Yield losses of soybean and maize by competition with interseeded cover crops and weeds in organic-based cropping systems

Abstract

Weed management is a major issue in organic farming systems. Although interseeding cover crops is one alternative to herbicides, cover crops often suppress not only weeds but also main crops. Therefore, using cover crops for weed control without adverse effects on main crop growth is important. To verify the effect of cover crops on competition between main crops, cover crops and weeds in snowy-cold region, main crops soybean (Glycine max Merr.) in 2005 and maize (Zea mays L.) in 2006 were grown with cover crops winter rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth), respectively. The cover crops were sown on three sowing dates: before main crop planting (Pre-MC), on the same date of main crop planting (Syn-MC) and after main crop planting (Post-MC). A plot without cover crops (Sole-MC) was used as a control. The dry weight (DW), vegetation cover ratio (VCR), vertical community structure and chlorophyll content were measured to estimate the competition between main crops, cover crops and weeds. Weed DW was suppressed significantly by sowing cover crops in both soybean and maize. This weed suppression was associated with the increase of VCR of main crops plus cover crops at the early 2 growth stage of main crops. Soil seed banks of dominant weed also became lower by sowing cover crops, implying the importance of proper weed management for suppressing weeds successively. In addition, the sowing dates of cover crops had large effects on main crops DW especially in maize, i.e., it was significantly lower in Pre-MC and Syn-MC than in Post-MC. Although the cover crop height was markedly shorter than the main crop height, the chlorophyll content of the main crops was significantly lower when cover crops were sown earlier. These results suggest that the growth inhibition of main crops by cover crops was partly caused by competition for nutrients between main crops and cover crops, and this growth inhibition was alleviated when cover crops were sown after the establishment of main crops. Consequently, soybean yield was the highest in Post-MC and decreased by 29%, 18% and 7% in Sole-MC, Pre-MC and Syn-MC, respectively, and maize yield was also the highest in Post-MC and decreased by 68%, 100% and 24% in Sole-MC, Pre-MC and Syn-MC, respectively. It was concluded that weeds could be controlled effectively by sowing cover crops after planting main crops in organic farming systems in snowy-cold

Response of leaf area and dry matter of crop, weeds and cover crops to competition and fertilizer resources

“…Jedrszczyk and Poniedziałek (2007) reported cover crops increased the content of corn dry matter in comparison to monoculture of corn in weedy condition. Uchino et al, (2009) resulted in increased coverage of corn, soybean and cover crop, declined weed dry matter. Weeds were suppressed effectively and stably without yield reductions of main crops by inter-seeded cover crops with sufficient fertilization in organic farming systems (Uchino et al, 2012).…”

“…Therefore, farmers interested in weed management have to rely on other control approaches (Hollander et al, 2007). An alternative weed control method is the use of cover crops (Uchino et al, 2009), which can suppress the growth of weeds by competition for light, soil moisture and nutrients, and also by producing allelopathic compounds (Compigla et al, 2010). Cover crops have been successfully integrated into conservational agriculture systems in many parts of the world.…”

Spring-Interseeded Winter Rye Seeding Rates Influence Weed Control and Organic Soybean Yield

“…However, winter rye residue cannot provide full-season weed suppression [16,17,21,22]. When used in an organic production system, winter rye has suppressed weeds through physical interference as a living mulch, but this system may also decrease crop grain yields [6,11,23]. Management of rye 2 International Journal of Agronomy using cultivation was necessary to minimize yield reductions, particularly in dry years, because no alternative methods exist to control rye in organic soybean.…”

Effect of cover crops on maize-velvet leaf competition: leaf area density and light interception

“…4). The highest yield of soybean and maize was observed in treatment sowing of cover crops planted 21 days after sowing main crops (Uchino et al, 2009). Abdin et al (2000) also cited that maize grain yield in interseeded cover crop treatments was higher than maize pure stand under weedy conditions.…”

“…In this treatment, the maximum intercepted light by maize was recorded at upper canopy layers. Uchino et al (2009) reported that intercepted light by main crop canopy reduced because most of the solar radiation was absorbed by upper canopy layers of weeds with high plant height. In addition, weed density and biomass decreased by reduction in available light (Bilalis et al, 2009).…”