Caring for Your Vegetable Crop

	Irrigation
	Weeding
	Thinning

Irrigation

Gardens in most areas of California require regular irrigation to provide the soil with the moisture needed for maximum plant growth. During years of normal rainfall (12 inches or more), winter rains in most areas usually -wet the soil, by spring, to a depth of 6 feet. If the soil is not wet to this depth, irrigate before seeding so that the soil is wet to a depth of several feet.

The chapter in your Master Gardener Handbook on Soil, Fertilizers, and Irrigation in the Home Garden includes extensive information on soil water, the water-holding capacity of various soil types, plant-available water and irrigation, including methods to determine irrigation frequency and the amount of water to use at each irrigation in the home garden. Drought management techniques are also discussed at length. Irrigation as it applied to home vegetable gardens is presented here in a very brief format.

Vary the amount and frequency of irrigation according to each variety of vegetable you grow. In the home garden, it is usually best to adjust irrigation to meet the needs of shallow-rooted crops. If their needs are met, the medium- and deep-rooted crops automatically get enough water. This same rule applies where the topsoil is shallow -- only 1 or 2 feet of soil available for root growth. Shallow-rooted crops are those whose main root system is in the top 1 - 2 feet of soil. Examples are cabbage, cauliflower, lettuce, celery, sweet corn, onion, white potato, and radish. Moderately deep-rooted crops are those that have the main root system in the top 1-4 feet of soil. Examples are snap bean, carrot, cucumber, eggplant, peas, pepper, and summer squash. Deep-rooted crops are those whose main root system is in the top 1 - 6 feet of soil. Examples are asparagus, globe artichoke, cantaloupe, pumpkin, tomato, and watermelon. (The maximum rooting depths given here are the potential rooting depths under ideal soil conditions.)

Irrigate your vegetable garden about one or two times a week in summer. Wet the soil to a depth of at least 2 feet at each watering. If you only keep the surface of the soil moist, most of the water evaporates to the air and is lost to the roots.

Do not waste water. There are simple ways to measure how much water you give your garden. If you use a garden hose, turn it on to the force you commonly use and time it to find out how many minutes it takes to fill a 1-gallon can. This gives you the rate of water flow per minute. One gallon of water will wet 1 square- foot of ground to a depth of 1.6 inches. If you use a sprinkler system, place some empty cans under the sprinkler spray at various spots. Keep track of the length of time the sprinklers are on and then measure the depth of the water in the cans when you turn off the water. Average the various depths to determine how much water is being applied to the garden at each sprinkling.

Furrow irrigation, unlike sprinklers, has the advantage of not wetting the leaves. Water on plant foliage sometimes increases the incidence of plant diseases. If you plan to use furrow irrigation, use raised beds that are 5 or 6 inches high and 32 to 40 inches apart from center to center. Rake the tops of the beds flat and make them 18 inches wide. Locate the seed rows about 3 inches from each edge of the flattened bed top. Raised beds are also good for winter crops because they allow excess rain water to drain off. Apply irrigation water in furrows placed between the beds. If you use the furrow irrigation method, you need to apply more water to wet the soil to the necessary depth of 2 feet than if you use sprinklers.

Drip irrigation is a relatively new method that offers several advantages to home gardeners:

1. water is placed more accurately in the root zone;

2. water is applied at a slow rate so there is little or no waste;

3. the furrows are dry so you can work in the garden while irrigation is in process;

4. less water is required;

5. little or no management is required while irrigating.

The disadvantages are the added costs of the drip irrigation equipment and occasional problems of plugging of the tiny orifices. However, the advantages outweigh the disadvantages, and a drip irrigation system, when correctly installed and maintained, can be very helpful to the serious gardener.

Soaker hoses are a form of drip irrigation and can be used to advantage if rows are short (20 to 25 feet) and the soil is level. For longer rows or on sloping soil, soaker hoses cannot be expected to provide as uniform an irrigation as that provided by a true drip system.

Return to top of page

Weeding

Weeds are one of your worst enemies. They adversely affect crop growth by competing with them for nutrients, water, and sunlight. The key to successful weed control is to prevent them from getting well established.

The chief methods of weed control are cultivation, mulching, and hand weeding. Proper cultivation include scraping the soil surface or very shallow penetration of the soil with a hoe or other suitable tool to cut off and remove small weeds. Deep cultivation can prune crop roots, which can cause loss of yield.

Mulching offers a potentially more efficient means of weed control, and it also serves to conserve soil moisture. Organic mulches, such as weathered sawdust, compost, rotted manure, lawn clippings, or other such materials, should be applied 2 to 4 inches deep on the soil. These mulches can be tilled under periodically to improve the condition of the soil. Some of these materials will require nitrogen during the decaying process, so apply about 2 pounds of fertilizer per 100 square feet to assure that adequate nitrogen is available to the mulch and crops.

Black plastic film, newspapers, and other such materials can also serve as mulches. They serve the same functions as organic mulches, but they do not offer the soil conditioning potential of organic mulches. Black plastic can be placed on the soil and properly anchored against wind immediately after the soil is prepared for planting. Transplants can then be set through the plastic by cutting holes just large enough for the plant to fit through.

Return to top of page

Thinning

Overcrowded plants cannot grow rapidly or reach a good size. Thin small root crops, salad crops, and those grown for greens early at the second or third true leaf stage. Thin root crops, such as beets or carrots, so the plants are 2 inches apart in the row. Thin radishes so plants are 1 inch apart and head lettuce to 12 inches apart. Table 2, Vegetable Gardening at a Glance: How to Plant and Store, lists standard spacing for each crop. However, different spacing may be required in your garden.