December 2007

Grower 101: When Water Becomes an Issue By Sylvain HŽlie

Growers have been using capillary mats for about 75 years. Initially, they were made of different types of fibrous wool or cotton, and more recently, they've been produced from synthetic fibers such as fiberglass polypropylene, polyester and acrylic. Their principal use was to provide uniform watering on greenhouses benches. This is one of the reasons why growers continue to use them. They lost some of their original popularity because of disease problems and the algae propagation that can result from their open structure, which remains wet all the time while constantly evaporating water.

Capillary mats have never been popular for their ability to save water (in the past, they never did) but were instead used because of the aid they provided in producing and maintaining a uniform crop. Today, growers and gardeners are facing more water restrictions than ever before, and this new generation of capillary mat is designed to save both water and energy. It's intended to solve major runoff and environmental problems, and improved materials help reduce its prior issue of propagating algae.

Form and Function

The key to the capillary mat irrigation system is the nonabsorbent, resilient fuzz layer placed between the root-proof top layer and bottom layer of absorbent felt. This separation keeps the top layer dry and stops virtually all evaporation from occurring. The weight of the pot will collapse the fuzz layer and allow the pot to wick water from the bottom felt pad. This simple design addressed the main problem plaguing capillary mats since 1946 when the first mat was patented. Water is inserted inside the mat through multiple pressure compensating drip tubes running the length of the mat. Growers can just plumb the manifold at the end of the mat, put the mat on a timer and, as needed, insert short shots of water (pulse irrigate) throughout the day.

A field test found that, after about _-inch rainfall, the mat's built-in reservoir fills up. This can potentially supply watering needs for about a week, saving costs. Some growers have also found that their weed problems are reduced, compared to when they were using an overhead watering system. This results from the top of the soil staying drier, thus reducing the chance of weed germination and leaving more water for the intended plant.

Positive Results

Tests were conducted to find whether costs could be lessened for growers who use capillary mats. At Carroll Brothers Nursery in Clearwater, Fla., a nursery that uses 18 million gal. of water annually to supply irrigation, installed capillary mats and water meters on each zone to collect data. Preliminary data shows a reduction to 1.7 million gal. of water used. A weather station, moisture sensors and water meters were installed to monitor water reduction. In a test area of 16,254 sq.ft., there was a water reduction of 240,000 gal. per month. In each section, moisture uniformity when using the mat was 90 percent, versus 80 percent for a drip and 60 percent for overhead watering. Water cost savings were more impressive, with 96-percent savings for the mat compared to overhead watering and 78-percent savings compared to the container drip tube system.

Another test at Daniel Lemieux's Greenhouses, St. Remi, Quebec, Canada, used 1,000 sq.ft. of capillary mat and installed it over a BioTherm system on the propagation area. The mats absorbed the heat well and distributed it uniformly without a drying pattern on cell trays. Moreover, a fuel saving of at least 25 percent was calculated at the time. The grower used overhead misting on the cutting area, and realized great water and crop uniformity, with more than 90 percent yield compared to 50 percent before.

Environmentally (and Plant) Friendly

Using capillary mats should result in using much less water, and this watering method can increase crop uniformity and reduce risks of foliar disease. Bottom watering has been known to create stronger root systems and to prevent foliage damage. Additionally, the total containment can help to decrease pest problems as there should be less standing water around plants and greenhouse films can stay drier.

Growers can develop a custom watering schedule to fit their own plans and the needs of their crops. For example, programs may vary from 1 to 3 minutes once or twice a day, depending on weather conditions and crop stage. Through correct timing, crops can stay moist through to the next day's cycle. This uniformity will encourage even crop growth. The total containment water system the mat incorporates should reduce the amount of fertilizers that growers need to use as there will be less loss.

There are incentive programs for growers looking to replace their existing irrigation system in an effort to reduce water and energy usage. The following programs will provide grower cost-share assistance:

1. Natural Resource Conservation Services (NRCS) and their cost-sharing program called EQIP (Environmental Quality Improvement Program)

2. Best Management Practices (BMP)

3. Your local water management office

As a result of the above product evaluation, EQIP is listing this type of product on its national program on Practice Code No. 443 as capillary mat with an evaporation block layer.