Nitrogen Requirement for Optimal Yield and Quality of Sugarcane Grown On Alluvial Soils in Louisiana.

Nitrogen (N) is the most important nutrient in sugarcane production and considered as the highest expense among fertilizer inputs. Excessive or deficient N supply may result in reduction in both cane yield and sucrose content of cane stalk. This study was conducted to determine the N requirement of sugarcane varieties grown in the alluvial plains of Louisiana for optimal cane yield and sugar quality. Three N x variety trials were conducted from 2004 to 2007 at the LSU AgCenter Sugarcane Research Station in St. Gabriel, LA on a Commerce silt loam to determine the optimum N requirement of current sugarcane varieties. The trials consisted of three cane varieties (2004 to 2006 – LCP85-384, CP70-321, HoCP91-555: 2005 to 2007 – LCP85-384, Ho95-988, L97-128 and 2007 to 2009 – LCP85-384, HoCP96-540 and L99-226) and four N rates that ranged from 0 to 179 kg N ha^-1. Treatments were arranged in a randomized complete block designed with four replications. Cane yield and sugar quality parameters were determined at harvest and were regressed with N rates using non-linear regression analysis in SAS to estimate optimum N rates. Linear-plateau models estimated N rates ranging from 44 to 106 kg N ha^-1 for optimum cane and sugar yield of the varieties tested. Sucrose content and recoverable sugar were similar at N rates between 0 and 95 kg N ha^-1.  Cane yield, sucrose content and recoverable sugar were reduced with N application rates of 134 and 179 kg N ha^-1. Optimal N requirement of sugarcane should be established based on both cane yield and sucrose content to maximize sugar yield.