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Factors associated with soil fertility in different land uses of the Ecuadorian Amazon Region

Abstract:

Ecuadorian Amazon Region (EAR) represents one of the largest ecological reserves for humanity mainly due to the great biodiversity of flora and fauna and the ecosystem services it provides. The aim of this study was to characterize the physical and chemical fertility of the soil by a principal component analysis (PCA) in different land uses located in the provinces of Napo and Pastaza, Ecuador. They were selected 8 land uses in three altitudinal floors, coded as: A) Cocoa Agroforestry (CAF), b) Cocoa monoculture (CMC), c) naranjilla (NA), d) gramalote grass (Axonopus scoparius) with trees (GGWT), e) gramalote grass without trees (GGT), f) Dallis grass (Paspalum dilatatum) with trees (DGT), g) Dallis grass without trees (DGWT) and h) secondary forest (SF). In each land use was established a transect with five points sampling, and each point were collected disturbed and undisturbed soil samples at depths 0-10 and 10-30 cm. Four principals components that accounted for 70.54% of the variability of the system were identified. The first component explained the most variance (26.08%) with indicators mainly related to physical soil fertility. Our results suggest that the variation of soil fertility in the EAR is mainly affected The results suggest that the variation of soil fertility in the SAR is mainly affected by climate floor, depth, some physical and chemical indicators such as: bulk density, total porosity, porosity retention, pH, TOC; N, P, K+1, S, Ca+2, B and Zn. The high content of organic matter in these soils favors adequate physical fertility characterized by low values of Da, high infiltration capacity, high water retention, both related to the high values of Ksat and retention pores (Rp), and high aeration capacity reflected by the total porosity and the presence of suitable percentage of macropores. The low nutrient content, high acidity of reference soils (secondary forest) suggests that a change of land use from forest to agriculture and livestock systems, leading to the application of amendments and nutrients to cover crop needs.