Sugarcane straw removal effects on Ultisols and Oxisols in south-central Brazil
2017
Satiro, Lucas Santos | Cherubin, Maurício Roberto | Safanelli, José Lucas | Lisboa, Izaias Pinheiro | Rocha Junior, Paulo Roberto da | Cerri, Carlos Eduardo Pellegrino | Cerri, Carlos Clemente
The maintenance of sugarcane straw on the field has an important role in preserving the soil properties and organic carbon content. However, there is a growing interest in removing part of this residue to use in bioenergy production. The effect of straw removal on soil quality is still poorly studied. The aim of this study was to evaluate the impact of short-term (2years) straw removal from soil surface on soil quality. Two experiments were carried out in São Paulo state, Brazil: one in an Oxisol (sandy clay loam soil) and another in an Ultisol (sandy loam soil). We have tested five rates of straw removal (i.e., equivalent to 0, 25, 50, 75 and 100%). Soil samples were taken from 0 to 2.5, 2.5–5, 5–10, 10–20 and 20–30cm layers to analyze pH, total C and N, P, K, Ca, Mg, bulk density and soil penetration resistance. The effects of straw removal were limited to the soil surface layer and differed between the two types of soil. Under the Oxisol, the straw removal favored soil physical degradation (i.e., increased soil compaction and resistance to penetration) and depletion of soil C stocks. On the other hand, straw removal management only affected chemical properties in the Ultisol, reducing nutrient contents (e.g., Ca and Mg). Based on a multivariate analysis that involving all attributes, the sandy texture soil (Ultisol) showed more sensitivity to straw removal management, even over this short period (2years), in which the removal of any amount of straw caused a negative impact on soil quality. In contrast, in the sand-clay-loam soil (Oxisol) the removal rate of up to 50% of the straw (i.e., the maintenance of ~ 8.7Mgha⁻¹ of straw on soil surface) proved to be sustainable. Therefore, sugarcane straw removal should be site-specific, taking into account intrinsic soil properties and climate conditions, which preventing soil degradation and negative impacts on the provision of multiple ecosystem services. This guarantees the sustainability of the Brazilian bioenergy production.
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