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.

This study aimed to compare different herbicide application schemes in winter wheat, including the application of glyphosate-containing herbicides in stubble and autumn or spring post-emergence application. Field experiments were conducted in 2022–2024, on two different farms, with two fields selected each year on each farm, where the pre-crop was either winter wheat (Triticum aestivum L.) or oilseed rape (Brassica napus L.). Glyphosate application had a significant effect on weed biomass reduction if the pre-crop was oilseed rape with herbicide application in one of the years, but not if it was winter wheat. The effect of glyphosate application also depended on the year and was most pronounced in the year when the sowing was performed later, reaching up to 57% weed biomass reduction without the application of post-emergence herbicides. A positive effect of glyphosate application on the grain yield was observed if the pre-crop was oilseed rape. The application of post-emergence herbicides resulted in a median weed biomass reduction of 95–96% of the untreated control. Additional herbicide application in spring did not improve weed control nor result in a yield increase. The likely causes of this are the competitive ability of winter wheat, as well as lower weed density and deeper stubble cultivation in the trials where the pre-crop was wheat. Further trials must be conducted in fields infested with grass-weed species to compare the effect of one versus two post-emergence applications. Post-emergence herbicide application, but not glyphosate application, had a negative effect on the alpha diversity of weed species, whereas higher weed diversity was associated with a higher yield increase when the pre-crop was winter oilseed rape, in the absence of highly competitive grass-weed species.