PHYSICAL-CHEMICAL CHARACTERIZATION OF SOILS AFFECTED BY SALT IN THE MAUE RIVER WATER BASIN, ANGÓNIA

Abstract

Salinity and sodicity in salt-affected soils pose the greatest threat to agriculture on a global scale. The first mainly affects water absorption by plants, due to the reduction in the osmotic potential of the soil solution, while the second affects soil structure and, indirectly, water availability (Bernardo, 1995). The presence of salts in the soil can also cause toxicity problems for plants. All of these problems will result in a decrease in agricultural production. This article aimed to physically and chemically to assess the soils affected by salts in the Maue River basin in Angónia to guide the levels of soil management and conservation, both by family farmers and the private sector, as well as the Government. The methodological procedures used consisted of a bibliographic review, geoprocessing techniques, and physical-chemical analyzes of soils described in EMBRAPA (2011 and 2013). The physics were based on particle size (clay, silt and sand fraction), clay dispersed in water and electrical conductivity of the saturation extract. In turn, the chemicals were limited to pH in H₂O and KCl; Ca²⁺, Mg²⁺, Na⁺, P, K, Al⁺ and Al³⁺ + H⁺) and Organic Carbon (C.O) according to EMBRAPA (2011). Based on them, the values ​​of the sum of bases (SB), cation exchange capacity (CTC), base saturation (V), percentage of exchangeable sodium (PST), hydrogen potential (pH) and aluminum saturation index (m).  Finally, with the analytical results (physical-chemical) and morphological descriptions of the soils in the field, the soils of the basin were characterized and classified up to the fifth (5th) categorical level in accordance with the Brazilian Soil Classification System (EMBRAPA, 2013). The research results showed the existence of 10 soil classes in an area of ​​4596.52ha corresponding to 46km². The soils studied were greatly affected by sodicity, given that 76.7% (3522.41ha) of the soils are sodic, for the classes: 1) HYDROMORPHIC VERTISSOLO Typical sodic, Ta eutrophic; 2) ARGILUVIC PLINTOSOL Ta Eutrophic sodic, gleissolic; 3)RED-YELLOW ARGISSOLO Ta Eutofico sodico, gleisolic; 5) YELLOW LATOSOL Ta Eutrocoeso sodic, clayey texture; 6) HAPLIC GLEISOL Ta Sodic, carbonatic eutrophic; 7) NATRIC PLANOSOL Ta Eutrocoeso latosolic, sodic lithopetroplintic; 8) FLUVIC CAMBISSOLO Ta Eutrocohesive duric, sodic lithopetroplintic; 9) NATRIC PLANOSOL Ta Typical eutrophic, petroplintic. In turn, 23.3% (1070.15ha) of the soils are saline-sodic, with a eutrophic character and without any chemical restrictions, for the classes: 4) HAPLIC CAMBISSOLE Ta Eutrophic, conglomeratic; and 10) RED-YELLOW LATOSSOLO Tb Eutrocoeso, typical very clayey texture, respectively. Physically, the soils present restrictions (cohesion, densification, cementation of horizons, endostoniness and rockiness) for the classes of Cambisols and Planosols. Despite this, they lend themselves to farming, but when subjected to corrections and management aimed at improving their structure and fertility. Aiming at soil recovery, the use of phytoremediation plants, such as: salt grass (Atiplex numulária), mesquite (Prospis juliflora); determining electrical conductivity, liming, washing and incorporating organic matter into the soil is effective in correcting it and, therefore, improving its fertility. Finally, the promotion of environmental education is very important to raise public awareness about the risks posed by the intense use of chemical fertilizers, both for ecosystems and public health.