Crop diversification in rotations is an important part of sustainable crop production. The aim of this research was to analyse soil tillage and crop rotation influence on the yield (t ha⁻¹) of different field crops, their energy yield (GJ ha⁻¹) and the economical profitability (EUR ha⁻¹) of crop rotation. The field trial was conducted in Latvia during four harvest seasons (2017–2020) in a long-term experiment that started in 2009. Three crop rotations with a different share of winter wheat (Triticum aestivum) were studied: 100% wheat (repeated sowings), 67% wheat (three-year rotation with winter oilseed rape (Brassica napus ssp. oleifera) and two years following wheat) and 25% wheat (four-year rotation: field bean (Vicia faba)–wheat–winter oilseed rape–spring barley (Hordeum vulgare). Conventional and reduced soil tillage systems were used for rotation variants. Crop rotations “67% wheat” and “25% wheat” ensured significantly higher average wheat grain yields in comparison to “100% wheat”. Wheat and oilseed rape were the most valuable crops in terms of accumulated energy and economic value in this trial. Higher energy yields were gained from variants in the rotations “67% wheat” and “25% wheat”. Average gross profit was higher from crop rotations with diverse crops, mainly due to the positive forecrop effect on winter wheat.

Winter wheat (Triticum aestivum) is a crop of which production is associated with rather large investments for nitrogen fertilization and disease control. The aim of this study was to estimate the effect of five variants of fungicide application and four levels of N (nitrogen) top-dressing rate on the yield and grain quality of winter wheat. Field trials were carried out in Latvia (56° 31′ N; 23° 42′ E) for four seasons. Grain yield and quality depended significantly on the conditions of the trial year, as three of them were characterized by drought in varying degrees. Although the average four-year grain yield increased significantly in all fungicide application variants, the effect of this factor was different in individual years. The application of fungicides increased the yield significantly in one year, decreased significantly in another year, while it had no significant effect on the yield in remaining two seasons. The enhancement of N top-dressing rate increased the grain yield significantly every year. The interaction between both examined factors was significant; however, the use of higher N rates not always means that also spraying with fungicides has to be more intensive. A clear effect of fungicide application was observed on 1000 grain weight and volume weight, while the effect of N top-dressing rate was observed on the crude protein, wet gluten and starch content, and Zeleny index.

Grain quality traits important in feed barley: Spring barley (Hordeum vulgare L.) traditionally has been a major cereal crop for animal feed especially in Northern areas and also in Latvia. It is complicated to define what the ideal feed barley should be, as the requirements widely differ not only for different species, but even for different age groups of the same species of animals. Therefore, the breeding of feed barley has been developing very slowly and building on the basis of agronomic and beer barley quality parameters. Targeted breeding of barley varieties for a definite application purpose of the grain is connected with selection according to different criteria. The present article shows that the feed quality of barley is influenced both by physical grain quality indicators (colour, grain weight and size, hull content, 1000 grain weight, volume weight and grain hardness) and by the chemical composition (carbohydrates, non-starch polysaccharides, amino acids, fibre, protein, fat, minerals and vitamins). On the basis of the information collected, a profile of a high quality feed barley variety for different groups of animals is defined.