Atributos químicos e físicos do solo diante dos usos da terra na microrregião de Caxias - MA

Abstract

The increasing use of land, without taking into account its potentialities and limitations, occurs in changes in soil attributes, especially when there is no proper management of these. Thus, the main objective of this research was to evaluate the Chemical and physical atributes of soils under diferente land uses in the Microregion of Caxias – MA. The region known historically for its economic and environmental importance has been experiencing strong problems associated with land use, interconnected with inadequate land management. In the meantime, this research was developed from the concept of landscape, consisting in the discussion of geography as a science that comprises the process of construction between time and space through the interrelationship between nature and assisted society in the landscape. In conducting the research, we analyzed the characterization of the regional and local landscapes of the study area, Pedological characterization of Maranhão, as well as the climatic characterization of the region. As main results, two soil profiles were classified and characterized in each municipality of the Microregion, totaling 12 profiles and 58 deformed samples, these were collected under the Ecological Zoning of Maranhão (2021/2022). The soils were classified up to the fourth categorical level (subgroups) of the Brazilian Soil Classification System, according to Santos et al. (2018). The description and collection of samples were performed following the procedures recommended by IBGE (2015), chemical and physical analyses according to Embrapa (1997), and from Camargo et al. (2009), the basic descriptive statistical analysis. The characterization of land use relationships in the Microregion of Caxias under capoeira system, pasture, área of primary vegetation and legal reserve was also carried out and the temporal analysis of changes in land use of the municipalities belonging to the Microregion between the years of 1985, 2010 and 2020, according to data from MapBiomas (2020). As a result, it was observed that in the Chemical analyzes of the soils, a pH (4.6 to 5.3), strongly acidic in the profile in the Legal Reserve area, in the capoeira area are moderately acidic (5.6 to 6.5), (5, 9 and 6.1), (5.73 and 6.0) and only Profile 08 showed a strongly acidic reaction, with pH between (4.31 and 4.61). The two profiles in the pasture area showed pH in the range of (5.09 and 6.01) and (5.5 and 5.8) and the profiles in the primary vegetation area pH between (5.9 and 6.0), (5.0 and 5.4), (5.6 and 6.1), (5.3 and 6), respectively, which allows classifying them as moderately acidic. These are soils with limitations in terms of their physical and Chemical attributes, with low natural fertility (except profile 11). They are soils withlow base saturation, presence of erosion and tenders regarding drainage. Regarding the potential of the analyzed soils, the high amount of organic matterand there lief form (flat and gently undulating) stand out, which facilitates the use of the land in several cultures, especially mechanized agriculture, due to the agricultural machinery be facilitated in these types of relief. The statistical analysis showed that the K+, Ca+ and Mg+ contentes varied between the diferente soil uses, as well as thePotassium (K) contentes of the profiles in capoeira system, primary vegetation and pasture, which presented greater homogeneity, while the contentes of Ca+Mg and Ca2 showed less homogeneity. Mean K valueswerelower in thepasture system, dueto inadequate soil management or overgrazing. Despitethis, the potassium content in the soil can be increased with the development of a potassium management strategy with the fertilization of essential nutrients. The statistical analysis proved that the average of the chemical attributes (pH, Al, P, Ca, Mg, H, Al, SB and MO) are below the desirable for a productive soil. In the evaluation of land use changes in the Caxias microregion between 1985, 2010 and 2020, it was found that there was a significant increase in livestock and a reduction in natural vegetation.