While Ipomeabatata (L), Lam. is a mycotic crop, few results are reported in establishing the requirements of phosphoric fertilizers associated with the inoculation of arbuscular mycorrhizal fungus (AMF) strains. For these purposes, two experiments were carried out, evaluating the response of 'INIVIT B2-2005' or 'CEMSA 78-354'clones to the application of five doses of phosphoric fertilizer with or without the application of Rhizoglomu sirregulare/(INCAM-11) species on a carbonated loose Brown soil, at a random block design with factorial arrangement and four repetitions. The experiments were carried out with 'INIVIT B2-2005' and 'CEMSA 78-354'clones always in the period November-April and they were carried out in two years. The yield of tubers, percentage of mycorrhizal colonization, content of mycorrhizal spores in 50 grams of soil and phosphorus content in the leaf, stem and tuberous root were evaluated. A significant response (p <0.05) to mineral fertilization was found in the yield with an optimum dose of 75 kg ha-1 which decreased to 50 kg ha-1 when inoculated with R. irregulare, keeping equivalent yields. This effect was similar in both clones and in both years. The inoculation increased the colonization percentage and the spores significantly, and the highest values were always obtained in the treatment of 50 kg ha-1 of P 2 O 5 , lower and higher fertilizations had lower values. The phosphorus contents in different organs also presented a similar response. It is concluded that the inoculation of an efficient AMF strain causes an adequate mycorrhizal functioning in presence of medium doses of fertilizers, guaranteeing high yields with lower doses of these ones.

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