Arbuscular mycorrhizal (AM) effects on maize growth and AM colonization ofroots under various soil moisture conditions

The effects of arbuscular mycorrhizal (AM) inoculation on growth, P uptake, and AM formation of maize (Zea mays L.) were examined at different soil mo isture levels. Arbuscular mycorrhizal inoculum was added to pots filled wit h sterilized Andosol at concentrations of 0, 10, and 50 g kg(-1) dry soil. From 11 to 75 d after sowing, the soil water potential was adjusted to arou nd -10 (wet: W), -50 (moist: M), or < -63 kPa (dry: D). The effect of inocu lation on maize growth and P uptake was distinct in dry soil, in which AM c olonization of roots occurred significantly more frequently in inoculated t han in non-inoculated soil. The effect, however, was less pronounced with t he increase in the soil moisture status, despite wide differences in the AM spore population and AM colonization. The increased AM colonization with t he increase in the soil moisture status indicated that a higher soil moistu re status improved the efficiency of AM colonization of roots. The increase in the shoot weight of non-inoculated maize with the improvement in the so il moisture status was presumably due to a higher P availability under a hi gher soil moisture status. Such effects may in turn stimulate P uptake and enhance plant growth, thereby masking the influence of the AM population.