Improving weed management in organic spring barley: physical weed control vs. interspecific competition

Abstract

Few options exist for effectively managing weeds in organic spring cereals. Establishing a competitive crop through increased seeding rate provides improved weed suppression, but competition with inter-row weeds is delayed, compared with an alternative, more uniform spatial pattern of sowing. We speculated that (i) enhanced interspecific competition or (ii) improved physical weed control with a strategy of wide-row sowing and inter-row hoeing would both provide better weed control than current regional organic practices. However, whether one of these strategies is superior to the other depends on an economic analysis of the relative costs of seed and equipment. We tested this hypothesis in two field experiments with spring barley (Hordeum vulgare) at three row spacings (11.4, 17.7 and 22.8 cm), and by sowing in a more uniform pattern, using condiment mustard (Sinapis alba) as a surrogate weed. Standard regional organic practice (17.7 cm rows, 200 plants m )2 ) had the highest weed biomass at the conclusion of both seasons. Weeds in this treatment accounted for 57% of total above-ground plant biomass in 2007 and 27% in 2008. The more uniform sowing pattern reduced weed biomass by 26% compared with the regional standard, averaged over 2 years of the experiment. Although we expected enhancing crop competition to be the most economical practice, high cost of organic seed resulted in intermediate net returns. At high weed density, the wide row strategy offered improved weed control, yields and profitability. However, with lower weed density, spring barley was sufficiently competitive that it did not benefit from cultivation.-2008 Minnesota machinery total cost per ha for a high-residue cultivator with guidance system.Managing weeds in organic spring cereals 603

Phytosociology and Behavior of Weeds in Maize as Influenced by Spatial Arrangements

“…One of the causes must be related to the rapid canopy closure between the rows by maize plants, in reduced spacing and in high population, struggling the germination and growth of weeds between the rows of the maize crop. The results described here are in agreement with those obtained by Kolb, Gallandt, and Molloy (2010). They studied physical weed control versus interspecific competition in organic spring barley and found improvements with respect to weed control at wide row strategy.…”

Composition of weed flora in spring cereals in Finland - a fourth survey

“…Therefore, measures promoting crop competition, as well as reliance on physical weed control should be emphasized in organic cropping (Kolb et al 2010). For instance, the abundance of E. repens in organic cropping is a cause for some concern and calls for improved control strategies.…”

Weed growth and crop yield loss in wheat as influenced by row spacing and weed emergence times

“…In weed-crop competition, availability of resources (water, nutrients, and space) and environmental factors like light and temperature affect the extent of the competition (Kropff et al, 1993;Weiner et al, 2001;Guillemin et al, 2013). Studies with a number of crops like wheat (Kristensen et al, 2008;Mashingaidze et al, 2009), rice (Chauhan and Johnson, 2010a;Khaliq et al, 2014a,b), barley (Kolb et al, 2010), cotton (Reddy, 2001), millet (Shinggu et al, 2009), sorghum (Grichar et al, 2004), and soybean (Hock et al, 2006), have shown inverse relationships between narrow crop rows and weed growth. Although wider crop rows facilitate weed control by intercultural operations, weed growth in wheat is usually suppressed by narrow row spacing (Shrestha and Fidelibus, 2005).…”