Getting the basics right is important in oats

Oats are well suited to our maritime climate and were once grown throughout Ireland, being more tolerant of marginal soils than other cereals such as wheat and barley.

In the 19th century, relatively little barley and wheat was grown in the country whereas the area of oats exceeded 1.5m acres. Since then, the area of oats has fallen globally.

However, there is now renewed interest in oats as a result of a new appreciation of the health benefits of oat grains. Oat grains do not contain gluten and substantial markets have developed for gluten-free oats which are produced without contamination from other cereals grains. Additionally, the consumption of oat grains has been shown to reduce the risk of diabetes and coronary heart disease.

Oat grains are a good source of fibre, essential amino acids, unsaturated fatty acids, minerals and vitamins. The value of oats as a feed for horses is well known, although the value of oats as a ruminant feed is often questioned. Many feeding trials, however, have shown that oats are comparable to barley and wheat as a feed for ruminants.

As a result of the fall in the acreage of oats, relatively little research has been conducted on the crop over the past few decades but research activity on oats is increasing as a result of renewed interest in the crop.

In Teagasc, research is focused on several key areas including seeding rates, nutrition, lodging and disease control, the objective being to optimise the management of the crop. This research is helping to provide an understanding of the crop and how it differs from other cereals. Some key points are given below.

Differences between oats and other cereal crops

Like other cereals, yield determination in oats is primarily governed by the number of grains which can be formed by the crop. While there are many similarities between oats and other cereals, there are also important differences. The most visible difference is the head of the oat plant which is called a panicle.

Oat panicles are divided into a number of horizontal layers called whorls. There are typically eight whorls per panicle. Each whorl has a number of branches. Grains are contained in structures called spikelets which hang off the branches. Spikelets generally contain two grains, a larger primary grain together with a smaller secondary grain.

Oat panicles are visibly different from the heads of wheat and barley, but there is also another important difference.

Oat panicles can produce a much larger number of grains compared to the heads of wheat and barley.

As a result, the formation of large number of heads is less important in oat crops compared to wheat and barley. For example, two-row winter barley crops typically require in excess of 1,000 heads/m2 to produce the number of grains required to optimise yield as two row winter barley heads typically only contain 15-20 grains. In contrast, oat panicles typically have 80 to 100 grains and are capable of producing much higher grain numbers per panicle.

Spring plant populations

Autumn-sown crops of Husky and Barra generally start the process of panicle formation in mid- to late February and have reached GS30 sometime in March. This year, however, crop development is running later than normal as a result of lower temperatures.

The plant populations of autumn-sown crops declines over the winter. This effect is more pronounced in crops sown at higher seeding rates (>400 seeds/m2) in which spring establishment can be as low as 65% of the seeds planted the previous October.

However, for autumn-sown crops, spring plant populations of 250 plants/m2 are adequate to produce high yielding crops. In addition, crops can compensate for lower plant populations by producing additional tillers and higher numbers of grains per panicle.

All cereal crops can compensate for low plant populations although the way that oat crops compensate for low plant populations differs from wheat and barley as the primary compensation mechanism of oats crops is to increase the number of grains per panicle whereas wheat and barley crops tend to produce more tillers.

Nitrogen fertilisation

Oat crops are quite flexible in their response to the timing of nitrogen fertilisation as long as nitrogen has been applied by GS32, in time to support the important stem extension phase of growth.

For index 1 soils, there is unlikely to be a yield response above 150kg N/ha and the economic optimum nitrogen rate will generally be between 120 and 150kg N/ha depending on field history and nitrogen mineralisation.

Although nitrogen rates of up to 185kg N/ha are allowed for winter oats where proof of high yields is available, the use of rates greater than 150kg N/ha will not result in higher yields.

Also, the use of higher nitrogen rates will predispose the crop to lodging pressure and will also decrease hectolitre weight which falls with increasing nitrogen application rates. Although yield will not be affected by the timing of nitrogen fertilisation or the manner in which nitrogen is split, the manner in which nitrogen is split does have an effect on hectolitre weight.

Research has shown that hectolitre weight increases with the proportion of the overall nitrogen application rate applied early in the growing season and a 50:50 split of nitrogen between GS30 and GS32 is recommended to optimise hectolitre weight.

Growth regulators

Two spray programmes are generally sufficient but the most critical crop growth stage for applying a growth regulator timing is GS32. Earlier growth regulator applications (GS30/31) can also be effective although the effectiveness of early applications of growth regulator are typically dependent on the temperature and the rate of growth at the time of application.

Some growth regulator products are approved for use up until GS39 and a late growth regulator application can often be more effective than an early growth regulator application at GS30 particularly if temperatures are low during the early part of the growing season.