Inoculation with arbuscular mycorrhizal fungi increases the yield of potatoes in a high P soil

Arbuscular mycorrhizal (AM) fungi are potentially important tools in agricultural systems that reduce or ehirtinate chemical inputs common in modern agriculture. We tested the response of potato (Solanum tuberosum L. cv. Superior) to inoculation with AM fungi in a field with very high available P (375 mu g g(-1) soil) in two growing seasons. Inoculation treatments included a commercially available inoculum containing Glomus intraradices, mixed species inocula produced on-farm in mixtures of compost and vermiculite, and a control treatment consisting of a freshly prepared compost and vermiculite mixture. In addition, two farming systems were imposed: conventional chemical fertilizers or dairy manure composted with leaves were applied to meet recommended nutrient requirements. Yields of tubers on a fresh weight basis in the first year were increased by AM fungus inoculum, 33% under conventional fertilizer application and 45% with compost addition vs. controls in each system. The response to inoculation the second year was less; however yields of inoculated plants were 10 to 20% greater than control,.;. There was a significant positive treatment effect of inoculation upon production of larger sized potatoes in the second year. Neither year saw a marked difference in yield response among AM fungus inocula. These results demonstrate the potential yield benefits of inoculation of potatoes with AM fungi produced on the farm.