The efficiency of non-chemical weed control in winter rapeseed

There are favourable conditions for spread of weeds, pests and diseases in rapeseed crop grown in organic farming, and this is results in low rapeseed productivity. The aim of the research was to determine the efficiency of non-chemical weed control methods (thermal, mechanical and smothering) in winter rapeseed crop. Field experiment was carried out in 2014–2017 at the Experimental Station of Aleksandras Stulginskis University (54°53′ N, 23°50′ E). Soil – Calc(ar)i-Endohypogleyic Luvisol. Winter rapeseed (Brassica napus L. spp. oleifera biennis Metzg.), variety ‘Cult’ (3 kg ha-1) was grown in soil with a regular (23–25 cm) (Experiment I) and thickened (45–50 cm) (Experiment II) humus layers. Experimental treatments: Factor A: non-chemical weed control: 1) thermal (water steam); 2) mechanical (inter-row loosening); 3) smothering (self-regulation with narrow spacing); Factor B: use of bio-preparations: 1) no application, 2) with application (bio-organic fertilisers used: ‘Nagro’ applied for rapeseeds before sowing, ‘Terra Sorb Foliar’ was sprayed in autumn (2 l ha-1), and in spring – ‘Terra Sorb Foliar’ (1 l ha-1) and 0.3 % Conflic). In the winter rapeseed crop, annual weed species dominated: Chenopodium album L., Tripleurospermum perforatum (Merat) M. Lainz, Stellaria media (L.) Vill., Veronica arvensis L., Capsella bursa-pastoris (L.) Medik., and Poa annua L. During vegetation period of organic winter rapeseed crop, mechanical weed control was the most effective method both in autumn (efficiency was 26.8–71.5% in the soil with regular and 40.6–76.0% with thickened humus layers) and in spring (efficiency was accordingly 36.9–76, 5% and 46.4–73.3%). The effectiveness of thermal weed control compared to mechanical was lower. Bio-preparations increased the effectiveness of thermal and mechanical weed control methods only in autumn of 2014 and spring of 2015Vytauto Didžiojo universitetasŽemės ūkio akademij