Effect of interseeding cover crops and fertilization on weed suppression under an organic and rotational cropping system

Abstract

Interseeding cover crops is an alternative to laborious intertillages and hand weeding followed in organic farming. The objective of this study was to evaluate the effect of fertilization and interseeding cover crops on the growth of main crops and weeds and the stability of weed suppression over years and main crop species under four-year rotational organic farming. Two cover crops, winter rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth), were interseeded in furrows of potato (Solanum tuberosum L.), soybean (Glycine max Merr.) and maize (Zea mays L.) at 3-5 weeks after planting the main crops. The number and dry weight of weeds were measured at the maximum plant height stage of main crops and main crop yields were recorded at their physiological maturity. The light competition between main crops, cover crops and weeds was analyzed by vertical community structure and vegetation cover ratio (VCR) of each 2 crop. Since light competition of main crops with cover crops and weeds was not severe, main crop yields were not suppressed significantly by either cover crops or weeds. Weed growth was suppressed significantly by interseeding cover crops through increasing the VCR of main crops plus cover crops. This weed suppression by interseeding cover crops was stable to the main crop species in rotational cropping systems and to the various environmental conditions, because the cover crops compensated the low VCR of main crops alone at early growth stage especially when main crop growth was depressed by unfavorable environmental conditions. In addition, input of compost and fermented organic fertilizer had positive effects on the main crop yield and weed suppression. It is concluded, therefore, that weeds can be suppressed effectively and stably without yield reductions of main crops by interseeding cover crops with sufficient fertilization in organic farming systems.

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

“…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).…”

“…The risk of weeds not only reducing crop yields but also decreasing the commercial quality and the feeding palatability of main crops and enhance the soil seed bank of weeds, which may cause continuous weed infestation of field crops (Uchino et al, 2012).…”

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

“…In the presence of bean and soybean, intercepted light by velvetleaf reduced significantly. Uchino et al (2012) noted that light competition of main and cover crops with weeds affected the weed growth. The high leaf area index of maize, bean and soybean enhanced the ability of intercepting solar radiation by these plants and therefore decreased the absorbed light by velvetleaf (Poggio, 2005).…”

“…Our findings was in according to Vazin et al (2010) results. Uchino et al (2012) reported that LAI of weed decreased due to increasing of leaf area and growth of main crops and cover crops. The LAD of bean was higher than velvetleaf LAD at both planting dates (Figures 1a, 1d).…”

“…Moreover, vertical profile of leaf area density affects the light interception and consumption, dry matter accumulation and grain yield (Ciganda et al, 2008). In a mixed canopy, vertical distribution of leaf and solar radiation can be used to study of light competition among plants (Uchino et al, 2012). Steinmaus et al (2008) also noted that cover crops suppressed weed through reduction of light interception by weed.…”