Understanding. Media Surfactants. for use in. Soilless Media

Transcription

1 Understanding Media Surfactants for use in Soilless Media

2 Media wetting agents or media surfactants were first introduced to the horticultural industry over 40 years ago with the advent of soilless potting mixes. Wetting agents were added to bagged or baled peat-based media to ensure easy wet out or good initial wetting when first irrigated. Today, wetting agents are widely used in almost all horticultural growing media sold to greenhouses, nurseries, homeowners, or anyone who is growing plants in containers. Soilless media (or substrates ) usually contains sphagnum peat moss or bark (though coir, rice hulls, compost, or other organic substrates are sometimes used). In addition, they often contain vermiculite and/or perlite to aid in drainage, and limestone to help regulate ph levels. Different combinations of media components are used to meet different growing requirements. Examples include very fine media for small plants or seedlings grown in very small containers, coarse media components for enhanced drainage when growing woody ornamentals or large foliage plants outdoors, highly acidic substrates for growing specialty plants such as azaleas, or general potting soil for homeowners and hobbyists growing typical indoor potted plants or outdoor vegetables in containers. For any given plant or growing condition there are usually many types and brands of acceptable media available, but all would share one common characteristic were it not for the use of wetting agents: an inability to rewet uniformly after drying. How Wetting Agents Work Media that dry out commonly fail to rewet properly for a number of reasons. Waxes, resins, organic acids, and other chemicals present in organic media components are inherently water repellent. When peat moss or bark in media dries out, these chemicals are exposed to air, which causes them to become even more water repellent. Different types of bark used in media often contain waxes and resins that are very water repellent. Water repellency ( hydrophobicity ) is a condition that prevents water from adhering to and moving uniformly into and through a medium. The reason media do not wet consistently is that the particle surfaces and pores within these media are constantly changing every time they undergo wet-to-dry cycles. A media wetting agent imparts a film to all of the particle surfaces within the medium and allows the medium to retain its ability to uniformly wet out for several days to several weeks. Water can then freely infiltrate and drain from a medium. It surprises many people to learn that drainage is actually enhanced by the use of a quality wetting agent. If drainage is properly enhanced, it is far less likey that a medium will remain overly wet near the container bottom. This lowers the perched water table that occurs and improves air to water ratios in the bottom of the pot, especially in smaller containers. In addition, uniform wetting aids in the distribution and utilization of dissolved fertilizers, pesticides and other water soluble chemicals.

3 Economics and Price Wetting agents aid in the uniform wetting and rewetting of media. They pay for their use by preventing plant loss and damage due to non-uniform movement of water in the medium. While plant roots cannot be readily seen growing in the medium, they may be injured. Plants grown in a medium that does not wet uniformly can develop stunted root systems and uneven root distribution. Roots can be easily damaged or killed by lack of water or oxygen. These are situations that can be prevented with the addition of a wetting agent. Manufacturers typically add wetting agents to the media they manufacture at the rate of a few ounces per cubic yard., so the cost in minimal. Most professional growers consider this to be very inexpensive insurance against wetting problems in their media. Granular surfactants, while slightly more expensive, provide an alternative to liquid surfactants when manufacturing a small amount ( batch ) of media, or when topdressing in a container is desired. Cautions Media surfactants differ very significantly from foliar surfactants which are typically used to enhance the uptake of pesticides (e.g., Roundup) into the leaf of a plant. Foliar surfactants usually work quickly, then rapidly become ineffective. Media surfactants are designed to do their job in the soil or media. They also work quickly, but a quality wetting agent will continue working for weeks. In Canada, Aquatrols has a registered product specifically for media producers; the registration was granted due to the proof of efficacy and safety that Aquatrols products provide. Customers must be careful not to purchase inferior or unregistered products. Wetting agents are available from several manufac- turers. Be careful to choose a wetting agent manufactured by a reputable company, one that has considerable technical information about their products. They will support their product with a money back guarantee and qualified customer service in person, as well as by phone, mail or the internet. Their products will have been thoroughly tested at independent laboratories, with professional consultants, at leading agricultural universities, as well as in their own laboratories. Ask around: Testimonials from other users can often be an excellent source of information about wetting agents. Be sure to ask very specific questions of the wetting agent manufacturer regarding what tests they have performed on the wetting agent that they are selling. Not all wetting agents are the same!

