Do positive intercropping effects carry over to the subsequent crop in the rotation?

Amit Kumar, Siobhan Protic and Vicky Temperton, Leuphana University of Lüneburg, Lüneburg, Germany, Christoph Rosinger, Hao Chen and Michael Bonkowski, University of Cologne, Cologne, Germany

Background/Question/Methods
Mixed cultures and intercropping often lead to improved productivity of individual species compared to monocultures. This has been attributed to changes in soil biotic and abiotic properties as well as complementary and facilitative interactions between the species growing together. We have practically little knowledge of whether any facilitation effects and soil legacies from intercropping can indirectly affect the succeeding crop in a crop rotation through plant-soil feedback (PSF) effects. To test this, we used a two-phased field experiment where we combined intercropping and crop rotation in moderately fertile agricultural soils. During intercropping, we grew maize, faba bean, and lupine in monocultures or two-species crop combinations. The following season, we grew winter barely on the soil previously used for intercropping to test PSF effects under field conditions.
Results/Conclusions
We found evidence for facilitative effects on aboveground biomass production that were species-specific with faba bean and maize biomass benefitting when intercropped compared to their expected biomasses in monocultures. Lupine, in contrast, performed best in monocultures. After the intercropping phase, total mineral nitrogen was higher in faba bean and lupine monocultures creating soil legacies but this did not affect microbial parameters (microbial biomass and potential enzyme activities) and barley biomass production in the follow-up rotation phase. We found support for species-specific positive (for maize and faba bean) and negative (for lupine) interactions in intercropping. Our results also demonstrate that soil legacies play no significant role under moderately high nutrient environments.