The bibliometric analysis highlighted a significant rise in research publications related to adaptation to climatic risk, particularly after 2007 with release of AR4 report of IPCC (2007), reflecting growing global efforts to address climate challenges. Experimentation remained the dominant methodology, though simulation/modelling studies are increasingly emerging as complementary approaches. Regionally, India leads with the highest number of publications, followed by Bangladesh and Pakistan, while countries like Nepal, Sri Lanka, Afghanistan, Bhutan, and the Maldives had limited publication. Drought is the most extensively studied hazard, followed by heat and floods. Among adaptation options, variety selection is the most studied, followed by agronomic practices, policy and insurance, soil health, and water management, with limited focus on other technologies. The analysis highlighted a growing focus on climate change adaptation technologies, particularly crop management practices. Among these, EI emerged as a new strategy, leveraging localized farming practices aligned to regional conditions to enhance maize productivity under climatic stress.
This research synthesized the effects of various adaptation technologies on maize yield across South Asia, focusing on the influence of agro-climatic zones, soil textures, and seasonal conditions. Our findings revealed that certain options offer significant improvements in maize yield under climatic stress, especially drought, heat, and rainfall variability. These include EI, V, I, IC, MC, MA, NM, and ZT, each targeting environmental challenges faced by maize in South Asia.
4.1 Effectiveness of Adaptation Options on Maize Yield
The observed pattern highlighted the varying effectiveness of adaptation options on maize yield, as reflected by their mean effect sizes and statistical significance. Among them, IC and I demonstrated the most substantial and significant impacts, whereas MA exhibited the smallest and least consistent effects. The ranking of adaptation technologies, based on their mean effect sizes, is as follows: IC (45.63%), I (13.19%), MC (6.77%), NM (6.29%), T (4.29%). Inter-cropping (IC) has emerged as a promising strategy for improving resource utilization, especially under high-temperature and water-stressed conditions. By creating microenvironments that buffer crops against climatic extremes, intercropping has been shown to enhance maize productivity (Lithourgidis et al. 2011). In contrast to mono-cropping, which benefits from reduced competition for resources, maize/legume intercropping faces competition that can limit yields. Studies by Pierre et al. 2022; Saudy et al. 2015 showed that IC offers ecological benefits, such as nitrogen-use rationalization and weed suppression, which can enhance sustainability despite the competition. Although the number of observations for IC were limited, the existing evidence highlights their potential to enhance yields and provide important ecosystem services. This underscores the promising role of this practice, particularly maize-legume intercropping, in contribution to ecological and sustainable crop production (Zhao et al. 2024). While further research is needed to expand the scope and validate these findings, the current evidence suggests significant potential for improving food security and environmental sustainability. Similarly, irrigation management, such as micro and supplemental irrigation, play a crucial role in mitigating drought and rainfall variability, ensuring sustained maize growth and yield (Gupta et al. 2023; Wang et al. 2023; Jat et al. 2019; Comas et al. 2019). However, despite IC and I demonstrating the highest effect sizes, their limited number of observations reduces their reliability for broader application. The meta-analysis also identified MC as another effective strategy, delivering a consistent and strong positive impact on maize yield. This aligns with previous research emphasizing the role of in-situ moisture conservation in mitigating stressors such as drought, mild drought, and rainfall variability through soil moisture retention and reduced evaporation (Demo and Asefa Bogale 2024; (Ngetich et al. 2014). Also evidenced by Ademe et al. (2018) and Chimdessa et al. (2019), in-situ MC practices effectively increased maize yield by reducing evapotranspiration, retaining soil moisture within the root zone and consistent water supply to the crop under drought or water-stressed conditions. NM and ZT also demonstrated notable improvements in maize yield although the effect was less compared to MC. Efficient NM, including balanced fertilization, enhances maize resilience by promoting root growth and nutrient uptake, essential for survival during drought conditions (Hussain et al. 2017 ; Aslam et al. 2012). Residue management and reduced tillage practices can reduce the impact of drought and rainfall variability, although their effectiveness is location-dependent and influenced by environmental conditions (Sarangi et al. 2020; Parihar et al. 2019). ZT broad bed planting with residue retention has been reported to enhance the grain yield (Saad et al. 2015, Ghosh et al. 2021), and carbon sequestration, contributing to improved maize productivity under drought and heat stress (Jayaraman et al. 2024, Bhatt et al. 2017). In contrast to our findings, previous studies have shown that ZT practices can negatively affect maize yield due to increased bulk density, reduced water intake, and higher weed infestations compared to conventional tillage (Mafongoya et al. 2015; Liu et al. 2022).
