The impact of non-chemical weed control methods and biopreparations on winter oilseed rape preparation for over-wintering and productivity

Abstract

The current study was aimed to establish the impact of non-chemical weed control methods (thermal, mechanical andsmothering) and biopreparations on winter oilseed rape (Brassica napus L.) preparation for over-wintering and productivity under the conditions of the organic farming system. During the 2014–2016 period, a field experiment was conducted at the Experimental Station of Aleksandras Stulginskis University on Calc(ar)i-Endohypogleyic Luvisol (LVg-n-w-cc). The field experiment treatments were the following: Factor A – non-chemical weed control methods: 1) thermal (water steam), 2) mechanical (inter-row loosening), 3) smothering (self-regulation, sowing with narrow inter-rows); Factor B – application of biopreparations: 1) without application, 2) with application. During the period of autumn vegetation, in the smothering method plots, where the winter oilseed rape crop density was 1.5–2.4 times lower than that in the plots of thermal and mechanical weed control methods, the significantly highest aboveground mass of plant, number of leaves per plant, diameter of root collar, root area, total root length, root biomass of plant and leaf area of plant were determined, and in 2015 the highest chlorophyll index was measured in the leaves. In 2014 the application of biopreprations in the smothering method plots significantly increased the aboveground mass of plant (41.3%), the total root length (33.2%) and the root biomass of plant (28.0%). In 2004 the diameter of winter oilseed rape root collar depended on the leaf area of plant (r = 0.83, P < 0.05) and the root area of plant (r = 0.86, P < 0.05), and in 2015 it depended on the leaf area of plant (r = 0.89, P < 0.05), the root area (r = 0.99, P < 0.01), the total root length (r = 0.98, P < 0.01) and the root biomass of plant (r = 0.99, P < 0.01). Positive, strong and very strong, and statistically significant relationships were established between the leaf area of oilseed rape and the root area, the total root length and the root biomass of plant. In the spring of 2015, during the renewed oilseed rape vegetation stage, the highest crop density (98.0 units m^–2) and over-wintering (96.0%) were obtained in the plots of the mechanical weed control method in combination with biopreparations. In the spring of 2016, different nonchemical weed control methods and biopreparations did not have any significant effect on the oilseed rape over-wintering and the crop density. In 2015, different non-chemical weed control methods did not have any significant influence on oilseed rape biometric parameters before harvesting. In 2016, in the smothering method plots a significantly lower mass of oilseed rape and the number of branches per plant were formed compared to those of other used treatments. The highest number of pods per plant was determined in the smothering method plots in combination with biopreparations. In 2015 biopreprations in the smothering method plots significantly increased the 1 000 seed mass, and in 2016 they increased the number of pods per plant, respectively 7.2 and 35.6%. In the droughty year of 2015, the significantly highest winter oilseed rape seed yield was recorded in the plots of the mechanical weed control method, and in the moist year of 2016, the highest yield was in the smothering method plots with biopreparations. In 2015 biopreprations significantly increased the oilseed rape seed yield in the plots of thermal and mechanical weed control methods, and in 2016 they increased the yield in the smothering method plots, respectively 43.4, 25.1 and 51.5%. In 2015 the winter oilseed rape seed yield depended on the crop density (r = 0.86, P < 0.05) and the plant height (r = 0.94, P < 0.01), and in 2016 it depended on the number of pods per plant (r = 0.98, P < 0.01) and the plant height (r = 0.85, P < 0.05).