|Viator, Blaine -|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 10, 2014
Publication Date: N/A
Technical Abstract: If sugar and cane yields are to be optimized and profitability improved, it is critical that a sugarcane crop receive the proper levels of plant nutrients. Under-fertilization can result in reduced cane yields, while over-fertilization can reduce sugar recovery. Potassium (K) has been associated with plant water use and may aid in drought tolerance and potassium deficient plants are also more prone to certain diseases and are more likely to lodge. It is therefore critical that the proper rates of K be applied to achieve a balance between cane and sugar yields. The twofold objective of these studies was first to determine the optimum rates of potassium fertilizer and then to determine if variable-rate application of K could help optimize sugarcane yields, while increasing production efficiency. To determine the optimum rates of potassium fertilizer, six studies were initiated in plant-cane, first- and second-ratoon fields of HoCP 96-540 and L 99-226. Potassium fertilizer was applied at rates ranging from 0 to 160 lbs K2O/A. For VR studies, a 7.0-ha commercial field of plant cane Ho-CP 96-540 was selected. Potassium management zones were determined by grid soil sampling, using a 0.75-ha grid. Three zones were developed with corresponding rates of 110, 147, 184 kg K¬2O ha-1. It was not possible to determine yields from a uniform application in the K trials for comparison, but yield variability was evaluated. To estimate yields from VR studies, selected rows from each field were harvested in 30.5-m increments, using a John Deere, single-row chopper harvester. Cane yields were determined using a field transport wagon equipped with electronic load sensors, and theoretically, recoverable sucrose (TRS) levels were estimated by the core-press method. A similar method was used to harvest plots from potassium rate studies. In 2012, first-stubble L 99-226 showed a significant response to potassium in both cane (P=0.15) and sugar (P=0.05) yields. In second stubble L 99-226, a significant response in sugar yield (P=0.1) was observed. In first stubble HoCP 96-540, a significant response in cane yields was observed (P=0.15). There was not a significant response in either cane or sugar yields in second stubble and plant-cane trials, although positive trends were observed in both plant-cane trials. In 2013, first-stubble L 99-226 showed a significant response to potassium in both cane (P=0.05) and sugar (P=0.10) yields. In second stubble L 99-226, a significant response was also obtained in both cane (P=0.05) and sugar yields (P=0.05). In first stubble HoCP 96-540, a significant response was observed in both cane (P=0.05) and sugar (P=0.05) yields. Finally, there was also a significant response in cane and sugar yields in the second stubble HoCP 96-540 trials (P=0.05). In 2012, VR K studies, significant variability was observed, with yields ranging from 84-161 t cane ha-1, 116-147 kg sugar t-1, and 11,160 to 21,000 kg sugar ha-1, respectively. In 2013, cane and sugar yields from the first-ratoon crop exhibited a similar level of variability that was exhibited in the plant-cane trial, with yields ranging from 69-110 t cane ha-1, 112-137 kg sugar t-1, and 8,500 to 13,683 kg sugar ha-1, respectively. Spatial maps of cane and sugar yields from both years exhibited significant spatial correlation, with variability in the K trial closely correlated with the developed management zones. Results suggest that VR application of K may offer Louisiana sugarcane producers a viable method to decrease costs, while increasing production efficiency.