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.

Environmental factors, including weather and soil conditions, can affect the competitive effects of weeds on crops. This work aimed at a comparison of the competitive abilities of winter wheat toward bentgrass (Apera spica-venti (L.) P. Beauv) with single herbicide resistance, multiple herbicide resistance, or a susceptible biotype in different environmental conditions of Poland. A replacement series competition model was applied in field conditions in 2017–2018 and 2018–2019 across the country. A competitive ratio (CR) was calculated for the relative biomass of plants and grain number. A canonical variate analysis (CVA) was performed for biological parameters and a day-difference in emergence between winter wheat and bentgrass with the hydrothermal coefficient and soil texture in all of the sites in each season separately. Winter wheat emergence was correlated with the amount of precipitation after seeding, and was fastest for five days in humid conditions, and slowest up to 22 days, when the precipitation in October was low. The CVA proved that winter wheat’s competitive effects toward the susceptible or herbicide-resistant biotypes of bentgrass are site-specific. During the dry season, the bentgrass biotype with multiple herbicide resistance was more competitive toward winter wheat than the susceptible one. The wheat CR < 1 with regard to biomass and both biomass and the grain number was in 64% and 50% of all the combinations with the resistant biotype. In conclusion, weather affects the competitive effects of winter wheat toward herbicide-susceptible or resistant bentgrass.

The profitability of growing soybean (Glycine max (L.) Merr.) is largely determined by the successful elimination of weeds and the weather conditions, the adverse effect of which can be minimized by the use of biostimulants. This study aims to evaluate the effect of several herbicides and biostimulants on the seed yield and contents of protein, fat, amino acids, and fatty acids in soybean seeds. The results demonstrate that the yield and quality of soybean seeds were most beneficially affected by the use of prosulfocarb immediately after sowing in combination with a subsequent foliar application of bentazone and imazamox with an adjuvant containing methyl oleate and fatty alcohol. This treatment ensured the highest seed yield (3.32 t ha⁻¹⁾, the highest contents in seeds of protein (342.4 g kg⁻¹ DM), phenylalanine (15.65 g kg⁻¹ DM), leucine (23.54 g kg⁻¹ DM), and most of the endogenous amino acids. All herbicide treatments increased the contents of tryptophan, serine, and glutamic acid compared to the seeds without herbicide treatment. The study results indicate that soybean responded positively to all biostimulants, as indicated by a higher seed yield (from 5.3% to 11.3%), plant height, and contents of tryptophan, serine, glutamic acid, cysteine, tyrosine, and C18:1n9c + C18:1n9t acids in the seeds.

Competitive ability of cereals against segetal weeds depends among other things, on soil properties and the weather. Concerning cornflower (Centaurea cyanus L.), this issue is poorly recognized, as there are no reports on the impact of environmental conditions on the competitiveness of wheat against susceptible and resistant biotypes. Our study aimed to evaluate the effects of site and weather conditions on the competitive effects between winter wheat (WW) and two cornflower biotypes, either florasulam and tribenuron-methyl resistant (R) or sensitive (S). The experiment was conducted in a replacement series model at six sites across Poland in three growing seasons. The competitive relations were determined on the basis of two indices, i.e., the relative biomass and the number of seeds produced by the tested plants. The relative yield of wheat and weed were plotted on graphs and fitted to one of five competition models. In addition, a competitive ratio (CR) was calculated on the basis of fresh plant biomass and the number of seeds. Correlation coefficients were determined between the length of the plant, yield, biomass, the number of seeds per plant, hydrothermal coefficient K, and soil texture. Biometric parameters of wheat for its competition with two cornflower biotypes were analyzed using canonical variate analysis (CVA). The number of days to WW emergence and the day-difference between WW and cornflower (B) emergence were also calculated. The environmental characteristics of the sites, i.e., hydrothermal coefficient K and soil texture, were used as categorizing variables. Drought generally favored the greater competitive ability of WW against B for both biomass accumulation and seed production. During the first season of the research (relatively dry), only in one case out of 12 cases cornflower was more competitive than wheat. In the second year of the experiment (dry season), the competition of WW against B for resources was lower. It depended more on the site than on the cornflower biotype or the proportion of plants in the mixture. Under high or optimal rainfalls (the third year of the experiment), the competitiveness of WW toward B was significantly lower than in years with rainfall deficiency. In addition, the ability of wheat competition against the weed may have been influenced by the earlier emergence of wheat than cornflower. Even though it was sown together with wheat, cornflower emerged 0–12 days later than the tested cereal. It was also noticed that wheat was more competitive on light soils against the herbicide-susceptible (S) biotype. In contrast, greater WW competitiveness was observed against herbicide-resistant (R) cornflower on heavy soils. In conclusion, winter wheat competitiveness against herbicide-resistant or herbicide-sensitive cornflower biotypes is significantly dependent on weather and soil conditions. It is therefore reasonable to study this phenomenon in more detail. It would also be interesting to learn more about the underground competition on varying soil types under different water availability.