MEASURING WATER STRESS IN COTTON IN TWO PRODUCTION SYSTEMS

Authors: Sassenrath, Gretchen; Williford, Julius

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/4/2005
Publication Date: 6/1/2006
Citation: Sassenrath, G.F., Williford, J.R. 2006. Measuring water stress in cotton in two production systems. National Cotton Council Beltwide Cotton Conference, January 3-6,2006, San Antonio, Texas. 2006 CD-ROM

Interpretive Summary: Plant water status can be determined fairly accurately on individual leaves. However, when trying to determine the water status for a crop, it is challenging to extrapolate from individual leaf measurements to a realistic estimate of total-canopy water status. Area-wide monitoring methods, such as remote sensing or environment based methods, can potentially estimate the crop water use for scheduling irrigation. To better correlate these large-scale measurements with accurate within-field measurements, we are examining different physiologically based methods of determining plant moisture level in cotton. We measured leaf water potential in two production systems: a conservation system and a conventional system, for both irrigated and rain fed cotton. The Scholander pressure bomb, while more consistent, was limited in the number of replications by time constraints. Remote imagery was relatively quick and easy to obtain, but was limited by its sensitivity to ambient environmental conditions.

Technical Abstract: Various methods of estimating crop water status are available. Most commonly used methods are suitable for small-scale laboratory studies, but are not well-suited for the large scale monitoring needed for production research. To avoid yield-limiting water stress, we need to have an accurate, easy to use method of measuring plant water potential. Direct measures of leaf water potential, such as the Scholander pressure bomb and the dew point hydrometer, are time consuming, limiting the number of samples that can be accurately read in a short period of time. Remotely sensed methods such as canopy temperature and reflectance measurements are sensitive to environmental conditions (temperature and sunlight) during the measurement period, and are not well correlated to physiological changes in leaves. Moreover, remotely sensed methods are susceptible to interference from ancillary factors that contribute to the overall measurements, particularly from the soil. In this study, we determined leaf water status in field-grown cotton plants from two production systems, conservation and conventional, for irrigated and rain fed cotton. Preliminary results show the pressure bomb to give the most consistent readings across replications, while remote sensing methods were the easiest to obtain.