Drought and water scarcity are global challenges affecting even non-arid regions through seasonal occurrences. As a primary constraint on agricultural development, drought-induced losses surpass all other natural disasters in economic impact.
The application of soil additives—specifically drought-resistant water-retaining agents—has become fundamental to plant drought resistance strategies.
While traditional polyacrylate-based superabsorbent polymers (SAPs) dominate current research and field applications, emerging γ-polyglutamic acid (γ-PGA) represents a biodegradable alternative with distinct advantages
Compared with the polyacrylic-based SAPs currently promoted in drought-prone regions in China, γ-PGA has two key advantages: lower cost with superior water absorption performance, and better biodegradability, avoiding environmental pollution.
Current research on γ-PGA is mainly concentrated in medical materials, with relatively few studies on its application in drought resistance and water conservation. Let’s examine its practical performance.
Materials for the Experiment
Test material: γ-PGA, a new-generation biodegradable superabsorbent agent.
Control material: Commercially available polyacrylic resin.
Water Absorption Performance Testing
Measurement of maximum water absorption rates for γ-PGA and polyacrylic resin.
Measurement of γ-PGA’s water absorption rate in soil.
Simulated soil moisture levels: 10%, 20%, and 30%.
Material burial depth: 3 cm.
Two replicates per treatment.
Results of Natural Water Absorption Rates for γ-PGA and Polyacrylic Resin (Table 1)
| Material Name | Replicate | Material Dosage/g | Saturated Water Absorption Time/h | Water Absorption Weight/g | Water Absorption Multiple |
| polyacrylic resin | Replicate 1 | 0.2 | 6 | 80.2 | 401.0 |
| polyacrylic resin | Replicate 2 | 0.22 | 6 | 95.6 | 434.5 |
| γ-PGA | Replicate 1 | 0.16 | 18 | 178.0 | 1112.5 |
| γ-PGA | Replicate 2 | 0.23 | 18 | 254.0 | 1104.3 |
The data in Table 1 show that the average water absorption rate of polyacrylic resin (two replicates) was 417.65 times, while γ-PGA’s average maximum absorption rate was 1,108.4 times—2.65 times higher than that of polyacrylic resin. However, γ-PGA’s saturation time was three times longer, indicating minimal difference in absorption speed between the two materials.
| Soil mass moisture content/% | Average γ-PGA application amount/g | γ-PGA burial depth/cm | Water absorption time/h | Water absorption weight/g | Water absorption multiple |
| 10 | 0.61 | 3.0 | 56 | 18.0 | 29.5 |
| 20 | 0.43 | 3.0 | 56 | 18.6 | 43.3 |
| 30 | 0.44 | 3.0 | 56 | 35.6 | 80.9 |
Table 2 presents γ-PGA’s water absorption rate under pot conditions with soil moisture levels of 10%, 20%, and 30% and a burial depth of 3 cm. The results demonstrate that γ-PGA’s absorption rate increased significantly with higher soil moisture content, though the actual absorption multiple was notably lower than in distilled water. This is attributed to soil particles’ adsorption force on water.
The tested soil was medium loam, with the three moisture levels roughly corresponding to the wilting point, 70% field capacity, and field capacity, respectively. This suggests that γ-PGA’s actual water absorption efficiency in soil varies with moisture content. Based on pot experiments, γ-PGA’s practical absorption rate in soil is likely below 100 times.
Conclusions and Discussion
This analysis evaluates the practical performance of these two soil additives under field conditions, proposing γ-PGA as a sustainable alternative for drought-prone agroecosystems.
γ-PGA’s average maximum water absorption rate was 1,108.4 times, 2.65 times higher than that of commercially available polyacrylic SAP. Both materials exhibited similar absorption speeds.
γ-PGA’s absorption rate in soil increased with higher soil moisture content, with practical absorption likely below 100 times due to soil particles’ adsorption force on water.
As the concept of circular agriculture advances, bio-based soil additives like γ-PGA may redefine drought resilience benchmarks, with their integration into smart irrigation systems meriting further investigation.
For extended application cases and technical specifications of γ-PGA in agricultural settings, visit γ-PGA Product Portal. Further field trials are encouraged to validate its performance under diverse soil conditions.