4 Why Use A Media Wetting Agent? Wetting agents are used so that media will wet out ( hydrate ) uniformly when watered. This is very important when the medium is relatively dry, as it often is when brand new, or when it fails to get watered on a regular schedule. Many times when a containerized (potted) plant is watered, the water will pond or puddle on top or channel down the insides of the container without readily infiltrating the medium. Both of these situations illustrate common examples of the need for a wetting agent. By adding a small amount of wetting agent to the medium or irrigation water, ponding on top or channeling down the insides of the container can be rapidly and effectively eliminated for several weeks. If the container were cut in half (see photo), you would see that a medium treated with a wetting agent is uniformly wet after irrigation. Media not treated would show wet and dry (hydrophobic) areas. Wetting agents work to create an environment in media that promotes uniform water movement and wetting. Improved air to water ratios, vital for optimum plant growth, are also established in the medium when a quality wetting agent is used. An effective wetting agent does its job regardless of the type of media component used (e.g., peat, bark, etc.). When the medium dries out between irrigation cycles, it will rewet rapidly and uniformly if it has been treated with a quality wetting agent. A quality wetting agent can dramatically speed up the time it takes for water to infiltrate (enter) a medium. By reducing ponding and channeling in media, wetting agents actually save time with each watering. A large measure of insurance is gained knowing that the medium will wet out uniformly again when dry. This is referred to as good rewetting. More uniform distribution of water (and dissolved nutrients) allows plants to grow more vigorously and promotes optimum root growth. For the professional grower, plants remain healthier and more marketable for a longer period of time. This is especially true once plants arrive in the retail environment where watering may be sporadic or uneven. Untreated Treated

5 Chemistry Wetting agents are also called surfactants. The word surfactant is actually formed from the words, surface active agent. Quality wetting agents from reputable manufacturers are very thoroughly tested and evaluated to be certain that plants growing in the media are not adversely affected by the wetting agent. Plant parts such as foliage, flowers, and roots are thoroughly tested and evaluated for injury by quality wetting agent manufacturers. Phytotoxicity (leaf burn or worse) or damage to roots and flowers is rarely a problem with a reputable wetting agent when used at the labeled rate. In fact, a reputable wetting agent can provide insurance that minimizes the damage done to roots, leaves and flowers from inadequate and non-uniform wetting. Wetting agents used in horticultural growing media (potting soil) should be non-ionic (i.e., no net electrical charge) in nature to avoid possible root injury. Formulations Wetting agents are available in liquid and granular formulations. Liquid formulations mix readily with water to form true chemical solutions. Granular formulations use an inert carrier such as fine vermiculite to deliver the wetting agent to the media. When the medium is wet, the wetting agent readily dissolves off of the carrier and into the water. It then travels throughout the medium with the water. Hydrogels: It is important to understand that polyacrylamide crystals are not wetting agents. These whitish crystals look like sand or gravel when dry. They can be added to media to act like little sponges that absorb and give up water to roots that come in contact with them. They do not facilitate rewetting, do not promote uniform wetting, and do not improve drainage. Polyacrylamide crystals will not speed initial wetting of a dry medium or enhance air to water ratios favorable to a healthy root zone environment. Polyacrylamide crystals added to a medium will increase the amount of water held by the medium. This can be a benefit in situations where less frequent watering cycles are desired.

6 About Aquatrols... Aquatrols pioneered the use of wetting agents in turf and ornamental production in Since that time, Aquatrols has become the world leader in the development, testing and marketing of wetting agents used in horticultural growing media. Most golf courses in the United States, Canada and other countries use at least one soil surfactant from Aquatrols. Most manufactured growing media in North America contain an Aquatrols wetting agent to ensure good initial wetting when used by the grower or consumer. Aquatrols works with dozens of industry experts at university, government and industry laboratories across the U.S., Canada and some foreign countries to continuously test and evaluate its products. Aquatrols is the only wetting agent manufacturer equipped with a dedicated full time R&D team and extensive laboratory facility to test and evaluate wetting agents used in agriculture, horticulture and turf markets. Aquatrols is equipped with the knowledge and experience to offer first-time or long-time customers consulting advice free of charge when they are ready to set up or expand a media manufacturing production line. While other companies say to use their product at X or Y rate, Aquatrols recognizes that different types of manufactured media wet out differently. Some media are easy to wet and some are difficult to wet. Because there are many different types and grades of peat moss, bark, and other media components, a wetting agent rate that works for one type of media may not work properly on another type of media. An Aquatrols Soilless Media Specialist is available for consultation to help you determine proper wetting agent rates for your specific medium. AquaGro 2000M: ( M stands for Mixer.) This is the industry s premier media surfactant. It has been extensively tested and used on a wide variety of media. AquaGro 2000M outperforms all other media surfactants available today on the widest range of media types. 2-7 liquid ounces per cubic yard is the rate range most commonly utilized in manufactured media, depending on the wettability of the mix. AquaGro 2000G: ( G stands for Granular.) AquaGro 2000G is a dry granular media surfactant utilizing a # 4 (fine) vermiculite as a carrier of its active ingredients. It is the media surfactant of choice when mixing batches of media in a dry batch system. It is mixed into the media being manufactured at rates up to 16 dry ounces per cubic yard, depending on the wettability of the mix Imperial Way Paulsboro, NJ USA Fax