*3.5. Water-Use E*ffi*ciency*

The harvest of each crop was measured in entire plots and the WUE calculated with Equation (6) is shown in Figure 6 for the barley, corn, and sorghum crops. This value increased over the years, mainly due to the fact that the farmers and the supervisory personnel accepted the design of the optimal flow provided. Accepting the irrigation design represented a generational change in the way of watering for farmers, since most mentioned that the way of watering was as their father had taught them, and that in several cases there was no knowledge of irrigation water needs. However, in the last year of evaluation, increases in the WUE of 54.0%, 43.8%, and 23.0% were achieved for barley, corn, and sorghum, respectively.

**Figure 6.** The water-use efficiency obtained by cycle.

The WUE in the evaluated gravity irrigation systems was also affected by various factors: environmental, social, management practices, payment for the service, land rent, among others. These results coincide with other studies where they show that farmers who do not use irrigation devices such as probes or tensiometers for estimating the soil water potential or volumetric water content tend to over-irrigate [9,25]. In this sense, in the plots with the most unfavorable slopes and those where they had waterlogging problems, it was recommended to perform land leveling (1200 ha). This practice helped to increase the efficiency in the use of water in the following agricultural cycle, as well as to obtain a better yield in the harvest.

The water savings obtained with an efficient design helped us to have increases in crop productivity, since without a prescription in the case of barley for the last year, 0.700 kg was harvested for each cubic meter of water used, and with the designed irrigation, for the same cubic meter of water, 1078 kg of grain were harvested; in the case of sorghum, this increase represented an additional 0.307 kg and in the case of corn it corresponded to 0.591 kg.

With the efficient design of optimal flow, we managed to reduce the amount of water used to produce 1 kg of biomass (Figure 7). In the case of barley, this reduction was 47.45%, going from 1.96 m3/kg to 0.93 m3/kg, while in the case of corn and sorghum crops, the reduction was 38% and 27%, respectively. These data are an important indicator in areas with essential water resources and allow calculating the economic value of the irrigation water that can be maximized, and therefore will be one of the main requirements in making decisions about the distribution and use policies of water in food production.

**Figure 7.** The water productivity obtained by cycle.

#### **4. Conclusions**

The reduction in irrigation time per hectare had a considerable impact on the irrigation depth applied to crops. In general, it can be seen that the minimum saving is of the order of 450 m3 in clay loam, silty, and silty clay soils. The plots where there are more savings are those where they correspond to the loam, sandy clay, and silty clay loam textures. Despite the fact that this program was implemented for only 5 years, the savings obtained per cycle were still significant for the farmers, since in the low rainfall season the dams do not have enough storage to provide water, and this is where the impact of this design has been reflected: with less water, they have irrigated the same irrigation area and, on occasions, as in the 2018–2019 cycle, the savings allowed to give an additional irrigation of 15 cm to 2500 ha.

Finally, it was possible to verify that, with a design for optimal flow in each border or furrow, it helped to improve the efficiency in the use of water and helped increase the productivity of the three crops that were irrigated by gravity. Although with pressurized irrigation systems (sprinkler or drip) there is a higher WUE, this design provides an opportunity to make better use of the resource, increase productivity, and improve crop yield.

**Author Contributions:** Conceptualization, C.C.; methodology, C.C., I.L.-J.; B.E.-A., J.A.L.-H. and E.B.-F., software, C.C., and J.T.-A.; validation, C.C., I.L.-J.; B.E.-A., J.A.L.-H. and E.B.-F.; formal analysis, C.C., and J.T.-A.; investigation, C.C.; resources, C.C.; data curation, C.C., I.L.-J., B.E.-A., J.A.L.-H., E.B.-F. and J.T.-A.; writing—original draft preparation, C.C. and J.T.-A.; writing—review and editing, C.C.; supervision, C.C., B.E.-A. and J.A.L.-H.; project administration, C.C.; funding acquisition, C.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported as part of a collaboration between the National Water Commission (CONAGUA, according to its Spanish acronym); The Water Users Association of Second Unit of Module Two, Irrigation District No. 023; the Irrigation District 023, San Juan del Río, Querétaro; and the Autonomous University of Queretaro, under the program RIGRAT 2015–2019.

**Acknowledgments:** We would like to thank the editor and the expert reviewers for their detailed comments and suggestion for the manuscript. These were very useful to hopefully improve the quality of the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
