|WALCOTT, M - LSU Agcenter|
Submitted to: Louisiana Agriculture
Publication Type: Popular Publication
Publication Acceptance Date: 4/25/2008
Publication Date: 7/2/2008
Citation: Viator, H.P., Johnson, R.M., and Walcott, M. 2008. The Application of Precision Agriculture Technologies to Sugarcane. Louisiana Agriculture. 51(2):40-42.
Technical Abstract: The availability of global positioning systems (GPS) has made it possible to abandon traditional ways of managing sugarcane fields as whole units in favor of approaches that address within-field variability. A series of experiments was initiated to determine if soil electrical conductivity (EC) mapping techniques could be used to develop management zones for variable rate (VR) lime and nitrogen fertilizer application. The study was also designed to investigate alternate methods to estimate lime requirements for sugarcane grown on Louisiana soils. Soil EC levels were found to be correlated with soil type and texture and were used to develop zones for the VR application of nitrogen. Sugarcane yields were not equal across all application zones in a consistent fashion using five nitrogen application rates, due to variation in soil moisture and pH. In a subsequent VR nitrogen study where soil pH levels were corrected prior to the application of nitrogen, a relatively “smooth” yield map was achieved with average zonal yields ranging from 37 to 39 tons of cane per acre . In a VR lime study, soil pH was found to vary from 4.1 to 8.1 in a commercial sugarcane field following soil grid sampling. The corresponding lime recommendations were also variable with the calculated lime rates ranging from 0-3.5, 0-3.3 and 0-1.5 tons per acre for the Shoemaker-McLean-Pratt, Adams-Evans and Woodruff lime requirement methods, respectively. Soil EC measurements were also correlated with soil pH levels from grid soil samples with pH increasing with soil EC levels. Sugarcane yield results from this study showed a significant advantage in the theoretically recoverable sugar (TRS) levels with several of the alternative lime requirement procedures, with the Adams-Evans VR treatment resulting in the highest TRS of all methods; however, sugar yield (lbs/A) was highest with the Woodruff VR method. These results are promising, because if similar yields can be obtained with the VR system while actually applying fewer inputs, then Louisiana sugarcane producers can show an overall increase in profitability. These combined data suggest that sufficient variability exists in both soil properties and cane and sugar yields to justify a precision management approach.