Forage Radish and Cereal Rye Cover Crop Effects On Mycorrhizal Colonization of Corn Roots.

Forage radish (Raphanus sativus L. var. longipinnatus) is being used by increasing numbers of farmers as a winter cover crop in the Mid-Atlantic USA. It is a non-host to arbuscular mycorrhizal fungi (AMF) and releases anti-fungal isothiocyanates (ITCs) upon decomposition in the winter.  Field experiments were conducted to determine the effect of forage radish and cereal rye (Secale cereale L.) cover crops on arbuscular mycorrhizal colonization of and P acquisition by a subsequent corn (Zea mays L.) silage crop.  Cover crop treatments included forage radish, rye, a mix of forage radish and rye, and no cover crop.  Mycorrhizal colonization of corn roots at the V4 stage following forage radish cover crops was not significantly different from that in the no cover crop treatment.  In 3 out of 6 site-years, a rye cover crop increased AMF colonization of V4 stage corn roots compared to no cover crop.  Across sites, AMF colonization of corn roots at the V4 stage was positively correlated with V4 and V8 stage corn shoot P concentration in both years of the study.  These findings suggest that forage radish cover crops do not have a negative effect on AMF colonization of subsequent crops.