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.

No abstract

No abstract

Oilseed rape cultivation under organic farming conditions presents a high risk of increased incidence of weeds, pests and diseases, resulting in low rapeseed yielding capacity. The current study aimed to estimate the effects of nonchemical weed management methods: thermal, mechanical and self-regulation (natural weed / crop competition), on the incidence of fungal diseases in winter oilseed rape (Brassica napus L.) stands and on rapeseed yield in the organic production system. A field experiment was conducted in 2014-2017 at Aleksandras Stulginskis University's Experimental Station. The soil of the experimental site is Endocalcaric Endogleyic Luvisol (LV-can.gln). Under less favourable conditions for the occurrence of phoma stem canker, both thermal and mechanical weed control methods were shown to inhibit the spread of the disease in the oilseed rape crop compared with the selfregulation weed control treatment. However, under the conditions conducive to the spread of phoma stem canker, only mechanical weed control method in combination with the bio-preparations proved to be effective. In 2015 and 2016, the lowest incidence of the verticillium wilt was recorded in the oilseed rape plots where weeds had been managed by steaming. In 2017 significantly, from 2.3 to 3.3 times lower number of verticillium wilt-affected stems was determined in the mechanical weed control plots as compared with that in the plots where other weed control methods had been applied. Application of bio-preparations decreased the number of verticillium wilt-affected stems by on average 11.1-15.6%. The lowest incidence of dark leaf and pod spot was established in the plots where weeds had been controlled by water steam and no bio-preparations had been used. The bio-preparations were found to increase the severity of dark leaf and pod spot on oilseed rape siliques by on average 13.1-79.4%. Significantly the highest rapeseed yield in 2015 and significantly higher compared with self-regulation in 2017 was recorded in the mechanical weed control treatment, while in 2016 the highest rapeseed yield was established in the self-regulation treatment applied with the bio-preparations. In 2017, the verticillium wilt severity in the winter oilseed rape crop was found to negatively, strongly and statistically significantly correlate with rapeseed yield (r 2 = 0.69, P < 0.05).

In this study, our investigated hypothesis was that different pre-crops would have different effects on earthworm activity and soil CO2 emissions. We also hypothesized that a pre-crop clover–timothy mixture would perform best in terms of increasing the share of organic carbon in soil and, in this way, contribute to improving the sustainability of agroecosystems. The aim of this study was to explore the residual effects of using a 50-year-term of three different crop rotations and a continuous bare fallow period on soil CO2 emissions by investigating the soil earthworm populations, soil agrochemical properties, and winter wheat yields. A field experiment was carried out from 2016 to 2017 at Vytautas Magnus University in Lithuania (54°53′ N, 23°50′ E). The experiment was conducted in crop stands of winter wheat cv. ‘Skagen’, which were sown in three crop rotations with different pre-crops and a continuous bare fallow period. The pre-crop used for winter wheat in the cereal crop rotation (CE) was a vetch and oat mixture for green forage, LEG-CER; the pre-crop used for winter wheat in the field with row crops (FWR) crop rotation was black fallow, FAL-CER; the pre-crop used for winter wheat in the Norfolk (NOR) crop rotation was a clover–timothy mixture, GRS-CER; and finally, continuous bare fallow, FAL-CONTROL, was used as well. The highest soil CO2 emission intensity was determined after the pre-crops that left a large amount of plant residues (clover and timothy mixture) in the soil. Plant residues remaining after the pre-crop had the greatest effect on the number of earthworms in the soil after the harvesting of winter wheat. Winter wheat had the best yield when grown in grass and legume sequences. Crop rotation sequences that included perennial grasses accumulated higher contents of total nitrogen and organic carbon. The best values for the productivity indicators of wheat were obtained when it was grown after a fallow crop fertilized with cattle manure. An appropriate crop rotation that promotes the steady long-term contribution of organic matter and increases the content of organic carbon in the soil will have a positive effect on the agrochemical, biological, and physical properties of soil and agroecosystem sustainability; moreover, these effects cannot be achieved by technological means alone.