There is evidence that signal (SG) and ruzi (RG) grass have an allelopathic effect on weeds. This study aim to evaluate this effects on difficult-to-control weeds: hairy beggarticks (HB), benghal dayflower (BD), horseweed (H), sourgrass (S) and tall windmill grass (TWG). The first experiment was installed in a completely randomized design with 2 donor species (SG and RG) × 4 extract concentrations (0, 75, 150 and 225 mg ml−1) in factorial scheme with four replicates. Weed germination percentage was evaluated in three-day intervals. In the second experiment, the weeds emerged in substrates previously cultivated with SG and RG, in completely randomised block design with four replicates. The emergence, shoot growth and root growth were evaluated. The results were as follows: (i) on horseweed (H), 84% germination inhibition by RG leaf extracts and 38% emergence inhibition by SG root exudates were observed; (ii) on benghal dayflower (BD), 84% germination inhibition by RG leaf extracts and 37% emergence inhibition and 4.3 times the SRL values than control by RG root exudates; (iii) on hairy beggarticks (HB) 52% germination inhibition by RG leaf extracts scored, while SG root exudates reduced 43% of the emergence, 24% shoots biomass accumulation and 11.3% root length; (iv) on sourgrass (S) 71% germination inhibition by both donor plants and 75% germination inhibition by RG leaf extracts were measured. Finally, on tall windmill grass (TWG) 69% germination inhibition was observed upon using both donor plants. It can be concluded that foliar allelochemicals inhibit the germination of: BD > S > TWG > H > HB, while root exudate allelochemicals, inhibit the emergence and root development of all weeds
In fruit crops like citrus, weeds coexist throughout their long cycle and can cause several yield losses. Ecological mowing (ECO) is an integrated weed management (IWM) option for citrus, as it produces an in-situ mulch that suppresses the weeds; however, there is a lack of information on the impacts of tree-row conventional (CONV) and ECO mechanical weed control when combined with residual or non-residual herbicides, or standard frequent mechanical (MECH) control. This study aimed to evaluate, for 3 years in a young orange orchard, IWM using ECO and conventional mowing when combined with one of five weed control programmes: pre-emergent (PRE) herbicides (sulfentrazone [spring], indaziflam [summer]), post-emergence (POST) herbicides (glyphosate [spring], saflufenacil [summer]), PRE + POST herbicides (sulfentrazone + glyphosate [spring], indaziflam + saflufenacil [summer]) and P/P (pre/post-emergence duality) herbicides (flumioxazin [spring], diuron [summer]). Impacts on cover crop biomass deposition, weed density, population dynamics, biomass accumulation and seed banks were evaluated. Alternanthera tenella Colla (joyweed), Bidens pilosa L. (hairy beggarticks), Digitaria horizontalis Willd (crabgrass), Galinsoga parviflora Cav. (smallflower galinsoga) and Raphanus raphanistrum L. (wild radish) were the most critical weeds with changes in their population dynamics over time. The ECO treatment promoted greater biomass deposition in the tree-rows (up to ≈8.0 t ha À1 ), reducing weed density and biomass accumulation by mulch formation; similarly, MECH resulted in low weed density and a reduction in biomass accumulation. The POST and P/P treatments resulted in low levels of weed control, while ECO + PRE + POST led to almost absolute weed control (>95%). Thus, we suggest ECO + PRE + POST is an efficient IWM option in citrus tree-row crops with low-risk herbicide resistance (up to 5 MoA year À1 + mulch).
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