Search

Background and Aims: Selection effect (SE) and complementarity effect (CE) are often considered as two key indicators to mediate the positive diversity-productivity relationship in the maize-legume intercropping system, as intercropping generally enables crops to use the available resources more efficiently than monoculture. Yet, it is unclear whether soil moisture drives the SE and CE transformation, plant-plant interaction, and accordingly affect the productivity. Methods: A two-year field experiment was conducted to explore the impacts of soil water status (with and without plastic mulching) on interspecific interaction and productivity and its key mechanism in the maize-faba bean intercropping system. Results: Low soil moisture reduced the net effect (NE) and land equivalent ratio (LER) with evident yield loss (NE < 0 and LER = 1.05), whereas the improved soil moisture reversed this trend and resulted in overyielding (NE > 0 and LER = 1.13). Regardless of soil moisture, faba bean was the dominant species and maize was the inferior one. Low soil moisture promoted the contribution of SE to productivity (P < 0.05). In contrast, high moisture turned to lower the competition intensity of faba bean against maize and accordingly promote the transformation of biodiversity effect from SE to CE. The main mechanism was that the water competition imposed by faba bean strips on maize ones decreased the NE through reducing photosynthetic rate and water use efficiency of maize. Conclusion: The adaptive transitions of interspecific relationship and the biodiversity effect were driven by soil water availability. This novel phenomenon should be emphasized in the crop diversity management of intercropping system in the rainfed region. [ABSTRACT FROM AUTHOR]

Aims: Plant-plant interactions are determined by resource availability. However, its responses to differences in soil phosphorus (P) and water and the rhizospheric driving mechanism have not been systematically revealed. Methods: A pot-culture experiment was conducted in monoculture and in mixture with maize and grass pea. Resource stress treatments were created by organic and inorganic P applications (phytate and KH2PO4) as well as drought and well-watered treatments to address the above issue. Results: Intercropping increased system yield and biomass by 3.5% and 4.5% on average in soils with sufficient P and water, and by 12.0% and 11.7% under stressful conditions respectively. With increasing water and P availability, the yield-based interaction types transited from mutually facilitated to maize facilitated with grass pea as facilitator. Comparatively, the biomass-based facilitation shifting from maize facilitated and grass pea neutral to both being facilitated with increasing stress. This shift was probably mediated by complementary use of soil water in the two species, and rhizospheric acidification in grass pea. Also, rhizospheric interactions promoted phosphatase secretion by 5.3–22.2%, and mobilized organic P to buffer P limitation under P-deficient soils. Regardless of crop species, reproductive and vegetative biomass fell into a typical allometric pattern (α > 1). The rhizospheric interactions drove the differentiated biomass allocation patterns and the species-specific interaction transition. Conclusion: High P and water environments intensified the asymmetric interspecific competition. The trait-dependent facilitation shift was mechanically driven by rhizospheric interaction in intercropping systems. The findings update the understanding on stress gradient hypothesis in a modified model. [ABSTRACT FROM AUTHOR]