Climate warming and a shift in the timing of phenological phases, which lead to changes in the duration of the vegetation period may have an essential impact on the productivity of winter crops. The main purpose of this study is to examine climate change-related long-term (1961-2015) changes in the duration of both initial (pre-winter) and main (post-winter) winter wheat vegetation seasons and to present the projection of future phenological changes until the end of this century. Delay and shortening of pre-winter vegetation period, as well as the advancement and slight extension of the post-winter vegetation period, resulted in the reduction of whole winter wheat vegetation period by more than 1 week over the investigated 55 years. Projected changes in the timing of phenological phases which define limits of a main vegetation period differ essentially from the observed period. According to pessimistic (Representative Concentration Pathways 8.5) scenario, the advancement of winter wheat maturity phase by almost 30 days and the shortening of post-winter vegetation season by 15 days are foreseen for a far (2071-2100) projection. An increase in the available chilling amount is specific not only to the investigated historical period (1960-2015) but also to the projected period according to the climate change scenarios of climate warming for all three projection periods. Consequently, the projected climate warming does not pose a threat of plant vernalization shortage in the investigated geographical latitudes.

One of the reasons why the area sown with oilseed rape in organic farms is not expanding is problems with weed, disease, and pest control as well as low seed yield. There is a lack of investigations on oilseed rape cultivated in an organic system, especially employing innovative weed control methods. To fill this gap in knowledge, field experiments were conducted at the Experimental Station of Aleksandras Stulginskis University in 2012-2013 with the aim of identifying and assessing the impact of different non-chemical weed control methods (thermal -TWC, mechanical -MWC and smothering -SMT) on weed competitiveness in winter oilseed rape (Brassica napus L.) crops during the autumn vegetation period in an organic farming system with and without the use of plant bio-activators in a soil with a regular (23-25 cm) (1 st experiment) and with a thickened (48-50 cm) (2 nd experiment) humus layer. It was found, that compared with thermal and mechanical weed control, in the treatment using smothering weed control and spraying with plant bio-activators or not spraying, the density of winter rape crop in the soil with a regular humus layer was significantly (P ≤ 0.05) lower (1.2 to 5.3 times); in the soil with a thickened humus layer, the density of winter rape crop was 1.5 to 5.9 times lower. In winter oilseed rape during autumn vegetation period, 20-22 weed species were found, including 18-19 annuals. Stellaria media (L.) Vill., Veronica arvensis L., Sinapis arvensis L. and Capsella bursa-pastoris (L.) Medik. were the predominant weeds.In the soil with a regular and a thickened humus layer, thermal and mechanical weed control significantly (P ≤ 0.05) decreased the number of weed seedlings (1.1 to 1.9 times) when plant bio-activators were used compared with the smothering treatment. Weed control in the smothering treatment in the soil with a regular and thickened humus layers was not effective. Mechanical weed control was more efficient than thermal. Application of plant bio-activators increased the efficiency of the thermal weed control.

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Equally effective way to achieve sustainable farming and the challenge set by the European Commission on 20 May 2020: proper crop rotation and thus reduction of the quantity of on-farm chemicals. Long-term stationary field experiments were established in 1966 at Vytautas Magnus University Experimental Station (54°53′ N, 23°50′ E). The study was conducted with intensive, three-course, field rotation with row crops, for green manure crop rotations, and rye monoculture as well during the last 5-year period of a 50-year investigation to determine the effect of crop rotation combinations and rye monoculture on weed density and seed bank and grain yield. In cereal crops, weed counting was performed twice: weed density was determined before the application of herbicides, and weed counting was done before the harvest. Weed seedlings were counted, their botanical species were determined, annual and perennial weed number was estimated. Weed seed bank was established before primary tillage in soil. The results obtained confirmed the hypothesis that with climate change and intensive farming, long-term crop rotations are likely to increase crop productivity, reduce weeds and weed seed banks in the soil, and thus contribute to maintaining agroecosystem sustainability. The winter rye 1000 grain weight and yield decreases as weed mass increases showing strong negative correlations: y = 475.56 − 11.93x, r = −0.91, p ≤ 0.05; y = 82.97 −14.82x, r = −0.97, p ≤ 0.01. Reseeding of rye crops leads to a growing prevalence of weeds such as Equisetum arvense L. and Mentha arvensis. Crop structures these days are dominated by cereals, which inevitably increase the spread of weeds, and therefore, the importance of crop rotations increases in the context of intensive farming.

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