Effect of mycorrhiza application on plant growth and yield in potato production under field conditions. Zohrab Adavi 1*and Mahmoud Reza Tadayoun 2

The effect of mycorrhiza fungi was studied on growth and yield of potato (Solanum tuberosum L.) in Fereidoonshahr, Esfahan, Iran during 2013 growing season. The experiment treatments were arranged in a factorial design based on a complete randomized block design with three replications. Four phosphorus fertilizer levels of 25%, 50% 75% and 100% P recommended with two levels of Mycorrhiza: with and without Mycorrhiza (control) were assigned in a factorial combination. Results showed that tuber size, number of tuber per plant, tuber yield, and starch yield were significantly higher in inoculated plants than in non-inoculated plants. Tuber size, number of tuber per plant, tuber weight per plant , number of tuber in m2, tuber yield, and starch yield increased with increasing P level above 75% P recommended in non-inoculated plants, whereas no significant difference was observed between 75% and 100% P recommended. The positive effect of mycorrhizal inoculation decreased with increasing P levels due to decreased percentage of root colonization at higher P levels. According to the results of this experiment, application of mycorrhiza in the presence of 50% P recommended had a favorable result and could increase tuber yield and starch production to an acceptable level. Therefore, mycorrhiza could be considered as a suitable substitute for chemical phosphorus fertilizer in organic agricultural systems.