ICOM1 Abstract

talk session 8: Applications CUENCA, GISELA, ZITA DE ANDRADE & GLADYS ESCALANTE. Instituto Venezolano de Investigaciones Cient’ficas (IVIC), Centro de Ecolog’a, Apartado 21827, Caracas 1020-A, Venezuela. - Arbuscular mycorrhizae in the rehabilitation of tropical fragile degraded lands The aim of this work was to study the effect of arbuscular mycorrhizae (AM) in the rehabilitation of areas that have been severely degraded. A field experiment was carried out in La Gran Sabana, Venezuela, in an area that was disturbed five years ago and in which no spontaneous recolonization by plant species has occurred. Five treatments were performed in which and introduced grass, Brachiaria decumbens, was sowed (30 kg/ha). The treatments were: NI= non inoculated control; I= inoculated with AM fungi at 1650 kg/ha; P= fertilized with triple superphosphate, 100 kg/ha; I+P= inoculated with AM fungi and fertilized with triple superphosphate; and S= previously sterilized AM inoculum. A soil microorganism inoculum free of mycorrhizae, was added to all the treatments. Five months after sowing the grass, above and below ground biomass, % AM colonization, root length and nutrient uptake were measured. The re-entry of plant species native to the neighboring undisturbed savanna was also evaluated. The results showed a noticeable increase in plant cover, biomass and uptake of nutrients in the I+P treatment in comparison with all the other treatments. The reintroduction of mycorrhizae (I) produced a slight increase in the growth of B.decumbens. The P uptake of this treatment increased tenfold in relation to the control even in the absence of exchangeable P in the soil .Of native species re-entering the different treatments, 81% were mycorrhizal. The results obtained indicate that the presence of mycorrhizae seems to be a required condition to achieve the rehabilitation of these lands.