Soil is the foundation for plant growth and agricultural production. In response to the issues of abnormal climate drought and lack of rain in 2024, implementing agricultural drought resistance and water conservation as well as efficient use of water resources has become a crucial direction for global agricultural development.
Regarding soil drought resistance and water conservation, the application of water retaining agents represents a chemical water-saving technology that improves the root-soil interface environment for plants and supplies water to them. Utilizing drought-resistant water retaining agents is an important measure to promote the improvement of soil structure, enhance water and fertilizer retention capacity, and boost plant production.
Drought-resistant water retaining agents are a type of polymer compound with super high water absorption and water retention capabilities. Translated as Super Absorbent Polymer (SAP), they can rapidly absorb hundreds to thousands of times their weight in pure water and have the function of repeated water absorption. After absorbing water, they can slowly release it for crops to utilize. At the same time, water retaining agents can improve soil structure, increase soil’s water and fertilizer retention capacity, promote plant growth and biomass increase. They possess the characteristics of wide application, low investment, and quick results, and have a broad range of applications and excellent development prospects in agricultural production and ecological environment governance.
The Principle of Water Absorption, Water Retention, and Water Release of Water Retainers
Water retainers can absorb 200-1000 times pure water. Generally, polyacrylates absorb more, while organic-inorganic composites and starch water retainers absorb less. Most of the absorbed water is effective water that can be used by plants. Some people refer to water retainers as “small reservoirs” for plant roots in the soil.
The Principle of Water Retainers to Improve Soil and Retain Water
In the soil solution, the water absorption of water retainers is only 1/3 – 1/4 of that in pure water. The main reason for the reduced water absorption capacity is that cations such as calcium and magnesium in the soil exchange with sodium and potassium ions in the water retainers, destroying the network structure of the water retainers. At the same time, calcium and magnesium ions in the soil combine with the soil surface. When water retainers are applied, they form a granular structure through the soil, increasing soil aggregates and improving soil structure, greatly enhancing the water retention capacity of the soil itself. Our experiments have shown that water retainers have the most obvious effect on the formation of soil granular structure with a particle size of 0.5 – 5 mm. The potted bean experiment proved that when the water retaining agent dosage in the culture medium was 0.27%, 0.54%, and 0.81%, the field water holding capacity increased by 9%, 18%, and 36% respectively compared to the control, and the watering amount decreased by 37%, 45%, and 55% respectively. In addition, the increase in granular structure also increases the soil’s ability to retain water and reduces the evaporation of soil water. Our experiment found that the seedling period of tobacco transplanted in the soil with 0.05% – 0.5% water retaining agent was shortened by 2 days, and the number of days of survival under water shortage was 5 – 20 days longer than the control.
The Effect Principle of Water Retaining Agent on Agricultural Materials such as Fertilizers and Pesticides
The effect principle of water retaining agents on agricultural products such as fertilizers and pesticides mainly lies in the adsorption and ion exchange effects of the surface molecules of water retaining agents. Functional groups such as ammonium ions in fertilizers and pesticides can be ion exchanged or complexed by water retaining agents, reducing the leaching of fertilizer and drug effects. Field tests have shown that the use of water retainers in combination with nitrogen fertilizers or nitrogen and phosphorus fertilizers can increase nitrogen absorption and nitrogen fertilizer utilization by 18.72% and 27.06% respectively. When water retainers are mixed with nitrogen and phosphorus fertilizers, the utilization rate of phosphorus fertilizers increases from 16.49% to 20.91%. The potato experiment in Yan’an dry terraces found that the potato yield increased by 40.67% and 33.33% respectively when water retainers were applied alone and N fertilizer was used alone with a furrow of 10 – 15 cm. Water retainers plus N fertilizer increased potato yield by more than 75%.
Plant Growth and Water Retainers
The plant growth effect is mainly related to the application method of water retainers. Seed treatment mainly involves water retainers providing a relatively moist microenvironment for seeds. Soil application includes hole application or furrow application, which is mainly related to the water retainer changing the root soil water environment, causing part of the root system to be in a drought state, generating ABA signals and regulating plant physiological water conservation. Our simulation experiments have proved that crops have the ability to adapt to the alternating dry and wet soil environment during their growth. That is, when crops are subjected to a certain degree of water stress, they can compensate for the reduction in yield or reduce damage through the compensation effect. When half of the corn root system is in water and the other half is in drought, the ABA (abscisic acid) content of the roots in the drought state increases, and ABA is transmitted to the aboveground part of the crop through the xylem vessels, regulating the stomatal opening and reducing plant transpiration. At the same time, the roots undergo a certain degree of drought training under water stress, and the water conduction after rehydration is higher than that without water stress training. These two aspects make the crop root system show a compensation effect.
At present, water retainers are rapidly promoted and applied in agricultural production and ecological environment governance. Water retainers are included in the relevant standards for forest and grass slope planting and spray planting, and the actual application area is also increasing. Here, you can learn about Dora γ-PGA and get to know the new organic, green, and pollution-free water retaining agent.