SOIL ATTRIBUTES AND RESISTANCE TO PENETRATION IN AGROFORESTRY SYSTEM AREAS IN SOUTHWESTERN AMAZON

Abstract

Os sistemas agroflorestais (SAFs) t\ueam sido propostos para aliar a preserva\ue7\ue3o das florestas a modelos agr\uedcolas sustent\ue1veis. O objetivo do estudo foi avaliar atributos ed\ue1ficos e correlacion\ue1-los com a resist\ueancia mec\ue2nica do solo \ue0 penetra\ue7\ue3o (RMSP) de tr\ueas classes de solo na Amaz\uf4nia Ocidental, em \ue1reas de SAFs do projeto Reflorestamento Econ\uf4mico Consorciado e Adensado (RECA), em Rond\uf4nia. Foram selecionadas 14 \ue1reas de SAF com 20 anos de implanta\ue7\ue3o e composi\ue7\ue3o, estrutura e espa\ue7amento entre \ue1rvores semelhantes, al\ue9m de duas \ue1reas de refer\ueancia, com cobertura de mata e pastagem. Al\ue9m das avalia\ue7\uf5es de atributos dos solos, foram realizados testes para medir a RMSP e determinado o estoque de C no solo at\ue9 um metro. Os perfis de solo foram classificados como Latossolos, Argissolos e Cambissolos, todos com argila de baixa atividade e reduzidos estoques de nutrientes, car\ue1ter distr\uf3fico e \ue0s vezes alum\uednico. Nas \ue1reas de SAF, os valores de RMSP variaram de 0,96 a 4,59 MPa, sem restri\ue7\uf5es ao sistema radicular em superf\uedcie, por\ue9m, aumentando em profundidade. Em geral, os Latossolos mostraram menores valores de RMSP que os Cambissolos e Argissolos, e os valores mais altos ocorreram na \ue1rea de refer\ueancia com pastagem. Os estoques de C variaram de 45,19 a 126,04 Mg C ha-1, e metade das \ue1reas de SAF apresentaram valores pr\uf3ximos ou at\ue9 superiores aos da \ue1rea de mata. A an\ue1lise de componentes principais mostrou uma distin\ue7\ue3o entre os Cambissolos e as demais classes de solos. Os principais atributos que diferenciaram as \ue1reas foram o teor de Al, pH e a granulometria.Agroforestry systems (AFS) have been proposed to combine the forest preservation with sustainable agricultural models. The objective of this study was to evaluate soil attributes and to correlate them with soil mechanical resistance to penetration (SMRP) of three soil classes in southwestern Amazon, in AFS areas of the project RECA, in Rond\uf4nia state. Were selected 14 areas of AFS with 20 years and similar composition, structure and tree spacing, plus two reference areas, with pasture and forest. Besides soil attributes, SMRP and soil C stock up to one meter depth were measured. Soils were classified as Oxisols, Ultisols, and Inceptisols, all with low activity clays and low nutrient levels, dystrophic character and some with very high aluminum. In the AFS areas, the SMRP values varied from 0.96 to 4.59 MPa, without restriction to plant root system in the surface, but increasing with soil depth. In general, the Oxisols showed lower values of SMRP than the Inceptisols and Ultisols, and the highest values were in the pasture reference area. The carbon stock varied from 45.19 to 126.04 Mg C ha-1, and half of the AFS areas showed values near or even higher than the C stocks in the forest reference area. The principal component analyses showed a distinction between Inceptisols and the other soil classes. The main attributes differentiating the areas were Al content, pH and granulometry