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

Abstract

Weed control in organic spinach for the processing market is challenging because of the low tolerance of weed contamination in the harvested produce and the limited physical weeding options. Optimisation of weed control systems is therefore urgently needed. Three field experiments with autumn spinach were carried out in organic fields to evaluate the impact of cultivar choice, seeding rate (300 and 400 seeds m−2), plant spacing management (10.5-cm-wide single rows and 21-cm-wide single or twin rows) and integrated weed management strategy (combinations of pre-sowing, pre-emergence and post-emergence tactics) on weed biomass and spinach yield and quality. Spinach cultivars with a planophile growth habit and a high growth rate were more weed suppressive than the cultivar with an erectophile growth habit and a slower growth rate. Spinach density was significantly negatively correlated with weed biomass and weed biomass fraction in the harvested produce, but significantly positively correlated with (marketable) spinach biomass and petiole fraction in the harvested produce. Narrow row spacing systems with post-emergence broadcast harrowing had the lowest weed biomass and weed biomass fraction but also the lowest (marketable) spinach biomass as a result of the thinning action of harrowing. Post-emergence harrowing is of key importance for reducing weed biomass in any integrated weed control strategy. Weediness was lowest in systems comprising flaming on false seedbed or in pre-emergence followed by post-emergence harrowing. To mitigate the risk of crop failure, the field should preferably be cropped with quickly growing spinach plants arranged in narrow spaced rows at high plant density and weeded by pre-sowing or pre-emergence flaming followed by post-emergence harrowing.

False Seedbed for Agroecological Weed Management in Forage Cereal–Legume Intercrops and Monocultures in Greece

“…At the first forage harvest, weed biomass decreased in both FSB 1 and FSB 2 subplots compared to NSB subplots. These results are consistent with those of De Cauwer et al [38], who also indicated that false seedbed is a cultural practice for agroecological weed management that reduces weed biomass at harvest. In another recent study conducted on wheat (Triticum aestivum L.), Shahzad et al [39] found that a false seedbed significantly reduced weed density and biomass compared to conventional seedbed manipulations.…”

“…In addition, Naeem et al [42] reported that a false seedbed compared to a conventional seedbed preparation resulted in lower weed density and higher yields in barley. Similar results were reported by De Cauwer et al [38] in spinach. In addition, FSB 1 increased forage yield compared to NSB, while FSB 2 further improved forage yield compared to FSB 1.…”

Cultural Practices and Mechanical Weed Control for the Management of a Low-Diversity Weed Community in Spinach

“…Similar reports indicated that the use of increased plant populations within the row can improve the competitiveness of even low-competitive crops with slow early growth rates [28,29]. In addition, such practices can be combined with mechanical weed control treatments between crop rows to further suppress weeds [9,[28][29][30]. The study by De Cauwer et al [9] provided evidence on the potential of such practices for weed suppression in spinach in Central Europe.…”

“…Weeds are an important obstacle to spinach productivity, as they reduce its commercial biomass and affect the quality of the harvested product [9][10][11]. The impact of weed competition on spinach yield is likely to be higher in fields infested with low-diversity weed communities.…”

“…Increasing the populations of crop plants in the row is an effective strategy for suppressing weeds and achieving higher yields [27]. De Cauwer et al [9] found that narrow intra-row spacings reduced weed biomass and increased total and commercial spinach biomass. Similar reports indicated that the use of increased plant populations within the row can improve the competitiveness of even low-competitive crops with slow early growth rates [28,29].…”