Influence of Irrigation and Water Use on Agronomic Traits of Crops—2nd Edition

The escalating challenge of global water scarcity continues to threaten agricultural sustainability, making the optimization of water management practices more critical than ever before. Understanding how soil moisture dynamics dictate plant growth and resource utilization is essential for securing future food production. Following the foundational discussions established in our previous publication, this second volume of the Special Issue “Influence of Irrigation and Water Use on Agronomic Traits of Crops” brings together seven novel studies. These contributions dive deeply into innovative watering strategies, the complex balance of soil salinity and nutrients, and the physiological resilience of crops, providing a focused examination of how tailored water applications shape agronomic performance.

Refining irrigation schedules and field drainage systems can significantly elevate both crop yield and overall water productivity. For instance, research conducted in the black soil region of Northeast China demonstrated that implementing a mild Alternate Wetting and Drying (AWD) threshold (−10 kPa) in rice paddies optimally boosted dry matter accumulation and the availability of soil nutrients, clearly outperforming traditional continuous flooding techniques [1]. Exploring agricultural water management from a subterranean perspective, a study in Egypt revealed that maintaining a shallow groundwater table (0.4 m) via a subirrigation-controlled drainage system remarkably conserved irrigation water while amplifying the biomass of Egyptian clover. While this method proved highly efficient, the authors rightly emphasized the need for vigilant root-zone salt monitoring [2]. Furthermore, integrating spatial crop arrangements with precise watering can fundamentally alter moisture loss pathways. In a semi-arid Iraqi environment, utilizing a double-row planting pattern alongside frequent drip irrigation (a 25% depletion threshold) successfully maximized the productive transpiration of faba beans, effectively minimizing unproductive soil evaporation and lowering the total water footprint [3].

Beyond the sheer volume of water applied, the chemical quality of irrigation sources and the resulting soil ion balance profoundly impact plant establishment. Addressing severe freshwater limitations in the Bohai Lowland of China, researchers confirmed that supplementing deficit-irrigated winter wheat with a single application of moderately saline water substantially enhanced crop yields. Crucially, the subsequent heavy summer rains naturally leached the accumulated salts, ensuring no negative carry-over effects for the succeeding maize crop in the rotation [4]. However, the specific ionic composition within saline environments dictates actual plant health. This was clearly illustrated by a greenhouse experiment focusing on sunflower seedlings, which discovered that an excessive potassium-to-sodium ratio in the soil solution competitively inhibited the plant’s magnesium uptake. This nutrient imbalance ultimately degraded leaf chlorophyll and hindered photosynthetic capacity, underscoring the absolute necessity of precise fertilizer and ion management in saline-irrigated agriculture [5].

Crop adaptation to moisture deficits and the physical preservation of the surrounding soil matrix are also central themes in this volume. By evaluating six distinct almond varieties under differing moisture regimes in Spain, researchers identified robust physiological markers—such as canopy volume growth and leaf-to-air temperature gradients—to accurately quantify drought resistance. Their findings pinpointed specific cultivars, notably ‘Guara’ and ‘Masbovera’, as highly resilient choices for cultivation in increasingly arid landscapes [6]. Concurrently, maintaining the structural integrity of the soil is vital for efficient moisture retention. A laboratory investigation showed that applying a low concentration of a biodegradable superabsorbent polymer to clay soils dramatically improved aggregate stability, delayed runoff, and mitigated soil erosion under simulated rainfall. This offers a highly sustainable, eco-friendly approach to soil conservation and hydrological management in vulnerable agricultural zones [7].

Across all case studies compiled in this Special Issue, three convergent research frontiers stand out as the shared core of contemporary agricultural water management: precision irrigation regulation oriented to crop physiological demand, coordinated regulation of water–salt–nutrient coupling in varied soil environments, and eco-friendly soil improvement synergizing water conservation and erosion control. Existing achievements have effectively broken the empirical irrigation stereotype relying on fixed irrigation quotas, shifting field water management from empirical scheduling toward physiology-driven, site-specific precise regulation. Nevertheless, prominent research gaps still constrain further progress toward sustainable water use in global agriculture. First, most current experiments are confined to plot-scale or short-term greenhouse observations, while long-term field monitoring across multi-year climate fluctuations and at the regional farmland scale remains insufficient, limiting the popularization of mature irrigation schemes under complex field backgrounds. Second, interactive coupling between variable climate change, soil salinization evolution, and crop water demand is rarely quantified systematically; few models can dynamically adjust irrigation regimes in response to real-time meteorological and soil property variations. Looking ahead, future agricultural water management will gradually integrate remote sensing monitoring, hydrological numerical simulations, such as HYDRUS, and intelligent drip irrigation control technology to construct whole-process digital water regulation systems. In addition, developing low-cost biodegradable soil amendments and optimal saline water utilization patterns tailored to regional geochemical features will become indispensable research directions to cope with worsening global freshwater shortages and expanding soil salinization worldwide.

Collectively, these seven articles provide rigorous, multidimensional insights into optimizing agricultural water use. By elucidating the physiological mechanisms of environmental stress tolerance and proposing highly practical adjustments to irrigation and drainage frameworks, this volume equips researchers and agricultural practitioners with evidence-based strategies to sustain crop productivity amidst shifting climatic realities. As the Guest Editor, I sincerely thank all the contributing authors for sharing their innovative research, as well as the peer reviewers whose invaluable and dedicated feedback ensured the high scientific quality of this publication.