Reduction in field emergence and seedbank density of Galinsoga quadriradiata and other weeds after contrasting false seedbed strategies in organic vegetable fields

Abstract

Summary Mechanical weed control in low competitive, organic vegetable production systems is challenging, particularly in fields with large populations of Galinsoga spp. (Asteraceae). Various false seedbed techniques are used prior to crop planting or sowing to prevent weed emergence, albeit with variable success. This study investigated the impact of machinery type (flamer, hoe and harrow), number of passes (2 and 4), tillage depth (1–4 cm) and intensity (double and single hoeing, and hoeing with or without additional harrowing) on weed emergence and seedbank density in 0–5 cm topsoil of organic vegetable fields. False seedbed machinery that did not or minimally disturb the soil was most appropriate for preventive control of Galinsoga quadriradiata (Hairy galinsoga) and total weed seeds, with reductions in seedling emergence up to 99% and 73%, respectively, for flaming, and 74% and 67%, respectively, for 1 cm deep hoeing, 1 month after false seedbed creation. Compared with 1 cm deep hoeing, 1 cm deep harrowing was 16% less effective in the control of emerged seedlings, while flaming was highly effective in preventing weed seedling emergence, even after a low number of passes. Tillage intensity was less important than tillage depth for the reduction in weed emergence and seedbank density. Overall, tillage was more effective for seedbank reduction than flaming.

Optimisation of Weed Control in Organic Processing Spinach (Spinacia oleracea L.): Impacts of Cultivar, Seeding Rate, Plant Spacing and Integrated Weed Management Strategy

“…In plots with pre-emergence flaming, harrowing on false seedbed entrained 14 g m −2 additional weed biomass and 0.17 percentage points more weed biomass fraction relative to a false seedbed with no curative treatment, although not in a significant way. This points to the stimulatory effect of soil tillage on weed germination as shown in the false seedbed experiments of De Cauwer et al [12].…”

“…One day after (false) seedbed preparation, the seedbank density in the 0-5 cm topsoil of experiments 1, 2 and 3 was 1421, 1207 and 2665 live seeds m −2 , respectively, and was dominated by Poa annua L. (annual bluegrass) and U. urens with relative densities of 24.6% and 7.2% in experiment 1, 71.4% and 5.4% in experiment 2, and 26.7 and 29.5% in experiment 3. The seedling emergence method [11] was used to quantify seed density and followed the protocol described by De Cauwer et al [12]. Daily rainfall, irrigation and average minimum and maximum air temperatures during the experimental periods were recorded (Figure 1).…”

Weed emergence and seedbank after three years of repetitive shallow cultivation in a muck soil field

“…Hairy galinsoga emergence was also modified by shallow cultivation. False seedbed strategies have been shown to reduce subsequent emergence in this species but tillage intensity (single versus double passes) did not modify results (De Cauwer et al 2019). De Cauwer et al (2020 also recommend not inverting the soil which we did every spring and this could have promoted seedbank persistence.…”

Improving Weed Management Based on the Timing of Emergence Peaks: A Case Study of Problematic Weeds in Northeast USA

“…Fallow periods are perhaps most feasible during the spring since more than one tillage pass or burndown herbicide application is sometimes necessary to prepare for planting, and spacing out these events allows emergence flushes between control timings. Although it is best to finish the sequence with minimal disturbance, such as with herbicides or flaming (Caldwell and Mohler, 2001), initiating with shallow tillage set to the germination depth of the target weed species can enhance the depletion of the seedbank (De Cauwer et al, 2019). But while tillage may affect the emergence of some species, the timing and magnitude of common ragweed emergence has been shown to be unaffected (Barnes et al, 2017).…”