Sarah E. Lingle

Soil salinity effects on crop growth and yield-illustration of an analysis and mapping methodology for sugarcane

Summary The effects of soil salinity on growth and yield of sugarcane ( Saccharum spp. hybrids) are used to illustrate how soil and plant samples («ground truths), digital videographic or SPOT HRV spectral observations, and image analysis by unsupervised classification can be used jointly to quantify and map variations in weighted electrical conductivity (WEC, dS m -1 ) of the root zone and YIELD (metric tons of millable stalks ha -1 ). The combined data for the 1992 and 1993 growing seasons of the study showed that each dS m -1 increase in WEC reduced stalk population by 0.6 stalks m -2 , stalk weight by 0.14 kg, and stalk yields by 13.7 metric tons ha -1 . Sugarcane growth and yield were not affected by root zone salinities less than about 2dS m -1 , but no millable stalks were produced at salinities in excess of 10 dS m -1 . The 25 pixels ha -1 of SPOT is a good scale for mapping salt stress patterns and taking site-specific ameliorative actions. The combination of satellite or aerial spectral observations, ground truth, and image classification procedures demonstrated in this study is readily applicable to other vegetation stresses.