Photosynthesis, yield, energy balance, and water-use of intercropped maize and soybean

Authors: PELECH, ELENA - University Of Illinois; ALEXANDER, BRENDAN C S - Agriculture And Agri-Food Canada; Bernacchi, Carl

Submitted to: Plant Direct
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2021
Publication Date: 12/14/2021
Citation: Pelech, E.A., Alexander, B.C.S., Bernacchi, C.J. 2021. Photosynthesis, yield, energy balance, and water-use of intercropped maize and soybean. Plant Direct. 5(12). Article e365. https://doi.org/10.1002/pld3.365.
DOI: https://doi.org/10.1002/pld3.365

Interpretive Summary: Most cropping systems consist of monocultures - one cultivar of one species over a large areal extent. However, most natural ecosystems consist of plants that occupy different zone and often use resources more efficiently. This research focuses on growing intercropped species, corn and soybean together, to determine whether there are improvements to photosynthesis, yield, water use and the energy use of the ecosystem compared with the traditional monocultures. The hypothesis is that both species will have lower yields but when added together the sum will be greater than either monoculture. The results show that there were no benefits to yield of the intercropped system, although it used slightly less water. While none of the changes provided substantial benefits, there also were no detrimental impacts which suggests that optimizing a intercropped system with species that have not been bred for monocultures can only improve yields and water and energy use.

Technical Abstract: By 2050, the U.S. Corn Belt will likely face a 23% increase in vapour pressure deficit (VPD), the driving force of evapotranspiration (ET), which may restrict maize yield improvements for rainfed agroecosystems. Alternative cropping systems, such as maize and legume intercrops, have previously demonstrated yield and resource-use advantages over monocultures. In this study, the residual energy balance approach was used to gain insights into how an additive simultaneous maize and soybean intercrop system regulates ET and water-use efficiency (WUE) compared to standard maize and soybean monoculture systems of the U.S. Corn Belt. Experimental field plots were rain-fed and arranged in a randomised complete block design in three blocks. Photosynthetic capacity and grain yield of maize were conserved in the intercrop. However, its competitive dominance shaded 80-90% of incident light for intercropped soybean at canopy closure, leading to a 94% decrease in grain yield compared to soybean monoculture. The total grain yield per unit area of the additive intercrop (land-use efficiency) increased by 11% ± 6% (1 SE). Compared to maize monoculture, the intercrop had higher latent heat fluxes ('ET) at night but lower daytime 'ET as the intercrop canopy surface temperature was approximately 0.25°C warmer, partitioning more energy to sensible heat flux. However, the diel differences in 'ET fluxes were not sufficient to establish a statistically significant or biologically relevant decrease in seasonal water-use (?ET). Likewise, the increase in land-use efficiency by the intercrop was not sufficient to establish an increase in seasonal water-use efficiency. Intercropping high-performing maize and soybean cultivars in a dense configuration without negative impact suggests that efforts to increase yield and WUE may lead to improved benefits.