Influence of Irrigation and Water Use on the Agronomic Traits of Crops

Water scarcity is a significant challenge to the sustainable development of agriculture. Irrigation plays a critical role in bridging the gap between soil water supply and crop demand, enhancing both crop yield and land use efficiency, making it widely adopted in arid and semi-arid regions. The interaction between crops and soil water is highly complex. Crops adjust to varying soil moisture levels by modifying root and leaf economic traits, resource allocation, and other agronomic characteristics to balance survival and productivity. Gaining insight into how irrigation influences crop agronomic traits is essential for improving water management strategies. However, the multidimensional impacts of irrigation on both aboveground and belowground crop structures present challenges in understanding the connection between agronomic traits and efficient water use. Therefore, further research is required to examine how crop traits adapt to varying irrigation levels, explore their relationship with water-use efficiency, and refine irrigation management practices.

This Special Issue contains thirteen papers featuring integrated knowledge on the mechanisms of irrigation effects on crop agronomic traits. The research covers a range of topics, including irrigation methods, crop-water relationships, and strategies for improving water management. Below are brief introductions to each work, designed to help readers quickly understand the key points.

Integrating irrigation strategies with nutrient management is essential for maximizing crop productivity while minimizing resource use. Li et al. evaluated the effects of two drip irrigation treatments—conventional drip irrigation (DIO) and drip irrigation with water stress (DIS)—on rice growth, with four nitrogen levels [1]. The study found that water stress under DIS significantly reduced rice yield due to the mismatch between nitrogen distribution in the soil and the rice root distribution. Optimizing nitrogen management alongside appropriate irrigation can help enhance rice yield under drip irrigation. Further studies by Dou and Sun and Xiong et al. also examined how nitrogen management and irrigation strategies affect soil nutrient distribution, root growth, and crop productivity. Dou and Sun found that increasing nitrogen application in aeolian sandy soil under drip irrigation improved water and nitrate retention, though the distribution became less uniform at lower water conditions [2]. Xiong et al. showed that water and fertilizer management were critical for optimizing productivity in apple intercropping systems in the Loess Plateau [3].

In this Special Issue, several articles highlight the benefits of deficit irrigation. Wan et al. analyzed subsurface drip irrigation for tomato cultivation in Yunnan Province, finding that deficit irrigation improved water productivity and tomato quality, with higher chlorophyll content and increased levels of soluble sugars, solids, and vitamin C, despite slightly lower yields compared to surface drip irrigation [4]. Bezerra et al. studied deficit irrigation with brackish water on forage cactus and found that it could achieve similar productivity and economic efficiency to full irrigation, improving dry matter productivity and farmer income [5]. Demir et al. compared conventional deficit irrigation (DI) and partial root drying (PRD) techniques in cabbage production. The study found that both methods impacted cabbage yields, with the highest yields from full irrigation and treatments involving 25% more water [6]. Water use efficiency (WUE) was improved under these treatments, and the PRD technique, though not widely studied for cabbage, showed potential in increasing WUE without reducing yield, offering a viable solution for water-scarce conditions.

In arid regions, water-saving strategies are critical. Ma et al. investigated the “Dry Sowing and Wet Emergence” water regulation strategy for cotton in southern Xinjiang [7]. They found that increased seedling water and higher-frequency irrigation treatments boosted cotton yield and growth, providing a practical solution for water conservation. Likewise, Chang et al. explored the impact of drip irrigation flow rate and layout on cotton growth, showing that higher flow rates and optimized layouts enhanced soil moisture distribution and increased yield [8].

In saline and seasonally changing environments, several articles have provided valuable insights. Dou et al. focused on soil enzyme activities under drip irrigation with saline groundwater in saline areas and found that soil quality improved over time [9]. Luo et al. investigated the effects of seasonal freezing and thawing on soil moisture and salinity in the Hetao Irrigation District, highlighting the importance of considering seasonal soil variations for effective water management [10]. Li et al. also made an important contribution by assessing the impacts of water stress on maize seedlings, showing that drought and waterlogging stress had negative effects on plant height, leaf area, and chlorophyll content, and the increased antioxidant enzyme activity and decreased NDVI indicated poorer plant health [11].

Regarding water resource allocation and crop yield improvement, Zou et al. explored the trade-off and synergy mechanisms of agricultural water resource allocation in monsoon climates [12]. Using Shandong Province as a case study for reservoir layout optimization, they developed a bi-objective optimization model integrating water demand and reservoir suitability. This model significantly reduced the water supply-demand gap by 74.3% and improved water resource utilization efficiency. Additionally, Yang et al. examined how straw mulching and supplemental irrigation together impact apple orchards in the Loess Plateau [13]. Their findings indicated that straw mulching improved soil moisture while reducing soil temperature, and supplemental irrigation further boosted both soil moisture and apple yield.

In conclusion, this Special Issue includes thirteen contributions that collectively emphasize the need for adopting irrigation practices to address the challenges of water scarcity in agriculture. From optimizing irrigation management and elucidating the relationship between agronomic traits and water use to revealing the mechanisms by which crop agronomic traits are adapted to irrigation practices, these research findings provide valuable strategies for enhancing agricultural productivity. As water scarcity is exacerbated by continued global population growth and climate change, the adoption of such approaches is critical to ensuring food security and sustainable agricultural development.