While the results of V, EI, and MA technologies were not significant in our study, their potential for mitigating climate-related stresses on maize production cannot be dismissed. These technologies have shown promise in other studies and are considered crucial components of broader technologies aimed at improving resilience and productivity in stress-prone regions. Despite the lack of significant findings in our analysis, the underlying mechanisms and the adaptability of these technologies under varying environmental conditions highlight their relevance for future research and implementation. Heat- and drought-tolerant maize varieties are equally important for mitigating drought-related stresses, ensuring sustained productivity in stress-prone regions. These varieties play a pivotal role in enhancing maize resilience under adverse climatic conditions, as corroborated by numerous studies (DeMeyer et al. 2024; Singh et al. 2024). On the other hand, EI and MA technologies showed comparatively less but positive improvement in maize yield. Recent literature has reported significant yield improvements with EI, averaging 48.6% over traditional methods and resilience under climatic stress by leveraging local farmers’ practices optimized to regional conditions (Rusere et al. 2019; Salakinkop et al. 2024; AICRP reports 2017–2020). Combining multiple adaptation options, such as irrigation, variety, and nutrient management, strengthens maize adaptability to climate-induced stresses (Rao et al. 2024 ; Grigorieva et al. 2023). However, our study found that MA had the smallest and least consistent impact. Shifting planting dates is often suggested as a strategy to adapt to heat stress or terminal heat impacts on maize, but such shifts have also been reported to induce chilling stress, resulting in yield loss under lower temperatures. This effect can be alleviated through the application of plant growth regulators (Waqas et al. 2017 ; Ahmad et al. 2014).
Our study confirms that different adaptation options vary in their effectiveness in improving maize yields under climatic stress. These findings are consistent with Challinor et al. (2014), who reported that crop-level adaptation technologies could increase simulated yields by 7–15%. Similarly, Maitra et al. (2021) and Al Mamun et al. (2024) emphasized the critical role of adaptation strategies, such as crop rotation and early-maturing varieties, in enhancing maize production efficiency amidst climate challenges. These results underscore the importance of adopting a combination of region-specific, context-driven technologies to enhance maize productivity and resilience to climate change across South Asia. The variations in the effectiveness of adaptation options are further influenced by soil texture, which plays a critical role in determining how these technologies interact with the soil's physical and chemical properties. Razzaghi et al. (2022) emphasized that soil texture significantly influences nitrogen (N) availability to plants, as it impacts N mineralization and rooting depth and distribution. Our analysed showed that NM performed well in fine textured soil where nutrient uptake was more optimised due to moisture retention and addressed the nutrient imbalance resulting in yield improvement. Our findings are supported by Ahmadi et al. (2011) which stressed upon the role of soil texture on nutrient uptake, NUE and leaching losses. Medium textured soils (S2), responded well to MC technologies due to their moderate capacity for water storage. Onyekwelu and Sharda (2024) simulated the impact of climate change on rainfed maize productivity, they found that root proliferation as an adaptation strategy improved yield by 27% and rainfall productivity by 28%, with better performance in silty clay loam and clay loam soils. The in-situ MC helped in improving water retention and nutrient availability of the soil, leading to a significant increase in yield (Jiang et al. 2024, Demo and Asefa Bogale 2024; Abdallah et al, 2021). IC also performed strongly in medium soils due to its ability to improve soil fertility and nutrient cycling through the integration of legumes, which fix nitrogen and enhance soil health. Most of the technologies performed well in coarse textured soil compared to other soil types with greater benefits from technologies like MC and IC. However, IC was found to be highly effective as it promotes better nutrient utilization through complementary plant interactions, while also reducing soil erosion and improving water availability (Maitra et al. 2021; Stomph et al. 2020). Irrigation management supports this by ensuring consistent water supply, which is critical in coarse soils that tend to drain quickly (Eisenhauer et al. 2021; (Wankmüller et al. 2024). Our findings align with previous research highlighting the importance of adapting technologies based on soil type to optimize productivity (Gabhane et al. 2023; Rehman et al. 2019).
