Preliminary results on N2O emission factor calculation in hydroponic struvite fertilization of lettuce production

Recent work has revealed the great potential of struvite in hydroponic agriculture as well as the reduction of P emissions into leachate water. The nitrogen form in struvite is NH4+, which, when released, can undergo processes of nitrification and denitrification through the bacteria present in the substrate. The present work aims to determine N2O emission to air of struvite in hydroponic production compared to synthetic NO3- fertilizer. For the determination of the GHG N2O the chosen methodology is the closed chamber in the ICTA-UAB. Each side of the closed chamber was equipped with sensors for temperature and humidity as well as an inlet for a vacuum sampler and has room for 16 plant pots planted with lettuce (Lactuca sativa). One side was fertilized with a full nutrient solution and the other with a N, P-free nutrient solution. Chamber closing periods were chosen for pre and post air sampling into airtight 1-L bags for each side. Samples were analysed with gas chromatograph and the HP-PLOT-Q injected manually with an airtight Pressure-Lok Syringe. Previous validation experiments were made to ensure lettuce production with struvite as only source of N. The results show that the given quantity of struvite was sufficient to sustain the lettuce production while reducing N emission to water. When regarding the N2O peaks at time O and time 1, 3 and 5 no great increase can be noted between treatments and closing times obtaining results between 125 and 250 ppbv. While initial results indicate low emissions of N2O for both treatments, further work is encouraged to increase N2O detection.

Automated summary

Recent research has shown the potential of struvite in hydroponic agriculture for reducing nitrogen emissions to water, while sustaining plant growth. Further work is needed to improve N2O detection.