Plant interactions with soil microbiota are important drivers of biodiversity and ecosystem function, but climate change can modify these interactions by directly altering the soil community, which can affect the direction and magnitude of such interactions. We manipulated water quantity and soil microbiota of two populations of three plant species that differ in their interactions with soil microbiota and assessed germination and biomass production under conditions that mimicked a rainfall gradient in southeastern Spain. We assessed the importance of soil microbiota from home and away (drier) sites for alleviating or exacerbating the effects of drier conditions. Our results suggest that home soil microbiota enhanced germination of the legume Trifolium stellatum. Conversely, we found that the grass, Lagurus ovatus, and the forb, Sisymbrium erysimoides, produced more biomass under moderate drying with soil microbiota from a drier site than with home soil microbiota, suggesting that dry‐adapted soil microbiota alleviated the negative effects of drier conditions for these species. This maintenance of productivity with dry‐adapted soil microbiota under drier conditions was found despite simultaneous reductions in leaf dry matter content and root‐to‐shoot ratio that would typically be less optimal traits changes under reduced water availability. Severe water limitation resulted in decreased plant biomass regardless of the plant species and soil inoculum, indicating a threshold effect whereby severe water limitation on growth supersedes the beneficial effects of soil microbiota. Overall, our results show that species identity, the severity of water limitation, and soil microbiota interact to determine the response of plants to drier conditions.

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Aim of study: Intensive agriculture impacts physical, chemical, and biological characteristics of soil; therefore, the addition of organic matter (OM) to soil can have significant implications for crop production. This study investigated the impact of three crop management systems on tomato production and soil microbial communities in intensive greenhouse farming. Area of study: Province of Almería (Spain). Material and methods: The three crop management systems included: (1) conventional management, using synthetic chemical fertilizers without OM application (CM); (2) conventional management, using synthetic chemical fertilizers with at least one OM application in the last three years (CMOM); and (3) fully organic management, featuring yearly OM applications and no use of synthetic chemical fertilizers (ORG). Main results: Compared to CM soils, OM addition in CMOM and ORG led to higher soil NO3- and NH4+ content, which in turn increased nitrogen (N) availability, leading to an increase in soil respiration. The addition of OM also altered the composition of prokaryotic and fungal soil communities. Besides, the addition of OM reduced the presence and abundance of potential fungal pathogenic organisms, like Sclerotinia sp. and Plectosphaerella cucumerina. OM addition to conventionally managed greenhouses (CMOM) led to higher crop yields compared to CM greenhouses, resulting in an overall increase of 880 g m-2. Production under fully organic management (ORG) was lowest, possibly due to the nutrient and pest management practices used. Research highlights: Our data show the importance of organic matter management in shaping microbial communities in intensive greenhouse systems, which can be a key factor in developing a more sustainable agriculture to feed a growing human population.