The effect of nitrogen on grain yield and quality in oats

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

This research project investigated the effect of nitrogen rates, variety, and environment on grain yield components, nitrogen use efficiencies, milling quality characteristics, the nutritional composition, and whole grain and groat size parameters of winter and spring oats. The relationship between traits were also explored. Field trials were conducted at Aberystwyth (Wales), Carlow (Ireland), Balgonie (Scotland), Gleadthorpe and Rosemaund (England). Between 2017-2019 four winter oat varieties were tested under 6 nitrogen regimes from 0-280 kg ha-1 ; complementary winter oat trials were carried out between 2019-2021 which included three varieties and nitrogen rates from 0-300 kg ha-1. The results from these trials strengthened previous findings. Between 2019-2021 spring oat field trials were also conducted including three varieties tested under six nitrogen rates from 0-300 kg ha-1 . For all traits, the stability of the varieties’ performance in response to different environments were analysed to identify varieties that could maintain performance across a range of environments and in particular identify varieties that were well adapted to low yielding environments.
Several responses to increasing levels of nitrogen were found. For winter and spring oats, a curvilinear response was found for grain and biomass yield to nitrogen despite a positive linear response for nitrogen uptake and groat N %. Panicle numbers m-2 , grain number panicle-1 and grain number m-2 all increased with additional nitrogen, conversely individual grain weight was reduced. The yield component with the greatest association to grain yield was grain number m-2 which was highly influenced by grain number panicle-1 . Panicles m-2 had the greatest negative association with thousand grain weight, which could be limiting yield potential. Improving nitrogen use efficiency will also improve grain yield while minimising environmental impact. Grain screenings, kernel content, hullability, β-glucan and protein content increased with additional nitrogen, whereas specific weight and oil content were reduced. Non-destructive image analysis revealed that longer more slender grains were produced at higher nitrogen rates, and rounder more plump grains were produced at lower levels of nitrogen. The results emphasised the importance of variety choice when growing oats for the milling trade. In 2021, additional crop assessments were carried out during the season on the spring oat trial along with unmanned aerial vehicle (UAV) multispectral imaging. Relationships found between phenotypic measurements and vegetation indices will assist in machine learning to predict grain yield from UAV analysis and aid in precision farming, i.e., nutrient and disease management practices.
Date of Award2022
Original languageEnglish
Awarding Institution
  • Aberystwyth University
SupervisorCatherine Howarth (Supervisor) & Sandy Cowan (Supervisor)

Keywords

  • oats
  • nitrogen
  • milling quality
  • ß-glucan
  • UAV analysis

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