Effects of Potassium Fertilizer on Cane and Sugar Yields in Louisiana Sugarcane.

In recent years, many Louisiana sugarcane producers have elected to eliminate potassium from their soil fertility programs due to the high cost.  In 2011, four potassium fertility studies were initiated in plant-cane and first-ratoon fields of HoCP 96-540 and L 99-226 to determine the influence of potassium fertilizer on cane and sugar yields.  These studies were continued in 2012, in the first- and second-ratoon fields and the studies were repeated by initiating two new plant-cane studies in fields of HoCP 96-540 and L 99-226.  Soil samples were collected prior to fertilizer application and after harvest.  All of the sites selected for these studies tested low or very low for potassium.  Five potassium rates were applied to each field ranging from 0 to 179 kg K₂O/ha.  All plots were harvested with a chopper harvester and weigh wagon equipped with a billet-sampler to collect samples for juice quality analysis. Cane and sugar yield data from 2011 to 2014 varied between location, crop age and variety.  For HoCP 96-540, potassium significantly increased cane and sugar yields in 25% of the trials; whereas positive trends were displayed in 50% of the trials for cane yields and 38% for sugar yields. For L 99-226, potassium significantly increased cane yields in 57% and sugar yields in 43% of the trials and positive trends were displayed in 71% and 86% of the trials for cane and sugar yields, respectively.  Results from these studies demonstrate that significant increases in cane and sugar yields can be achieved with potassium fertilizer application in both plant-cane and ratoon fields of two of the major Louisiana sugarcane varieties.  Louisiana sugarcane producers that have eliminated potassium from their soil fertility programs may experience decreases in their cane and sugar yields as potassium levels fall to limiting levels.