# Soluble Elements Released from Organic Wastes to Increase Available Nutrients for Soil and Crops
## 3 Results and Discussion
### Physical and Chemical Characteristics of Wastes  
It is important to ensure that nutrients released during decomposition are synchronized with the crop nutrient requirement curve [23]. Therefore, studies on the possibility of applying organic wastes to soil to take advantage of its nutrients must begin with an analysis of its physical and chemical properties and elemental composition. The results obtained for the selected waste are presented in Table 2.  
For all residues, Table 2 shows a low \(\rho_{\text{b}}\), between 0.23 and 0.40 g cm\({}^{-3}\). Although OP and SC get the highest values, they are far from 1.6 g cm\({}^{-3}\) of soil, as \(\rho_{\text{b}}\) can interfere with root growth [59]. In the work performed by [PERSON] et al. [59], organic amendments improved soil properties and succeeded in decreasing soil \(\rho_{\text{b}}\) to a greater extent than inorganic fertilizers. Similar results were achieved by [PERSON] et al. [40] and [PERSON] et al. [60]. This means that, in general, the use of these residues can contribute positively to the reduction of the bulk density of the soil. In such a way, all residues are suitable for reducing \(\rho_{\text{b}}\) soils. Table 2 shows variation in OM depending on the type of residue considered in our work. SC is the one with the lowest amount of OM, and the rest get high OM values in the range of 90-94%. OM of VP (Table 2) is like that obtained by [PERSON] et al. [40]. These residues can contribute to an increase in OM in soil [20; 25; 28; 53; 61] and is important since they may modify physical soil properties [53; 59; 60; 62], carbon sequestration [21; 63], nutrient cycling and crop yield [28; 59] and bioavailability of nutrients (Fe, Mn, Cu, Zn) [64; 65]. [PERSON] et al. [59] proved that OM could reduce nutrient leaching. Therefore, all tested residues may improve soil OM according to the amount applied, even doubling its initial content [66] and the content of recalcitrant material [67]; it is, however, subjected to environmental conditions. [PERSON] and [PERSON] [68] considered that in Mediterranean conditions \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Residue**} & \multicolumn{2}{c}{\(\rho_{\text{b}}\) (g cm\({}^{-3}\))} & \multicolumn{2}{c}{**OM (\%)**} & \multicolumn{2}{c}{**MC (\%)**} & \multicolumn{2}{c}{**pH (units)**} & \multicolumn{2}{c}{**EC (\(\mu\)S cm\({}^{-1}\))**} \\ \cline{2-10}  & \(\overline{\kappa}\) & \(\sigma\) & \(\overline{\kappa}\) & \(\sigma\) & \(\overline{\kappa}\) & \(\sigma\) & \(\overline{\kappa}\) & \(\sigma\) & \(\overline{\kappa}\) & \(\sigma\) \\ \hline AP & 0.36 a & 0.006 & 93.2 b & 0.6 & 8.0 b & 0.03 & 4.66 a & 0.007 & 665 b & 0.8 \\ \hline CP & 0.37 a & 0.004 & 91.0 a & 0.9 & 52.7 c & 0.41 & 5.02 b & 0.031 & 1447 a & 3.1 \\ \hline OP & 0.40 b & 0.003 & 94.1 b & 0.1 & 6.3 d & 0.21 & 4.78 c & 0.004 & 1444 a & 3.0 \\ \hline PN & 0.31 c & 0.009 & 91.9 a & 0.3 & 8.95 a & 0.67 & 5.94 d & 0.005 & 753 c & 1.0 \\ \hline PP & 0.26 d & 0.010 & 90.9 a & 0.3 & 8.6 ab & 0.17 & 4.90 e & 0.097 & 4358 d & 4.0 \\ \hline SC & 0.40 b & 0.008 & 59.0 c & 1.1 & 26.0 e & 0.73 & 7.34 f & 0.017 & 3380 e & 1.0 \\ \hline VP & 0.23 e & 0.009 & 94.0 b & 0.5 & 9.3 a & 0.15 & 5.42 g & 0.007 & 1286 f & 0.6 \\ \hline F\({}^{1}\) & 422 *** & & 1992 *** & & 8190 *** & & 2913 *** & & 6 \(\times\)10\({}^{6}\)*** \\ \hline \hline \end{tabular}  
* F values followed by *** 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 2: Bulk density (\(\rho_{\text{b}}\)), OM, MC, pH and EC of each residue, average (\(\overline{\kappa}\)) and standard deviation (\(\sigma\)). (low precipitations and high temperatures), OM decomposes faster inside soil than on soil since moisture is better retained in lower layers. So, the MC of each residue is analyzed (Table 2); CP and SC get the highest content (52.7% and 26%, respectively), and VP (9.3%) is the lowest among the studied pruning waste.