## 3 Results  
The initial values of Olsen-P and total Cd, Cu, Cr, Pb and Zn (Table 1) from the composite samples were below the limits of 150 P kg\({}^{-1}\), 1.5 mg Cd kg\({}^{-1}\), 100 mg Cu kg\({}^{-1}\), 100 mg Pb kg\({}^{-1}\) and 200 mg Zn kg\({}^{-1}\) established by [11; 12; 39]. In all treatments, values of hexavalent chromium, mercury, selenium and silver were lower than 0.5 mg Cr (VI) kg\({}^{-1}\), 0.4 mg Hg kg\({}^{-1}\), 1.5 mg Se kg\({}^{-1}\) and 5.0 mg Ag kg\({}^{-1}\), respectively, which also satisfied the legislation. Fertilization treatments did not affect soil Pb availability (DTPA extraction), with average values of 1.9 mg Pb kg\({}^{-1}\), while they did for Cd, Cu, Fe, Mn and Zn (Table A1). Sewage sludges increased Cd, Cu and Fe availability in the soil when compared with MIN treatment. Availability ranged from 52 to 57 ug Cd kg\({}^{-1}\), from 8.5 to 11.6 mg Cu kg\({}^{-1}\) and from 11.4 to 19.9 mg Fe kg\({}^{-1}\). The availability of Zn increased in the following order: \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Source**} & **Oxidizable-OM** & **Olsen-P** & **K (NH\({}_{4}\)OAc)** & **Total-Cd** & **Total-Cu** & **Total-Cr** & **Total-Pb** & **Total-Zn** \\ \cline{2-9}  & **(g kg\({}^{-1}\))** & & & & **(mg kg\({}^{-1}\))** & & & \\ \hline MIN-Soil & 12 & 14.9 & 99 & \textless{}0.5 & 44.3 & 18 & 17.8 & 72.2 \\ SPC-Soil & 15 & 39.2 & 96 & \textless{}0.5 & 52.4 & 19.5 & 18.6 & 82.2 \\ SNC-Soil & 16 & 57.1 & 87 & \textless{}0.5 & 52.5 & 17.4 & 19.1 & 82.8 \\ Sludge & 69.2 & 19.5 & 3.04 & 1.16 & 668 & 38 & 68 & 1208 \\ \hline \hline \end{tabular} \({}^{1}\) All results are expressed over dry-matter basis.  
\end{table} 
Table 1: Soil physicochemical parameters \({}^{1}\) of the upper layer (0–0.2 m) in October 2018 sampling, and from the different treatments: mineral (MIN), sludge N criterion (SNC), sludge P criterion (P). Parameter results from the sewage sludge (SS) applied in March 2019 are also included. MIN< SPC < SNC treatments, from 1.9 to 4.6 mg Zn kg\({}^{-1}\), while Mn availability increased following an inverse order, from 6.1 mg Mn kg\({}^{-1}\) in SNC to 7.9 mg Mn kg\({}^{-1}\) in MIN (Figure 1). The yields of the grain, the cob and the rest of the plant biomass were not significantly different based on the fertilization treatments applied (Table 2). The average biomass yield values were 13,779, 2293 and 11,024 kg ha\({}^{-1}\) for the grain, the cob and the rest of the plant, respectively (Figure 2). Concentrations and fractionated extractions for maize are presented in Figures 3 and 4, respectively. The concentrations of Cr, Co and F in grain; concentrations of P and Mn in the cob; and concentrations of Cr, Co, and Pb in the plant were statistically different with the fertilization treatments, but no differences were found for the rest of the analyzed elements in the different parts of maize plants (Tables 3-4; Figure 3). Figure 1: Average values of soil available Cd (mg 10\({}^{2}\) Cd kg\({}^{-1}\)) and available Cu, Fe, Mn, Pb, and Zn (mg kg\({}^{-1}\)) in soil, determined by DTPA extraction, for each fertilization strategy (MIN: mineral; SPC: sewage sludge, P criterion; SNC: sewage sludge, N criterion). For each element, means with different letters are significantly different according to the [PERSON]’s multiple-range test (\(\alpha\) = 0.05). Figure 2: Accumulated dry-matter yield (Mg ha\({}^{-1}\)) from different parts of maize plants and for each treatment (MIN: mineral; SPC: sewage sludge, P criterion; SNC: sewage sludge, N criterion). No significant differences were found between fertilization treatments in dry-matter yields. Figure 3: Average concentrations of N and K (**a**); P, Mg and S (**b**); Fe, Mn and Zn (**c**); Cr and Cu (**d**); Co and Pb (**e**); and Cd (**f**); in different parts of maize plants for each treatment (MIN: mineral; SPC: sewage sludge, P criterion; SNC: sewage sludges, N criterion).