In addition to the influence of soil texture, the effectiveness of adaptation options is also dependent on distinct climatic conditions and challenges of different agro-climatic zones, necessitating the adoption of region-specific technologies to optimize maize productivity. The meta-analysis evaluated the performance of various adaptation options for various climate hazards on maize yield across different agro-climatic zones and provided valuable insights into their effectiveness. In CWZ, where maize faces temperature stress, drought due to rainfall variability, I Management and V have emerged as the most effective technologies. Among the various options, I was found to be crucial in ensuring optimal water availability during dry spells, significantly enhancing maize growth and yield. Aryal et al. (2020) and Jat et al. (2019) demonstrated that integrating conservation agriculture with sub-surface drip irrigation (CA+) significantly improved crop productivity, water use efficiency in western zone saving up to 95.5% of irrigation water in maize-wheat rotations offering a sustainable solution for water-scarce regions. V Selection, focused on heat-resistant and drought-tolerant varieties, offering the best performance in adapting to fluctuating temperatures and water stress, thus outperforming other techniques in this zone. The study by Abdallah et al. (2021), and Jat et al. (2019) emphasizes the effectiveness of crop and varietal diversification for managing drought in the rainfed maize ecosystems of western zone providing higher yields and better water use efficiency during drought years. Maize hybrid developed for high-altitude ecologies in hilly zone, demonstrated significant yield potential, producing 7.0-8.2 t ha⁻¹ compared to the 2.5-4.0 t ha⁻¹ of local landraces (Ahangar et al. 2020). In both NHZ and NEPZ, MC and IC have shown the best results. These two technologies outperform others in these regions by improving soil moisture retention. Sarangi et al. 2020 reported improvement in maize yield by conserving soil moisture in the eastern plain zone using raised-bed sowing, followed by conventional tillage and zero-tillage. Intercropping not only optimizes land use but also reduces pest pressure and boosts resource efficiency, enhancing resilience to temperature extremes and thus offering significant benefits over other methods. In NWPZ, where heat stress and water scarcity are key challenges, Nutrient Management and Irrigation Management performed better than other adaptation options. Rehman et al. 2019, demonstrated that nutrient management treatments, such as salicylic acid and moringa leaf extracts, effectively mitigated chilling stress in maize, enhancing growth and yield in cold-prone regions like the NWPZ. Nutrient Management addresses soil fertility issues and ensures that maize can withstand heat stress, while irrigation management mitigates the impact of erratic rainfall and water scarcity, making these two options more effective than others in this zone. Whereas, in PZ, Moisture Conservation stands out as the most effective technology for improving maize yields by providing a more stable and resilient growing environment. Based on our analysis certain adaptation options were not studied in specific agro-climatic zones. For example, Irrigation Management (I) was not studied in NEPZ, NHZ, and PZ. IC was not evaluated in CWZ, NEPZ and PZ. Additionally, MA and V were not evaluated in PZ. The present findings suggest that these technologies may either be less relevant or underutilized in these zones due to factors such as local climatic conditions, agricultural practices, or resource constraints. Further research is needed to explore the reasons behind the limited application of these options in the respective regions.
Furthermore, while agro-climatic zones provide a framework for understanding regional variations, climatic factors such as temperature and rainfall play a pivotal role in determining the efficacy of adaptation technologies, highlighting the need for tailored technologies that address specific climatic hazards. Xu et al. 2024b projected a 21.4% reduction in maize yields in Northeast China, primarily due to rising temperatures. While elevated CO2 and precipitation provided some compensation, adaptation options like optimizing planting dates had limited benefits due to heat stress, highlighting the need for specific approaches to mitigate climate impacts on maize. The results of meta-analysis highlight the significant influence of rainfall and temperature on the effectiveness of different adaptation options in maize. The categorization of rainfall into three distinct groups (R1, R2, R3) and temperature into three categories (T1, T2, T3) offers a more nuanced understanding of the impact of these climatic factors on maize yield improvement when employing various technologies. Based on rainfall: in R1 regions, IC and NM are the most reliable technologies, providing significant positive effects on maize yield. I and MC technologies are also effective in R1 and R3, showing promising results. ZT is suitable for R2 and R3 rainfall regions, demonstrating consistent positive effects in R3 and moderate impact in R2. EI, MA, and V should be avoided in high or moderate rainfall areas, as they show weaker or less consistent performance. Yasin et al. (2024) observed that the effects of water stress during pre-flowering and grain-filling stages in maize reduced grain yield more in non-drought tolerant varieties compared to drought-tolerant ones. Heat stress reduces yields, grain quality, and increases pest susceptibility and thus is a major challenge for maize (Ahmad et al. 2024). The analysis based on temperature suggested that: for T1 (25–30°C), IC and MC technologies are highly recommended, as they show significant positive effects on maize yield. In T3 (> 30°C), V technology should be prioritized, as it has the highest positive effect on maize yield. Waqas et al. 2021 suggested that cultural practices, exogenous protectants, and breeding climate-resilient crops can help in mitigating temperature related stress in maize. I technology also performed well in T1, making it a strong option for this temperature range. ZT and EI technologies are less effective, particularly in T2, where their impact is minimal. MA technology showed the lowest performance across all temperature categories in our analysis. For R1 and T1, IC, NM, and MC technologies are the most effective options for maize yield improvement. These findings suggest that the performance of adaptation options is strongly influenced by both rainfall and temperature.