Soil carbon, nitrogen and phosphorus dynamics in sugarcane plantations converted from tropical dry forest

Abstract

Sugarcane (Saccharum officinarum) cultivation is one of the most widespread agricultural systems in tropical areas. The increasing energetic demand for sugar and ethanol in the last decade has led to further expansion of this crop over preserved areas of tropical and subtropical dry forests. The aim of this study was to compare soil essential elements, such as carbon (C), nitrogen (N), phosphorus (P), and soil C and N transformation processes, between remaining fragments of tropical dry forests and sugarcane plantations. Furthermore, net ammonification, net nitrification, and soil C and N mineralization potential net rate, soil physicochemical properties (texture, pH, CIC), NH4+, NO3− and P-Bray concentrations were also determined. Sugarcane cultivation time (1 to 50 years) was the main factor of interest in this study. Our results indicate modifications on the N cycle in the soil of sugarcane plantations compared to the soil of tropical dry forest. Over time, sugarcane plantations could be becoming an open source system of nitrate and soluble P, lowering concentrations of essential elements and reducing soil C and N fluxes. Sugarcane plantations seem to have less ability to transform C and retain N in the soil compared to tropical dry forest, even more in plantations with 21 to 50 years of cultivation. Agricultural practices such as annual fertilization and burning of crop residues could explain these results.