Drip Irrigation for Fall Planting

Considering the hot, dry weather conditions we’ve recently experienced, some readers may wonder if transplants of even recommended plants will survive. I know they will survive because numerous horticulturists and commercial growers have tested all recommended plants before they are ever recommended. In fact, these plants originated in hot, tropical climates so they thrive on heat IF they are moisturized.

The only fate worse than thirst for a plant is death. In fact, they often accompany one another! Even if some folks are wise enough to know when to water a thirsty plant just seconds before it crosses death's threshold, these procrastinators are still losers. When a plant thirsts and is severely stressed, overall vigor and production is decreased. This is especially true of plants which are expected to produce fruit. Not only will total yield be decreased, but fruit quality will also decline. Carrots, onions and tomatoes start cracking! Eggplant fruit gets bitter! Shrubs display foliage abnormalities! Flowers bloom with mediocrity! Trees do not grow rapidly! The house's foundation cracks! What is causing all of these calamities? Lack of water, and its improper application, is the culprit of all of these problems. Root zones are not being moisturized.

Most people don't intentionally make their plants suffer. There are three categories of “thirst-inflicters”—those who don't know when to water, those who don't know how to water and those who are so absent?minded they forget to water. Some may qualify for more than one of these categories.

How do you know when to water? Some people say to water when the plant wilts. When a plant wilts, it is obviously in a stressed, de?moisturized condition and the damage (foliage burn, foul?tasting fruit and production loss) has already occurred. Besides, does the wilting of a plant indicate drought? I have seen wilted plants standing in water, i.e., they were water?logged. Plants wilt with root rot diseases. So wilt is not a reliable indication. Soil moisture is the best criterion for watering. If the soil moisture is adequate, don't water, even if the plant is wilted. To test for soil moisture, probe around plants with your finger. If the soil is moist several inches deep, your plant is alright.

Rooting depth is the most limiting plant characteristic in relation to water uptake. Crops with shallow root systems require more frequent irrigations than deep?rooted crops.

Very shallow rooted crops include celery, lettuce, onion and radish.

Shallow?rooted crops include broccoli, cabbage, cauliflower, Chinese cabbage, cucumber, muskmelon, pepper (transplanted), spinach, and tomato (transplanted); intermediate rooted crops include bean (snap), beet, carrot, eggplant, pea, pepper (seeded), rutabaga, and summer squash.

Deep?rooted crops include asparagus, beans (lima), parsnip, pumpkin, winter squash, tomato (seeded), and watermelon.

The most critical stages of growth for vegetable crops, and when moisture stress is the most damaging to yields are:

asparagus (fern growth)
snap bean (pod?filling)
broccoli (establishment, head development)
cabbage ( establishment, head development)
carrot (establishment, head development)
cauliflower (establishment, head development)
celery (establishment, rapid growth during hot periods)
sweet corn (tasseling, silking, and ear filling)
cucumber (flowering, fruit enlargement)
eggplant (flowering, fruit development)
lettuce (head development)
muskmelon (flowering, fruit enlargement)
onion (bulb enlargement)
pea (flowering, pod? filling)
pepper (transplanting, fruit set and development)
squash and pumpkin (flowering, fruit development)
radish ( root enlargement)
summer squash (flowering, fruit development)
tomato (flowering, fruit set and enlargement)
turnip (root enlargement)

Now that you know when to water, you may not know how. The "how" may be the most important part. First, plants need to be thoroughly moisturized and not soaked. These are not swamp plants we are trying to grow and, if treated as such, these plants will respond appropriately and die. Deep moisturization is desirable to insure the development of a deep, drought?tolerant root system.

Systems such as flooding or sprinkle involve wetting an entire area rather than just the area where plants are growing. A sprinkle system has the added disadvantage of wetting the plant foliage that can encourage plant diseases. There is an easier way to moisturize plants deeply and thoroughly. It is called drip irrigation.

"Drip or trickle" irrigation is a unique irrigation method. It allows precise applications of water in the immediate vicinity of plant roots. Soil moisture in the area around the plant is maintained at a uniformly high level throughout the growing period. Small amounts of water are applied frequently, perhaps daily, to replace that withdrawn by soil evaporation and plant transpiration. Growth and production of a plant is greater when they are moisturized (kept moist, not too wet or dry) rather than subjected to wet and dry cycles which normally occur with other irrigation methods. This is very apparent in situations where plants are growing near a leaking faucet. These plants always out perform neighboring plants. This has often been verified in tests throughout the country. Data indicates that tomatoes can yield 30- to 40% more fruit, and peppers as much as 30 % more fruit when grown with drip irrigation. All of this increase in production occurs even though much less water is used. In an article that appeared in Progressive Farmer entitled "How to Grow 300?Bushel Corn," the statement is made that "if corn is allowed to water stress for just two days, two bushels per acre per day can be lost." Of course, few of us have an acre of corn, but the concept of yield reduction applies to small gardens as well. The operation of a drip system for three hours per day every other day will insure that adequate moisture is present. Distribution and evaporation losses are minimized. Less of the total soil area is fully wetted than with sprinkler and furrow systems. Normally, only 25% of the soil surface is wetted with drip irrigation. This significantly reduces the amount of water required for irrigation.

Drip irrigation also simplifies irrigation procedures and reduces labor requirements. This is imperative if you have a family allergic to dirt and sweat who will let plants die of thirst when you are away if a quick?and?easy watering technique is not available. Drip systems can be easily activated from one faucet. A drip irrigation system also waters the otherwise forgotten or missed plants. Once the drip hose is installed around shrubs, vegetables and flowers, it never "forgets" to water—it specifically waters each and every plant. Of course, someone must remember to activate the drip system for three hours a day every other day by turning the water faucet on!

Drip systems are available at most local nurseries. Try one this season and reap the many rewards which they have to offer.

A more complete write-up about drip irrigation can be found at:

http://aggie-horticulture.tamu.edu/extension/homelandscape/water/water.html