Weeds promote greater arbuscular mycorrhizal fungi benefit in organically managed spring wheat (Triticum aestivum L.) cultivation system

Weeds appear to enhance soil microbial benefit in organic agricultuer. We examined effects of weed and microbial effects on spring wheat ( Triticum aestivum L.) yield and quality under organic management systems. Canadian spring wheat cultivars were planted in weed-free and weedy treatments in 2010 and 2011, and soil microbial profiles were examined using phospholipid fatty acid (PLFA) analysis. The proportion of arbuscular mycorrhizal fungi (AMF) increased and was greater in the weedy plots than in the weed-free plots over the growing season. This greater proportion was associated with greater total plant biomass accumulation but lowered grain yield in the weedy plots. The high yielding semi-dwarf and later maturing cultivars appeared to be yield-stable in organic systems. It may be effective to choose late maturing semi-dwarf cultivars to achieve higher grain yields and benefit through soil microbial communities in organic systems.