To grow a vegetable garden, irrigation is a necessity. It is ironic that in dry environments, one of the most common causes of plant death is excess water. Studies show that as a rule, two to three times more water than is actually needed is applied to plants. Appropriate water application promotes good plant health and water conservation -- both worthy goals for the home gardener in any environment.
It is important to use water-saving gardening methods from the beginning of the garden season to insure a healthy harvest of crops. Watering schedules are dependant upon climate and weather. The best way to water vegetables is to irrigate thoroughly, then let the soil dry out between applications. The water should reach six to eight inches deep to the roots of the plants. Use a probe or your fingers to check how deep the water is reaching. Let the soil dry out a little before watering again; over-watering will cause the plants to rot. The best time of day to water is in the early morning because it gives the leaves a chance to dry while the temperatures are warm.
Water is a most precious natural resource. It is very important to do all that is necessary to preserve and protect local water supplies. Each day over 82 billion gallons of water are consumed in the United States, of which 7.3 billion gallons are for domestic use.
Less than one percent of that water is used for irrigating landscape plants and maintaining the environment for those plants. In desert regions, the percentage of water used for irrigation is higher than in other areas, but growing healthy, bounteous gardens, while conserving this precious resource, is still possible.
1. Condition plants for dry weather from the beginning of the season by irrigating less frequently but longer. Nurture tender transplants with frequent irrigations. Gradually over a period of a couple of weeks, decrease the frequency and increase the water penetration at each watering to encourage deep rooting. Deeper root systems will be more drought-tolerant. Avoid light, frequent irrigations which promote shallow rooting and the need for continued frequent irrigations.
2. Use mulches freely in the garden. Compost, bark, shavings, sawdust, and many other mulches are excellent choices. These not only prevent evaporation from the soil surface, but will also help control weeds. Weeds are a major cause of water loss from the landscape and may actually consume more water than the landscape plants. Some vegetable crops develop conditions such as blossom end rot when subjected to alternating wet/dry cycles.
3. Apply water through a drip irrigation system if possible. Drip irrigation systems apply water only where needed and reduce water loss due to evaporation. As an additional benefit, drip systems do not moisten the space between the rows, reducing the opportunity for weeds to grow.
4. Water during the early morning hours or at night. During these hours, temperatures are the lowest and winds are generally less intense. This reduces the amount of water loss to evaporation.
5. Check water frequently. Application times and amounts should be carefully monitored to avoid runoff. Water slowly enough to allow moisture to penetrate at least 6" to 8" into the soil.
In the heat of the summer, apply approximately 2 to 2 1/2" of water to the soil each week for most plants. In cooler or rainy weather, apply less water.
Over-application of water not only wastes this precious natural resource, but also does a great deal of damage to the plants by increasing problems with root rot and fungal diseases.
Furrow irrigation is a traditional method of watering particularly suited to straight row planting. Dig a furrow – a small, level, shallow ditch – alongside of, or between, vegetable rows. Water enters the furrow at one end and seeps down into the soil to the roots of the plants. This is the least efficient method of irrigation, but when ditch irrigation water is available, it is widely used.
Built-in sprinkler systems work well and are particularly useful on large gardens. When sprinkle irrigating, measure the amount of water released by sprinklers. Place tall, straight-sided cans at various spots in the area covered by sprinklers. Check in thirty minutes to see how much water has collected in the cans. Divide the amount of water required per week by the amount in the cans and multiply that number by thirty minutes to apply the correct amount of water. Timers on sprinkling systems can be set to provide appropriate amounts of water using these findings.
Done correctly, these systems are the most efficient watering methods because water is applied only where it is needed – near the roots of the plants. Water drips through holes in tubing or from emitters on tubes directly onto the soil. Run drip systems for a few minutes before planting to mark the areas where plants should be placed for optimum watering. These systems are usually installed on a timer. Drip systems water very slowly and may need to run for several hours to let water soak deeply. However, less total water is used and no water is wasted to run-off or evaporation. If plants in a certain spot begin to wilt or grow more slowly than others, check the hose to make sure it is not plugged.
Hand watering is not a very effective way to water because proper watering requires deep soaking. Most people who hand water will not spend enough time to saturate the soil as deeply as they should. Occasional hand watering can be useful as a way to check on plant progress or to offer supplemental spot water to thirsty areas.
