Diagnóstico, monitoramento e mitigação da compactação de solos cultivados com palma de óleo na Amazônia oriental.

Abstract

Oil palm produces one of the most demanded oils in the world, and its management requires mechanized operations, from soil preparation to periodic fruit harvesting, which can lead to soil compaction. The general objective of this research was to analyze soil physical properties for diagnosis and monitoring, and to propose measures to mitigate the compression of soils cultivated with oil palm in the state of Pará, Eastern Amazonia. The study was conducted in three replantations with oil palm (1999, 2013, 2017), where soil samples were collected in three management zones (crowning, planting line and traffic line) next to twelve plants in each site. During June/2021 to July/2022, soil moisture, root penetration resistance (PR) and aeration porosity (AP) were collected monthly in all sites and management zones. In addition to monitoring the production of fresh fruit bunches. The water contents for the tillage limits were estimated using van Genutchen parameters, and the PR was adjusted to equations that had soil moisture and bulk density as predictor variables. A factorial incubation experiment with residues from the oil palm production chain was conducted under controlled conditions ((4 residues (petiole, leaf, Empty fruit bunches – EFB, MIX) x 6 times – (0, 0.04, 0.08, 0.12, 0.16, 0.22 and 0.30 year)) + 1, distributed in four blocks. Where the C-CO2 emission flux was monitored, in addition to the remaining dry mass of the residue (msR), nutrient and the half-life of the residues were calculated. Another experiment was conducted using EFB for uniaxial factorial tests (2 initial bulk densities - BDi x 5 amounts of EFB on the surface - 0, 20, 40, 60, 80 Mg ha-1), with 4 replications. In this test, the compression curve was adjusted, and the pre-consolidation pressure and compression index were taken from it. The results indicated that, in general, the highest water contents limiting tillage occurred in the planting line and the lowest in the traffic zone. Soil organic carbon and bulk density influenced the range of water contents for tillage. The temporal variation in soil moisture influenced the production of fresh bunches and lower PR values. In the wetter trimesters, the soils had AP below the critical limit (10%). There was immobilization of native nitrogen in the soil and greater mineralization of potassium from the residues. After incubation with the residues, there was an increase in soil organic carbon in the physical fractions of soil organic matter. The application of 40 Mg ha-1 of EFB increased the pre-consolidation pressure in the sandy soil and the compression index showed that the low initial density increases the soil's susceptibility to compression. Evaluations over time have made it possible to identify compression processes, which can be minimized by conservation management and the application of residues to the soil, which also increase the nutrient levels available to plants.