Soil water and carbon dynamics of barley - pea intercropping in a temperate environment under projected climate change

Intercropping is an emerging potential nature-based solution for sustainable crop production in temperate environments. However, its long-term role in contributing to climate mitigation and adaptation remains unclear. This work presents the first evidence of potential long-term water and carbon effects of barley (Hordeum vulgare L.) and pea (Pisum sativum L.) intercropping versus its barley monoculture for a typical temperate environment in Scotland. Based on experimental data, water (HYDRUS 5) and soil carbon (RothC) models were coupled to project water-carbon dynamics for the short-term during a two-season field trial (2022-2023) and the long-term future (2024-2050) under a worst-case climate scenario (Representative Concentration Pathway, RCP 8.5). The coupled water-carbon model effectively captured the water-carbon dynamics observed in the short-term. Compared to barley monoculture, intercropping increased evapotranspiration up to ∼20 % in the short-term, dominated by the dry weather conditions in 2022. Long-term intercropping projected lower interannual variability in evapotranspiration than barley monoculture, but showed higher plant transpiration in dry years, indicating more adaptive water use and hydrological resilience. As intercropping is projected to increase transpiration but reduce soil evaporation compared with barley monoculture, it maintained similar levels of soil water content and storage in the topsoil (0-30 cm). In addition, by 2050, soil carbon was predicted to increase in the upper topsoil (0-5 cm) of intercropping by 16 % (1.91 kg m^-2) compared to barley monoculture (1.63 kg m^-2). These novel findings suggest that intercropping could play a critical role in enhancing hydrological resilience and carbon sequestration in temperate environments for sustainable land management.