Oats have traditionally been a major cereal crop in Ireland, with up to 650,000ha grown up until the middle of the 19th century. As well as being the major “fuel” for horses in that era, oats was important for humans and oatmeal formed a key part of the diet.

The health benefits of oat-based products are being officially recognised again. Its gluten-free status enables its inclusion in coeliac diets.

A recent report published by Fortune Business Insights forecasts that the value of the global oat market will increase by 33% over the period 2020-2027. These subtle shifts in consumer preferences present opportunities to Irish growers.

The research objectives

Ireland is recognised as the country with the highest yield potential in the world for oats, at an average yield of 7.1t/ha. However, genetic and agronomic progress in oats has been slow relative to other crops.

The overall challenge facing oat producers is the lack of yield and quality consistency across seasons. Factors such as lodging, fertiliser rates and limited knowledge of the factors influencing grain-fill, all contribute to this.

To help address some of these issues, a four-year PhD research project was sponsored by Origin Enterprises plc and the Irish Research Council under Professor Jimmy Burke at UCD. The objective was to determine the key agronomic factors influencing the production of milling oats.

Field trials were located in north Leinster on medium to heavy soils. The trials aimed to establish the role of variety, seed rate and plant growth regulator on grain yield and quality of spring- and winter-sown oats. This article presents the key findings from this research based on the average responses from four spring-sown and three winter-sown oat trials over three years.

Sowing date

Oat acreage has been relatively consistent in Ireland in recent years at 25,000ha, but the proportion sown as winter depends primarily on autumn planting conditions.

In this research, winter-sown oats yielded 9.13t/ha on average, with spring-sown oats yielding 7.2t/ha. Within these averages, winter-sown oats was more consistent across seasons. In 2018 it yielded 8.74t/ha compared with 4.75t/ha from spring sowing (Table 1).

In winter-sown oats, higher yield potential comes mainly from higher grain number/panicle, with higher grain weight also contributing.

Hectolitre weight was generally similar with winter and spring-sown, although kernel content tends to be higher in spring-sown oats.

Grain quality in oats is linked to grain-fill, with grain yield highly linked to grain number. If climatic conditions are poor during grain-fill (2018), this can create a situation where competition within the ear (panicle) leads to reduced TGW and kernel content.

Therefore crop management should target high grain number/m2 while still enabling good levels of grain fill to ensure quality. I should also note that lodging levels were lower in winter-sown oats.

Nitrogen responses

Its susceptibility to lodging means that nitrogen use presents a real challenge on oat crops. Some of the N rates applied in this research were higher than are officially allowed.

Yield and lodging responses to applied N are shown in Figures 1 and 2.

Yield increased up to 130kg N/ha in spring-sown oats and up to 170kg N/ha in winter-sown oats, where lodging was not a problem.

In spring-sown oats specific weight decreased as N rate increased, but this was not seen with winter-sown. However, while specific weight decreased with increasing N rates in the spring crop, kernel content actually increased slightly (0.8%) with higher N rates.

N application timing

A separate set of experiments was conducted to investigate the role of N timing on yield and quality. Three key timings were used – mid-tillering, GS30 and GS50. N was applied at the relevant growth stage in increments of 30kg up to 150kg N/ha for spring sown and 200kg N/ha for winter.

This trial focused on individual timings, with no combination of timings tested. With spring planting, earlier N applications resulted in significantly higher grain yield than the later application (Figure 3). This was due to increased panicle number and higher grains/panicle.

While overall yield was somewhat lower across all N rates at the GS50 timing, grain quality in spring oats increased with later N timings. Later application also gave increases in specific weight and kernel content.

This late application of N had no effect on crop lodging, regardless of application rate, but there was significant lodging observed at earlier application timings at the higher rates of applied N.

The impact of N rate and timing on the winter-sown crop is shown in Figure 4.

Variety responses

Genetic progress is delivered through oat breeding and breeders around Europe are now focused on developing varieties suitable for a new range of uses.

This research used Husky and Keely. Husky had a higher grain yield (7.36t/ha) than Keely (7.01t/ha) when spring-sown, with no differences observed when winter-sown.

The key difference between the varieties related to their yield response to N. The higher standing power of Husky conferred a yield advantage over Keely as the rate of applied N was increased. Husky continued to respond to applied N up to 130kg N/ha with lodging in Keely limiting yield response above 100kg N/ha.

This highlights the continued requirement for good lodging resistance, as Keely’s higher yield potential was restricted by lodging.

Keely had higher kernel content but there were no variety effects on specific weight. This is no surprise, as it is well known that oat quality is mainly linked with variety.

Higher seed rates

Significant yield responses were observed as seed rate increased in spring and winter-sown oats, with the increases more important when winter-sown. Increasing the seed rate from 250 seeds/m2 resulted in a yield increase of 0.3t/ha in spring oats with no benefit observed from increasing it beyond 350 seeds/m2.

In winter oats the difference between 250 and 450 seeds/m2 was 0.8t/ha.

This is due to some level of winter plant loss. Establishment was in the range of 80% to 81% in low seed rate plots in 2017 and 2019 but dropped to 51% after the cold conditions in the spring of 2018. Establishment also dropped by between 10% and 13% as seed rate increased up to 450 seeds/m2.

There is a classic negative relationship in oats between panicle number and grains/panicle. This sometimes leads to a compensatory effect as grains/panicle will be higher where panicle number is lower.

While this effect was observed, it did not result in yield stability across seed rates.

Specific weight and kernel content were unaffected by changes in seed rate with spring and winter sowing.

Importance of growth regulation

The use of plant growth regulators (PGRs) on oat crops has been a very important input in recent decades. On average, a yield response of 0.3t/ha was recorded, but at higher rates of applied N (>130kg N/ha) this response was in the range of 0.5t/ha to 0.6t/ha.

Any increases in yield components, such as ear number, were generally offset by reductions in TGW to result in similar yield levels in treated and untreated plots in the absence of lodging.

However, plant growth regulator does have some slight but consistent negative effects on grain quality. Small reductions were observed in specific weight and kernel content, although these are minor consequences when the risk of lodging is considered.

A key issue with PGRs in oats is that it can potentially be detected at trace levels in food products, and a move away from their use may be appealing from a marketing perspective.

However, such a move would require specific management to avoid crop lodging and the negative quality traits that come with it.

Push to milling

The results of this study demonstrate that the production of high yield and quality in oats is mainly affected by sowing date, variety, and applied N rate. In Ireland, an estimated 30% to 35% of oats is used for milling but this figure is over 70% in the UK.

While a good proportion of the other oat uses in Ireland is used to supply high-value equine oats, there is still considerable potential in the milling market in comparison to our nearest neighbours.

Milling oats command a price premium and the continued development of strong brands and marketing campaigns have the potential to lead to price benefits for growers who meet the specifications. Hopefully, the renewed interest in this crop can be translated into a sustained campaign to increase the value and profitability of oat production systems.


I would like to thank the Irish Research Council and Origin Enterprises plc for their funding; Professor Jimmy Burke for his supervision; Clodagh Whelan, Angela Ryan, and Brian Fitzpatrick in Backweston; and Danny Janssens and Nicholas McCabe for field access.