## 3 Results
### Moisture Retention Tests
#### 3.1.2 Fine-Grained Silica Sand  
Results of moisture retention tests are depicted in Figure 6 (exact values are appended in Table 10). Four days (96 h) after treatment, the control sample, which was treated with water, contained 2.5% (SD = 0.7) of the initially applied 20.3 g of water. In the following, results of the polysaccharide and protein applications to the fine-grained silica sand are presented and compared. _Polysaccharides_. In relation to the control sample, a 1 wt% (XG = 0.25 wt%) biopolymer treatment decreased the moisture retention of substrates treated with CS, NLS, PES, and POS, whereas an increase was observed for samples amended with CMC, WS, and XG. Increasing the concentration to 2 wt% (XG = 0.50 wt%) significantly decreased the moisture retention of XG-treated samples, and CMC had a negligible effect. By contrast, significant increases in moisture retention were observed for samples subject to applications with CS, NLS, PES, POS, and WS. _Proteins_. Biopolymer applications at 1 wt% reduced the moisture retention for samples amended with HEA, PP, WP, and WPC compared to the control group. At the same time, significant increases were observed for FBPC, HG, and TG, respectively. When the concentration was doubled to 2 wt%, the moisture retention of the TG-treated silica sand decreased slightly, while the remaining proteins increased moisture retention. \begin{table}
\begin{tabular}{l l r r r r r} \hline
**Group** & **Factor** & **SS** & **df** & **MS** & **F** & \(p\) \\ \hline \multicolumn{6}{l}{Medium-grained sand} \\ \hline \multirow{4}{*}{Polysaccharides} & Type & 0.01297 & 6 & 0.00216 & 20.578 & \(<.001\) \\  & Concentration & 0.00003 & 1 & 0.00003 & 0.288 &.596 \\  & Interaction & 0.00219 & 6 & 0.00036 & 3.48 &.011 \\  & Error & 0.00294 & 28 & 0.00011 & 0 & \\ \hline \multirow{4}{*}{Proteins} & Type & 0.03497 & 6 & 0.00583 & 34.945 & \(<.001\) \\  & Concentration & 0.00009 & 1 & 0.00009 & 0.538 &.469 \\  & Interaction & 0.00075 & 6 & 0.00013 & 0.752 &.613 \\  & Error & 0.00467 & 28 & 0.00017 & & \\ \hline \multicolumn{6}{l}{Fine-grained silica sand} \\ \hline \multirow{4}{*}{Polysaccharides} & Type & 0.00241 & 6 & 0.00040 & 20.551 & \(<.001\) \\  & Concentration & 0.00008 & 1 & 0.00008 & 4.136 &.052 \\  & Interaction & 0.00089 & 6 & 0.00015 & 7.598 & \(<.001\) \\  & Error & 0.00055 & 28 & 0.00002 & & \\ \hline \multirow{4}{*}{Proteins} & Type & 0.04336 & 6 & 0.00723 & 197.484 & \(<.001\) \\  & Concentration & 0.00056 & 1 & 0.00056 & 15.193 & \(<.001\) \\ \cline{1-1}  & Interaction & 0.00103 & 6 & 0.00017 & 4.691 &.020 \\ \cline{1-1}  & Error & 0.00102 & 28 & 0.00004 & & \\ \hline \end{tabular} Note. SS = sum of squares, df = degrees of freedom, MS = mean square, F = F-value, \(p\) = \(p\)-value.  
\end{table} 
Table 3: Results of two-way ANOVA (\(\alpha\) =.05) of moisture retention. Percentage values were transformed via square root transformation prior to performing two-way ANOVA. Comparison of polysaccharide and protein treatmentsAt both tested biopolymer concentrations, the protein-treated samples, on average, showed significantly higher moisture retention than the polysaccharide-amended soils. A comparison of the polysaccharide- and protein-treated silica sand samples that achieved the highest moisture retention shows that the proteins performed better regardless of the tested concentration. Statistical analysisResults of the two-way ANOVA (Table 3) show that the types of polysaccharide (\(p<.001\)) and protein (\(p<.001\)) have a significant effect on moisture retention, with some biopolymers having a negligible effect, others decreasing moisture retention, and some resulting in the retention rate increasing significantly. Doubling the biopolymer concentration slightly or even considerably increases moisture retention for all biopolymers except XG and TG. A significant effect of concentration on moisture retention is only indicated for the tested proteins (\(p<.001\)) and not for the polysaccharides (\(p=.052\)).