Atributos físicos e carbono do solo em sistemas agroflorestais e monocultivo com palma de óleo na Amazônia.

Abstract

Oil palm (Elaeis guineensis Jacq.) is traditionally cultivated in the Amazon in monoculture systems. However, agroforestry systems (AFS) with oil palm have been studied and recommended as an alternative with less environmental impact to the monoculture of this crop. In the current scenario of climate change, the search for management practices and production systems that provide more environmental services, such as soil and water conservation, is urgent. In this sense, AFS with oil palm have great potential to improve the physical quality of the soil and store more carbon in aggregates than oil palm monoculture. Thus, the objective of this work was to evaluate if management practices and if the cultivation systems (AFS and monoculture) with oil palm affect the physical quality and carbon of the soil. We carried out the study in two AFS and one oil palm monoculture, located in the municipality of Tomé-Açu, state of Pará, Eastern Amazon, Brazil. We collected undisturbed and deformed soil samples in the 0-5, 5-10, 10-20 and 20-30 cm soil layers in the management zones (weeded circle, harvest path, leaf pile, and diversified strip). In the laboratory we determined the soil density, porosity, aggregate stability, water retention curve and carbon content in soil macro and microaggregates. The penetration resistance (PR) was determined in the field, using a Stolf model impact penetrometer. In general, the management zones without machine traffic (weeded circle, leaf pile, and diversified strip) had higher carbon content and better physical soil quality in the superficial layers (0-5 cm and 5-10 cm) than the harvest path, which presented worse physical soil quality, ie, lower aggregation, porosity, water retention, carbon content and higher soil density. In the SAF, probably the greater accumulation of litter on the soil influenced in higher humidity and, consequently, lower PR than in the monoculture. Overall, oil palm cropping systems store more carbon in macroaggregates than microaggregates. AFS showed greater potential to store carbon in soil macroaggregates than oil palm monoculture. Depending on the water content of the soil, the PR reached critical values, which can limit root growth. Management practices that increase carbon levels on the way to harvest should be prioritized to reduce the degradation of physical soil quality in this management zone. Therefore, oil palm cultivation in AFS has great potential to store more carbon in aggregates and improve the physical quality of the soil in the long term than oil palm monoculture.