Green-Cane Harvested Sugarcane Crop Residue Decomposition as a Function of Temperature, Soil Moisture, and Particle Size

Sugarcane, a complex hybrid of Saccharum species, is grown on over 170,000 ha in the state of Louisiana. In 2016, the crop was worth $750 million US. Green-cane harvest, widely used in sugarcane producing countries, deposits up to 20 Mg ha−1 of crop residue annually. Green cane harvesting of sugarcane is recognized to be a more sustainable management opportunity than burning residue, or standing or heaped stalks. In Louisiana, cool, wet winters coupled with the crop residue left on the field reduce ratoon yields by as much as 10% year−1. However, the residue represents an important opportunity to improve degraded, low organic matter soils to facilitate sustainable sugarcane production. Our objective was to evaluate how temperature, soil moisture, and particle size influence sugarcane residue decomposition rates. In laboratory experiments, we observed rapid residue carbon (C) mineralization rates at temperatures of ≥ 23 °C across all soil moisture levels tested, and calculated the residue decomposed by 71–95% over the course of the 155 days experiment. Particle size also increased decomposition, with 61, 72, and 91% decomposition observed for the > 2.0, 0.25–2.0, and < 0.25 mm particle size fractions, respectively. The results indicate that earlier cut cane fields have the best chance to decompose green-cane harvested residue by taking advantage of warmer October temperatures, and that shredding the residue further increases its susceptibility to microbial decomposition. Future experiments will study field decomposition of residue in situ as well as incorporation of residue C into soil organic matter.