Sugarcane Response to Water Table , Periodic Flood , and Foliar Nitrogen on Organic Soil

Sugarcane (Saccharum spp.) is routinely exposed to periodic floods and highwater tables in Florida’s EvergladesAgriculturalArea. Learning sugarcane responses to these conditions will help improve yields. This study evaluated the effects of constant water-table depths, periodic floods, and N on cane and sucrose yields of two sugarcane cultivars. In 2001 and 2002, two foliar N and four water treatments were applied to the first two crop-growth cycles (plant and first-ratoon crops) of ‘CP 722086’ and ‘CP 80-1827’ in lysimeters filled with Pahokee muck soil. Constant water-table depths were 23, 37, and 51 cm.A fourth treatment was flooding for 2 d in each of eight 14-d cycles per year; otherwise its water-table depth was 44 cm. Foliar N did not consistently affect yields. In nonflooded treatments across cultivars and crop growth cycles, for every centimeter increase in water-table depth, theoretical recoverable sucrose decreased by 0.13 g kg, and cane and sucrose yields increased by 0.16 and 0.02 kgm, respectively. By cultivar and crop-growth cycle, the only significant linear responses to nonflooded water-table treatments were in the first-ratoon crop, where for each centimeter increase in water-table depth, cane and sucrose yields increased by 0.38 and 0.04 kg m, respectively. Periodic flooding increased cane and sucrose yields in the plant crop and sustained or improved these yields in the first-ratoon crop.After rains, allowing floods to remain for up to 2dmay improve yields and reduce P discharge to the Everglades. THE Everglades Agricultural Area (EAA) is a 280 000-ha basin of Histosols that lie on limestone bedrock in the northern region of the historic Everglades in Florida. Sugarcane is grown on about 146 000 ha in the EAA (Glaz, 2002). Before construction of an extensive public/private system of canals through the northern Everglades, the EAA was flooded most of the time (SnyderandDavidson,1994). Until recently, farmersused the canal system to effectively manage desired watertable depths of 40 to 95 cm in sugarcane fields (Omary and Izuno, 1995). The canal system still helps control water tables in EAA sugarcane fields. However, it is now common for sugarcane to be exposed to high water tables and periodic floods in all crop-growth cycles. Three major reasons for the reduced effectiveness of the canal system are the rising of water tables in the EAA by about 10 cm for each centimeter of rainfall, loss of soil depth due to soil subsidence, and voluntary and regulated pumping restrictions to control P discharge from the EAA. These factors were described previously in more detail (Glaz et al., 2004). Previous research found that some sugarcane genotypes yielded well in Florida at water-table depths of #30 cm. In a field study, Kang et al. (1986) compared sugar concentrations and cane yields of 16 clones of sugarcane (Saccharum spp.), one of S. robustum, one of S. officinarum, and one of Ripidium spp. at field watertable depths of 30 and 56 cm. They found that, at the 30-cm water-table depth, in the plant-cane and firstratoon crops, respectively, overall mean sugar concentrations were 15.7 and 17.6% higher, and overall mean cane yields were 27.5 and 25.3% higher. In a field study, Glaz et al. (2002) maintained nine cultivars under summer water-table depths of ,15 cm and between 15 and 38 cm for the plant through the second-ratoon crops. Overall sucrose yields under the shallow water table (,15 cm) were 91.7% of those at the deeper water table, and sucrose yield of one cultivar, CP 80-1743, was reduced by 25% by the shallow water table. However, sucrose yields of two cultivars, CP 72-2086 and CP 821172, were not affected by water-table depth. In a lysimeter study with two genotypes, Glaz et al. (2004) reported yield losses attributable to periodic floods of 1-wk duration and drainage to 50 cm compared with a continuous water-table depth of 50 cm for CP 95-1376, a genotype that did not form constitutive stalk aerenchyma. As water-table depth during nonflood periods increased from16 to50cm,yieldsofCP95-1376 increased linearly. Yields of CP 95-1429, which formed constitutive stalk aerenchyma, were not affected by periodic floods or water-table depth. Under routine growing conditions, it is thought that microbial oxidation of organic soils in the EAA makes excessive N available to sugarcane. Annual rate of soil loss in the EAA is about 1.3 cm (Shih et al., 1998). Terry (1980) estimated that 686 kg N ha are mineralized for each cm of soil lost to microbial oxidation. Thus, about 892 kg N ha are mineralized annually. Coale et al. (1993) estimated annual N accumulation by a sugarcane crop on Florida Histosols at 142 kg ha, well below the estimated 892 kg ha that is mineralized. However, the recent discovery by Morris et al. (2004) that microbial oxidation was controlled by periodic floods and drainage to a depth of 16 cm raises the question of whether intervals of flood and drainage to shallow depths in EAA fields may result in periods of insufficient N availability for optimum sugarcane yields. Adding to this concern was the report by Cisar B. Glaz, USDA-ARS Sugarcane Field Station, 12990 U.S. Hwy. 441 N, Canal Point, FL 33438; R.A. Gilbert, Univ. of Florida, Everglades Res. and Educ. Ctr. , 3200 East Palm Beach Rd., Belle Glade, FL 33430. Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by USDA or the University of Florida over others not mentioned. Received 7 Aug. 2005. *Corresponding author (bglaz@saa.ars.usda.gov). Published in Agron. J. 98:616–621 (2006).