Sunday, November 12, 2006 - 3:45 PM

Use of Vegetation Index to Determine Potential Yield Loss: A Risk Managment Tool for Asian Soybean Rust.

George Clements1, Saratha Kumudini1, Joseph Omielan2, and Elena Prior1. (1) Univ of Kentucky, 437 Plant Science Bldg, 1405 Veterans Dr, Lexington, KY 40546, (2) University of Kentucky, UK Plant & Soil Sciences, 1405 Veterans Drive, Lexington, KY 40546-0312

The most effective method for determining soybean yield loss due to defoliation is through a mechanistic understanding of crop growth and yield development.  Remaining leaf area index (LAI) is considered to be the better predictor of yield.   However, we need a non destructive measurement of remaining LAI.  One means of achieving this is through the use of a vegetative index such as NDVI. The objective of this study was to develop a relationship between LAI measurements and NDVI at different stages of development and using two different maturity groups (MG). LAI and NDVI measurements were taken from soybean plots in Lexington, KY and Londrina, Brazil.  In Lexington, MG III and IVs were used, a MG VII was used in Brazil.  Different levels of defoliation were simulated by picking the leaves off of plants. Destructive LAI samples were compared to NDVI measurements taken with the GreenSeeker.  Similar procedures were conducted in Brazil but in Brazil, rust infected plots were also available for measurement.  The Brazilian data illustrated a good relationship between LAI and NDVI.  In summary, the use of NDVI measurements appears to be a good tool in estimating soybean LAI levels when LAI levels are lower than optimal.  Potential yield loss is more likely under low LAI levels. Therefore the use of the vegetative index NDVI appears to be good tool for estimating potential yield loss due to Asian soybean rust.