## 2 Materials and Methods
### GHG Emissions of the Bio-Based Fertilisers after Soil Application  
A GHG experiment was conducted under controlled conditions in soil microcosms to study the outcome of fertiliser addition on soil respiration under controlled conditions. For this, the air-dried soil was pre-incubated at 40% WFPS for 7 days followed by application of fertilisers at 170 kg N/ha soil and incubation at 80% WFPS. Each microcosm was made using a 1L borosilicate glass bottle (height--23.6 cm, diameter--10.8 cm) fitted with a GL45-thread smart cap (model: SW45-2A). Each smart cap has two 2 mm threaded openings that can be closed with blind plugs or fitted with valves to serve as inlet and outlet ports for sampling. At 80% WFPS, 568 g of pre-incubated soil mixed with fertilisers was moderately compacted in Duran bottles to attain the bulk density of 1.3 kg m\({}^{-3}\). The slightly lower bulk density (compared with incubations) was chosen in this case to maintain effective aerobic conditions inside the mesocosom. A total of 15 mesoccosms (3 replicates \(\times\) 3 BBFs; 2 replicates each of CAN, urea and unfertilized blank) were established for the study. One of the two threaded openings on the smart cap were left open allowing aerobic respiration. Over a period of 18 days, the GHG monitoring was carried out by using a photoacoustic infrared spectroscopy multi-gas analyser (Gasera 1; Turku, Finland) calibrated for measurements of CO\({}_{2}\), CH\({}_{4}\), and N\({}_{2}\)O. The measurement was carried out on days 0, 1, 2, 4, 7, 9, 11, 14, 16, and 18. The analyser was connected to the mesocosom via two 1 m long Teflon tubes with 2 mm inner diameter in a closed circuit. During the measurement, gases were pumped out of the headspace (at flow rate of 800 mL/min), passed through the analyser, and then returned to the mesocosom in a closed loop. Gas concentrations in the headspace of the mesoccosms were measured at 4, 8, 12, and 16 min after connecting the tubing to the mesocosom. During each 4 min time step, the analyser detected the change in concentration of the measured gases. For the gaseous emissions, the fluxes of CO\({}_{2}\), CH\({}_{4}\), and N\({}_{2}\)O, were calculated from concentration change over time, considering the volume of the headspace, the piping, and the area of the soil surface. The measurement of NH\({}_{3}\) was not considered due to unreliability of photoacoustic gas analysers in measuring ammonia gas. The conversion of gas concentrations (in ppm) to emission flux was carried out using ideal gas law (Equation (3)) [21]:  
\[\mathrm{Flux_{area}}=\frac{\Delta\mathrm{gas}}{\Delta t}\times\frac{\mathrm{P \times M\times n}}{\mathrm{R\times T}}\times\frac{\mathrm{V}}{\Delta} \tag{3}\]where Flux \({}_{\rm area}\) is the elemental flux released as a gas, in \(\mu\)g m\({}^{-2}\) h\({}^{-1}\) or \(\mu\)g kg\({}^{-1}\) h\({}^{-1}\); \(\Delta\)gas/\(\Delta\)t is the slope of the linear regression of gas concentration against time; P is the pressure in the cell (0.838 atm); M is the molar mass of the element (e.g., 14 for N); n is the number of atoms of the element in the gas (e.g., 2 N in N\({}_{2}\)O); R is the ideal gas constant (0.08206 L atm mol\({}^{-1}\) K\({}^{-1}\)); T is the average atmospheric temperature (294 K); V is the total volume of the headspace, tubing, and analyser cell (0.623 L); and A is the surface area of the soil in the mesocosm (0.0069 m\({}^{2}\)). A linear interpolation between two measurement days was used to compute the cumulative flow for each gas. In all cumulative fertiliser emissions, the cumulative fluxes obtained with the soil control were deducted.