SUGARCANE ROOT BIOMASS IN NO-TILLAGE AND CONVENCIONAL SYSTEMS WITH AND WITHOUT LIMING

The cultivation system can influence physical and chemical soil properties by changing the root development of crops. The aim of this study was to evaluate the effect of no-tillage (NT) and conventional tillage (CT) and of liming (0 and 2.0 t ha(-1)) on the root system of sugarcane. The study was conducted on an Oxisol in a long-term experiment initiated in 1998, after three sugarcane cycles of four years without burning the cane trash at harvest. The soil was sampled to evaluate some physical properties (density, porosity and penetration resistance) and soil fertility. Roots were sampled with a probe, in four seasons defined by the regional soil water balance, at six sampling points equidistant from the crop rows, in 0.20 m layers down to a depth of 1.0 m. As a result, no-tillage with liming resulted in highest values of the liming-related properties, such as base saturation and calcium concentrations in the surface layer only. Soil density and soil resistance were highest under no-tillage and between the rows. In the crop row there was no difference among treatments. On average, about 4.0 Mg ha(-1) of sugarcane roots remained in the soil layer to a depth of 1.0 m. The differences among layers and sampling positions were significant, and although the sugarcane roots were concentrated at the surface and near the crop rows, 25-30 % of the roots were in the interrows (0.6 m away from the row) and 15-30 % below 0.60 m, indicating that sugarcane roots explore a large soil volume. The variation in the root biomass was more influenced by crop growth and soil water status than by management practices. The root biomass was largest at the maximum water surplus and lowest at the time of soil water recharge. The largest variations in the root biomass between seasons were observed in the conventional system without liming. In the no-tillage treatments with liming the root mass varied little with sampling times. The changes in physical and chemical soil properties under the influence of no-tillage and limestone were not sufficient to significantly affect the development of the sugarcane root system.