The 2013 Precision Ag Action Summit was held on January 21 & 22 in North Dakota. Richard B. Ferguson of the University of Nebraska-Lincoln gave a presentation on “Vegetation Indices and Crop Stress”. Some indicators of crop stress include color, leaf or plant shape, patterns within leaves, patterns of leaves on plant and patterns of plants within a field. Vegetation Index is measured by a combination of surface reflectance at two or more wavelengths designed to highlight a particular property of vegetation.

Summary from his presentation:
— Plant color is highly correlated with chlorophyll content, which is highly correlated with nitrogen stress.
— Crop color and biomass can be measured with optical sensors in visible and near-infrared wavelengths.
— Vegetation indices measure the relationship between canopy reflectance characteristics and crop properties of interest, such as nitrogen stress.
— Sensors to manage N stress are commercially available. Sensors for water deficit and other sources of stress are in development.

Click here to view his full presentation.