Mistura dos horizontes A e B com o caráter coeso para a mitigação da limitação física do solo

Abstract

The cohesive character is associated with soils whose subsurface horizons are compacted and exhibit consistency ranging from very hard to extremely hard when dry, and friable to firm when moist. The presence of these horizons have implications for agriculture, especially when they are closer to the soil surface, hindering root development. There is a lack of research to address this type of physical impediment related to cohesive horizons. The hypothesis is that soil penetration resistance and soil density decrease by mixing Horizon A, which lacks cohesive character, with Horizon B, which exhibits this condition. Thus, this study was developed with the aim of assessing whether the mixture of cohesive and non-cohesive horizons A and B reduces soil density and penetration resistance. To do so, material was collected from the Ap horizon, representing soil without cohesive character, and the Bt horizon, which has cohesive character, from the profile of Argissolo Amarelo Eutrocoeso típico located in the Departamento de Engenharia Agrícola at the Universidade Federal do Ceará. Subsequently, three mixtures of different proportions of soil with and without cohesive character were prepared, labeled as treatments TM1, with 75% cohesive soil + 25% non-cohesive soil; TM2, with 50% cohesive soil + 50% non-cohesive soil, and TM3, with 25% cohesive soil + 75% non-cohesive soil. Two controls were also used: TC (100% cohesive soil) with material from the Bt horizon and TNC (100% non-cohesive soil) collected from the Ap horizon. The samples were placed in PVC tubes and subjected to nine cycles of wetting and drying, followed by an evaluation of quantitative parameters measuring soil cohesion: penetration resistance (RP) and soil density (Ds). As a result, RP showed a significant reduction from treatment TM2, with a treatment mean of 0.98 MPa, while Ds obtained higher significant values in treatments TM2, TM3, and TNC when compared to TC. There was a noticeable difference in density between the controls, where TC registered an average of 1.28 g cm-3, and TNC demonstrated a higher average value, approximately 1.36 g cm-3. This result can be justified by the higher proportion of the sand fraction observed in the Ap horizon.