Speaker
Description
Exploring the potential of wheat-soybean intercropping as a climate change adaptation in crop production
1. Introduction
Due to climate change and agricultural intensification, crop production has been negatively influenced since the early 2000s. Yet, crop production needs to be doubled to feed the growing population by 2050. Crop diversification has the potential to enhance yield stability and increase sustainability under climate change (Birthal and Hazrana 2019; Bowles et al 2020). Intercropping, referring to two or more crops growing in the same field simultaneously is a vital option in crop diversification, which has been studied to outperform sole cropping in productivity, yield stability, and resilience to environmental stresses. Process-based crop models have been employed to simulate crop growth under future climate scenarios but focus only on main-stream cropping systems. To gain insights into intercropping of its essential mechanistic process and explore its potential adaptation strategy under climate change, we employ wheat-soybean relay-row intercropping as an example to: a) establish a low-parameter required crop model that can capture the light-competition of intercropping. (b) Investigate how climate change influences wheat and soybean yield in both sole and intercropped systems. 3) Explore to what extent a combination of intercropping and sowing date adjustments offset the negative impacts of climate change on crop productivity and save cultivated area.
2. Materials and methods
A two-year field experiment was conducted in Münche¬berg, Germany. Winter wheat and soybean in sole and Relay intercropping were cultivated in both rainfed and irrigation conditions. Field observations were used for model calibration and validation. The model is a revised version of the agro-ecosystem process-based model MONICA specified for relay-row intercropping, based on the ‘Horizontal Homogeneous Canopy’ model. Three general circulation models (GCMs) and two emission scenarios were employed to simulate the sole and intercropping wheat and soybean yield in Germany. Different sowing date combinations for wheat (six dates) and soybean (four dates) were tested under both moderate (RCP 2.6) and extreme (RCP 8.5) climate scenarios.
3. Results
By integrating the light-competition module into MONICA, and combining intercropping-specific calibration, the model showed acceptable prediction accuracy under both rainfed and irrigated conditions. The upscaling simulation to Germany showed that compared to the historical period (1981-2010), wheat soybean relay-row intercropping can achieve higher land-use efficiency (median Land Equivalent Ratio: 1.21, CV: 8%) than sole cropping under the futuristic high emission scenario (2031-2060). Even though, intercropping will decrease the total yield by 9% (median Transgressive Overyielding Index: 0.91, CV: 11%) under RCP 8.5. Optimizing sowing dates for component crops in intercropping can elevate productivity and land-use efficiency, with the highest value found when wheat is sown 30 days earlier and soybean plant 10 days later. The intercropping under the high-emission scenario has higher median LERs and lower CVs than that under the low-emission scenario, indicating its potential to stabilize crop yield under climate change.
4. Discussion
The intercropping version of MONICA focuses on the light competition, while below-ground competition regarding water and fertilization remains out of our scope. This simulation study was based on the experiment conducted in Germany, more field experiments involving various locations, component crops, or cultivars should be conducted for wider adoption possibilities. Under the current management level, transforming from sole cropping to intercropping increased the land-use efficiency but did not increase the total yield production. Optimizing sowing dates can aid the yield penalty but considering the feasibility of shifting sowing dates, fine-tuning and adapted machinery for intercropping are required. The indicators LER and TOI mainly emphasize yield production. Ecosystem services empowered by crop diversification were not evaluated in this study.
5. Reference
Birthal, P. S., & Hazrana, J. (2019). Crop diversification and resilience of agriculture to climatic shocks: Evidence from India. Agricultural Systems, 173, 345-354.
Bowles, T. M., Mooshammer, M., Socolar, Y., Calderón, F., Cavigelli, M. A., Culman, S. W., et al. (2020). Long-Term Evidence Shows that Crop-Rotation Diversification Increases Agricultural Resilience to Adverse Growing Conditions in North America. One Earth, 2(3), 284-293.
| Keywords | Diversification; Agro-ecosystem modelling; Cropping system; Sowing date; Yield |
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