Effects of Potassium Fertilizer on Sugarcane Yields and Plant and Soil Potassium Levels in Louisiana

The influence of potassium fertilizer on sugarcane (interspecific hybrids of Saccharum Spp.) yields and leaf and soil potassium levels was evaluated at six locations in Louisiana. The objective of this study was to determine if the sugarcane yields in Louisiana could be improved with potassium application. Different rates of potassium fertilizer (0–179 kg K2O ha−1) were applied to plant cane and ratoon sugarcane fields in Louisiana. Soil samples and sugarcane leaf samples were also collected from all experiments. Yield data were collected by harvesting plots with a single row, chopper harvester and a field transport wagon equipped with electronic load sensors. At all locations and soil types, potassium fertilizer did not increase cane or sugar yields. Soil properties data showed that significant increases in soil potassium levels did not occur until the second ratoon crop, where soil potassium increased by 30% for the high rate. Increases in plant potassium were also not observed until the second ratoon crop, where plant potassium increased by 10.5% for the high rate. The potential cause of the observed lack of response may be explained by interference from calcium and magnesium, combined with fixation by smectite and vermiculite clay minerals. Our soil and plant uptake data would suggest that repeated K applications at recommended rates, which currently vary from 90 to 157 kg ha−1, may be required to achieve the potential benefits of K fertilizer in Louisiana sugarcane soils. However, this must be verified by additional on-farm trials.