Water is a vital resource for plants. It helps them grow and develop. Water is required in the soil to be used for photosynthesis, solubilising soil nutrients, cooling itself by transpiration, and maintaining internal moisture and structural rigidity. The plant can reach a point when the amount of water in the soil starts to decrease. It will then use water faster than the plant is able to access it. The wilting stage is the first sign of dehydration.
A certain amount of soil moisture, in addition to water for the turfgrass plants, is needed to maintain a suitable playing surface for most sports. If soil moisture is allowed to reach 0%, it can cause injuries to football players. A golf green will roll too fast and a cricket field will bounce too hard. In sportsturf management the main objective is to present the playing surfaces. Soil and surface moisture are therefore of great importance.
What is the function of soil wetting agents?
The unpredictable and extreme climate of Australia often necessitates the use of soil-wetting agents to achieve acceptable turfgrass surfaces. In the Australian turf industry, there are many types of soil wetting agent. Each one serves a different purpose. All of them rely on the ability of their active ingredients to alter surface tension and water’s physical behavior. The water molecules’ interactions with each other, and their surroundings are altered. Different formulations have different modes of action, which results in different products and their applications. Some wetting agents are designed to overcome hydrophobic conditions, re-wet soil and others can be penetrants or highly residual.
Surfactants, which are surface-acting agents, work by changing the surface tension of the water at the molecular scale. Water’s polarity (charge), which is a measure of its polarity, produces adhesive forces that cause molecules to adhere to surfaces and cohesive forces to cling together. Hydrophobic surfaces repel water while hydrophilic surfaces are attracted or have an affinity to water. Hydrophobicity is often observed in soils when organic matter breakdown results in the formation of natural acids. These acids can coat soil particles with a waxy coating. The waxy coating repels water and so the soil particles are hydrophobic.
If straight water is applied on a hydrophobic surface, the water will pool at the top and not enter the profile. It may infiltrate soil over time, but it won’t actually wet it. Instead it drains through the profile leaving it dry. The water will move past the hydrophobic particles of soil, but it won’t adsorb to them or attach to them. It will simply find its way out and through the bottom. This will allow for the water to interact more with the hydrophobic soil particles.
Surface tension is reduced when a wetting agent pushes between two water molecules. This forces them apart, reducing the cohesive bond. The water is “thinned” out by the wetting agent molecule, which allows the molecules to spread over a larger surface area, rather than sticking together. Water can move freely and enter the soil with the help of gravity. The wetting agent acts as a bridge between the soil and water once the surface tension is reduced. The surfactant molecules have a wax-loving end (lipophilic) that adheres to water repellent surfaces, and a hydrophilic side that sticks with the water molecule. Hydrophobic soils will need to be wetted regularly for a long time without the use of a wetting agent. By the time the plant rehydrates, it will have likely passed the wilting stage and may be beyond recovery.
Water in sand-based profile
Water retention, quantity and longevity in soils are heavily dependent on soil type and environmental conditions. Water infiltration and retention are influenced by the texture of soil. Finer or heavier soils have a larger surface area to which water can cling. As a result, they will hold more water over a longer time period. A soil with a coarser texture has a smaller surface area to which water can cling, so it will hold less water over a shorter time. Organic matter is also important in retaining water in soil profiles, as it acts like a sponge to absorb the non-absorbent conditions. Organic matter is essential in a profile based on sand to provide turf roots with an available reservoir of water.
It is important to manage these issues, as coarse sand-based material is generally desired in many sportsturf building methods like USGA specifications. Stamina balance is an innovative and complex formulation of surfactant molecule designed to achieve specific goals. This formulation contains a polymer with a long chain for uniform lateral wetting, a surface-acting agent for initial penetration and heavy surfactant molecules for optimal residual performance. These three modes of operation work together to transform a sand-based soil into one that is able to receive and retain the water needed by turfgrass plants.
Different surfactants play different roles in soil wetting agents
- Long chained Polymer: Significantly increases water retention in root zones based on sand. These polymers increase the depth and uniformity in wetting.
- Surfactant with high surface tension: Increases initial water penetration to the plant and maximizes water availability.
- Residual Surfactant: Offers residual activity and rewetting capabilities.
Manage Localised Dry Spot
Localised Dry Spot is a condition that occurs when turfgrass suffers from drought. Hydrophobic soils form in patches, causing a non-uniform moistening of the soil. This is visible on the surface of the turf as patches of foliage start to wilt. Regular applications of residual wetting agents are the most effective way to prevent LDS.
It will also prevent the development of hydrophobic conditions when irrigation or rainfall are infrequent. Stamina 90, a specialty wetting agent concentrated for the long-term prevention and control of LDS as well as general hydrophobicity. Stamina 90 has a larger molecule than most other wetting agents. This molecule resists degradation and lasts longer in soil. Regular applications of Stamina90 not only guard against LDS but also build a healthy environment in the soil by retaining moisture throughout the profile.
Stamina Rescue is the best wetting agent to use for LDS treatment. Stamina Rescue’s formulation is unique because it combines a surface-active agent that overcomes hydrophobicity with a heavier molecule to provide residual performance. The formulation contains two surfactant molecules as well as a mixture of amino acids and humates to help with plant recovery. This improves surface regeneration and recovery following LDS injury, especially when used with biostimulants that rebuild root health.