Soil structure changes induced by tillage and reduction of machinery traffic on sugarcane – A diversity of assessment scales

Abstract

Conventional tillage disturbs soil structure, increasing the soil’s susceptibility to compaction by machinery traffic in sugarcane fields. In this sense, the adoption of reduced tillage or no-tillage practices associated with traffic control has been proposed to preserve the functionality of soil structure, thus reducing soil compaction and plant growth restrictions. A long-term sugarcane experiment was carried out to evaluate the effects of conventional and reduced tillage practices with random and without machinery traffic on soil structure in southeastern Brazil. The soil structural quality was evaluated using a diversity of assessment scales, including on-farm Visual Evaluation of Soil Structure (VESS) in the “macroscale”, aggregate stability (e.g., mean weight diameter-MWD) in the “mesoscale” and 2D micro-morphometric image analysis (size and shape of pores, and total pore area) in the “microscale”. The conventional tillage and reduced tillage with random traffic treatments showed a similar soil structure after the fourth-cycle of sugarcane ratoon in the macro (i.e., VESS Sq), meso (i.e., MWD), and micro scale (shape and total pore area). However, the reduced tillage without traffic improved soil structure (e.g., lower VESS Sq, higher total pore area, and greater percentage of complex pores) when compared to the treatments with random traffic in the 0–10 cm soil layer. While conventional tillage does not bring additional benefits in alleviating soil compaction compared to reduced tillage, the preservation of soil structure under reduced tillage is conditioned by the adoption of traffic-free seedbed zones. A diversity of assessment scales showed that different methods and scales are related to specific soil functions and have a distinct objective, but it is an advisable strategy to assess the soil structural quality.