## 2 Materials and Methods
### Applicability of Bio-Based Fertilisers in a Full-Scale Field Trial  
Two of the BBFs (LFD and AS) were tested in a full-scale field trial in Eersel (Figure 2). The soil characteristics of the field and the fertiliser recommendations are reported in Table 2. Before the growing season, the field was ploughed using a Lemken Juvel 8 plough and scanned using a Dualem 21 (H)S soil scanner. All treatments, except the control, received 100% of the recommended amount of N (310 kg N/ha) to analyse the maximum performance of the BBFs. Additionally, all treatments, including the control, received 23 kg SO\({}_{3}\)/ha, 70 kg K\({}_{2}\)O/ha, and 75 kg CaO/ha, which was recommended for potato growing (Table 2). The LFD and AS were tested in combinations applied with and without a base application of pig manure. This resulted in six treatments: (1) MF CAN and manure, (2) LFD and manure, (3) AS and manure, (4) only LFD, (5) only AS, and (6) a blank control with no application of N fertiliser. Each treatment had 3 replicates, which resulted in a total of 18 plots. The plots with and without manure treatment were arranged randomly and the surface area of one plot was approximately 0.75 ha (Figure 2). Manure (80 t ha\({}^{-1}\)) was applied at the left side of the field at the beginning of the growing season using a drag hose injector (April 2020). The composition of the manure is given in Table 1. At the same moment in time, the fields with only LFD or AS received 31 t ha\({}^{-1}\) LFD and 2 t ha\({}^{-1}\) AS, which corresponds to the amount of N that the manure-treated plots received. AS was applied using a Duport Liquiliser and LFD was applied using a precision agriculture tank Tandem Premium Line in combination with the Terraject Disc.  
On April 29 th, the consumption potatoes (variety Fontane, size 40-50 mm) were planted using a Miedema CP42 planter. The distance between the planting rows was 75 cm and the distance between the potatoes in the row was about 30 cm. The second fertilisation took place on 11 June, and was applied at the beginning of the tuber bulking stage. Both BBFs were applied between the ridges using a drag hose system to ensure the tuber did not have direct contact with the fertiliser which can cause burning. Besides, fertiliser recommendations for K (70 kg ha\({}^{-1}\)) and S (23 kg ha\({}^{-1}\)) were met by complementing the fertilisation with Kali60 and MgSO\({}_{4}\) where needed. Manual test probing and drone flights to obtain thermal and NIR images took place at three moments during the growing season to monitor the plant growth. The test probing took place on 19 June, 28 July, and September 8, and the thermal and NIR images were taken on 21 June, 19 July, and August 7. The potatoes were harvested on October 14. After harvest, the underwater weight, number, and size of the tubers, and net yield were measured using a robot that was specifically designed for the potato farmer.  
The NO\({}_{3}\)-N residue in the soil profile (0-90 cm) was measured after harvest. We assume this to be a good indicator for potential N leaching to ground and surface water, which causes a serious environmental risk in the Netherlands. To measure NO\({}_{3}\)-N residue in the soil profile, homogenised soil samples were taken per plot at three depths (0-30 cm, 30-60 cm, and 60-90 cm) using an auger. A 5-point sampling strategy (the centre and the 4 corners) was used to obtain a representative soil sample from each plot. The samples were collected in polyethylene sampling bags and transported from the crop field to the laboratory and stored in the freezer (\(-18\)\({}^{\circ}\)C) until the analysis. The collected soil samples were extracted with 1M KCl and measured colourimetrically by a continuous flow auto-analyser (Skalar Chemlab System 4) for NO\({}_{3}\)-N.