Pumping restrictions, limited water require efficient irrigation
By Jenna Smith, November 2004
For more information regarding this subject, contact:
Giovanni Piccinni
(830) 278-9151
g-piccinni@tamu.edu
Efficient water use in the Rio Grande Basin is critical to conserving limited supplies. Limited water availability and pumping restrictions have impacted both urban and agricultural water users, necessitating the use of efficient methods for conserving water.
By 2008, agricultural producers will need to reduce their water use by approximately 80,000 acre-feet so that water supplies in South Texas last into the future and natural springs continue to flow.
Giovanni Piccinni, assistant professor of crop stress physiology at the Texas A&M Research and Extension Center at Uvalde, and a team of researchers are developing efficient irrigation practices and proper management techniques to help farmers produce the most crop with the least amount of water. Their work is supported in part by the Rio Grande Basin Initiative.
The Texas A&M Agricultural Research and Extension Center in Uvalde is one of the few centers in the nation with a state-of-the-art in-ground lysimeter facility capable of measuring crop water use.
“Here in the Winter Garden, we produce crops 12 months out of the year, so we must have adequate water supplies for our entire growing season,” Piccinni said. “Many of the crops we plant are already drought-tolerant, so efficient management practices are key to conserving our water sources.”
Piccinni said that by monitoring plant population and row spacing, reducing tillage practices, utilizing water capture techniques such as furrow dikes and circled rows under center pivots, and using accurate crop coefficients, 25 percent of the water currently used in the region can be saved. Crop coefficients are used in evapotranspiration formulas to calculate the amount of water lost by a particular crop at a certain stage of maturity at an exact point in time.
To date, Piccinni and his team have identified accurate crop coefficients for corn and spinach and will have accurate measures for both sorghum and onions within the next year.
“Utilizing accurate crop coefficients will help with current limited irrigation strategies,” Piccinni said. “However, producers must know how much water to apply in the first place.”
Farmers irrigating with less water than the amount required to replace evapotranspiration losses will be able to adhere to limited irrigation schedules. Evapotranspiration is the maximum amount of water lost in a cropping system in a given time period from both plant transpiration and soil evaporation.
Crop yields may decrease to an extent, but the water saved can be used on additional crop acreage or can be sold, thereby producing maximum profits with two harvests and minimizing the costs of pumping and wasting excess water.
In collaboration with Thomas Marek and Don Dusek from the Amarillo Research and Extension Center, Piccinni has also developed an online potential evapotranspiration program in which farmers can use their typical planting dates and plant maturity stages to determine how much water will be needed by their crop.
“We have the data necessary to help conserve water, but we must be able to tell producers when to irrigate,” Piccinni said. “We need tools for these producers to use so that they know the point to which their plants can be stressed before applying water.”
Piccinni’s additional component of water conservation in the Winter Garden includes using remote sensing to detect canopy temperatures in the field. When plants are stressed, by disease or water shortages, they register a higher canopy temperature than the surrounding air temperature.
If diseases, such as root rot in cotton, can be identified two to three weeks before they actually appear, steps can be taken to salvage the crop or halt irrigation applications if the crop is expected to die. If water shortages are the problem, farmers will be able to single out those areas of a field needing additional water instead of irrigating the entire field.
The next step for Piccinni is participating in on-farm research with area farmers. This opportunity will allow him to calibrate the irrigation scheduling model he is working with and adjust it to fit the needs of producers. Twelve farmers have already agreed to participate in the study.
“Teaching and showing farmers how this model applies to their individual situations is very effective,” Piccinni said. “Using these field demonstrations, we hope that neighboring farmers will understand how to conserve water through efficient irrigation strategies.”
