141 Effects of Two AM Fungi on the Yield and the Quality of Carrot (Daucus carota L.) Grown in Field Conditions

Two cultivars of carrot were sown in a sandy loam soil over two seasons with and without introduction of commercial inoculum of Glomus intraradices or Glomus etunicatum, which was spread with an experimental sowing machine. VAM fungi effects on the yield and the quality of carrot varied from season to season. In 1997, both of the VAM fungi enhanced the average saleable yield of the two cultivars from 66.21 t/ha to 69.85 t/ha and 80.81 t/ha, respectively, for the treatment without the introduction of VAM fungi, G. etunicatum, and G. intraradices. The slight difference (5.03%) that occured between G. intraradices and the non-inoculated treatment, although not significant, represented 20.38% of the total percentage of rejected carrots. For the last season, the amount of rejected carrots was in the same range for all the treatments (13% to 14%). Nevertheless, both of the cultivars responded differently to mycorrhization. In both of the seasons, mycorrhizal colonization was high in all plots, with an average of 70% in the treatment without inoculation and 75% in those that received G. intraradices or G. etunicatum. In our experimental conditions, reduction of phosphate fertilization to 50% of the recommanded quantity had no influence either on the mycorrhizal colonization or on the yields.