Soil compaction, root system and productivity of sugarcane under different row spacing and controlled traffic at harvest

The mechanized sugarcane harvesting using larger and heavier machines has accentuated soil compaction. The aim of this study was to quantify the impact of harvesting controlled traffic in sugarcane cultivated under different row spacing on physical-mechanical soil attributes, root system, and yield. The experiment was carried out in an Oxisol at Nova Europa county, Sao Paulo state, Southeastern Brazil, with three treatments: sugarcane cultivated with single-row spacing of 1.50 m and mechanized harvesting with no and with controlled traffic management (SR and SRCT, respectively) and sugarcane cultivated with double-combined row spacing of 1.50 x 0.90 m, and mechanized harvesting with controlled traffic management (DRCT). Soil samples were taken at the planting row (R), under the wheels track of the machinery (IRC) as well as in at mid-distance between the plant row and the traffic region, identified as seedbed (S), at the depths of: 0.00-0.10, 0.10-0.20, 0.20-0.30, 0.30-0.40, 0.40-0.50, 0.50-0.70, and 0.70-1.00 m. The following soil physical attributes were assessed: bulk density, soil porosity, and soil penetration resistance, in addition to the measure biometric variables of stalk diameter, plant height and yield. Root parameters were assessed only after the 2015/2016 harvest. Controlled traffic provided more favorable soil physical properties to plant growth as expressed by lower bulk density and higher soil macroporosity both in the planting row and seedbed. Regardless of the treatment, differences were found in the soil physical properties among the sampling sites R, IRC, and S. For SRCT, an increase of 17.9% root dry biomass has been found while an increase of 18.5% occurred for the DRCT treatment as well as higher density, length, volume, and root area compared to controlled traffic absence. Controlled traffic enabled sugarcane yield gains of 8.2 and 10.3 Mg ha(-1) for SRCT in the third and fourth harvests, and 18.8 and 15.7 Mg ha(-1) for DRCT in the same harvest sequence. These findings suggest that controlled traffic through automatic steering associated to double row spacing minimizes soil compaction and preserves soil physical conditions for roots as well as increases sugarcane yield.