Enrichment of the selenium concentration of cereals under organic and conventional management practices

Abstract

Selenium (Se) concentration of the major cereals has declined during recent times. At present, selenium malnutrition is a human dietary crisis which affects approximately 1 billion people worldwide. Key strategies are therefore urgently needed to increase the selenium content of major foods such as cereals. Therefore, the overall aim of this study was to evaluate the potential to enhance grain yield, quality and selenium content of wheat through agronomic management (crop protection, fertiliser type, crop species/variety) and selenium fertilisation. The effects of soil and foliar applications of selenium fertiliser on grain selenium concentration and yield of cereals were studied using a systematic review and meta-analysis approach. Results showed that soil and foliar selenium application significantly increased grain selenium concentration without affecting yield, indicating that supplying selenium does have positive effects. Field and glasshouse trials were conducted in 2016-2018. In 2016, four different fertiliser types (farmyard manure, mineral N, biogas digestate and cattle slurry) were studied with and without crop protection for their effect on the yield, quality and grain selenium concentration of the spring wheat variety Mulika. Results showed that the organic crop protection treatment significantly increased grain selenium concentration, but grain yield and grain quality (protein content, Hagberg falling number (HFN) and hectolitre weight) were significantly lower. Biogas digestate increased grain yield and protein content while grain selenium concentration was significantly higher in response to composted farmyard manure use than for the other organic fertiliser and mineral N treatments applied. In 2018, a selenium fertiliser response field trial showed that there was no significant effect of selenium application method (soil vs foliar) or rate applied (0, 15 and 30 g Se/ha applied via the soil and 30 g Se/ha of foliar applied) on crop growth, grain yield and quality. However, there were significant effects of method of application and rate on selenium accumulation in different plant tissues, with the highest concentrations in the leaf at GS55 and GS70 and then in the grain at final harvest. A glasshouse trial was also conducted in 2018 to look at the effect of soil application rate at 0, 15 and 30 g Se/ha. It showed no effect on grain yield and protein content, but selenium application significantly increased plant tissue concentrations such that at final harvest highest concentrations were in response to 30 g Se/ha. Grain samples were analysed from previous EU funded trials: Nitrogen Use Efficiency (NUE-CROPS), Healthy Minor Cereals (HMC) and Quality Low Input Food (QLIF) to evaluate the effects of wheat species/variety, fertiliser type and crop protection on grain yield, quality (protein content), thousand grain weight and grain selenium concentration. Results in all trials indicated that fertiliser type significantly affected grain selenium concentration. Grain selenium concentration in the NUE-CROPS and QLIF trials was significantly higher in response to composted farmyard manure than to the mineral N treatment, while in the HMC trial, composted farmyard manure resulted in a significantly higher grain selenium concentration than biogas digestate, cattle slurry and mineral N treatments. Crop protection treatment also significantly influenced grain selenium concentration in the QLIF trial. In terms of wheat species, spelt wheat had greater grain selenium compared to common wheat, but this was across trials carried out in different years. Data from the current study show that grain selenium concentrations can be improved through agronomic management of cereal crops via selection of fertiliser type, crop protection, crop species and variety. Pot and field-based studies also show that grain selenium concentration can be increased significantly via the use of selenium fertiliser, where a rate of 30 g Se/ha led to the greatest increases and soil-based application was more efficient than foliar.