Intercropping

The Indigenous companion planting technique known as the Three Sisters system improves soil health, weed control, and crop yields by combining mutually beneficial crops. However, existing research focuses on small-scale gardening, while modern agriculture’s reliance on large land and machinery makes the traditional garden-based approach impractical. This study is the first to explore the adaptation of the Three Sisters system to modern row-cropping practices. Two-year field experiments were conducted in Manitoba, Canada. The Three Sisters crops, sweet corn (Zea mays L.), pole bean, and summer squash, were grown under four planting modes: corn monoculture, corn with bean companion, corn with bean and squash companion, and squash monoculture. Key measurements included soil moisture content, leaf area index, crop yield components, and soil nitrogen levels. Results showed that companion plots with two or three crops generally had lower soil moisture compared to monocultures, with squash monoculture plots retaining the most soil moisture. Among the companion plots, similar soil moisture levels indicated corn as the dominant water consumer. The leaf area index of squash monoculture plots increased rapidly in mid-season, with plots containing squash achieving the highest indices later in the season. Bean contributions to leaf area index were minimal due to corn canopy dominance during early growth stages and squash canopy dominance later. Monoculture plots produced higher individual crop yields, whereas companion planting offered greater produce diversity and a higher total yield of combined crops. The timing of bean planting had inconclusive effects on corn yields but consistently improved bean yields when delayed. Companion plots with three crops exhibited lower residual soil nitrogen, suggesting potential water quality benefits. This study offers guidance on adapting the traditional Three Sisters system to modern row-cropping practices, presenting a sustainable approach that balances agricultural productivity with ecological and human health benefits.

Guo, J., Mooney, H., Wu, P. et al. Adapting the Indigenous Three Sisters system to modern row cropping practices. Agron. Sustain. Dev. 45, 47 (2025). https://doi.org/10.1007/s13593-025-01041-2

Green manure is widely employed to substitute chemical N fertilizer. However, the potential of further alleviating N₂O emission when combined with efficient management technologies has not been fully explored. To reduce this research gap, a 2-year field experiment was conducted in northwestern China. The aim was to investigate the impact of zeolite application on N₂O emission in the maize-common vetch intercropping system under 30% N reduction, as well as the possible mechanisms. The experiment included two cropping systems, namely monoculture maize and maize-common vetch intercropping, along with three amendment practices, namely conventional N, 70% conventional N, and zeolite application under 70% conventional N. Compared with monoculture maize under conventional N, maize-green manure intercropping combined with zeolite application under 70% chemical N achieved comparable yields. Simultaneously, this practice reduced cumulative N₂O and yield-scaled N₂O emissions by 36.9% and 39.2%, respectively. This reduction can be attributed to a decrease in soil ammonium-N by 20.9%–57.7%, nitrate-N by 47.7%–51.3%, nitrate reductase activities by 25.3%–34.4% and N₂O-producer (i.e., nirS and nirK) abundance by 17.3%–79.4% in denitrification, and an increase in the N₂O-reducer (i.e., nosZ) abundance by 40.0%–103.4%. Compared with 100% N input, 70% chemical N treatment reduced ammonium-N by 22.3%–41.0%, nitrate-N by 25.4%–41.0%, and N₂O-producer abundance by 17.1%–35.0% in denitrification. Zeolite application reduced denitrifying enzyme activities by 8.2%–12.9%, N₂O-producer abundance by 42.5%–56.4%, but increased N₂O-reducer abundance by 13.3%–23.3% in denitrification. PLS-PM analysis showed that N₂O emission mitigation was mainly related to reduced soil ammonium-N and nitrate-N, decreased N₂O-producer abundance, and increased N₂O-reducer abundance in denitrification. These findings provide new insights into the fact that intercropping green manure combined with zeolite application effectively mitigates N₂O emission by regulating mineral N, N-cycling enzymes, and denitrifier abundances while maintaining maize yield after cutting 30% N input.

Liu, R., Chang, D., Liang, H. et al. Applying green manure and zeolite and reducing N fertilization in maize mitigates N₂O emission while maintaining yield. Agron. Sustain. Dev. 45, 43 (2025). https://doi.org/10.1007/s13593-025-01033-2