In quantifying the least limiting water range (LLWR), different critical limits of resistance to penetration (RP) and moisture at field capacity (θFC) are generally used. For agricultural soils, these values are documented in the literature. However, for constructed soil after coal mining, there is a large information gap. The aim of this study was to quantify the least limiting water range of a constructed soil under different cover crops in a coal mining area in Candiota, RS (Southern Brazil), considering different critical limits of θFC and PR. A randomized block experimental design with four replications was used, with the following cover crops: Hemarthria altissima (Poir.) Stapf & C.E. Hubbard, treatment 1 (T1); Paspalum notatum Flüggé, treatment 2 (T2); Cynodon dactilon (L.) Pers., treatment 3 (T3); control of Urochloa brizantha (Hochst.) Stapf, treatment 4 (T4); and no cover crop, treatment 5 (reference treatment, T5). To determine the LLWR, different critical values were used for θFC (-0.006, -0.01, and -0.033 MPa) and RP (1.5, 2.0, 2.5, and 3.0 MPa), keeping the soil moisture constant at the permanent wilting point (θPWP) as equal to the value retained at 1.5 MPa and at air-filled porosity (AP) of 10 %. The variation in the LLWR was higher in the constructed soil under the Urochloa brizantha (T4) cover crop, and lower in the constructed soil under the Paspalum notatum (T2) cover crop, regardless of the critical limits of θFC and of RP adopted. The critical limits of θFC and RP used to calculate the LLWR values gave rise to different values for the critical bulk density (CBD) of the constructed soil under different cover crops. The lowest and highest values of CBD were obtained when a θFC of 0.033 MPa and an RP of 3 MPa were used as critical limits in calculating the LLWR. The soil bulk density (BD) values of the constructed soil under Urochloa brizantha and Hemarthria cover crops were very close to the value of CBD.
critical density; cover crops; soil quality; constructed soil