Impact of varying N fertiliser rate and timing on yield formation and grain filling in winter and spring-sown oats

Abstract

The influence of N timing and N rate on yield formation and grain-filling procedures in winter and spring-sown oats is unclear. Factorial trials investigating the effect of six rates of applied N fertiliser (0,30. 60. 90. 120 and 150 kg N ha−1) applied at three timings (Zadoks GS 21, 30 and 50) were conducted at four spring sown sites and three winter sown sites (Cv Husky) over the period 2016–2019 in the east of Ireland.Significant interactions were frequently observed on grain yield following spring and winter sowing, associated with increases in grain number where N was applied at early growth stages (GS 21, GS30) relative to GS50 application. This was linked with increases in panicles/m2 in response to available N during early developmental periods. Grain weight was maintained as the level of N applied at GS50 increased with reductions observed at earlier applications, but had no effect on yield.Responses to applied N rate were in the range of 0.5–1.9 t ha−1 in spring sown crops and 1.2–3 t ha−1 in winter sown crops, with grain yield reducing by 0.5–2.1 t/ha −1 (spring) and 1.2–1.5 t ha−1 (winter) as N application was delayed. N application timing impacted spikelet and grain number per panicle in winter crops, with spring crops unaffected.The relative importance of panicle number when spring sown, and grains/panicle when winter sown, is also discussed. This paper highlights the role of N application during early developmental in increasing the yield components contributing to grain number.