Effects of soil microbial communities associated to different soil fertilization practices on tomato growth in intensive greenhouse agriculture

Intensive greenhouse vegetable production is one of the most important economic activities in south-east Spain. Agricultural intensification has limited the application of organic matter (OM) in favor of synthetic chemical fertilizers, leading to altered soil microbial communities and production loss. We addressed the effects of soil microbial communities on plant productivity depending on different soil management practices in greenhouse agriculture. Greenhouse managements were i) conventional (i.e., with addition of synthetic chemical fertilizers) without organic amendments (CM), ii) conventional with organic amendments (CMOM) and with addition of synthetic chemical fertilizers, and iii) organic management with annual organic amendments and with no synthetic chemical fertilizer addition (ORG). We extracted soil microbial communities from five greenhouses per management type, added these inocula to pots with sterile substrate (peat:sand), and seeded disinfected tomato seeds. Plants grew for 2 months without nutrient addition (only water irrigation). Immediately prior to the end of the study, we measured photosynthetic rate, plant growth, and leaf functional traits. At the end of study, pot substrates inoculated with i) ORG soil communities had higher bacterial abundance (qPCR) compared to microbial communities inoculated with CM extracts; and ii) prokaryotic communities of CM and CMOM substrates differed in composition. Besides, substrates inoculated with CM inocula were significantly associated with the presence of a potential fungal pathogen. Plants inoculated with extracts from organic greenhouses grew more and had a higher photosynthetic rate than plants receiving soil microbial extracts from greenhouses with conventional management. There were differences in the NO3-, total N and organic matter contents of substrates between treatments at the end of the study, but not at the beginning of the study, suggesting differences in microbial activity between treatments. Although substrate N content differences did not translate into differences in leaf N, leaf delta N-15 differed between treatments, indicating that the source of the soil microbial inocula influenced the N compound used by the tomato plants. Overall, this study suggested that soil microbial communities from organic greenhouses had a positive effect on crop productivity in intensive greenhouse agriculture.

Automated summary

The study found that soil microbial communities from organic greenhouses have a positive effect on crop productivity, suggesting that organic management practices and organic amendments may improve the richness and diversity of soil microbial communities.