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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Water Management and Systems Research » Research » Publications at this Location » Publication #295687
Title: Minimizing instrumentation requirement for estimating crop water stress index and transpiration of maize

Author
item TAGHVAEIAN, SALEH - Colorado State University
item CHAVEZ, JOSE - Colorado State University
item BAUSCH, WALTER - Retired ARS Employee
item DeJonge, Kendall
item Trout, Thomas

Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2013
Publication Date: 9/11/2013
Citation: Taghvaeian, S., Chavez, J.L., Bausch, W., Dejonge, K.C., Trout, T.J. 2013. Minimizing instrumentation requirement for estimating crop water stress index and transpiration of maize. Irrigation Science. 32:53-65.

Interpretive Summary: Research was conducted in northern Colorado in 2011 to estimate the Crop Water Stress Index (CWSI) and actual water transpiration (Ta) of maize under a range of irrigation regimes. By transferring regional empirical baselines required for CWSI calculation, maize CWSI can be determined using only two instruments: an infrared thermometer and an air temperature/relative humidity sensor. Two hours after solar noon is recommended for once-a-day data acquisition if the goal is to capture maximum stress level. The time period from 10:00 to 11:00 a.m. is recommended if the goal is to monitor maize water use.

Technical Abstract: Research was conducted in northern Colorado in 2011 to estimate the Crop Water Stress Index (CWSI) and actual water transpiration (Ta) of maize under a range of irrigation regimes. The main goal was to obtain these parameters with minimum instrumentation and measurements. The results confirmed that empirical baselines required for CWSI calculation are transferable within regions with similar climatic conditions, eliminating the need to develop them for each irrigation scheme. This means that maize CWSI can be determined using only two instruments: an infrared thermometer and an air temperature/relative humidity sensor. Reference evapotranspiration data obtained from a modified atmometer were similar to those estimated at a standard weather station, suggesting that maize Ta can be calculated based on CWSI and by adding one additional instrument: a modified atmometer. Estimated CWSI during four hourly periods centered around solar noon was largest during the two hours after solar noon. Hence, this time window is recommended for once-a-day data acquisition if the goal is to capture maximum stress level. Maize Ta based on CWSI during the first hourly period (10:00-11:00) was similar to Ta estimates from a widely-used crop coefficient model. Thus, this time window is recommended if the goal is to monitor maize water use. Average CWSI over all hours and during the study period (early Aug to late Sep, 2011) was 0.15, 0.52, and 0.18 for plots under full, low-frequency deficit, and high-frequency deficit irrigation regimes, respectively. During the same period (50 days), total CWSI-based maize Ta was 195, 116, and 189 mm for the same treatments, respectively.