14. Effects of Deficit Irrigation and Mulching on the Water Footprint of Maize Production in the Koga Irrigation Scheme, Ethiopia

In Ethiopia, it is crucial to utilize water management strategies such as mulching and deficit irrigation that use less water per unit of a product to address the water challenges that the country faces. This chapter presents findings on the effects of deficit irrigation (DI) and mulching materials on the reduction in the blue water footprint (WFb) of maize. The experiment has 12 treatments comprising four levels of water application depths (50 (DI4), 60 (DI3), 80 (DI2), and 100% (DI1) of the crop water requirement) and three types of mulching (no mulch (NM), wheat straw (SM), and white transparent polyethylene materials (PM)). The experiment was laid in a randomized complete block design with three replications in factorial arrangements. Water applied per irrigation event and soil moisture contents just before and 24 h after each irrigation event were monitored throughout the season. The data were analyzed using the R statistical package. The moisture monitoring results showed that lower evapotranspiration (ET) was recorded in the plastic mulch treatments and higher ET in the no-mulch treatments. The variance analysis showed that mulching and DI significantly affected the WFb and grain yield of maize; soil temperature (soil T^o) and hundred kernel weight (HKwt) were affected by mulch application only. However, there were no interaction effects between the two factors. The PM treatment resulted in the highest grain yield (8.17 tons ha⁻¹) and the lowest WFb (794.74 m³ ton⁻¹). The PM treatment also gave the best HKwt of 34.0 g, which was 6.56% higher than that of the NM treatment. A significantly higher soil T^o was recorded at the application of PM because much of the heat is retained by PM. The DI treatments showed that DI4 gave the lowest WFb (720.31 m³ ton⁻¹), which had a 38.93% water consumption reduction, followed by DI3. The results showed that there was a significant grain yield difference among DI1, DI3, and DI4. The application of DI1 produced the largest grain yields (7.74 tons ha^–1), while the application of DI4 had the smallest yield (6.59 tons ha^–1), which was 14.86% lower than that of DI1. Therefore, the application of 60% ETc DI and plastic mulch could be an important practice for blue water footprint reduction in this study area and areas with similar agroecology.