抄録
The responses of soybean (cv. T202) to Vesicular-Arbuscular Mycorrhizal Fungus (VAMF ; Glomus elunicatum) under 3 different phosphorus application levels (P_1, 100 mg P ; P_5, 500 mg P ; P_<30>, 3000 mg P/2×10^<-4> a pot, 2.3 kg air dry Soil) in an Andosoil (Bray II-P < 0.1 μg g^<-1>ds. ) weere examined in regards to growth, VAM formation, acetylene reduction activity (ARA), N accumulation and P absorption at the growth stages of initial flowering, milk-ripening and maturing. Positive effects of VAMF infection on growth, P and N accumulation, and ARA were obtained, especially in the earlier growth stage, corresponding to the level of VAMF infection rates and infected root lengths which were higher in lower P applications (P_1, & P_5). In the initial flowering stage, significant stimulations of ARA and P accumulation in nodules were observed due to VAMF infection at lower P application levels (P_1, P_5), resulting in earlier N accumulation in pod-grain at the milk-ripening stage, however, accompanying steep decreases in ARA and nodule P concentrations at this stage as compared to non-VAMF treatment. Even under the 50% cut-off of light by shading from just before milk-ripening to the maturing stage, positive effects of VAMF on growth and N and P accumulations were found. Under the high-P application level (P_<30>), VAMF infection affected soybean growth negatively in the milk-ripening stage, whereas in the final maturing stage, it brought about stimulative effects on drymatter production and N and P accumulations in pod-grain through maintaining ARA activity, maybe due to unknown factors except the improvement of P nutrition.
