Response of Sugarcane to Carbon Dioxide Enrichment and Elevated Air Temperature

Abstract

Four sugarcane (Saccharum officinarum) cultivars (CP72-2086, CP73-1547, CP88-1508, and CP80-1827) were grown in elongated temperature-gradient greenhouses (TGG) at ambient or elevated carbon dioxide (CO₂) of 360 or 720 μmol·mol^-1 CO₂ air (ppm, mole fraction basis), respectively. Elevated CO₂ was maintained by injection and feedback control. Each TGG maintained air temperatures in four zones at Base temperature with respect to Gainesville, FL ambient (Zone 1), Base + 1.5 °C (Zone 2), Base + 3.0 °C (Zone 3), and Base + 4.5 °C (Zone 4) via computer-controlled ventilation fans and electric heaters. Data from Zones 1 and 4 are reported herein. Germinated sugarcane seed pieces of each cultivar were planted in early March 1997 in 8 tubs in each zone of each TGG. Four tubs contained mineral soil and four contained organic soil (peat). Two tubs of each soil had a high water table (20 cm) and two had a low water table (~50 cm). Biomass harvests were conducted each June and December of 1997 through 1999. Extracted juice volume and Brix were measured at each harvest from a subset of plants in Zone 1 and Zone 4, and sucrose yield (g per plant) calculated. Over these six harvests, sucrose was 23% greater in doubled CO₂, 23% greater at + 4.5 °C, 63% greater in mineral than organic soil, and 36% greater at the higher water table.