No-tillage soil structure increases sugarcane root elongation under mechanical and hydric stresses in an Oxisol

Abstract

Abstract Background and aims Mechanical and hydric stresses limit root elongation, while preserved soil structure in no-tillage mitigates these effects. We quantified the effects of physical stress on sugarcane root elongation and the role of soil structure in mitigating them, providing experimentally based parameterisations for soil–root interaction via semi-empirical models. Methods Five levels of mechanical and hydric stress were established in soil samples from a long-term experiment under no-tillage (NT 31 ) and conventional tillage (CT 5 ). Repacked soil samples (T 0 ) were created to isolate the pore network effects in mitigating physical stress. Sugarcane seedlings were grown in each structural and physical stress condition, measuring the root elongation rate after 95 h. Semi-empirical models were developed using root elongation rate from each condition as a function of soil penetration resistance and degree of water saturation. Root growth was simulated for 45 days using RootBox model. Results Root elongation rate decreased by 30% in NT 31 and up to 84% in T 0 . The 3D Gaussian model explained 47% (CT 5 ), 71% (NT 31 ), and 78% (T 0 ) of the elongation variability. Under high soil moisture (95%) and penetration resistance (6.2 MPa), root elongation rate in NT 31 was 8.2 times higher than in T 0 and 1.8 times greater than in CT 5 . Simulations showed rooting depth was 2 times greater in NT 31 than in T 0 . Conclusion The semi-empirical models highlighted the key role of soil structure in mitigating physical stress on root elongation, as well as the potential of no-tillage to maintain and recover soil physical functions for root growth.