Short and long-term effects of co-cropping systems in temperate regions: water-carbon interlinkages and the role of cultivar traits

Co-cropping, the cultivation of two or more crops simultaneously on the same field, is a nature-based solution that has high potential to improve climate change adaptation and mitigation in arable systems. The short-term benefits of co-cropping, such as higher yields, better productivity, improved soil carbon and enhanced water uptake, are well-established in temperate regions, but evidence is still generally lacking for humid temperate environments. In addition, the interlinkages between water and carbon dynamics in co-cropping and the longer-term functioning, resilience and sustainability of these systems under future scenarios remain unclear. This study focuses on addressing these knowledge gaps by monitoring the short-term (2 years) and modelling the longer-term (~20 years) impact on water and carbon dynamics in different agricultural co-cropping systems for a typical temperate agroecosystem in Scotland.

The experimental study focussed on two barley (Hordeum vulgare) cultivars with contrasting phenotypic traits (high yielding and stress tolerant), co-cropped with pea (Pisum sativum) and their three corresponding monoculture systems. Crops were grown without agrochemical inputs to investigate the potential for co-cropping in low input systems. On 6 occasions during a two-year field experiment, we investigated soil physical, carbon and nitrogen properties at two depths (i.e. upper (<5 cm) and lower (25-30 cm) topsoil). Crop production and grain quality (i.e. grain carbon and nitrogen contents) were also assessed. Analyses of hydrometric monitoring, and soil and plant samples for stable water isotopes further informed the hydro-climatological conditions and plant water uptake interactions. In the short term, we found that co-cropping modified barley water uptake strategies and enhanced soil carbon, crop production and grain quality, although barley cultivar traits determined the specific effects.

The data also informed a modelling study that coupled a soil carbon (RothC) and water balance model (Hydrus-1) to test how crop water uptake patterns and carbon change interact in co-cropping systems throughout the growing season under different conditions of climate change and water availability. The findings of this study provide an evidence-base for sustainable agricultural practices in temperate systems and determine the resilience of co-cropping systems to future climatic conditions.