Irrigating by Maximizing Water Input Efficiency
The objective is to limit the portion of water supplied that is not utilized by the crop through irrigation management (timing and dose) and proper adjustment and verification of equipment in order to reduce losses by drainage, runoff, evaporation, or drift.
Presentation
Performing water balance calculations, monitoring information provided by advisory organizations, monitoring soil moisture using capacitive probes, or water tension using tensiometric sensors, allows adapting water inputs (start, dose-frequency rhythm, stopping irrigation) to crop needs and thus limit losses by drainage or runoff.
Verifying proper equipment adjustment helps avoid losses by drainage/runoff caused by poor spatial distribution of irrigation water.
Finally, applying water inputs in the absence of wind and outside the hot hours of the day helps limit losses by drift and evaporation.
Implementation example
For corn irrigated by travelling gun, installing tensiometric probes allows monitoring the evolution of soil water tension. Comparing the measured tension to tensiometric thresholds enables decision-making :
- triggering the first irrigation
- resuming irrigation cycles by possibly adjusting the base rhythm per environment according to rainfall
- ending irrigations.
Irrigation cycles are performed in the absence of wind to avoid drift losses, preferably early morning, evening, or night to avoid evaporation losses. Finally, proper adjustment of the travelling gun (advance speed, applied dose, and rotation angle) ensures good spatial distribution of water.
Application of the technique to...
All crops : Easily generalizable.
All soil types : Easily generalizable.
All climatic contexts : Easily generalizable.
Effects on cropping system sustainability
"Environmental" criteria
Effect on air quality : Optimizing irrigation efficiency reduces greenhouse gas emissions related to the ineffective portion of water inputs (pumping, travelling gun movement).
Effect on water quality : Irrigation management and proper equipment adjustment reduce the risk of nitrogen transfers to aquatic environments via drainage and help minimize winter residual nitrogen.
Effect on fossil resource consumption : Optimizing irrigation efficiency reduces energy consumption related to the ineffective portion of water inputs (pumping, travelling gun movement).
"Agronomic" criteria
Productivity : Under restrictive conditions, irrigation management and proper equipment adjustment allow better use of available water, thus improving crop and system productivity. Under non-restrictive conditions, these techniques enable achieving the same yield with less water.
Product quality : Irrigation management can also play an important role in the quality of productions (open-field vegetables...).
Water stress : Decreasing. However, improving irrigation efficiency involves better exploitation of soil water resources, which can lead to greater water deficit at crop harvest (but less than after a dry summer crop), potentially limiting the establishment of a winter crop or an intermediate crop. In systems based on spring crops, the water reserve is generally replenished by winter rainfall before the next crop is planted.
Functional Biodiversity : No effect.
"Economic" criteria
Operating costs : No effect.
Mechanization costs : Irrigation management may involve additional costs (from €0 for performing a water balance, about €450 for a tensiometric kit to equip a plot, up to €3,000 for certain capacitive probes). This cost is offset in the short to medium term if management avoids irrigation cycles (an irrigation cycle costs about €30/ha).
Margin : Irrigation management and proper equipment adjustment help improve profitability either by reducing costs related to irrigation for the same yield or by increasing yield for the same amount of water applied.
"Social" criteria
Working time : Irrigation management can reduce workload related to moving travelling guns if it leads to fewer irrigation cycles.
Image of agriculture : Water resource sharing increasingly causes conflicts between agriculture and other users. Reducing the volume of water used for irrigation helps improve agriculture's image.
Observation time : Performing water balances, monitoring measurements from capacitive probes or tensiometric sensors requires observation and interpretation time, about one day per campaign.
Further reading
- Technical basics of sprinkler irrigation - Mathieu C. - Ed. Lavoisier, Book, 2007.
- Practical guide to irrigation - Chossat J.C. & Rieul L. - Ed. Cemagref, Book.
- Irrigation management – From strategy to irrigation control - RNED-HA - Ed. Cemagref, Book, 1995.
- Optimizing irrigation management - Finer strategies and more precise tools - Milou C. - Cultivar n°626, p32-33, Press article, 2009.
- Irrigation treatise - Tiercelin - Ed. Lavoisier, Book, 2006.
Contacts
Cédric Jaffry - CA 47 - cedric.jaffry@lot-et-garonne.chambagri.fr - Agen (47).
Rémy Ballot - INRA - remy.ballot@grignon.inra.fr - Grignon (78).
