Corn poppy (Papaver rhoeas L.) and cornflower (Centaurea cyanus L.) are two overwintering weed species found in crop fields in Europe. They are characterised by a similar life cycle, similar competitive efforts, and a spectrum of herbicides recommended for their control. This review summarises the biology and herbicide resistance phenomena of corn poppy and cornflower in Europe. Corn poppy is one of the most dangerous dicotyledonous weeds, having developed herbicide resistance to acetolactate synthase inhibitors and growth regulators, especially in Mediterranean countries and Great Britain. Target site resistance to acetolactate synthase inhibitors dominates among herbicide-resistant poppy biotypes. The importance of non-target site resistance to acetolactate synthase inhibitors in this species may be underestimated because non-target site resistance is very often associated with target site resistance. Cornflower, meanwhile, is increasingly rare in European agricultural landscapes, with acetolactate synthase inhibitors-resistant biotypes only listed in Poland. However, the mechanisms of cornflower herbicide resistance are not well recognised. Currently, herbicides mainly from acetolactate synthase and photosystem II inhibitors as well as from synthetic auxins groups are recommended for the control of both weeds. Integrated methods of management of both weeds, especially herbicide-resistant biotypes, continue to be underrepresented.

Under the pro-environmental principles of agricultural production, soil cultivation and organic fertilization are of particular importance as strategical elements in reducing weed infestation in the context of sustainable agriculture. The aim of this study was to determine the effect of long-term practices that are used in regenerative agriculture (reducing soil tillage, cover crop management, and mineral nitrogen fertilization) on canopy weed infestation and the elements of spring barley architecture. Understanding the impact of the studied factors influences decision-making regarding weed infestation control, and thus may contribute to a reduction in herbicide use. A two-factor field experiment was conducted using the split-plot method. The main factors were four cultivation methods: 1. conventional tillage without a cover crop, 2. conventional tillage + cover crop, 3. reduced tillage + cover crop, and 4. no tillage + cover crop. The subplot factor was differentiated via nitrogen fertilization, at 40, 80, or 120 kg N∙ha⁻¹. The research covered canopy weed infestation and the parameters of spring barley canopy architecture. The species composition; the number and weight of weeds; and, for barley, the leaf area index (LAI), density, length, and tillers were determined. The test results were statistically analyzed (ANOVA) in a series of experiments while using Tukey’s test for a significance level of p = 0.05. Additionally, simple linear regression analysis, principal component analysis (PCA), and data clustering (CA) were utilized. The study showed that simplified tillage contributed to reducing the number of weeds in the barley tillering stage, while also contributing to an increase in weed infestation during grain harvest. Plowing in the cover crop did not reduce the presence of undesirable plants in the canopy, while increasing doses of nitrogen fertilization contributed to a reduction in the number of weeds without affecting their mass. Weed infestation was also affected by meteorological conditions. Increased rainfall in the early stages of barley development benefits the number of weeds, especially in terms of traditional cultivation. Simplified tillage resulted in a reduction in barley density, height, and LAI, as well as an increase in the branching of the tested cereal. A significant negative correlation was also found between the weed infestation of the barley canopy and the characteristics of the canopy architecture. The PCA showed that the highest tillering of barley was provided at the lowest intensity of weed infestation. In turn, the CA indicated that the significantly higher LAI that resulted from a higher density and length of barley was attributed to the simplified cultivation treatments and the practice of direct sowing. It is a comprehensive method that can favor barley growth and development conditions while weakening weed infestation potential.

Rye brome is a rare and nuisance weed in winter wheat canopies. In recent years, farmers have complained about the inadequate chemical control of this species. This study aimed to assess the effectiveness of seed meals obtained from allelopathic crops as an environmentally-friendly alternative for the control of herbicide-susceptible (S) and -resistant (R) rye brome biotypes in winter wheat. The pot experiment was conducted in a greenhouse at the Swojczyce Research and Training Station in Wrocław (Poland) to determine the impact of seed meals from: Fagopyrum esculentum, Sinapis alba, Phacelia tanacetifolia, Lupinus luteus, Raphanus sativus var. oleiformis and Ornithopus sativus, at 1 and 3% doses. Wheat emergence (>90%) and early growth were not affected by the presence in the soil of seed meals (only at 1% concentration) from P. tanacetifolia and R. sativus. The efficacy of these meals (reduction of aboveground biomass) at rye brome control was the same as the herbicide or higher. Seed meals from P. tanacetifolia reduced the emergence of the S and R biotypes by approximately 70 percentage points (p.p.) and 30 p.p., respectively, and limited the initial growth of both biotypes. Addition to soil meals from F. esculentum and R. sativus generally reduced only initial weed growth.

Wild oat is a nuisance monocot weed mainly in cereal canopies. The increasing problem of herbicide resistance and the implementation of integrated pest management includes the use of seed meals from species with allelopathic potential. This study aimed to assess the efficacy of seed meals as an environmentally friendly alternative for the control of herbicide-susceptible (S) and -resistant (R) wild oat biotypes. A pot experiment was carried out under greenhouse conditions at the Swojczyce Research and Training Station in Wrocław (Poland) to determine the impact of seed meals from Fagopyrum esculentum, Lupinus luteus, Ornithopus sativus, Phacelia tanacetifolia, Raphanus sativus var. oleiformis and Sinapis alba at two concentrations—1 and 3%. The lowest percentage of seedling emergence was recorded after the application of S. alba seed meal. Seed meals from S. alba reduced the emergence of both S and R biotypes by approximately 82 and 61 percentage points, respectively, and limited the initial growth of both biotypes. F. esculentum, O. sativus and R. sativus seed meals generally did not decrease the number of seedlings. Almost all the seed meals inhibited the growth of the aboveground parts of the susceptible biotype of wild oat to a greater extent than the herbicide treatment.

Wheat malts are necessary to produce wheat beers. In this study, wheat was grown with addition of seed meals into the soil, to determine whether such agricultural practice could improve the quality of the grain and, therefore, improve the quality of wheat malt produced from these grains. It was determined, that malt produced from the grains of the winter wheat cultivated with the use of seed meals is characterised with improved technological properties, such as saccharification time, filtration time and extract content and some of the seed meals had a positive impact on the content of various volatile compounds present in the produced malts.

Rye brome (Bromus secalinus L.) is a species of monocotyledonous weed, threatening cereal crops. Producers in Poland have limited possibilities of chemical control of this rare species by active substances from ALS inhibitor group. It may result in resistance of rye brome onto herbicides. The aim of the study was signalling the threat of potentially resistant biotypes of rye brome in Lower Silesia. The efficacy of three active substances (sulfosulfuron, propoxycarbazone-sodium and pyroxysulam) was evaluated in biological tests. Among 20 analysed biotypes, only one showed susceptible to all active substances. The highest number of potentially resistant biotypes was found for sulfosulfuron. The threat of resistance to herbicides increased in the western part of the Lower Silesian Voivodeship and decreased in the fields with conventional tillage.