Quality in forage crops under drought and salinity stresses: Responses, simulation and field managements

The underlying food and nutrient crises caused by climate change are driving an increasing demand for forage crops and livestock products worldwide. However, the production of high-quality forages is challenged by potential soil drought and salinity risks. Research gaps exist in understanding the quality performance of forage crops under drought and salinity stresses and estimating the integrated quality traits. In this respect, the study provided a systematic overview of research regarding the plant responses, model simulation, and field management of forage crops under drought and salinity stresses. Here, the study reviewed the responses of growth- and quality-related processes for forage crops to drought and salinity stresses as well as the quality evaluation methods. Following that, the study elucidated the approaches for quantification of water-salinity-yield-quality relationships. Finally, the field practices for improving the quality of forage crops are highlighted. The review underlined the interrelated processes between quality formation and biomass accumulation, moderate water and salt stress generally can enhance most quality traits, though come at the expense of yield reduction. The empirical functions, process-based models, and machine learning as different estimation methods have limitations in terms of theoretical foundations, the ability to capture complex quality traits, and the exploitation of data fusion. With improved data availability by multi-source data, enhanced predictability and efficiency by machine learning, and solid theoretical processes, it is expected that the combination of the three methods can optimize crop quality prediction to a certain extent. Based on the above, the coping strategies from the view of water, soil, and plants sides are illustrated. Scientific irrigation water management, including proper timing, moderate amount, and water-saving technologies, can ensure high-efficiency forage production, while suitable tillage practice will enhance resources use efficiency. Furthermore, proper arrangements of forage crops from sowing to harvest in a cropping system are suggested to boost system benefits. This review offers a comprehensive insight into the responses of forage crops quality under drought and salinity stresses, along with simulation approaches and practical mitigation measures to cope with, thus enhanced the evidence base for quality research and for charting appropriate strategies for field managements.