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Reducing the yield loss of inferior crop species is crucial for improving the production of intercropping systems, particularly in drought-prone regions. Yet, the physiological mechanism of yield loss caused by interspecific competition in response to soil water availability is unclear. A two-year (2018–2019) field experiment was conducted to explore the impacts of interspecific competition on yield formation of the inferior crop in the maize-faba bean intercropping system with and without plastic film mulching in a semiarid rainfed region. The plant-water relation, and yield formation in association with nitrogen (N) remobilization were determined and compared. Results indicated that the land equivalent ratio of the intercropping system was greater than 1, regardless of whether treated with plastic mulching. However, the net effect of the intercropping system was significantly greater than 0 only under plastic mulching. Intercropping with faba beans prolonged the anthesis-silking interval of maize by 93.7% (p < 0.05) and the bald tip length by 56.2% (p < 0.05). This trend resulted in insufficient pollination of tassels and an increased kernel abortion rate in maize (p < 0.05). Moreover, the amount of dry matter and N transfer to grain in vegetative organs decreased by 34.0% and 23.2% (p < 0.05), respectively. Physiologically, this brought about yield loss in the intercropped maize. Water competition from faba bean significantly reduced the soil water availability in the intercropped maize strips, regardless of whether treated with plastic mulching. However, plastic mulching alleviated the competition for water between faba bean and maize, and thus kernel abortion in maize was significantly reduced. Our findings reveal the physiological mechanism of yield loss in intercropped inferior species, by connecting kernel formation and remobilization function, in the semi-arid and rainfed intercropping systems. Specific water or nutrient management strategies might be needed for inferior crops to further improve the total productivity of cereal-legume intercropping system in drought-prone environments. [Display omitted] • The yield loss mechanism of inferior crops in legume-based intercropping system is unclear. • Growth loss of maize in cogrowth period cannot be compensated in late seed filling period. • Water competition lowered remobilization function and increased kernel abortion of maize. • Plastic mulching (PM) weakened plant competition and conducive to maize final yield formation. • PM is a promising option to improve the productivity of intercropping system in rainfed regions. [ABSTRACT FROM AUTHOR]

We hypothesized that soil phosphorus (P) utilization might be tightly associated with interspecific interactions. To clarify this issue, a maize-grass pea intercropping system was investigated in a rainfed field with P addition (P0 and P +), water (rain-fed and plastic film mulching) and isolation (root barrier and root intermingling) treatments. The data indicated that total net effect was higher than 0 under all the conditions, displaying facilitative effects of biodiversity on agroecosystem productivity. The dynamics of total land equivalent ratio demonstrated that the intensity of plant-plant facilitation became greater under P-deficient condition. Maize was the facilitated species consistently, while grass pea changed from facilitated species under low soil P and moisture to facilitator under high soil P and moisture. The driving mechanism was associated with soil acidification and microbial community promotion effect under P-deficient condition. Intercropped rhizosphere soil phosphatase activity was increased by 4.9–17.2%, and Olsen-P availability was evidently enhanced relative to monoculture. Interestingly, drought stress significantly enhanced this trend. Critically, root isolation confirmed that plant-plant facilitation was briefly driven by interspecific rhizosphere interactions. Conclusively, this study confirmed the context-dependent facilitation shift in agroecosystem and provided a novel insight into the importance of rhizosphere interaction on soil P availability and utilization. [Display omitted] • Plant-plant facilitation was observed in the maize-grass pea intercropping system. • The intensity of facilitation decreased from low to high P and water gradients. • P deficiency promotes rhizosphere phosphatase activity and acidification process. • Drought and P deficiency led to the optimal soil microbial biomass and activities. • Intercropped grass pea fostered soil P mineralization and resource use efficiency. [ABSTRACT FROM AUTHOR]