Sugarcane Production in Brazil: The Effects of Sugarcane Trash Removal on Soil Water Content and Yield.

Brazil has one of the cleanest energy matrix of the world, with around 46% of renewable sources, of which sugarcane biomass represents around 35%.

The main solid residues from sugar and ethanol production are the sugarcane bagasse and the sugarcane-trash or -straw (SCT). The sugarcane bagasse is the fibrous waste that remains after crushing and extracting the sugar juice. The SCT is composed of sugarcane leaves (green and dry) and cane tops.

In the last decades, the introduction of mechanized sugarcane harvesting along with power cogeneration technology improvements in sugarmills changed tremendously the importance of sugarcane residues. On an energy basis (MJ.kg^-1), one ton of 50%-wet bagasse has around 1.6 barrels of fuel oil. About the same amount of energy is found in the SCT part.

Due to new possibilities to use SCT as feedstock for energy cogeneration and ethanol production, it has increased the interest to recover it from the field.

However, removing SCT mulch from the field could impact negatively weed control, soil erosion, soil water content, soil temperature, etc.

This work evaluated how SCT removal would impact soil water content (SWC) and therefore, sugarcane yields.

A completely randomized block design was set in Goias State, Brazil. The treatments comprehended 5 levels of SCT left in the field, i.e., 0; 25; 50; 75 and 100% left (or 100;75;50;25 and 0% remova, respectively). Gravimetric SWC was measured at 5; 15; 30; 50; 80 and 110cm depths, monthly, throughout the 2013/2014 crop year.

Results shown that when 0% SCT was left, SWC and yield were reduced. At most of the time, leaving 25% of SCT would be enough to maintain SWC and crop yield at the same levels reached by the 100% SCT treatment. Major effects occurred down to 15cm of soil depth, and before sugarcane reached full canopy cover.