Precision of Sugarcane Biomass Estimates in Pot Studies Using Fresh and Dry Weights

Sugarcane (Saccharum spp.) field studies generally report fresh weight (FW) rather than dry weight (DW) due to logistical difficulties in drying large amounts of biomass. Pot studies often measure biomass of young plants with DW under the assumption that DW provides a more precise estimate of treatment effects than FW. The purpose of our research was to compare experimental precision of FW and DW measurements on sugarcane green and brown leaves, and on stalks in pot studies. Four pot studies harvested after 2-6-months growth were conducted at Canal Point, FL from 2005 to 2009 with each experiment being a combination of some of the following treatments: genotype, crop cycle (plant-cane or first ratoon), water-table depth, water availability, soil type, or N rate. For green leaves, brown leaves, and stalks, we measured FW and DW, and calculated DW:FW ratio. Analyses of variance, regression, and estimates of CV and repeatability were used to compare treatment responses and appraise experimental precision. For all parameters, treatment responses were generally similar for FW and DW. Similar CVs and highly significant regressions (r 2 = 0.74-0.99****) were consistently found between FW and DW. The relationship between FW and DW:FW was consistently poor (r 2 = 0.00-0.25) with slopes of approximately 0 for the regression lines, indicating that changes in FW had little effect on DW:FW. Repeatability values were generally low for all traits, but similar between FW and DW. Results suggest that measuring biomass as FW rather than DW would save substantial resources in conducting pot studies.