Carbon Accumulation in a Two Year Sugarcane Rotation in Hawai'I, USA.

Sugarcane is a common bioenergy feedstock, and has been examined as feedstock for producing aviation fuel in the Pacific Basin.  Hawaii has been a major producer of sugarcane (Saccharum officinarum L.) in the Pacific, with its typical two-year production cycle having some of the highest reported rates of sugar production in the world.  While it maximizes sugar production, the two-year rotation has been less studied for total biomass accumulation.  We installed two Eddy Covariance in contrasting high (“Lee”) and low (“Windy”) elevation sugarcane fields.  Mean daily net productivity was significantly higher (p=0.015) in Windy than Lee (94.7 vs. 89.5 kg C/hectare/day) after adjusting for differences in tower establishment at the beginning of the cycle and harvest dates.  Contrary to our initial expectations, both fields had significant increases (p<0.001) in daily productivity in the 2^nd year (12-18 months after planting) compared to the full canopy during the first year of the cycle (7-12 months after planting).  Radiation Use Efficiency was statistically the same (p=0.63) between both fields from 7-18 months (radiation).  Differences in incoming solar radiation between Windy (10.2 GJ/m²) and Lee (9.6 GJ/m²) were the largest control of differing daily productivity during the same time periods.  The results suggest that the 2 year plant production cycle may produce total biomass exceeding annual sugarcane rotations with ratoon.