Vesicular-arbuscular mycorrhiza and growth in barley: Effects of irradiation and heating of soil

The influence of soil irradiation (0.25–4.0 Mrad) and soil heating on mycorrhizal survival, establishment and development after reinoculation, and on plant growth, was investigated.The lowest radiation dose applied, completely eliminated the infectivity of a soil with a high number of mycorrhizal propagules.Mycorrhiza developed more slowly after inoculation in irradiated soils than in untreated soils. This could have been due to the small amounts of inoculum used, but the high concentrations of nutrients released by irradiation of the soil were probably of greater significance particularly the increased amounts of plant-available N as indicated by incubation experiments. Inorganic N was increased to similar levels by the various treatments. Available soil P increased with increasing irradiation dose.Incubation of inoculum in soil for 40 days before sowing increased mycorrhizal infection.