Breaking biological and abiotic limits of agricultural water use efficiency – A review

Water use efficiency (WUE) is a multidimensional concept spanning genetic, agronomic, and hydrological scales, yet the lack of an integrated framework linking its biological and abiotic determinants continues to limit progress toward agricultural water saving. We propose a paradigm shift in agricultural WUE through dual-breakthrough: overcoming the biological limits to crop water use and addressing the abiotic limits on water delivery. We methodically review the definitions and developmental trajectory of agricultural WUE at micro, meso and macro spatial scales. We highlight that gene editing, synthetic biology, and nanotechnology will enhance water use efficiency in crops, but understanding system-level gene regulatory networks is needed to explore how micro-level interventions regulate plant traits. Overcoming abiotic constraints requires innovations in irrigation methods and equipment, as well as strategies for irrigation and water delivery. Improved water savings relies on mechanistic elucidation of interactions in the microbe-soil-crop-aquifer-atmosphere system, necessitating advanced big data processing, intelligent modelling, and adaptive water use decisions within digital entities. The ongoing digital transformation of biological systems, agricultural lands, and watersheds into high-fidelity digital representations means artificial intelligence will play an essential role in sustainable water management within complex ecosystems. Therefore, the primary challenge ahead lies in unlocking the complexities of biological systems and real-world environments to integrate the mechanisms that govern water use efficiency across multiple scales.