# Soluble Elements Released from Organic Wastes to Increase Available Nutrients for Soil and Crops
## 3 Results and Discussion
### Elemental Composition and Soluble Nutrients
#### 3.2.1 Elemental Composition  
Tables 3 and 4 present the results from the analysis of macro and micronutrients (total content). The highest amount of nutrients follows the sequence SC \(>\) OP \(>\) PN \(>\) PP \(>\) VP \(>\) AP \(>\) CP. Although there are some references dealing with the organic residue's elemental composition, a previous work that compared the nutrient content of organic residues concluded that sewage sludge had the highest nutrient rate [23], which agrees with the data obtained. [PERSON] et al. [76] obtained slightly lower concentrations of nutrients, except for Mn and Zn. SC has an important mineral fraction compared with the rest of the residues, which means that it is possible to have an increased content of these nutrients analyzed. In the reverse series (highest to lowest), the elements ordered from presence in the residues are Ca \(>\) K \(>\) Fe \(>\) Mg \(>\) Na \(>\) Zn \(>\) Mn \(>\) Cu. The top 3 nutrients with maximum concentration values are Ca in SC \(>\) Fe in SC \(>\) Ca in PN, whilst the minimum concentration values are Zn in AP \(>\) Cu in AP \(>\) Cu in PP, ordered from highest to lowest (Tables 3 and 4). These results are consistent with those of [PERSON] et al. [28] and suggest that organic residues contain a large number of nutrients that can be profitable for plants. [PERSON] et al. [77] analyzed pine needle (_Pinus contorta_) where nutrient content was K \(>\) Ca \(>\) Mg \(>\) Mn \(>\) Fe \(>\)Zn \(>\) Cu, and in our case, PN follows the sequence Ca \(>\) Mg \(>\) K \(>\) Fe \(>\) Na\(>\) Mn \(>\) Zn \(>\) Cu. For PN nutrient composition, compared with data from previous studies [55], K (950 mg kg\({}^{-1}\)), Ca (7570 mg kg\({}^{-1}\)), and Mg (1030 mg kg\({}^{-1}\)) differ in part from Table 3 results. Related to micronutrients, a work carried out in Slovakia analyzed needles of various pine species other than _Pinus halepensis_, obtaining higher values for Mn, except for _Pinus nigra_ and _Pinus wallichiana_, whose values are like those presented in Tables 3 and 4. Similar values of Fe and Cu were observed in _Pinus wallichiana_ and \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Reside**} & \multicolumn{2}{c}{**Na (mg kg\({}^{-1}\))**} & \multicolumn{2}{c}{**K (mg kg\({}^{-1}\))**} & \multicolumn{2}{c}{**Ca (mg kg\({}^{-1}\))**} & \multicolumn{2}{c}{**Mg (mg kg\({}^{-1}\))**} \\ \cline{2-7}  & \(\overline{\mathbf{x}}\) & \(\boldsymbol{\sigma}\) & \(\overline{\mathbf{x}}\) & \(\boldsymbol{\sigma}\) & \(\overline{\mathbf{x}}\) & \(\boldsymbol{\sigma}\) & \(\overline{\mathbf{x}}\) & \(\boldsymbol{\sigma}\) \\ \hline AP & 263 b & 47 & 1698 a & 191 & 7559 b & 509 & 924 c & 63 \\ \hline CP & 495 c & 10 & 1138 d & 17 & 6649 a & 93 & 1173 b & 25 \\ \hline OP & 160 a & 33 & 6889 c & 123 & 10599 c & 238 & 1220 b & 29 \\ \hline PN & 170 a & 27 & 1648 a & 81 & 14059 d & 220 & 1838 a & 60 \\ \hline PP & 1079 d & 32 & 6858 c & 470 & 6861 a & 277 & 2259 d & 85 \\ \hline SC & 1529 e & 44 & 4585 b & 20 & 64245 e & 257 & 5815 e & 35 \\ \hline VP & 173 a & 8 & 4620 b & 352 & 7609 b & 244 & 1746 a & 80 \\ \hline F \({}^{1}\) & 1151 *** & & 419 *** & & 21630 *** & & 3314 *** & \\ \hline \end{tabular} \({}^{\dagger}\) F values followed *** indicate significant differences at \(p=0.001\). By columns, mean values with letters in common are statistically equal to \(p=0.05\).  
\end{table} 
Table 3: Elemental macronutrient composition, average content (\(\overline{\mathbf{x}}\)) and standard deviation (\(\sigma\)) for each residue. _Pinus musgo._ However, Zn concentrations presented in needles from Slovakia were much higher [56]. These variations may be associated with species, habitat and soil type. [PERSON] et al. [78] studied the critical interval of nutrient concentration in palm leaves versus yield (maximum value as toxicity limit) in Tunisia palm groves. By comparing the values obtained (Tables 3 and 4), it should be noted that Mn is within the optimal yield range, and Ca and Mg are very close.