Nitrogen: is it time to change the guidance for oats?

Oats often stand in the shadow of its more widely grown cereal ‘cousins’. However, new research has put oats in the spotlight and helped close nutrient management knowledge gaps for nitrogen and sulphur.

The AHDB Early Bird Survey of planting intentions shows a decrease in the oat area over the last few seasons. Since the turn of the century, however, long-term trends reveal a relatively dramatic rise in the production and consumption of oats (albeit from a relatively low baseline).

Associated with a lower cost of production and increasing demand, oats remain a strong option for the arable rotation. To get the most from the crop, farmers need robust nutrient management guidance. However, compared to the arable crop ‘big guns’ (wheat, barley, and oilseed rape), investment in in agronomic research for oats has been relatively low. This holds back the potential of oats, especially in a market increasingly focused on quality. Oat millers require grain with a good specific weight and low levels of screenings, which are relatively easy to dehull and possess good kernel content.

In 2016, AHDB published the results from a comprehensive review of guidance from the Nutrient management guide (RB209). It revealed numerous knowledge gaps for winter and spring oats. At that time, the data (although limited) did result in increased nitrogen recommendations for winter oats – by 40 kg nitrogen/ha, for all soil nitrogen supply (SNS) indices and soil types. However, the absence of robust data for spring oats resulted in no change to the guidance. Information on optimum timing was also lacking for both crops.

In 2018, AHDB commissioned work to help plug RB209’s evidence gaps for oats. In addition to analysing a database, the ADAS-lead team conducted nitrogen rate and timing experiments on winter oats (Herefordshire and Nottinghamshire) and spring oats (Cambridgeshire, Lincolnshire, Suffolk, and Fife) across three harvest seasons, on several varieties. To supplement the core trials, the researchers analysed results from numerous other trials and investigated the effect of sulphur.

The project recently delivered its final report, with key findings outlined by ADAS researcher Sarah Clarke at the AHDB Agronomists’ Conference 2022.

• Numerous challenges were encountered during the core trials, such as high lodging (Herefordshire) and dry conditions (Nottinghamshire)
• Overall (all trial data sets), it was concluded that RB209 recommendations are generally appropriate for yield and quality
• However, the researchers did propose a new system for nitrogen-rate recommendations that removes the soil type categories from the RB209 tables, while retaining the focus on SNS indices
• They also demonstrated the potential to adjust nitrogen rates for expected yield (up or down from a yield benchmark), following a similar approach for spring barley
• Increased nitrogen rates influenced quality, increasing screenings and kernel content, while reducing specific weight – although, RB209 rates were shown to be acceptable
• The research also emphasised the influence of variety on grain quality, with some varieties being inherently more stable

• In general, current nitrogen recommendations may be too low, by around 25–30 kg nitrogen/ha
• The researchers warned that any decision to increase nitrogen rate must consider lodging risks
• There was no clear evidence that higher-yield spring crops required more nitrogen
• The application of a good proportion (at least 40 kg nitrogen/ha) to the seedbed and the remainder by the start of stem extension was associated with better and more consistent yield and quality
• Higher nitrogen rates were sometime associated with reduced quality (for some traits)
• More research is required to improve the strength of guidance for spring oats

• Where deficiency risks were high, such as on lighter soils, sulphur applications significantly improved yield
• However, variety had a greater effect on all grain quality traits measured than the addition of sulphur

This article is based on AHDB Project Report 643: Nitrogen and sulphur fertiliser management for yield and quality in winter and spring oats.

The work was led by researchers at ADAS and co-authored by a team at Aberystwyth University. The report also includes a list of recommended research activity.

Project data also informed the results of fast-track research that reported in spring 2022, which took account changes in the break-even ratio (BER) between grain and fertiliser prices, extending BER tables to account for higher fertiliser and grain prices.

The project has advanced understanding of nutrient management in oats. The conclusions are being considered by the body responsible for revising the AHDB Nutrient management guide (UK Partnership for Crop Nutrition).

A NIAB-led project on milling wheat has also delivered its final report to AHDB, providing evidence for nitrogen and sulphur fertiliser management guidelines.

Project results were presented at the AHDB Agronomists’ Conference 2022 by Sarah Clarke (ADAS).