Comparative Drought-Resilience Index (DRI) of Low-Water-Use Alternative Forage Crops: Integrating Water-Use Efficiency, Forage Quality, and Carbon Sequestration
Abstract
Increasing drought frequency and severity in arid and semi-arid regions threatens forage availability and livestock system resilience. This study develops a novel Drought-Resilience Index (DRI) integrating eight criteria across four dimensions: water-use and productivity, drought resistance and stability, soil–water mechanisms, and forage quality with soil organic carbon (SOC) contributions. Opuntia ficus-indica (OFI), sorghum (Sorghum bicolor), and barley (Hordeum vulgare) were evaluated in two semi-arid sites with contrasting soil textures (calcareous loam, sandy) over three years under full and deficit irrigation (50% ETc).
Criterion weights were determined using the Analytic Hierarchy Process (AHP) with input from ≥12 experts, while crop rankings were obtained via the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). HYDRUS-1D simulations and field measurements quantified changes in available water capacity (ΔAWC), soil evaporation reduction, and SOC fractions.
Results show that integrating soil–water mechanism criteria significantly elevates OFI’sranking, particularly in sandy soils where baseline water retention is low. OFI increased ΔAWC by +35 mm, reduced soil evaporation by >20%, and achieved TOPSIS closeness coefficients >0.75 across all scenarios, outperforming sorghum (0.68–0.71) and barley (≤0.66). Tornado sensitivity analysis revealed that ΔAWC and SOC jointly accounted for ~46% of OFI’sseparation from the ideal solution. These findings indicate that perennial succulents like OFI function not only as drought-resilient forage crops but also as landscape-level adaptation tools, delivering co-benefits for carbon sequestration, land degradation neutrality, and nature-based climate solutions. Incorporating OFI into regional forage systems could simultaneously advance agricultural productivity and environmental restoration under intensifying climate stress.
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Introduction
Climate change has intensified drought frequency and severity in arid and semi-arid regions, threatening forage availability and livestock production sustainability. In water-limited environments, selecting forage crops with high drought resilience is crucial for maintaining productivity, water-use efficiency (WUE), and soil health (Chaves et al., 2016; Farooq et al., 2009). Among candidate species, Opuntia ficus-indica (CAM photosynthetic pathway, succulent cladodes), sorghum (Sorghum bicolor, C₄ physiology), and barley (Hordeum vulgare, C₃ physiology) represent distinct water-use strategies and adaptation mechanisms.
Opuntia ficus-indica has demonstrated exceptional adaptation to water scarcity through its Crassulacean Acid Metabolism (CAM) photosynthesis, which minimizes transpirational losses by nocturnal CO₂ fixation (Nobel, 2002; Pimienta-Barrios & Nobel, 1994). The succulent cladodes act as both photosynthetic organs and water storage reservoirs, enabling prolonged physiological activity during extended drought periods (De Cortázar & Nobel, 1992). In addition, its shallow yet extensive root system facilitates rapid water uptake after sporadic precipitation events, while post-harvest residues enhance soil organic matter and aggregate stability (Felker et al., 2006). Sorghum (Sorghum bicolor), a C₄ grass, is widely recognized for its high WUE and ability to maintain yield under moderate water deficits due to its deep rooting system and osmotic adjustment mechanisms (Blum, 2004; Ibrahim et al., 2010). However, its performance declines sharply under prolonged drought or in sandy soils with low water-holding capacity (Akinseye et al., 2017). Barley (Hordeum vulgare), a C₃ cereal, offers high forage quality and cold tolerance but exhibits greater sensitivity to water stress, with significant yield reductions observed under precipitation thresholds below 250–300 mm yr⁻¹ (Baik & Ullrich, 2008; Acevedo et al., 1999).
Existing drought assessment frameworks—such as stress tolerance indices, yield stability coefficients, and water-use efficiency metrics—often focus on single performance indicators, failing to capture the synergistic effects of physiological traits, soil– water interactions, and carbon cycling that together determine long-term agroecosystem resilience (Farooq et al., 2009; Chaves et al., 2016). For example, incorporating soil available water capacity (AWC) changes and reductions in surface evaporation into resilience assessments could better reflect the capacity of certain species, such as Opuntia, to modify the soil microenvironment in ways that support sustained productivity under climate variability (Mekuria et al., 2021). In this study, we introduce a novel Drought-Resilience Index (DRI) that integrates eight measurable criteria across four dimensions: water use and productivity, drought resistance and stability, soil–water mechanisms, and forage quality with carbon storage potential. Using a multi-criteria decision-making (MCDM) framework combining the Analytic Hierarchy Process (AHP) for weight determination and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) for ranking, we compare the performance of O. ficus-indica, sorghum, and barley in two contrasting semi-arid soil types. By explicitly incorporating soil–water–carbon linkages, this approach aims to identify forage options that simultaneously maximize yield resilience, resource-use efficiency, and ecosystem service co-benefits under projected increases in drought frequency and severity.
Conclusion
This study demonstrates that incorporating soil–water mechanism criteria into drought-resilience assessments fundamentally changes the comparative evaluation of forage crops under water-limited conditions. By integrating HYDRUS-1D simulations, multi-year field measurements, and multi-criteria decision analysis, we developed and applied a Drought-Resilience Index (DRI) capable of capturing both agronomic performance and ecosystem-service contributions.
Results consistently placed Opuntia ficus-indica (OFI) at the top of the DRI rankings, particularly in sandy soils under deficit irrigation, where its contributions to available water capacity (ΔAWC) and soil organic carbon (SOC) accumulation were most pronounced. The crop’sability to enhance soil water retention and reduce evaporation losses positions it as a uniquely effective adaptation strategy in arid and semi-arid landscapes.
In contrast, sorghum’sperformance reflected its inherent drought tolerance and stable yield potential, yet without the same long-term soil hydrological benefits. Barley’shigh forage quality did not offset its greater sensitivity to water stress, limiting its suitability in environments where precipitation is both scarce and variable.
The DRI proved sensitive to weight changes in ΔAWC and SOC criteria, highlighting that policies and management systems prioritizing soil hydrology and carbon sequestration will magnify the advantages of perennial succulents. Beyond its role as a forage resource, OFI emerges as a multi-functional crop capable of contributing to land degradation neutrality, carbon sequestration targets, and broader nature-based climate solutions.
Given the projected intensification of drought under climate change, integrating OFI into regional forage systems offers a pathway to strengthen agricultural resilience while simultaneously advancing environmental restoration goals. Scaling such interventions will require coordinated research, extension, and policy support, but the potential benefits for both food security and ecosystem health are substantial.
CONFLICT OF INTEREST The authors declare no conflict of interest.
