Tools to help optimize grain corn irrigation to address climate change

By JA Martinez-López1, H. Martinez-López1, JJ Pardo1, A. Martinez-Romero1, J. Montero1, R. López-Urrea2, C. Casas1, JM Tarjuelo1, A. Domínguez1 (1Centro Regional de Estudios del Agua (CREA) ) of the University of Castilla La Mancha (UCLM) and 2Provincial Agricultural Technical Institute of Albacete (ITAP))

The lack of water resources is one of the main obstacles to the sustainability of agriculture and to guaranteeing the availability of food in much of the Mediterranean basin and many other areas of the world, a situation that is worsening due to global warming. To address the challenges presented by variability in water availability and high energy costs, different models and tools are being developed that provide effective advice for more sustainable and profitable management of irrigated crops in the face of climate change. an increasingly globalized market.

This article presents the results of the use and validation of the irrigation programming module (https://crea.uclm.es/siar/siarpr) of the MOPECO model (Model for the ECONOMIC OPTIMIZATION of the use of irrigation water on the farm). ) already implemented on a platform for free access end users ( crea.uclm.es/crea/descargas/MOPECO_app.php ). This module, which provides information and helps optimize irrigation scheduling, has been validated with a grain corn crop (Waxy variety), comparing the agronomic and economic productivity achieved with its use versus other traditional irrigation scheduling methods. . The results obtained in the 2021 campaign are presented below, using different key indicators of the production process for their interpretation.

Demonstration of agronomic and economic improvement with the use of MOPECO

The experience has been carried out on a 20-hectare plot irrigated by sprinkling with a pivot team during the 2021 campaign (Photo 1) , comparing the management carried out by the farmer in a pivot sector, with that carried out using the model MOPECO in two sectors, managing one of them without deficit (control, M.Sd) and another with 5200 m3 ha-1 (M.Cd), which corresponds to 80% of the water estimated as typical needs of corn in the area (6,500 m3 ha-1). For this last management, the ORDIL methodology (optimized deficit irrigation in stages) included in the MOPECO model was also used.

The use of the model requires knowing the daily climatic data, obtained in this study from the Albacete agroclimatic station, belonging to the SIAR network (Agroclimatic Information System for Irrigation, of the Ministry of Agriculture, eportal.mapa.gob.es //websiar /Home.aspx) which is located 6 km from the plot, in a flat area with a uniform climate. It is also necessary to know the water actually applied (from rain and in each irrigation), for which an evaluation was previously carried out on the pivot team, checking, in addition to the amount of water actually discharged during irrigation, the uniformity of its distribution in the plot in real working conditions.

To contrast the evolution of soil moisture estimated by MOPECO with that actually existing in the soil, the volumetric moisture content was measured, installing two 60 cm capacitance probes (FDR), with sensors every 10 cm deep, both in the plant line as well as between two lines, given that the structure of the plant concentrates rain and irrigation water in the crop line.

To calculate production costs and obtain the gross margin (MB, €/ha), the work, amount of fertilizers, phytosanitary treatments, etc. were supervised.

Quantification of the improvement achieved

The results indicate that the farmer used 24% more water and obtained 6% less yield than that obtained with MOPECO in the treatments without deficit (Table 1) . The difference in gross irrigation water occurred especially in the last stage of the crop, where the Farmer applied 48% more irrigation, generating 110 mm of percolation. This caused the agronomic (yield) and economic (gross margin) productivity of irrigation water to be, respectively, 24% and 37% lower than those achieved with MOPECO without a deficit. It is important to highlight that the yield values shown are those obtained with a harvester in each of the sectors, and that the manual sampling carried out showed similar results.

Figure 1 shows the comparison of the evolution of the daily water content in the soil estimated with MOPECO with the average humidity value indicated by the sensors in the soil profile, where it can be seen that the crop was not subjected to stress. water at any time.

The good correlation between the simulated evolution of soil moisture by MOPECO and the humidity recorded by the humidity probes validates the adjustment of the different soil water balance parameters used by MOPECO.

We do not want to finish without highlighting that, for the conditions of the study area, deficit irrigation was not profitable in corn since a 19% reduction in water (even when applied with the ORDIL methodology of deficit irrigation optimized in stages) generated a 36% less MB.

Thanks

This work has been developed within the framework of the project (SUPROMED) PRIMA-EU GA-1813 financed by the PRIMA Foundation of the European Union, and the regional project (PRODAGUA) SBPLY/19/180501/000144 (financed by the JCCM), with FEDER funds.

Bibliography

It is available to the interested reader at the author's email: josea.martinez@uclm.es.