## 2 Materials and Methods
### Field Data Acquisition  
During the crop season, fraction of vegetation (fCover) was measured with the Canopeo app [43]. The app is based on red-to-green color relations (R/G), blue-to-green colors (B/G), and an excess index of green (2G-R-B). Measurements were conducted at a height of 1.5 m above the ground [44]. In each plot, a sample of 8 m length of each plot (video composite of 20 photographs) was obtained as a percentage cover result.  
At physiological maturity (\(Z_{9.0}\)), wheat spikes from the 8 m\({}^{2}\) central rows in each plot were machine-harvested and weighed in the field, standardizing the values at 10% grain moisture (kg ha\({}^{-1}\)). The mineral composition of the tissues was determined by nitric perchloric acid digestion [45]. The total C and N content of the tissues samples was determined in automatic elemental microanalyzer (EuroVector elemental analyzer, Milan, Italy) and expressed as %N [46]. The total N of the grains was obtained and protein content (PB %) of the grain was determined using a conversion factor of 5.75 [47] and the hectoliter weight (HW %) was measured (kg hL\({}^{-1}\)).  
Statistical analyses were performed using the Infostat v.2020 statistical software package linked to the R programme v3.6.3 [48]. Normality of the data was tested using the Shapiro-Wilks test and the homogeneity of variance was assessed and confirmed using the Levene test (\(p>0.05\)).  
\begin{table}
\begin{tabular}{c c c c} \hline
**Treatment** & **ID** & **P Source** & **N Source** \\  & & **(Z\({}_{0.0}\))** & **(Z\({}_{2.3}\))** \\ \hline Control & 00 & – & – \\ P(MAP) + N(UREA) & 11 & MAP & Urea \\ \hline P(MAP + C) + N(UREA) & 21 & Compost + MAP & Urea \\ P(MAP + C) + N(UREA + C) & 22 & Compost + MAP & Compost + Urea \\ P(MAP + C) + N(BIM + C) & 23 & Compost + MAP & Compost + Blood meal \\ \hline P(BM + C) + N(UREA) & 31 & Compost + Bone meal & Urea \\ P(BM + C) + N(UREA + C) & 32 & Compost + Bone meal & Compost + Urea \\ P(BM + C) + N(BIM + C) & 33 & Compost + Bone meal & Compost + Blood meal \\ \hline P(Str+C) + N(UREA) & 41 & Compost + Struvite & Urea \\ P(Str + C) + N(UREA + C) & 42 & Compost + Struvite & Compost + Urea \\ P(Str + C) + N(BIM + C) & 43 & Compost + Struvite & Compost + Blood meal \\ \hline \end{tabular} Control: not fertilized. P and N indicate phosphorus and nitrogen, respectively. MAP: monoammonium phosphate (11-61-0); UREA: urea (46-0-0). C: compost; BIM: blood meal; BM: bone meal; Str: struvite.  
\end{table}
Table 1: Mineral fertilizer combinations and fertilization doses of wheat for the trial conducted at Aula Dei Experimental Station (EEAD-CSIC).  
The analysis of variance (ANOVA test at \(p<0.05\)) was performed for all the experimental variables using a generalized linear mixed model, with fertilizer treatments and sampling dates as fixed factors and each plot as a random factor. Multiple comparisons between the means were made using the LSD (least significant difference) Fisher test (\(\alpha=0.05\)). This approach tests for significant differences in the means of the experimental variables across fertilizer treatments and sampling dates, using the ANOVA technique as the primary method for evaluating factor-level effects.