Soil health indicators in oil palm agroforestry systems in the eastern Amazon, Brazil

• Published in: Geoderma Regional Vol. 37; p. e00806
• Main Authors: Gomes, Mila Façanha, Oliveira, Raimundo Leonardo Lima de, Costa, Lucélia Rosa de Jesus, Campos, Wilian Victor da Silva, Kato, Osvaldo Ryohei, Castellani, Debora Cristina, Vasconcelos, Steel Silva
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2024
• Subjects: acidity; aggregate stability; agroforestry; aluminum; Amazonia; Brazil; calcium; carbon sinks; Degraded soil; Elaeis guineensis; forests; magnesium; particulate organic carbon; phosphorus; physical health; potassium; soil carbon; soil density; Soil labile carbon; soil profiles; Soil quality; species diversity; Brazil; Amazonia; Soil quality; Amazonia; Degraded soil; Soil labile carbon
• ISSN: 2352-0094; 2352-0094
• DOI: 10.1016/j.geodrs.2024.e00806

Agroforestry systems (AFSs) are generally recognized for improving soil health and increasing soil carbon (C) stock. In the Amazon region, oil palm AFSs have been promoted as a productive strategy and may offer an additional benefit of recovering degraded areas. Our objective was to evaluate whether the management practices adopted in oil palm AFSs affect soil health indicators and C stock. We carried out a study in Tomé-Açu, state of Pará, eastern Amazon, through which we evaluated two oil palm AFSs that differed in species diversity: higher diversity (AFShigh) and lower diversity (AFSlow). We used a regenerating forest (FOR) to compare with the oil palm AFSs, as regenerating forests are also a model of environmental recovery in the eastern Amazon. In the 0–10, 10–20 and 20–30 cm soil layers, we evaluated chemical indicators (active acidity (pH), calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P), and aluminum (Al)), (b) physical indicators (density (SD) and stability of aggregates (AGGRE)), and (c) biological indicators (permanganate oxidizable carbon (POXC), particulate organic carbon (POC), total soil carbon (SOC content) and root stock (ROOT)). We also evaluated the total soil carbon stock (SOC stock). The values of the biological indicators in the most superficial layer, especially the C indicators, were higher in the AFSlow (C content: 1.63 ± 0.13%, POXC: 568 ± 17 mg kg−1, POC: 0.63 ± 0.10 g kg−1) and the AFShigh (C content: 1.84 ± 0.04%, POXC: 656 ± 24 mg kg−1, POC: 0.83 ± 0.06 g kg−1) than in FOR (C content: 1.35 ± 0.09%, POXC: 336 ± 10 mg kg−1, POC: 0.44 ± 0.03 g kg−1). In general, the values of chemical indicators were higher in the AFSs than in FOR, except for the Al content, which was higher in FOR than in the AFSs. The physical indicators did not show a specific pattern of variation between the AFSs and FOR; aggregate stability was higher in FOR (range throughout the soil profile: 5.57 ± 0.09 to 5.38 ± 0.24 mm) than in the AFSlow (5.41 ± 0.03 to 3.79 ± 0.07 mm) and the AFShigh (5.07 ± 0.01 to 3.79 ± 0.11 mm) in all the soil layers, and soil density was higher in the AFShigh and FOR than in the AFSlow in most subsurface layers. Therefore, oil palm AFSs improve the chemical and biological health of the soil, especially in the more superficial layers, but it does not improve the physical health of the soil when compared to the forest. •Oil palm agroforestry improves soil fertility.•Oil palm agroforestry shows higher carbon levels than regenerating forest.•Oil palm agroforestry does not improve soil physical health.