# Changes in Soil Moisture Improved by High-Performance Ester Materials under Dry-Wet Cycles
## 3 Results and Discussion
### Improvement on Soil Ecological Performance from High-Performance Ester Materials
It can be inferred that the decrease in water holding capacity and EC of the soil with materials caused by the dry-wet cycle is mainly due to changes in the soil's structure. After the dry-wet cycle, the soil aggregate structure will undergo irreversible changes. With repeated dry-wet cycles, water softens the connections between soil particles [15], soil cohesion decreases, soil clay content decreases, coarse particles continuously decompose into fine particles, and large aggregates decompose. This is precisely the reason why the dry-wet cycle leads to a decrease in soil's water holding capacity and EC, and a decrease in soil's ecological performance. Figure 10: The response of polymer water-retaining materials to dry–wet cycles. High-performance ester materials can significantly enhance soil's moisture and EC under dry-wet cycling conditions. Polymer water-retaining materials can increase soil porosity through expansion and contraction, and the dry-wet cycle will to some extent limit the expansion of water-retaining materials. However, from the test results, it can be seen that water-retaining materials still play key role in increasing soil's moisture capacity. Polymer adhesive materials can enhance the connection between soil particles, making their aggregates more stable and less prone to decomposition, and increasing the number of soil clay particles. To some extent, adhesive materials weaken the deterioration of soil's ecological performance caused by the dry-wet cycle process and improve its water holding capacity. Under the combined effect of the ester materials, the soil maintained a stable aggregate structure [10]. Data analysis was conducted on test groups CK and 1-9 (with two materials added), as shown in Figure 7a, to summarize the rules of improving soil moisture and EC using high-performance ester materials under dry-wet cycling conditions. The relationship was determined using the addition of water-retaining materials \(w\), adhesive materials \(a\), and dry-wet cycling times \(x\) as independent variables, and soil water holding capacity \(y\)1 and EC \(y\)2 as dependent variables. First, we took the quantity of dry-wet cycles \(x\) as the independent variable, and analysis the relationship between the dependent variables \(y\)1 and \(y\)2 for groups 0-9 was as follows:  
\[y=A_{1}\times e^{[-\frac{x}{1}]}+y_{0} \tag{2}\]  
For the water holding capacity \(y\)1, the formula fitting result is in Table 2.  
For EC \(y\)2, the formula fitting result is in Table 3.  
The added materials for each group were different, so the constant terms of the formula fitting results are different. We calculated the relationship between the material and the constant terms based on the water-retaining material's quantity \(w\) and adhesive material's quantity of a. For \(y\)1, \(y\)0 = 24.8\(w\) + 29.1\(a\) + 30.8, R2 = 0.76. \(A_{1}=7.6+15.1w-42.1a\), R2 = 0.94; \(t_{1}=5.1-7.4w-13.7a\), R2 = 0.83. The formula fitting results were as follows:  
\[y_{1}=(7.6+15.1w-42.1a)\times e^{[-\frac{x}{51-74w+137a}]}+24.8w+29.1a+30.8 \tag{3}\]  
For \(y\)2, \(y\)0 = 278.9\(w\) + 506\(a\) + 240, R2 = 0.98. \(A_{1}=140.4+39.1w-95.4a\), R2 = 0.98; \(t_{1}=5.08-2.4w+1.5a\), R2 = 0.82. The formula fitting results were as follows:  
\[y_{2}=(140.4+39.1w-95.4a)\times e^{[-\frac{x}{508-24w+1.5a}]}+278.9w+506a+240 \tag{4}\]  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Test Group** & **y\({}_{0}\)** & **A\({}_{1}\)** & **t\({}_{1}\)** & **R\({}^{2}\)** \\ \hline
0 & 29.00 & 7.41 & 5.38 & 0.96 \\ \hline
1 & 34.80 & 7.36 & 4.63 & 0.97 \\ \hline
2 & 35.18 & 8.31 & 4.36 & 0.98 \\ \hline
3 & 35.52 & 8.74 &In this formula, \(y_{1}\) is the soil's water holding capacity, %; \(y_{2}\) is the soil's EC, us/cm; \(w\) is the amount of water-retaining material added, %; \(a\) is the amount of adhesive material added, %; \(x\) is the number of dry-wet cycles; and \(w,a\), \(x\geq 0\).