Avaliação de leguminosas lenhosas para adubação verde em roças da terra indígena araçá, Roraima

Abstract

Mutamba’s community members are noticing a decrease in resources and available areas in “forest islands” and also a reduction in manioc field’s productivity which is associated with Populational growth, changes in land use and reduction in recovering time. This work is part of Guyagrofor Project with develops sustainable agroforestry systems in Guyana Shield, based upon traditional indigenous and quilombola knowledge. The present research work was conducted in three parts. First the Araçá’s (indigenous reserve) population, Mutamba`s community population and his traditional agriculture here historically characterized. To achieve this objective were conducted: guided visits in their agriculture fields; field observation; review of literature; and semi-structured interviews with seven local persons. Through literary research has described the history of savanna territory occupation and characterized ethnic groups that occupy this region and the indigenous populations who live in the TI Araçá. With the information gathered in the questionnaires was described the history and characterization of the community itself and agriculture, describing the historical use and management of plantations and the farmers perception about community’s natural resources and the occurrence of changes in management over time. Thus, it permitted the knowing and understanding of the community historical formation and constitution process, as well as the occupation processes, relationship within the residents and environment and changes over time, both in the environment and in their relationship with it. In the second part, three woody leguminosae species (Inga edulis Mart., Clitoria fairchildiana R.A. Howard and Cajanus cajan (L.) Millsp.) planted in traditional manioc fields in the “forest islands” of the Araçá indigenous land, in Roraima’s savanna were evaluated in order to determine which species are adapted to use in green manure in this ecosystem. The soil chemical characteristics analysis before experiment implantation showed that these soils are more fertile than most tropical soils in Roraima. A diagnosis of the indigenous history and agriculture were done emphasizing the manioc field’s management, in order to make description and register. On 35 th , 95 th and 165 th day, the following parameters were evaluated in the field: establishment of seedlings, growth, diameter and canopy cover. On 165 th day, plants here harvested and weighted, obtaining the fresh and dry weight and nutrient content. Cajanus cajan plants had significant higher growth and development characteristics means. The analysis result of nutrient content in biomass only showed significant differences in Ca, K and Mn, and the highest levels where observed in Inga, spontaneous weeds and palheteira respectively. In the third part it was studied the nitrogen mineralization coming from leguminosae vegetal material incorporation in these “forest island” typical soils, under controlled conditions. In nitrogen mineralization experiment, under controlled conditions, entirely casual delineation was used, with four repetitions and four treatments. Nitrate was the predominant form of mineral N in the studied soil. Cajanus cajan incorporation treatment had the lowest N mineralization values, being the immobilization process bigger than mineralization, during the incubation period. Moreover, Clitoria fairchildiana and Inga edulis treatments presented the highest mineral N liberations and a significant total N increase in soil, demonstrating the potential of these leguminosae as N sources in the soils of Roraima forest islands. The tree leguminosae evaluated provide significant K increase in soil, demonstrating the potential of these leguminosae as K sources in the soils of Roraima forest islands.