
Increases in panicle number accounted for yield increases in response to seed rate and N rate regardless of sowing date
This study demonstrated that oat grain yield under cool, humid conditions is associated with high levels of secondary grain fill
Summary
Grain yield in oats is predominantly determined by grain number (Peltonen-sainio et al, 2007; Finnan and Spink, 2017) with grain weight of lower importance. The response of oats to environmental variation is reflected in the plasticity of the key yield components responsible for the determination of total grain number (Mahadevan et al, 2016) with the following oat-specific hierarchy suggested: tiller number > grains/panicle > panicle number > grain weight, indicating the relative flexibility of tiller number and the stability of grain weight. This hierarchy may transfer to the capacity of an oat crop to respond to changes in agronomic practices. Establishing the impact of agronomic practices on the components contributing to total grain number and grain weight is a key target of this study
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