Submitted to: European Conference on Precision Agriculture Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/2/2008
Publication Date: 7/6/2009
Citation: Johnson, R.M., Viator, H.P. 2009. Variable-Rate Lime Application for Louisiana Sugarcane Production Systems. Proc. Joint International Agricultural Conference. 2009: ICT for Agriculture and Precision Farming, July 6-8, 2009, Wageningen, Netherlands, p. 277. Interpretive Summary:
Technical Abstract: Precision agriculture may offer sugarcane growers a management system that decreases costs and maximizes profits, while minimizing any potential negative environmental impact. Variable rate (VR) application of lime and fertilizers is one area in which significant advantages may be realized. A series of experiments was initiated in the summer of 2006 to determine the utility of VR lime application to Louisiana sugarcane production systems and to investigate alternate methods to estimate lime requirements for sugarcane. Soil electrical conductivity (EC) mapping techniques were also evaluated as potential tools to develop management zones for VR lime application. Soil samples (0-15-cm) were collected from a nine hectare field on a 0.3-ha grid to map variability in soil pH and lime requirement. Both shallow (0-30-cm) and deep (0-90-cm) soil EC data was also collected at the same time using a Veris soil EC mapping system. Soil samples were analyzed for soil pH and lime requirement was determined by the standard Shoemaker-McLean-Pratt (SMP) procedure and two additional methods (Adams-Evans (AE) and Woodruff (WD) lime requirement methods). VR application maps were prepared utilizing variogram analysis and kriging of the grid soils data. Treatments compared the SMP, AE and WD lime requirement estimates in both VR and uniform scenarios along with a no-lime control. Plots were seven rows wide (15-m) by ~85-m, and there were six replications. Lime treatments were applied with a Newton Crouch VR lime applicator equipped with a Mid-Tech VR controller. Soil pH was found to vary from 4.1 to 8.1 prior to lime application and the corresponding lime recommendations were also variable with the calculated lime rates ranging from 0-7.8, 0-7.4 and 0-3.4 Mg/ha for the Shoemaker-McLean-Pratt, Adams-Evans and Woodruff lime requirement methods, respectively. Soil EC measurements were 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 (kg/Mg) with VR lime application. The Adams-Evans VR treatment resulted in the highest TRS of all methods (237 kg/Mg) and the no-lime control the lowest (227 kg/Mg). Sugar yield (kg/ha) was significantly greater (P=0.18) with the Woodruff VR method (9450 kg/ha) as compared to the conventional SMP method (8800 kg/ha). These combined data suggest that sufficient variability exists in both soil properties and cane and sugar yields to justify a precision management approach 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.