Main Participants: LI Jiusheng, WANG Zhen, LI Yunkai, WANG Jun, XIAO Yang, LI Yanfeng, ZHAO Weixia, CHE Zheng, MA Chao, BO Xiaodong, GUO Yanhong, SUN Zhanghao, ZHANG Minne, LIU Hao, LIU Ke

The agricultural development of arid regions in Northwest China faces two major environmental and resource challenges: water scarcity and soil salinization. Achieving water conservation and salinity control is at the heart of efficient water resources utilization and sustainable agricultural development in the arid regions of Northwest China. Centered on this critical issue and with the support of the National Natural Science Foundation of China’s Major Research Program, this research has explored synergistic regulation mechanisms and technologies of water, nitrogen and salt for drip irrigation in arid regions, laying a solid foundation for the sustainable development of agriculture in arid regions of Northwest China.

·   Having explored the mechanism and regulation path of emitter clogging under the coupling effect of nitrogen and water quality, established an emitter clogging control technology that takes into account the sustained effect of clogging control, crop safety and soil environment security, and proposed an optimized performance layout model for large-scale drip irrigation systems.

·   Having researched the transmission pattern of uniformity from the outflow of drip irrigation systems to the distribution of soil water and salt, and subsequently to crop growth, evaluated the sensitivity of soil water and salt distribution uniformity to the regulation of drip irrigation system uniformity, and proposed an appropriate drip irrigation uniformity coefficient to prevent secondary soil salinization in arid regions.

·   Having studied the drip irrigation salinity control methods that meet the water and salt thresholds in the crop root zone under complex water flux conditions, revealed the coupling mechanism of water, nitrogen and salt transport and absorption within the soil-crop system, and established a regulation method for drip irrigation water, nitrogen and salt based on the dynamic thresholds of water and salt levels in the root zone.

·   Having revealed the mechanism underlying emitter clogging under the effects of water, salt and nitrogen, and innovatively proposed new technologies for emitter clogging control, such as applying acidic fertilizers and antagonistic microorganisms and the magnetization of irrigation water, enhancing the anti-clogging capability of emitters by 40%; having established new pipeline layout models at both unit and system scales, improving system uniformity by 9%.

·   Having innovatively introduced a comprehensive evaluation method for assessing the distribution of water and nitrogen as well as energy efficiency performance of the system, improving the testing accuracy by 30%; having identified for the first time pressure deviation and clogging as the critical factors respectively affecting uniformity during the early and mid-to-late stages of the irrigation season. Non-uniform drip irrigation (with a uniformity coefficient below 70%) significantly increases the nonuniformity of salt within irrigation units; and a soil salinity threshold of 5 g/kg was identified as the critical level that significantly elevate the risk of cotton yield reduction at the system scale.

·   Having elucidated the mechanism by which a moderate increase in nitrogen application reduces soil salt content, and innovatively proposed a synergistic regulation technology for water, nitrogen and salt that takes into account the salinity threshold difference across various growth stages. This approach reduces the nitrate nitrogen leaching rate by 9%- 18%, thereby resolving the conflict between salt leaching and nitrogen leaching loss.

·   The project has achieved remarkable outcomes, including 79 published papers, 15 invention patents (with 2 granted in the United States), 2 monographs, 3 standards, and training of 19 graduate students. Core team members were granted the 2024 ICID International Water-Saving Technology Award.

·   Research achievements have been directly applied to 98,000 mu of farmland, improving irrigation uniformity by 30%, extending system lifespan by more than 1.5 times, increasing water and nitrogen use efficiency by over 10%, andreducing farmland soil salinity by 8%. These advancements have played a crucial role in improving the performance of drip irrigation systems, increasing the water and nitrogen use efficiency, and controlling soil salinity accumulation, thereby yielding significant economic and social benefits.

Figure 1 Evaluation of System Performance and Its Mechanism Affecting Soil Water and Salt Distribution

Figure 2 Emitter Clogging Mechanism and Regulation Path

Figure 3 Interaction Mechanism and Quantitative Characterization of Water-Nitrogen-Salt in Drip Irrigation

Figure 4 Optimization of Synergistic Regulation Parameters of Water, Nitrogen and Salt for Drip Irrigation in Arid Regions in Northwest China