Speaker
Description
Introduction
Irrigation is a practice facing increasingly strong constraints, whether due to climatic reasons (extreme climatic demand, rainfall deficit...) or technical reasons (equipment park, instantaneous flow rates).
The operational management of irrigation is carried out by the agricultural world through modeling tools (water balances) or soil water monitoring probes. It is mainly done at the scale of the crop campaign and aims for optimal crop needs. At most, a restriction is applied only to the water quota in case of water deficit context.
Arvalis propose its own water balance tool : Irré-Lis. A new functionality, currently under development, allows, in a hypothesis of irrigation limitation, the determination of an a priori optimal irrigation strategy considering the agro-environmental context of the plot.
Irré-Lis Limited Volume (VL) was thus used in situ on maize in 2022 and 2023 to compare, at constant irrigation quota, the technical performance (yield component) between management by water balance via classic Irré-Lis versus management via Irré-Lis VL.
Materials, methods
Irré-Lis is a classical water balance model, operational in sell crops (Gendre et al., 2018). Its VL functionality, usable only in maize, simulates firstly, over the last 20 years, water balances to determine the volume necessary for a given context and sowing date. Then, by applying irrigation restrictions (farmer's quota, equipment constraints) and a set of irrigation strategies (start and end stage of irrigation, dose, water round return time, all over for 3 phases of the vegetative cycle), Irré-Lis VL determines the best strategy, a priori, in the given restriction context for the farmer.
In order to test, at identical quotas, the added value of VL management compared to classical management (irrigation as soon as the RU is exhausted), Arvalis, in partnership with the Maïsadour cooperative, tested in 2022 and 2023 with a farmer in Gers, in a trial with reel irrigation, the application of these two approaches on maize. The two VL scenarios were :
- 2022: 93 mm applied; 25 mm every 8 days from 15 leaves
- 2023: 122 mm applied; 20 mm every 10 days from 10 leaves then 25 mm every 8 days from SLAG
Results
In 2022, a year characterized by high climatic demand (ETR/ETM = 0.58), VL management led to a gain of +15.85 qx/ha, representing +16.36% compared to classical Irré-Lis management. By waiting for the 15 leaves stage (1st irrigation at +4 days/classical management), it allowed accompanying the plant during critical periods, including towards the end of the cycle.
In 2023, mechanical constraints prevented irrigation from starting on time (at 10 leaves). This prevented the discrimination of irrigation management. Ultimately, VL management resulted in -2.05 qx/ha, representing -1.42% compared to classical management (non-significant result), with the last irrigation occurring 8 days after the last VL irrigation.
Discussion
In a context of strong water stress (2022), the VL strategy, considering local climatology, produced particularly interesting results.
The observation is less better in humid conditions. The equipment factor (startup of installations) is a key element. The performance of Irré-Lis VL is therefore highly dependent on the campaign's climatology and the rigor of application of the proposed schedule.
Finally, only one VL strategy was tested. It would be interesting to test multiple strategies simultaneously to verify the robustness of the simulations and the ranking of potential scenarios by Irré-Lis VL.
References
Sophie Gendre. Focus - Irré-LIS®, example of an irrigation decision support tool. Sciences Eaux &Territoires, INRAE, 2020, pp.72-75. 10.14758/SET-REVUE.2020.5.13. hal-03405344
Soenen Baptiste & Piquemal Benoit & Gendre Sophie. (2018). Assimilating Leaf Area Index (LAI) Measurements in a Water Balance Model to Improve Water Consumption Estimation for Maize.
Gendre Sophie & Descazeaux, Pierre & Soenen Baptiste & Bouthier Alain. (2018). Development of an irrigation water requirements model on grain maize. 10.13140/RG.2.2.15436.26243.
| Keywords | irrigation ; water balance ; maize ; limited volume ; water restrictions |
|---|
