Effect of Fertigation with Struvite and Ammonium Nitrate on Substrate Microbiota and N<sub>2</sub>O Emissions in a Tomato Crop on Soilless Culture System
2024
Mar Carreras-Sempere | Miriam Guivernau | Rafaela Caceres | Carmen Biel | Joan Noguerol | Marc Viñas
Struvite and ammonium nitrate (AN), as wastewater-recovered products, are possible alternatives as raw materials for nutrient solutions. However, their impact on the rhizosphere microbiota and N<sub>2</sub>O emissions is scarcely known. Therefore, the present research studies the ecological changes in the bulk-substrate microbiome and its correlation with N<sub>2</sub>O emissions in a perlite-based system tomato crop under (i) conventional synthetic fertigation management; (ii) fertigation with struvite; and (iii) struvite and AN. A high bacterial diversity and the natural presence of plant-growth-promoting rhizobacteria in a soilless system are highlighted. However, the different N-NH<sub>4</sub><sup>+</sup>:N-NO<sub>3</sub><sup>−</sup> ratios influence the ecological niches of ammonia-oxidizing archaea (AOA) and bacteria (AOB), with a stronger response by AOB community, while AOA kept constant regarding the fertilization applied. Despite this, enrichment of N-transforming bacterial phylotypes was relatively enhanced (mainly Nitrosomonas, Nitrosospira, and Nitrospira) concomitant with the production of N<sub>2</sub>O emissions when ammonium fertilization was overapplied. In the absence of a plant, N<sub>2</sub>O emissions were positively correlated, respectively, with Nitrosospira and AOB:AOA ratio, suggesting potential indicators for ammonium availability in the substrate. Fertilizer blends using recovered nutrients are a feasible alternative for increasing circularity in horticulture. Nevertheless, optimum fertilizer management is needed due to its influence on rhizosphere microbiota and N<sub>2</sub>O emissions.
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