Influência do manejo na qualidade física de um argissolo distrocoeso em áreas de cerrado no leste maranhense

Abstract

The expansion of agricultural frontiers for the implantation of monocultures in Savanna areas in easter Maranhão has influenced the indicators of soil quality, among them, the physical indicators. The objective of this work was to evaluate the physical indicators of a Distrocoeso Yellow Argissol under natural vegetation and two different management systems. The study site is located in the municipality of Buriti (Ma). Three areas with different land use and management systems were selected, according to the description: (1) Native Savanna (CN)- employed as reference; (2) No-tillage system (SPD) with 4 years of implantation; (3) Conventional tillage system (SPC) – with 8 years of implantation. Soil samples were collected in the months of June/2018 and December/2018. In each of the three studied areas (CN, SPD, SPC) Five minitrenches were opened to collect undisturbed soil samples at depths of 0-10, 10-20, 20-30 and 30-40 cm for soil bulk density, macroporosity and microporosity analysis. A deformed sample composed with the dutch was also removed for the determination of particle size composition and density of particles. In the first trip to the field, monoliths were collected with dimensions of 10 cm x 10 cm x10 cm at depths of 0-10 and 10-20 cm to determine the stability of aggregates. The soil temperature was determined by the arithmetic mean of seven readings at 5 cm depth in each area one of the areas, three times a day (at 8hs, 12hs and 16hs). The results of the analytical determinations were subjected to analysis of variance, with the effects of depth and use and management, evaluated by the Tukey test at a 5% probability level. The areas of SPD and SPC showed higher clay dispersion and lower flocculation level compared to the native Cerrado. At depths of 0-10 and 10-20 cm, the SPD showed a tendency of lower soil density values compared to SPC. The values of total porosity and macroporosity were more expressive in the no-tillage system. Microporosity was not sensitive to changes in the different managements established in the first and second collection. The SPD and SPC caused the reduction of weighted average diameter and showed a higher proportion of stable aggregates in water of size < 2 mm, at different depths, in relation to the area used as reference. The SPD provided lower temperatures to the soil, at certain times, when compared to the SPC. The results showed that the use and management of the soil interfere in the physical indicators of quality