Gardeners sometimes erroneously think of fertilizer as food. Because of this thinking, gardeners often want to add large amounts of organic matter and fertilizers to their soils to make them more productive. Through photosynthesis, plants manufacture their own food. Fertilizers are salt materials that provide nutrients for the plants to use in manufacturing their food. Organic matter should be considered as a soil amendment to help improve soil structure.
Concentrated inorganic fertilizers may burn plants and add unneeded salt to the soil. When using these products, use the least amount needed to add the required nutrients. Adding more organic materials will generally only improve the soil.
Plants utilize many elements for healthy growth, but the three most important are nitrogen, phosphorus, and potassium. Commercial fertilizers list the percentage of each of the components inside the fertilizer mixture. They will be listed in order, with nitrogen represented as the first number, phosphorus as the second and potassium as the last. For example, if the label lists 10-10-10, the fertilizer contains 10% nitrogen, 10% phosphorus, and 10% potassium. The other 70% is a carrier that allows the fertilizer to be spread evenly into the soil.
Fertilizer is used to provide nutrients that may be inadequate in existing soil. Plants that grow slowly, are stunted, have pale or discolored leaves, or straggly growth, probably need a fertilizer.
Inorganic fertilizers provide nutrients much more efficiently than mulches, composts and manures. Providing needed nutrients requires several hundred pounds per thousand square feet of organic material.
Complete fertilizers contain all three of the essential nutrients in varying percentages. A caution about complete fertilizers -- they can cause phosphorous buildup. Always read the instructions carefully and apply as recommended.
The accompanying chart gives the relative amounts of nutrients of common organic amendments and also the amounts of nutrients of some common fertilizers.
There are many types of fertilizers and many ways to apply fertilizer. It is best to keep on a recommended and regular fertilization schedule, rather than waiting until your plants begin to suffer.
It is important to note that garden vegetables have varied requirements for fertilizer components. Most require fertilizer at planting time to help initiate healthy growth. Some, such as tomatoes, should not receive more nitrogen fertilizer during the growing season as it promotes vine growth at the expense of fruit production.
Nitrogen (N) is responsible for green growth in plants. Apply nitrogen in the spring to encourage new growth. Nitrogen deficiency is marked by yellow or pale leaves on the oldest part of the plant. While some vegetables require the addition of nitrogen during the growing season, others will not set fruit properly if they get too much nitrogen. Fertilizer supplementation specific to each plant is included under the individual plant information sections of this software.
Plants use phosphorus (P) in developing a healthy root system, flowers, seeds and fruits. Phosphorus deficiency is manifested by plants that grow slowly, or stems and older leaves that show a reddening color.
Potassium (K) helps the overall growth of the plant and makes the stems strong and resistant to diseases. If your plant’s stem can’t hold its leaves and blossoms, or if the older leaves begin to brown around the edges, it may need more potassium.
As the name implies, dry fertilizer comes in granules, powder or pellets which can be scattered or worked into the soil. It is partly soluble and dissolves with irrigation to spread through the soil.
Liquid fertilizer is fertilizer that dissolves completely in water to quickly provide nutrients to leaves and roots. It can be applied to leaves and soil in watering, or will flow through drip systems.
Foliar fertilizer is used as a spray on leaves. Nutrients are absorbed directly into the tissue and put to use immediately. Use only when weather is cool as it may damage leaves when used in hot weather
Time-release fertilizers are encased in tiny round capsules that dissolve slowly over a period from three to fourteen months. As the capsules dissolve, the nutrients are released to allow for constant feeding rather than the cyclic ups and downs of other fertilization methods.
Special-purpose fertilizers contain specific fertilizer blends suited to particular plants. They may be more expensive than other types.
Natural organic fertilizers are created from materials derived from plants or animals such as manure, bone meal or fish emulsion. They release slowly, are generally low in nutrient content and tend to be less balanced.
Zinc, manganese, iron, and other elements are known as micronutrients because they are required in very small amounts. Micronutrients are not required on a regular fertilizer basis, but are added when plants show symptoms.
Iron is the most common micro-nutrient deficiency in alkaline soils. Iron deficiency is known as chlorosis. It is typified by yellow leaf margins between veins and in severe cases, leaves may wither and die.
Micronutrient deficiencies can be difficult to analyze. If you suspect your plant is deficient in micronutrients, take a sample to your local extension agent or professional nurseryman for help in diagnosis.