Submitted to: National Irrigation Symposium
Publication Type: Proceedings
Publication Acceptance Date: November 14, 2000
Publication Date: N/A
Technical Abstract: The purpose of the study was to compare the sensitivity of leaf water potential (LWP), & remotely measured canopy temperature (CT) with the change in crop water status caused by abrupt change in irrigation. The low water level (WL) of corn was 0.66*PET (potential evapotranspiration) & rainfed in cotton. The high water level (WH) was 1.0*PET in both crops. The echange in irrigation in 1998 & 1999 began on 9 July & 7 July in corn & on 21 July & 26 July in cotton. The treatment that relieved water stress was TLH (water input changed from WL to WH) & the treatment which induced water stress was THL(water input changed from WH to WL). LWP of corn changed 5 days after reversing water levels & after 3 days in cotton in 1998. A change in LWP in 1999 required 8 days for corn & 3 days for cotton. LWP differences detected in corn ranged from 2-4 bars in corn & about 2 bars in cotton. The difference in CT between the TLH & THL treatments, expressed as sthe daily time that canopy temperature was >28C (DST), was not detected after 25 days in corn in 1998, but was noted in cotton after 4 days. In 1999 the difference in DST of corn was not detectable after 13 days, but occurred after 5 days in cotton. A DST difference of 1.0 was not detected in corn in the range between 9.5 & 11.3 DST, but a 1.0 difference in cotton between 9.9 & 11.9 DST was detected. The CT of corn was more variable than cotton which decreased its sensitivity to changing water status. The canopy architecture of corn results in a surface with more shaded area than the planofile surface of cotton when viewed from above. CT temperature was sensitive to crop water status & can be rapidly measured in a field compared to LWP which accurately measures water status but can not be automated with current technology.