Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2012
Publication Date: 7/15/2012
Citation: Johnson, R.M., Viator, R.P., White, W.H. 2012. Precision agricultural techniques for identifying yield limiting factors in Louisiana sugarcane. Journal of the American Society of Sugar Cane Technologists. 32:77.
Technical Abstract: Precision Agriculture enables growers to efficiently manage inputs, identify yield limiting soil properties, mitigate detrimental environmental or crop conditions, and increase profits. Soil grid sampling and yield mapping were used to document the extent of yield loss resulting from two very different factors, one abiotic the other biotic. In the first study, two fields that were subjected to salt water intrusion were grid soil sampled (0-20 cm) to determine salinity levels: a 4.0-ha field of 1st ratoon, ‘L 99-226’ in 2009 and a 2.5-ha field of plant-cane, ‘Ho 95-988’ in 2010 and 2011. Sugarcane yields were determined from selected rows from each field, which were harvested in 23-m increments using a 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. In the second experiment, four fields with natural infestations of the sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae) were grid sampled to quantify aphid levels and to determine the relations between aphid numbers and yield. At each grid point, soil samples (0-20-cm), aphid levels and plant heights were determined. Cane and sugar yields were determined as described above. In the first experiment, results from 2009-2011 showed that both cane and sugar yields exhibited significant variability in both fields with yields ranging from 0.6 to 103 Mg ha-1 and 53 to 12,120 kg ha-1, respectively. In all three years, spatial variability in cane and sugar yields were correlated with the spatial variability observed in soil salinity levels. In the second experiment, aphid numbers at the four locations exhibited significant variability with the coefficients of variation ranging from 112 to 361%. Aphid levels were negatively correlated with several soil properties, most notably potassium (r = -0.28** to -0.50***) and soil cation exchange capacity (CEC) (r = -0.34** to -0.47**). Contour plots and scatter diagrams of sugarcane yield and aphid numbers provide further evidence of a link between these two parameters. These data would suggest that aphid levels can have an influence on sugarcane yields, albeit small in most cases. The results of both experiments demonstrate how these techniques allow for the elucidation of yield limiting factors that may not be possible with traditional replicated field experiments. Traditional small plot research experiments often cannot incorporate the true degree of variation present at the field scale.