Leaf, plant, to canopy: A mechanistic study on aboveground plasticity and plant density within a maize–soybean intercrop system for the Midwest, USA

Authors: PELECH, ELENA - University Of Illinois; EVERS, JOCHEM - Wageningen University; PEDERSON, TAYLOR - University Of Illinois; DRAG, DAVID - University Of Illinois; FU, PENG - Harrisburg University; Bernacchi, Carl

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2022
Publication Date: 1/11/2023
Citation: Pelech, E.A., Evers, J.B., Pederson, T.L., Drag, D.W., Fu, P., Bernacchi, C.J. 2023. Leaf, plant, to canopy: A mechanistic study on aboveground plasticity and plant density within a maize–soybean intercrop system for the Midwest, USA. Plant Cell and Environment. 46(2):405-421. https://doi.org/10.1111/pce.14487.
DOI: https://doi.org/10.1111/pce.14487

Interpretive Summary: Most crops in the Midwestern U.S. are grown as monocultures consisting of only one crop species in a field each year. However, having two or more crops in the same field may provide improved benefits as different crop species may use resources differently. The hypothesis is that having two crops growing simultaneously will result in less yield for each crop, but the sum of the yield for both crops will be higher than a monoculture. To test this hypothesis, we designed an experiment with plots of monocultures of corn and soybean, corn in a "solar corridor" which involved having the same number of plants in a plot but wider rows (and thus planting closer together within a row) for corn, and "solar corridor" corn plots with soybean planted between the rows of corn. The results show that both crops showed physiological adjustments when planted together, suggesting that they adapt to the competition with each other. The solar corridor and the solar corridor plus soybean yielded lower than a corn monoculture, however, since corn and soybean are typically grown in a yearly rotation, the total of two years of yield for the solar corridor was greater than the sum of the yield of corn plus soybean. These results include only an analysis of yield and physiological adjustments, but the benefits of mixed stand cropping system can extend to other ecosystem services, which needs further study.

Technical Abstract: Plants have evolved to adapt to their neighbours through plastic trait responses. In intercrop systems, plant growth occurs at different spatial and temporal dimensions, creating a competitive light environment where aboveground plasticity may support complementarity in light-use efficiency, realizing yield gains per unit area compared with monoculture systems. Physiological and architectural plasticity including the consequences for light-use efficiency and yield in a maize-soybean solar corridor intercrop system was compared, empirically, with the standard monoculture systems of the Midwest, USA. The impact of reducing maize plant density on yield was investigated in the following year. Intercropped maize favoured physiological plasticity over architectural plasticity, which maintained harvest index (HI) but reduced light interception efficiency ('i) and conversion efficiency ('c). Intercropped soybean invested in both plasticity responses, which maintained 'i, but HI and 'c decreased. Reducing maize plant density within the solar corridor rows did not improve yields under monoculture and intercrop systems. Overall, the intercrop decreased land-use efficiency by 9%–19% and uncoordinated investment in aboveground plasticity by each crop under high maize plant density does not support complementarity in light-use efficiency. Nonetheless, the mechanistic understanding gained from this study may improve crop cultivars and intercrop designs for the Midwest to increase yield.