Diffuse Reflectance Infrared Fourier Transform (DRIFT) Spectroscopy to Assess Decomposition Dynamics of Sugarcane Straw

Abstract

Crop residue decomposition is an essential process that affects soil properties and ecosystem services related to nutrient recycling, soil organic matter, and aggregation. Therefore, understanding crop residue decomposition is recommended to evaluate soil changes and define a more sustainable sugarcane straw removal management for bioenergy production. The straw chemical composition may be an efficient indicator to investigate this complex process. Thus, we conducted a field study to assess the sugarcane straw composition changes over 1 year using DRIFT spectroscopy technique. The experimental design consisted of a split-plot and randomized block design, and straw removal rates provided the main plot factor with time of sampling as the split-plot factor. Three sugarcane straw removal rates were evaluated: no removal (~ 14.0 Mg ha−1 of dry mass), 50 (~ 7.0 Mg ha−1) and 75% (~ 3.5 Mg ha−1). Decreases in the absorbance associated with labile C (1200 to 1100 cm−1), and increases in more recalcitrant C (1800 to 1600 cm−1) were showed by the DRIFT spectra. In regional scale, the straw chemical composition was affected by environmental conditions, whereas at a local scale, the main driver was the decomposition time. Specific DRIFT peaks were correlated with the referential wet chemical method, commonly named Van Soest method. From the correlations between the Van Soest and DRIFT methods, we suggest using the absorbance of 896, 987, 1173, and 1447 cm−1 bands to assess cellulose and hemicellulose changes and 1500 cm−1 band for lignin changes in sugarcane straw. The application of DRIFT analysis to follow the decomposition process is a feasible and clean methodology to detect straw chemical changes induced by the environmental conditions and decomposition time.