Urea treatment of barley grain. Effect on storage properties and fungal growth

Authors

• Asko Hannukkala Department of Plant Pathology, University of Helsinki, SF-00710 HELSINKI, Finland
• Pekka Huhtanen Department of Animal Husbandry, University of Helsinki SF-00710 HELSINKI, Finland

DOI: https://doi.org/10.23986/afsci.72233

Abstract

Barley harvested at three different moisture contents (22, 25 and 32 %) was treated with varying levels of urea (1.0, 1.5, 2.0 and 2.5 % on fresh weight basis) and stored aerobically in experimental silos of 400 liters. The chemical composition of barley was analysed before treatment and after 12 months of storage. Fungal contamination of grain samples was analysed. Application of 1.5 % or more urea effectively preserved the grain for 12 months. At the highest moisture content, 1.0 % of urea did not prevent deterioration during storage. The average recovery of dry matter was 97.1 %, of nitrogen 93.9 %. Ammonia was released from hydrolysis of urea. The degree of hydrolysis increased with increasing moisture content of barley. Raising the levels of urea from 1.0 to 2.5 % significantly increased the quantity but tended to decrease the proportion of urea hydrolysed. Representatives of 33 genera of fungi and unidentified actinomycetes were present in the grain lots examined. Most fungi were found only occasionally and their incidence declined towards the end of storage. The grain stored at the highest moisture level (32 %) contained more fungi and less actinomycetes than other seed lots. All urea treatments reduced the number of fungi on seeds. Urea concentration of 2 % or more eliminated Fusarium- and Aspergillus species on all moisture levels. Scopulariopsis brevicaulis (Sacc.) Bain, and other species of Scopulariopsis were the most commonly encountered fungi after urea treatment. The total number of Scopulariopsis ssp. exceeded 100 % and the amount remained high for 40 weeks of storage until a rapid decline towards the end of storage. Urea treatment also favoured the occurrence of actinomycetes.