ARS | Publication request: Effect of Differential Irrigation on the Accumulation of Canopy Temperature-Based Heat Units in Cotton

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 2, 2012
Publication Date: N/A

Interpretive Summary: The ability to monitor and predict plant growth during the growing season is often valuable in optimizing management on the farm. Producers often rely on “heat units” to monitor the progress of the crop. Heat units use air temperature to predict and account for the effects of the local environment on the crop. Measuring the temperature of the plant has become almost as simple as measuring air temperature and in this study, canopy temperature was used to calculate canopy temperature-based heat units for monitoring the crop. The results suggest that canopy temperature-based heat units may provide additional insight to the producer particularly when crops are being grown under less than optimal irrigation conditions.

Technical Abstract: Agricultural management decisions are often timed to coincide with growth and development on the basis of accumulated air temperature heat units. Air temperature heat unit accumulation is affected by water deficits that alter the relationship between air and plant canopy temperature. Improved technology for monitoring canopy temperatures makes it possible to continuously monitor canopy temperature in production settings. The utility of cotton canopy temperature heat units was assessed by comparing decadal (2000 to 2009) air temperature heat unit variation with variation in canopy temperature heat unit accumulation due to variable irrigation in 2009. Irrigation-induced variation in canopy temperature heat units was similar to the decadal variation in air temperature heat units. Two heat unit-based management tools; 1) the assignment of irrigation crop coefficients and 2) the identification of a fiber thickening period were both sensitive to irrigation-induced changes in heat unit accumulation. The inclusion of canopy temperature heat units resulted in variability in both indicators that reflected effects of irrigation and climate on plant performance. Inclusion of canopy temperature measurements in heat unit accumulation may improve the utility of heat units. The practical implementation of a canopy temperature heat unit approach will require additional research to more fully develop the relationships between canopy heat units and crop development.