Water is essential for agriculture, but its scarcity and droughts have resulted in soil erosion and salinity, posing challenges to sustainable agriculture and food security. Drought stress results in inadequate irrigation practices and poor water management. This, in turn, negatively affects soil quality and reduces water holding capacity. Drought stress has been a cause for concern over the past few decades, as extreme weather events have reduced crop yields in tropical and subtropical climate zones. Drought stress has several effects on mango trees, such as decreased photosynthesis, leaf dropping, reduced root growth, inhibited fruit set and development, and decreased production. Any effort to enhance agricultural water use efficiency is worthwhile. Therefore, increasing water use efficiency in agriculture is of the highest priority. Rainwater harvesting, reservoirs, and streamflow diversion are utilized to meet water demand and supply. Soil improvement is the most effective method to increase soil water and nutrient retention, as well as decrease infiltration and drainage losses, resulting in enhanced plant growth.

Super-absorbent polymer (SAP) or hydrogel is useful for increasing the amount of moisture available in the root zone because polymers can absorb water 400–1500 times their dry weight (Figure 1 & 2). The use of SAPs in agriculture offers several potential advantages, including water conservation, improved plant growth, nutrient retention, reduced soil erosion, and environmental benefits. Under water stress conditions, plants could grow properly with the water retained with hydrogel. Hydrogel is an excellent medium for the cultivation of agricultural crops on sandy soils because, in times of water stress, it slows down the pace at which water evaporates from the soil.

To apply hydrogel, first choose the right type of SAP hydrogel. There are different types of superabsorbent polymers available, varying in absorption capacity and release rate. Choose a hydrogel suitable for agricultural use, typically labeled for soil or horticultural applications.

The amount of SAP hydrogel to use depends on the type of crop, soil conditions, and specific hydrogel product. Generally, the recommended rate is between 0.5 to 5 grams of hydrogel per kilogram of soil. Check the manufacturer’s guidelines for specific recommendations.

• Dry Application: Mix the dry SAP hydrogel granules directly with the soil. Spread the granules evenly and mix them thoroughly into the top soil. This method is suitable for larger areas.
• Pre-soaked Application: Soak the hydrogel in water until fully expanded, then mix the hydrated gel with the soil. This method allows for immediate water retention but can be more labor-intensive.

For planting individual plants or trees, add a small amount of dry or pre-soaked hydrogel directly into the planting hole. Mix it well with the soil at the bottom of the hole before placing the plant.

Additional Tips

• Compatibility: Ensure the SAP hydrogel is compatible with your soil type and crops. Some hydrogels may affect soil pH or interact with certain fertilizers.
• Environmental Considerations: Use biodegradable SAP hydrogels to minimize environmental impact.
• Safety: Wear gloves and a mask when handling dry hydrogel granules to avoid inhalation and skin irritation.

Using superabsorbent polymer hydrogel as a soil amendment can greatly enhance water management in your gardening or farming practices, leading to healthier plants and more efficient use of water resources.

Resource: https://pubmed.ncbi.nlm.nih.gov/36616513/ 

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