A review of the effects of crop agronomy on the management of Alopecurus myosuroides

Abstract

Summary This study reviews 52 field experiments, mostly from the UK, studying the effects of cultivation techniques, sowing date, crop density and cultivar choice on Alopecurus myosuroides infestations in cereal crops. Where possible, a statistical meta‐analysis has been used to calculate average responses to the various cultural practices and to estimate their variability. In 25 experiments, mouldboard ploughing prior to sowing winter cereals reduced A. myosuroides populations by an average of 69%, compared with non‐inversion tillage. Delaying drilling from September to the end of October decreased weed plant densities by approximately 50%. Sowing wheat in spring achieved an 88% reduction in A. myosuroides plant densities compared with autumn sowing. Increasing winter wheat crop density above 100 plants m−2 had no effect on weed plant numbers, but reduced the number of heads m−2 by 15% for every additional increase in 100 crop plants, up to the highest density tested (350 wheat plants m−2). Choosing more competitive cultivars could decrease A. myosuroides heads m−2 by 22%. With all cultural practices, outcomes were highly variable and effects inconsistent. Farmers are more likely to adopt cultural measures and so reduce their reliance on herbicides, if there were better predictions of likely outcomes at the individual field level.

Using simulation models to investigate the cumulative effects of sowing rate, sowing date and cultivar choice on weed competition

“…However, the model output was realistic in that it predicted that in the wheat – A. myosuroides scenario, the crop acquires a competitive advantage when sown at higher densities and at later sowing dates. The benefit of increased sowing density has been observed in various crop-weed associations (Christensen et al., 1994, Melander, 1995, Cosser et al., 1997, Roberts et al., 2001, Lutman et al., 2013). However, we demonstrated an additional benefit of delayed sowing; the difference in relative growth rate between the crop and the weed is greatest at warmer temperatures, earlier in the sowing window.…”

Management of herbicide resistance in wheat cropping systems: learning from the Australian experience

“…Recently, mouldboard ploughing has been reintroduced to invert the soil profile and bury the shallow weed seed banks, established under long‐term conservation cropping systems, to a depth from which there is no emergence (>30 cm) . Prior to the widespread adoption of conservation cropping practices, mouldboard ploughing was for decades routinely used for weed control across the world's wheat cropping regions . Even so, strategic mouldboard ploughing remains an effective weed control practice to target weed seed banks in conservation wheat production systems.…”

“…Predominantly, the opportunities for enhancing the competitive effects of wheat on weed populations are implemented at crop seeding. Wheat cultivar, seed size, seeding rate, row spacing and orientation and fertiliser placement can all be adjusted to ensure establishing wheat seedlings have a competitive advantage over any weeds present . These agronomic techniques are simple to implement and, although not typically leading to weed control, will substantially reduce weed biomass and reproductive capacity.…”

Wheat root length and not branching is altered in the presence of neighbours, including blackgrass

“…In order to test this new experimental system we selected a wheat cultivar (Hereward) that is known by growers as being particularly susceptible to blackgrass [14]. Hereward plants were grown in the presence of neighbours that were either another Hereward plant, a blackgrass or a Brachypodium dystachion L. ( Brachypodium ) individual.…”