### Crop Response Assessment  
Overall, the performance of AN\({}_{100\%}\) and AW at both doses being similar to CAN is attributed to their mineral nature, i.e., 100% of total N in these products is in the plant-available form. The performance of AN\({}_{50\%}\) was observed to be significantly higher than CAN\({}_{50\%}\). In a previous study conducted on lettuce growth using AN sourced from the same producer, a similar outcome was observed, where the plants fertilized with AN had a significantly higher yield than those treated with CAN [45]. Furthermore, in this study, AW + CaE\({}_{50\%}\) was the only treatment that showed significant differences in FW on the basis of dosage applied, wherein plants with 50% N dose had a significantly higher FW than the ones with 100% N. This result could be explained by the fact that the plants with 50% dosage also received less Na from the CaE content of AW + CaE, thus being subjected to lesser osmotic stress. Although, it is confounding why the same outcome was not seen in the case of AN + CaE\({}_{50\%}\). Plants treated with CaE (and subsequently the blends, except for AW + CaE\({}_{50\%}\)) demonstrated low N uptake values. Moreover, they also showed significantly higher Na content in comparison with the unfertil control and CAN. Treatments with blends were included in the experimental set-up to study the effect of optimization of NPK from RDFs for effective crop growth. A past study that attempted a tailor-made blend formulation for tomato growth demonstrated a better yield in treatments utilizing blends [70]. In the current study, similar results could not be replicated due to the impeding characteristic of Na present in CaE. A negative correlation between the N uptake and Na content of plant samples (Pearson correlation = \(-\)0.723; \(p\) < 0.001) was observed, leading to the hypothesis that the higher Na content (e.g., as symptomatic for salt stress) could have limited the N uptake and hence caused poor growth of the plants. A negative correlation observed between Na content and plant FW (Pearson correlation = \(-\)0.796; \(p\) < 0.001) further validated this supposition. Other studies reported experiments with wheat and rice, where the presence of Na\({}^{+}\) ions impaired the uptake of NH\({}_{4}\)\({}^{+}\) ions to the plant [71; 72]. The effect of osmotic stress was seen as a rapid inhibition of the state of the expansion of the young leaves and reduced the stomatal conductance of the mature leaves [73]. Inexplicably, a higher Na content was not observed for AW + CaE\({}_{50\%}\), which also contained CaE. Hence, the N uptake, and subsequently the FW, were not affected in this treatment. Since vegetables are considered to be a potential source of nitrate accumulation [74], and the presence of nitrate has been associated in the occurrence of methemoglobin, its content in edible plant tissues is an important criterion of vegetable quality [75]. All fertilized treatments showed nitrate content within the prescribed legal limit of 5000 mg kg\({}^{-1}\) FW for lettuce grown under cover and harvested in winter between 1 October to 31 March [76]. ANR and NFRV are agri-environmental tools used to determine the fertilizer performance of RDFs [22; 39; 77]. NFRV is the amount of synthetic fertilizer saved when using a bio-based alternative, while attaining the same crop yield, i.e., it indicates the substitutability of an RDF relative to a synthetic fertilizer. AN and AW at both doses showed NFRV above 100%. A study previously conducted to test the AN obtained from the same producer also demonstrated similar results of NFRV, i.e., above 100% [45]. The distribution of N forms in AN (59% NH\({}_{4}\)+-N and 41% NO\({}_{3}\)-N) was almost similar to that of the synthetic CAN (50% NH\({}_{4}\)+-N and NO\({}_{3}\)-N each), thus deriving the obtained results.