U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Wind Erosion and Water Conservation Research: Lubbock, TX
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                                    Software
                People

                    Staff Listing
                                    CareersSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Plains Area Lubbock, Texas Cropping Systems Research Laboratory Wind Erosion and Water Conservation Research Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications

Title:   Author  item
                                            Baker, Jeffreyitem
                                            Gitz, Dennisitem
                                            Payton, Paxtonitem
                                            Wanjura, Donalditem
                                            Upchurch, Dan
  Submitted to: Agronomy Journal
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 1/4/2007
                                    Publication  Date: 4/4/2007
                                    Citation: Baker, J.T., Gitz, D.C., Payton, P.R., Wanjura, D.F., Upchurch, D.R. 2007. Leaf gas exchange to quantify drought in cotton irrigated based on canopy temperature measurements. Agronomy Journal. 99(3):637-644.Interpretive Summary: Leaf temperatures often increase when plants lack sufficient water to cool themselves.  Taking advantage of this fact, some farmers use measurements of plant temperature as an indication of water stress. We used measurements of cotton leaf photosynthesis and leaf water loss or transpiration as direct indicators of the degree of water stress in order to assess how well plant temperature indicated the degree of water stress.  Using leaf photosynthesis and transpiration as proxies for the degree of drought stress we found that plant temperature alone was a rather poor predictor of the degree of drought stress.  However, we also found that the combination of leaf minus air temperature differential and a measure of the dryness of the atmosphere provided very good estimates of the degree of water stress that a cotton crop was currently experiencing.
                                Technical Abstract: Improvements in the efficient use of applied irrigation water are needed particularly in semiarid regions where sources of irrigation water are limited.  Canopy temperature (Tc) provides an easy to acquire indicator of crop water deficit that has been used in irrigation scheduling systems.  In order to detect drought stress and schedule irrigations, the stress-time index method of irrigation scheduling accumulates the amount of time during a day that TC is above a specified temperature threshold.  Our goal was to quantify the degree of drought stress in terms of leaf-level gas exchange parameters for cotton that was subsurface drip irrigated according to the stress-time index method of irrigation scheduling during two growing seasons. This was accomplished by measuring TC diurnally with hand held infrared thermometers and controlling cuvette leaf temperature TL equal to Tc and then measuring leaf level net assimilation (A) and stomatal conductance (g) at a photosynthetically active radiation level of 1500 μmols (photons) m-2 s-1.  In general, leaf level gas exchange tended to decline with rising TL.  However, we found that A and g could vary by more than two fold at a given TL indicating that Tc was not a particularly robust indicator of the degree of drought stress.  Furthermore, we found the leaf minus air temperature differential (TL-Ta) and vapor pressure deficit calculated based on leaf temperature (VPD) were better predictors of the degree of drought stress than TL alone.  Regression of A and g against  TL-Ta and VPD indicated that the combination of these two variables accounted for over 79% of the variability in A and g.  We conclude that the term Tc-Ta either alone or in combination with VPD should provide a better predictor of the degree of drought stress in cotton than Tc alone.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov