ATM-10
Implementation of Deficit Irrigation Regimes: Demonstration and Outreach
Project Description and Location
Location
This research was conducted by Colorado State University near Greeley, CO. Research was conducted at the Limited Irrigation Research Farm (LIRF) near Greeley, CO, managed by the U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS). The field workshops were also held at the LIRF farm.
Description
The motivation for the research-outreach project was based on the pressure that irrigated agriculture is under to be more efficient (more crop per drop) in saving water (consumptive use) for other uses (e.g., water transfer to municipal, industrial, recreational, etc.). This report documents an evaluation of different methods of monitoring crop water stress and consumptive use (CU) under deficit irrigation.
The objectives were:
- To evaluate the capability of certain methods for monitoring crop water stress (CWS) and crop consumptive use (CU) or evapotranspiration (ET) for crops managed under limited/deficit irrigation (one alternative Ag water transfer method (ATM) as a mean to conserve CU). The study reviewed infra-red thermometry/thermography (IRT) technology methods, including ground-based remote sensing (RS), airborne RS, and satellite RS.
- To demonstrate the implementation of crop water stress monitoring through field days, workshops, and publications.
Limited Irrigation Research Farm (LIRF) Projects and Collaborations
During this project, two field days were held at the LIRF USDA ARS farm near Greeley, CO, to show field data (results) and the different instrumentation needed to monitor crop water stress under different irrigation strategies (full, low-frequency deficit irrigation, and high-frequency deficit irrigation).
ATM Activities
Limited/deficit irrigation
Project Duration
No physical ATM activities were completed as a part of this study. The research was documented in the May 5, 2016 report. Workshops were held on August 8 of 2014 and April 21, 2016.
Project Funding
Involved co-sponsors and collaborators: Colorado State University (CSU), Colorado Northern Water Conservancy District, West Greeley Conservation District, Central Colorado Water Conservancy District, CSU Extension (Water Team), and USDA ARS Water Management Research Unit (Fort Collins, CO)
Corn Field - Photo by Bob Bowie (thedenverchannel.com)
Water Supply
Water supply for crops grown in the research project was not discussed, as the report focused on methods for monitoring crop water stress, crop consumptive use, and evapotranspiration.
Key Infrastructure or Project Components
Key infrastructure related to water supply was also not discussed.
Agronomic Benefits and Impacts
Agronomic benefits and impacts were not discussed, as the report focused on the process of methods of monitoring crop water stress, crop consumptive use, and evapotranspiration.
Project Successes and Lessons Learned
- The WISE (Water Irrigation Scheduler for Efficient Application) online tool seems to be a feasible option to estimate crop water requirements (amounts needed) and schedule irrigations. The tool seems to work well for well-managed/irrigated fields.
- If using an infra-red thermometer (IRT) sensor to measure crop stress, make sure that the sensor is reading canopy temperature only, otherwise, a model is needed to remove the bias/contamination of soil background temperature.
- Inexpensive handheld IRTs are not accurate and need a thorough calibration. The sensor underestimated true target temperature as they are affected by sensor body heating, air temperature, etc.
- The surface aerodynamic temperature (SAT energy balance) is one energy balance – remote sensing method that has the potential to monitor corn water use under different irrigation regimes.
- The crop water stress index (CWSI) model tends to under-estimate crop actual evapotranspiration (ETa) for stressed corn (limited/deficit irrigation), compared to the SAT method. Further work is needed on the method before routine operations for monitoring deficit irrigation effectively.
- If using soil water content sensor data to estimate crop actual ETa, sensors should be well-calibrated and well installed throughout the soil root zone.
- The inclusion of remote sensing vegetation indices may improve the estimation of crop water stress and thus be a valid tool to monitor reduced CU under limited irrigation regimes.
- The Remote Sensed Evapotranspiration (ReSET) algorithm using remote sensing images from Landsat (both reflectance and thermal) performed well in estimating ETa, but is resource-intensive (both in regards to data input and user interaction).
- The reflectance-based crop coefficient (Kc_refl) method based on Normalized Difference Vegetation Index (NDVI) and also Soil Adjusted Vegetation Index (SAVI) performed somewhat similar to ReSET; it is straight-forward and has shown potential for practical implementation of remote sensing to monitor deficit/limited irrigation.
Project Challenges and Identified Data Gaps
Challenges were identified associated with different tools for monitoring and measuring crop water stress (CWS) and crop consumptive use (CU) or evapotranspiration (ET). These challenges and identified next steps are discussed under the Lessons Learned section.
