USE OF NODULATE AND MYCORRIZAL FOREST LEGUMINOUS TREES AS AGENTS OF RECOVERY AN MAINTENANCE OF SOIL LIFE: A TECHNOLOGICAL MODEL

Abstract

Several leguminous trees are able to fix atmospheric nitrogen when in symbiosis with rhizobia and to form mycorrhizal associations which improve the efficiency of the absorption of water and mineral nutrients from the soil, especially phosphorus, the most important and limiting nutrient in tropical soils. Several experiments conducted at the National Research Center of Agrobiology (CNP AD), have identified efficient rhizobial and endomycorrhizal symbionts for several fast growing legume trees, which are adapted to stress conditions. These species when associated with the microsymbionts have been shown to be suitable for revegetation of degraded tropical acid soils, when the deficiencies of the major nutrients, other than nitrogen have been corrected. The addition of a large amount of organic matter (litter), with low eN ratio, besides protecting the soil from the direct impact of the raindrops and erosion, accelerates the cycling of soil nutrients and favors the return of life to the soil. In the Southeast region of Brazil the most promising species were found to be: Acacia mangium, A. auriculifromis, A. holocericea, Albizia samn, A. guachapelle, Enterolobium contortisiquum, Mimosa caesalpinifolia, M. scabrella, M. tenuiflora, Clitoria fairchildiana, Leucaena leucocephala and Paraserianthes falcataria. In the Amazonian region, besides the Acacias, C. fairchildiana and E. contortisiliquum,  other species such as  Strypphnodendrum adstringens and  Sclerolobium paniculatum have shown good potential for revegetation of dregraded soil.