Cultivar Dependent Sugarcane Response to Nitrogen1

Abstract

AbstractSugarcane (a complex trispecies of Saccharum) in Florida is moving from N‐rich Histosols to N‐deficient sands. Since little is known about the N‐use efficiency of cultivars grown in the continental United States, we conducted studies with four cultivars to compare N‐use efficiencies under varying N levels. Three of the cultivars were originally selected as commercial cultivars from the breeding program conducted on N‐rich Histosols of the Everglades while the fourth (CP 65‐357) was selected from N‐deficient soils in Louisiana. A greenhouse experiment, conducted in nutriculture solutions with three N concentrations (0.1, 1.0, and 10.0 mmol L−1) indicated that the highest dry weights were obtained at the second N level from CP 65‐357. However, CP 65‐357 did not accumulate more N than the other cultivars, suggesting more efficient utilization of accumulated N. The field study was conducted for 2 yr on a complex of Pompano (Typic Psammaquants) and Myakka (Aerie Haplaquod) fine sands of low‐N status. Nitrogen levels applied to the first crop were 0, 56, 112, and 224 kg ha−1. The cultivar CP 65‐357 gave the highest yields of cane and sucrose, had the highest external and internal N‐use efficiencies (kg yield kg−1 applied N and kg yield kg−1 N accumulated in above ground plant parts, respectively) regardless of N rate or year. In the ratoon crop, the external and internal N‐use efficiencies for sucrose yield were 24 and 110 kg kg−1, respectively, for CP 65‐357 over all N rates, and 7 and 44 kg kg−1, respectively, for CP 63‐588, the least N‐efficient but the most widely grown cultivar on Histosols in Florida during the period 1975 to 1981. The results suggest that N‐use efficiency of sugarcane can be enhanced by selection under low‐N conditions.