Physiological and Growth Responses of Sugarcane Genotypes to Nitrogen Rate on a Sand Soil

Yields of sugarcane (a complex hybrid of Saccharum spp .) in FL , USA , are lower on sand soils than on organic (muck) soils. Nitrogen ( N ) supply may limit sugarcane growth and yields on these sand soils. A 2‐year pot study was conducted to determine sugarcane genotypic variation in response to N rate on a sand soil. Treatments included four N rates (0, 75, 150 and 225 kg ha −1 ) and three sugarcane genotypes ( CP 80‐1743, CP 01‐2390 and TCP 87‐3388). Nitrogen fertilizer was equally split and applied at about 55 and 125 days after planting ( DAP ) for each treatment. During the experiment, the number of nodes and length of the primary stalks and tillers were recorded. Leaf relative chlorophyll (soil plant analysis development ( SPAD )) and net photosynthetic rate (Pn) were measured biweekly. All plants were harvested at 183 DAP to measure green leaf area ( GLA ), shoot biomass accumulation and partitioning, and fertilizer N use efficiency ( NUE ). Genotypes differed significantly in leaf SPAD , Pn, GLA , and shoot biomass accumulation and partitioning. CP 01‐2390 had the highest leaf Pn and shoot biomass, and CP 80‐1743 had the lowest GLA , shoot biomass and NUE among genotypes. Nitrogen rate affected leaf SPAD , GLA , shoot biomass and NUE , but had much less effect on leaf Pn. Green leaf area and biomass increased with increasing N rates. Our results suggest that a two‐pronged approach, selection of genotypes with high NUE while working to optimize N rates and delivery can improve sugarcane yields on sand soils.