The effect of sowing date, stale seedbed, row width and mechanical weed control on weeds and yields of organic winter wheat

Abstract

Three field experiments were carried out in organically grown winter wheat in Denmark. The treatments were sowing time (normal or late sowing) and false seedbed, row width (12 and 24 cm) and weed control method [untreated; mechanical weed control (weed harrowing at 12 cm supplemented with inter-row hoeing at 24 cm); and herbicide weed control]. Weed biomass in midsummer was greatest on plots sown at the normal sowing time (compared with delayed sowing) and was reduced by mechanical or chemical weed control (compared with untreated plots). Row width alone had no influence on weed biomass, but in the experiment with high weed pressure, the more intensive mechanical weed control used at a row width of 24 cm reduced weed biomass. Normal sowing time tended to give higher yields, but this was only statistically significant in one of the three experiments. Wide rows gave a yield decrease in the experiment with low weed pressure. The effect of weed control on yield was dependent on the weed pressure. At low weed pressure, mechanical weed control caused a yield decrease compared with untreated or herbicide treated. At intermediate weed levels there were no differences, whereas at high weed pressure, mechanical weed control and herbicide treatment caused a yield increase compared with untreated. False seedbeds were shown to contribute to a decrease in the soil seed reserve.*% Reduction in back-transformed values. Due to missing values, SEDs are different for different comparisons. The largest value is shown. àSignificant interactions with other treatments.Weed management in organic winter wheat 17

Crop Growth and Yield Losses in Wheat Due to Little Seed Canary Grass Infestation Differ with Weed Densities and Changes in Environment

“…Planting time of a crop is directly related to land preparation and soil disturbance during a critical period in growing season shall determine which weed seeds, at what stage of dormancy or viability, are available for germination. A study by Rasmussen (2004) has revealed that plots sown at optimum time have shown more weed biomass as compared with delayed planting. Weed related yield loss in corn and soybean was significantly less when planting was delayed beyond optimum time, presumably due to depleted weed seed banks (Buhler and Gunsolus, 1996;Gower et al, 2002).…”

Evaluation of 2,4-D-Choline Based Herbicide Systems in 2,4-D Tolerant Soybean (<i>Glycine max</i> L.)

“…Management of weeds is typically accomplished using a combination of cultural, mechanical, or chemical methods [9] [10]. Weeds are controlled chemically by the use of herbicides which are toxic to the targeted weed.…”

Competitividade de dois genótipos de milho (Zea mays) com plantas daninhas sob diferentes espaçamentos entre fileiras

“…A redução do espaçamento entre fileiras de milho não influenciou a produtividade da cultura e as produções de massa e de diás-poros por Abutilon theophrasti (Teasdale, 1998). Também em trigo, a produção de massa pelas plantas daninhas não foi afetada pelo espaça-mento entre fileiras (Rasmussen, 2004).…”