Struvites with comparable nitrogen and phosphorus composition have similar agronomic response but shape cherry tomato rhizosphere bacterial community structure differently

Abstract

Struvites are circular-economy based fertilisers which are set to reduce some of the demand on finite phosphate rock in the European Union. While they are near similar in P and N content, with low P water solubility, subtle chemical differences exist between recovered struvites from different wastewaters. The objectives of this study were to assess if two struvites similar in N and P, but differing feedstock material, similarly effect tomato growth and tomato rhizosphere bacteria. A glasshouse experiment was setup using low-P soil and applications of struvite from municipal wastewater (MWS), struvite from potato wastewater (PWS) and compared to single superphosphate (SSP). While Tomato aboveground biomass yields were similar between the struvites (39.5 and 37.4 g/pot), they were 17–22 % lower in comparison to the SSP treatment (47.8 g/pot) when harvested during the early fruiting stages. However, P uptake was not significantly different among all the treatments ranging 21.6 to 25.4 mg P/pot. The PWS treated soil had a plant available P of 5.52 mg P/L at the fruiting stage that was comparable to that of SSP (4.74 mg P/L) but significantly greater than that of the MWS treatment (4.37 mg P/L). PWS and SSP tomato rhizosphere bacteria were ecologically similar but ecologically distant to the MWS treatment. Slow growing oligotrophic bacteria of the Xanthobacteraceae, Planococcaceae, and Bacillaceae families were abundant in MWS possibly because of the presence of Fe which limited P dissolution from the struvite. We concluded that while tomato had a similar agronomic response to PWS and MWS, the struvites affected the soil bacteria in the tomato rhizosphere differently. Long-term studies at field scale are recommended to identify the long-term suitability of struvites for horticulture crops.