The impact of non-chemical weed control on soil biological properties in the winter rapeseed agrocenosis

Abstract

The aim of this study was to determine the influence of non-chemical weed control methods (thermal, mechanical and smothering) on the abundance of earthworms and the activity of soil enzymes in agrocenosis of winter rape (Brassica ncipus L. spp. Oleifera biennis Metzg.) grown in soil with regular (23-25 cm) and thickened (45-50 cm) humus layers. Field experiments were conducted in 2014-2017 at the Experimental Station of Aleksandras Stulginskis University. The soil of the experimental site is Endocalcaric Endogleyic Luvisol. The following three non-chemical weed control methods were examined (Factor A): 1) thermal (using water steam), 2) mechanical (inter-row loosening), and 3) smothering (self-regulation) as well as bio-preparations (Factor B): 1) without bio-preparations, 2) with bio-preparations. In the thermal and mechanical weed control treatments, winter oilseed rape was grown with an inter-row spacing of 48 cm and in weed smothering treatments with an inter-row spacing of 12 cm. Soil biological properties depended on meteorological conditions and weed control method applied in winter rapeseed crop. In soil with regular humus layer, the highest average number and the mass of earthworms in the ploughing layer were determined in plots with mechanical and thermal weed control using biological preparations, whereas in the soil with thickened humus layer - without the use of biological preparations, in comparison with the plots with weed smothering method. On average, the highest levels of soil enzymes saccharase and urease activity were found in the plots with smothering weed control and usage of biological preparations compared to the plots with thermal and mechanical weed control. There was a positive, strong and significant correlation between the mass of earthworms and the activity of the enzyme saccharase in the soil (v = 12.7 + 0.22x, r = 0.85, P < 0.05)