Cultivation of spring cereal mixtures (SCMs) is one of the ways to increase the yield of crops in mountainous areas of Poland. There are only a few current long-term studies on this topic. Our study aimed at analyzing yield and competitiveness as well as the economic indicators of spring cereals in pure or mixed sowings in integrated or organic crop rotations over nine years. A field experiment including pure sowings of oats, spring barley, or spring triticale and their two-component SCMs, each in two systems, organic and integrated crop rotation, was carried out in the Mountainous Experimental Station in Czyrna, Poland, in the years 2011–2019. On average, cereals in the pure sowings and mixtures yielded 18% lower in the organic rotations compared with the integrated ones. However, SCMs yielded higher than the pure sowings, and displayed a higher leaf area index and land equivalent ratio. The average gross margin without subsidies was almost two times higher in the organic crop rotations than in the integrated ones, which was influenced mainly by the cultivation of barley in pure sowing. Summing up, the cultivation of SCMs in the mountainous areas of southern Poland is advised because of both productive and economic factors.

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.

Caraway oil is a promising botanical herbicide. This study tested the phytotoxic potential of caraway oil, carvone and d-limonene on germination and seedlings’ growth of spring wheat, wild oat and chamomile. As a result, an inhibiting effect of caraway oil and carvone on all the tested species was found. Contrary, d-limonene displayed selective toxicity against chamomile and wild oat, which should be investigated further.

Caraway (Carum carvi L.) essential oil is a candidate for botanical herbicides. A hypothesis was formulated that the sand-applied maltodextrin-coated caraway oil (MCEO) does not affect the growth of maize (Zea mays L.). In the pot experiment, pre-emergence application of five doses of MCEO was tested on four maize cultivars up to the three-leaf growth stage. The morphological analyses were supported by the measurements of relative chlorophyll content (SPAD), two parameters of chlorophyll a fluorescence, e.g., Fv/Fm and Fv/F0, and fluorescence emission spectra. The analyzed MCEO contained 6.5% caraway EO with carvone and limonene as the main compounds, constituting 95% of the oil. The MCEO caused 7-day delays in maize emergence from the dose of 0.9 g per pot (equal to 96 g m⁻²). Maize development at the three-leaf growth stage, i.e., length of roots, length of leaves, and biomass of shoots and leaves, was significantly impaired already at the lowest dose of MCEO: 0.4 g per pot, equal to 44 g m⁻². A significant drop of both chlorophyll a fluorescence parameters was noted, on average, from the dose of 0.7 g per pot, equal to 69 g m⁻². Among the tested cultivars, cv. Rywal and Pomerania were less susceptible to the MCEO compared to the cv. Kurant and Podole. In summary, maize is susceptible to the pre-emergence, sand-applied MCEO from the dose of 44 g m⁻².

Essential oils are a rich source of compounds for botanical pesticides. This study aimed to characterize the chemical composition of essential oil from parsley seeds and its phytotoxicity against the germination and initial growth of wheat and mustard. The main compounds of the oil were α-pinene, β-pinene, and apiol. In a Petri dish experiment, the oil inhibited germination of seeds of both species. However, the growth of seedlings of both species was more inhibited, especially for wheat. In conclusion, parsley oil displays phytotoxic potential against the studied species, which should also be tested in soil conditions and against weeds.