Intercropping alfalfa during almond orchard establishment reduces winter soil nitrogen and water losses, provides on-farm revenue

Authors: Thao, Touyee; Begna, Sultan; Hale, Lauren; BALI, KHALED - Kearney Agricultural Center; Wang, Dong; Gao, Suduan

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2024
Publication Date: 11/8/2025
Citation: Thao, T., Begna, S.H., Hale, L.E., Bali, K.M., Wang, D., Gao, S. 2025. Intercropping alfalfa during almond orchard establishment reduces winter soil nitrogen and water losses, provides on-farm revenue. Agrosystems, Geosciences & Environment. 8(1). Article e70024. https://doi.org/10.1002/agg2.70024.
DOI: https://doi.org/10.1002/agg2.70024

Interpretive Summary: Intercropping alfalfa in almond orchard interrow spaces is a potential new practice to advance land use efficiency especially in the Central Valley of California where most almonds are grown. In this study, we evaluated the ecosystem benefits linked to this intercropped agroecosystem, particularly during the non-bearing orchard establishment stage. We used a soil hydrological model (HYDRUS-1D) and different field nitrogen sampling approaches to gauge soil water and nutrient losses during the rainy Winter 2023 to Spring 2024 season. Results from the model show that winter soil evaporative water loss was greatest for bare-soil control and lowest for alfalfa intercropped alleyway. Alternatively, root water uptake was greatest for alfalfa intercropped treatment, yielding 2.2-ton ha-1 for the first alfalfa cutting which equate to $500 ha-1 in farm revenue. Winter soil nitrogen loss was also observed to be lowest in the intercropped alfalfa interrow and highest for the bare-soil control interrow. These observations show that resource use efficiency during the winter-spring season is greatest for the intercropped alfalfa interrow and lowest for conventional bare-soil interrow.

Technical Abstract: The ecosystem benefits linked to intercropping and diversified agroecosystems is an area with increasing research interest, particularly in sustainable food production and farm resilience to extreme climate variability. Interrow cropping of alfalfa in almond orchards during the 3-4 non-bearing, establishment years has potential to advance sustainable intensification in agricultural regions such as the Central Valley of California. In this study we evaluated ecosystem benefits linked to this intercropped agroecosystem in contrast to conventional almond systems with interrow spaces maintained bare. From Winter 2023 to Spring 2024 (157 days) we modeled soil hydrological properties (HYDRUS-1D) and quantified soil nitrogen using various approaches. Simulation from HYDRUS revealed that winter soil evaporative loss was most substantial for a flood irrigated bare-soil control (208.1 mm), and lowest for the alfalfa intercropped interrow (59.2 mm). Estimated soil water storage was lowest in the alfalfa intercropped interrow and highest for bare-soil controls, indicating continuous plant water uptake throughout the winter period when almond trees are dormant. Winter soil N loss measured using suction lysimeters, ion exchange soil resins traps, and soil sampling (0-120 cm) indicated that N leaching was greatest in the bare-soil interrow spaces and lowest for alfalfa intercropped treatment. The utilization of free winter inputs, such as rainwater and slow-release mineralized N from dairy manure compost translated to a 2.22-ton ha-1 alfalfa yield and equated to a $500 ha-1 gross revenue for the first alfalfa cutting. Overall, the ecosystem benefits observed in this unique alfalfa-almond intercropped agroecosystem were attributed to augmentation in farm resource use efficiency and revenues generated during the winter season.