Quintais agroflorestais em área de terra-firme na Terra Indígena Kwatá-Laranjal, Amazonas

Abstract

Homegardens were studied in upland forest area of the Kwatá-Laranjal Indigenous Land, Amazonas, with the objective of characterizing these environments as to floristic composition, evaluating the effects of age and area (size) on species diversity and density of individuals, as well as assessing whether soil fertility parameters are related to age and area and if management practices contribute to the maintenance of soil fertility, through a comparison of the soil under homegardens with adjacent primary and secondary forests. In the 15 homegardens studied 2024 trees where found, distributed among 75 species, with 56 used as food and 28 of medicinal use. The most abundant species were: açaí-de-toiça (Euterpe oleracea Mart.), cupuaçu tree (Theobroma grandiflorum (Wild. ex Spreng) K. Schum) and acai-jussara (Euterpe precatoria var. precatoria Mart.), corresponding to 19.12%, 15.36% and 12.89% of the total of individuals, respectively. The most frequent species were: mango tree (Mangifera indica L.), cupuacu tree and orange tree (Citrus sinensis (L.) Osbeck), occurring in 100% and 93.3%, 80% of homegardens, respectively. Most of the agricultural production of the homegarden is used for domestic consumption, however 73.3% of the families generate income from products such as: fruits like Brazil nut (Bertholletia excelsa Bonpl.) and guaraná (Paullinia cupana Kunth). Both the Shannon Index (H ) as well as the density of individual trees have no significant relationship (p< 0,01) with homegarden age and area. The origin of germplasm for plantings, in most cases, is from the property or is acquired from neighbours and relatives, accounting for 66% and 53% of the species, respectively. In the homegardens of the Mari-Mari river, aluminum level in the soil was related with area and soil carbon was related with the age of the homegarden. The other parameters of soil fertility of in do not show relation with age and area of homegardens. Heavy clay texture predominates both in homegardens, as in adjacent primary and secondary forests. From the analysis of parameters of soil fertility (pH (H2O) and pH (KCl), Ca, Mg, Al, P, K and C), it can be concluded that some of the homegardens have features that allow them to be classified as Dystrophic Yellow Latosol caracteristic of Terra Mulata (TM; brown earths ) and Eutrophic Anthropic Yellow Latosol or Terra Preta de Índio (TPI; anthropogenic black earths), which have satisfactory pH (5.3 to 7.3) and high levels of calcium (above 4,0 cmolc/Kg) and magnesium (above 0.8 cmolc/Kg). In the remaining homegardens, the pH was considered low (below 5.3) and satisfactory levels of calcium (between 0.4 and 4,0 cmolc/Kg) and magnesium (between 0.2 and 0, 8cmolc/Kg) were observed in 46.6% and 31.1% homegardens respectively. Aluminum levels were elevated and considered as high (above 1.5 cmolc/Kg) in all homegardens. Potassium was considered low (below 0.15cmolc/Kg) in all homegardens, except for those of TM. Phosphorus was considered high (above 7,0 mg Kg-1) in 57.7% of homegardens and carbon was considered low (below 15g Kg-1) in 44.4% of homegardens. In comparing the soil of 4 homegardens with 4 adjacent areas of primary and secondary forests, homegardens were found to have higher pH (H2O), pH (KCl) and levels of calcium, magnesium, phosphorus and potassium (only 0-10 cm depth); and lower levels of aluminum and carbon. The agroforestry management practiced in homegardens seems to be contributing to the increase in levels of certain nutrients (calcium, magnesium, phosphorus and potassium), raising the pH and neutralization of aluminum, however practices that contribute to an increase in the organic matter in these systems could provide additional benefits in terms of biological, physical and chemical parameters.