Mycorrhal inoculation of precedents crops: a way to mycorrhize efficiently sweet potato (Ipomoea batatas Lam.)

Abstract

Ipomea batatas L. (Lam) is a culture with high response to the inoculation of efficient strains of arbuscular mycorrhizal fungi; however, the high quantities of inoculants required does not make its application accessible on a productive scale. This research was carried out with the objective of studying the feasibility of using the ‘effect of permanence’ of the mycorrhizal inoculant applied to the previous crop, as a way to efficiently mycorrhize the sweet potato in succession. Two types of preceding crops were evaluated in the two sowing seasons, in moderately washed Calcaric Cambisol brown soils and repeated for two years. In the rainy season the precedents were Zea maiz. L. / var. MC-4 and Vigna unguiculata (L.) Walp. / var. Guariba and in the dry season, corn and beans (Phaseolus vulgaris / var. BAT-306), in all cases the sweet potato variety ‘CEMSA 78-354’ was used and planted 30 days after the harvest of the preceding ones. The inoculation was performed with Rhizoglomus intraradices / INCAM-11 strain. In all crops and seasons a positive response was found to mycorrhizal inoculation, guaranteeing high yields of 3,6; 2,5 and 25 to 30 t ha^-1 of corn, beans and sweet potatoes respectively and an efficient mycorrhizal operation in the presence of only 50 % of the amounts of mineral fertilizers and with yields similar to those obtained in the different crops when receiving the 100 % fertilization. With any of the precedents inoculated and in both seasons, a positive effect of permanence of the inoculant was achieved, which allowed to efficiently mycorrhize the sweet potato in succession, not being necessary the direct inoculation of the sweet potato to reach the benefits of an effective mycorrhization.