Soil texture affects root penetration in Oxisols under sugarcane in Brazil

Two field trials were set up in Brazil to investigate the effects of soil tillage practices on soil physical condition, root distribution, and sugarcane yield in areas under sandy loam and clayey soils. Additionally, we identified the critical limits for sugarcane root development in soils under contrasting texture using the boundary line approach. The treatments with two tillage practices (conventional tillage - CT and no-tillage - NT) were established in a randomized block design with four replications within two paired areas, one under crop rotation and the other under bare fallow during the sugarcane replanting period. Measurements of soil bulk density (BD), macroporosity (MaP), microporosity (MiP), soil resistance to penetration (Pr), root biomass (RB) and sugarcane yield were performed. Soil MaP and MiP were not affected by the treatments in both soils. The Pr values were higher in NT than CT in both sites, especially in surface layers. For clayey soil, BD values were higher in NT at depths of 0.0-0.1 and 0.1-0.2 m in crop rotation and at the depth of 0.1-0.2 m in bare fallow area. Sugarcane yield for clayey soil (153 Mg ha−1) was more than twice that measured at the sandy soil (58 Mg ha−1). In general, the CT promoted a slight increase root production and did not affect sugarcane yields. In both soil types, most part of RB (60 to 70%) was concentrated near the sugarcane row (horizontal aspect) and within the top 0.4 m of depth (vertical profile), indicating that much of the root system is retained within the planting furrow. Our study demonstrates the potential for using the boundary line method to estimate the effects of BD and Pr on root growth. Root system was severely restricted at sandy soil when BD > 1.70 Mg m−3 and Pr > 1.5 MPa, while for clayey soil the critical values were BD > 1.25 Mg m−3 and Pr > 2.5 MPa. While our study provides valuable insights, we advocate that further studies should be done to better understand the effect of differing levels of BD and Pr for sugarcane yields in soils of different textures.