ARS | Publication request: Sugarcane Responses to Water-Table Depth and Periodic Flood

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 9, 2009
Publication Date: December 29, 2009
Repository URL: http://parking.nal.usda.gov/shortterm/21343_Glaz_and_Morris_2010.pdf
Citation: Glaz, B.S., Morris, D.R. 2009. Sugarcane Responses to Water-Table Depth and Periodic Flood. Agronomy Journal. 102:372-380.

Interpretive Summary: Undesired phosphorus export from the Everglades Agricultural Area (EAA) in Florida to the natural Everglades is reduced by minimizing pumping from farms to public canals. Therefore, sugarcane, the primary crop in the EAA, is exposed to high water tables and floods because farmers often do not optimally drain excess rainwater from their fields. This 3-year lysimeter study tested yield responses of four sugarcane cultivars, CP 88-1762, CP 89-2143, CP 89-2376, and CP 96-1252 to water-table depths and periodic floods. Treatments were target water-table depths of 20 and 45 cm below the soil surface with and without periodic flooding. Floods were applied for the first 7 days of a 21-day cycle that was repeated four or five times each year. During the next 7 days of each cycle, there was no irrigation or drainage, with the expectation that evapotranspiration would result in partial subsidence of floods as often occurs in commercial sugarcane fields in Florida. However, rainfall was greater than evapotranspiration during these 7-day periods in most 21-day cycles which resulted in lysimeters with flood treatments remaining flooded for up to 14 days. During the final 7 days of each cycle, flooded lysimeters were drained to 20 or 45 cm, the depths of their matching non-flooded lysimeters. Yields of one cultivar, CP 89-2143, were the least affected by water-table treatments. The other three cultivars generally had higher cane and sugar yields at the 45-cm water-table depth with or without flooding than at the 20-cm water-table depth with or without flooding. A surprising result was that the difference in the 20 and 45 cm water-table depths affected yields more than flooding vs. constant drainage. This result along with results from previous studies suggests that sugarcane roots function well under flood for up to 14 days, but will not grow well into soil that is saturated with water. This new theory helps explain the tolerance of sugarcane to flooding while also suggesting why a constant 20-cm water-table depth was more detrimental to sugarcane yields than repeated flood durations of 7-14 days with drainage to 45 cm. This new knowledge about sugarcane yield responses to flooding will provide additional flexibility to farmers as they implement best management practices in Florida aimed at controlling phosphorus discharge to the natural Everglades. As follow-up research further clarifies the theory on root responses to floods and water-table depth, farmers will be better able to develop water-management practices that improve yields and limit phosphorus discharge.

Technical Abstract: Sugarcane (Saccharum spp.) is routinely exposed to periodic floods and shallow water tables in Florida’s Everglades Agricultural Area (EAA). The purpose of this study was to examine the yields and juice quality of four sugarcane cultivars (CP 88-1762, CP 89-2143, CP 89-2376, and CP 96-1252) maintained at water-table depths near 20 (20CWT) and 45 cm (45CWT) with and without exposure to periodic summer flooding. In lysimeters, flood durations of 7 d were imposed during five, five, and four 21-d cycles in 2005 (plant-cane crop), 2006 (first-ratoon crop), and 2007 (second-ratoon crop), respectively. Flood treatments generally remained flooded during the next 7 days when they received no irrigation or drainage, and were drained to 20 (20FWT) or 45 cm (45FWT) depths for the final 7 days of each cycle. Water treatment did not affect commercial recoverable sucrose (CRS) except that CRS was reduced by the 45CWT treatment in the plant-cane crop. Cane and sucrose per ha yields of CP 89-2143 were least affected by the water treatments. The other three cultivars had consistent yield losses at a 20 compared with a 45 cm water-table depth, but yields under the 20CWT vs. 20FWT or 45CWT vs. 45FWT treatments were generally similar. These results suggest that sugarcane roots function well for up to 14 days in flood, but they generally will not grow well into water. If further research verifies this finding, it could provide new management options for sustaining high yields of sugarcane exposed to frequent periodic flooding.