As we enter another summer of drought, conserving water is essential. Luckily, there are a number of ways you can significantly reduce water use in your vegetable garden.
Mulch, mulch, mulch! Mulching is probably the single most important thing a gardener can do to reduce water consumption in a vegetable garden, or the home landscape in general. Mulching reduces evaporation from the soil by up to 35% and can significantly cut irrigation needs. Mulches also smother weeds, which compete with vegetables for water.
Mulching with black plastic sheeting is the most effective way to conserve soil moisture, but it also raises soil temperatures, so its use should be limited to heat-loving vegetables such as tomatoes, peppers, eggplants, cucumbers, squash and melons. Plan to lay down black plastic early in the season, so that by the time extreme summer temperatures arrive, plants will have matured and their leaves will shade the plastic.
Grass clippings make excellent mulch because they release nitrogen into the soil as they break down. To avoid matting, clippings should applied in thin layers between one-quarter and one-half an inch deep and be allowed to dry out between layers. Do not use grass clippings from lawns that have been treated with herbicides. Other organic mulches include wood shavings, compost, bark, straw, or alfalfa. Organic mulches should be one to three inches thick in vegetable gardens; the larger the mulch particles, the thicker the mulch needs to be. Also, thicker layers of shavings, straw, or bark may lead to a carbon-nitrogen imbalance in the soil. A layer of newspaper two sheets thick can be placed under organic mulches to enhance their effectiveness. (Do not use glossy printed material for this purpose, as the ink may be toxic to plants.)
When deciding which vegetables to plant, be aware that the amount of water needed by different crops varies. Corn and most beans require the greatest water use of commonly-planted garden vegetables. Vegetables that are more drought tolerant include chard, black-eyed peas (cowpeas), heat-tolerant tomatoes (including many cherry varieties), some varieties of okra, mustard greens, eggplant, jalapeno and poblano peppers, Black Knight zucchini, and New Zealand and Malabar spinach. Shallow-rooted crops, including potatoes, onions (and most other bulb, root or tuber crops), celery, and plants in the cabbage family, require more frequent irrigation. For this reason, mulch is especially beneficial for shallow-rooted crops. Tomatoes, sweet potatoes, melons and asparagus are more deep-rooted and can tolerate longer periods without irrigation. Beans, carrots, peppers, summer squash and cucumbers are intermediate in root depth. Additionally, low-growing plants and plants with smaller leaves tend to lose less water through their leaves than taller, leafier varieties. Bush beans, for example, use less water than pole beans. Also, miniature varieties of vegetables, such as mini bell peppers and eggplants, need less water for fruit development than standard varieties.
How a garden is irrigated can affect how much water it uses. Water early in the morning, so that water has a better chance to soak into the soil before it evaporates. A drip system (under mulch) is an efficient way to deliver water to crops with minimal evaporation loss. To avoid overwatering, monitor soil moisture. Generally, if garden soil has dried out to a depth of two to four inches, it's time to water. Including a timer as part of an irrigation system will reduce waste due to human error. Overhead sprinklers and hose-end sprayers are inefficient, result in high evaporation losses and are more likely to trigger diseases such as mildew. Also, the amount of water needed by plants varies over their life cycle. As a rule of thumb, water is most critical for plants during the first few weeks of development, immediately following transplanting, and during flowering and fruit production. Target the timing and amount of water with these plant needs in mind. It is also important to check and maintain your irrigation system frequently to keep it performing at top efficiency.
For more information, see “Water Conservation Suggestions for Your Home Vegetable Garden." UCCE Master Gardeners of Trinity County.
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UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at email@example.com (preferred) or call (530) 538-7201.
By Brent McGhie, UC Master Gardener of Butte County, May 19, 2017.
The most important advantage to drip irrigation is that it is more efficient than traditional irrigation methods. Drip emitters can be placed to deliver water only where it is needed, so water isn't wasted on unplanted areas. By applying water slowly, drip irrigation also allows water to be absorbed quickly into the soil instead of standing on the soil surface. This means that far less water is lost to evaporation than with flood irrigation or sprinklers. Additionally, because water sinks into the soil rather than puddling, there is less loss due to runoff, which makes drip irrigation a good choice for steep terrain. Another way in which drip systems can conserve water is by installing them under a layer of mulch, promoting even greater water savings by further reducing evaporation from the soil. Last but not least, it should be noted that by saving water, drip irrigation also saves the homeowner money.
Drip irrigation has several other advantages. In addition to water, plant roots also need air and when soil pores are completely flooded, roots can actually “suffocate.” The slow application of water by drip systems virtually guarantees a good soil/water environment with a balance of water and oxygen in the soil. Next, weeds don't grow if they don't have water, so they become far less of a problem when water is efficiently targeted to desirable plants by using drip irrigation. As a bonus, this means that herbicide use can be cut back or eliminated, which is better for both the environment and the pocketbook. A final advantage of drip irrigation is its flexibility. It can be installed in a variety of landscapes and, at a relatively low cost, it can be altered and changed as plants grow.
There are disadvantages to drip irrigation systems that should be considered as well. Sediment or bugs that find their way into the tubing can clog drip emitters. In-line filters can be installed to eliminate most of this clogging, but mineral deposits can also clog emitters. There is really no easy way for homeowners to eliminate this, but clogging due to mineral deposits can be delayed by using emitters with a greater flow rate. For example use a 2-gallon per hour (2gph) emitter rather than a 0.5gph emitter, but run it for a shorter time. The faster flow discourages mineral buildup which can cause clogging.
In addition to problems with clogging, drip irrigation systems, with their softer tubing and plastic emitters, are more easily damaged by animals than irrigation systems made of sturdier PVC or metal components. Some dogs seem to delight in chewing on drip tubing, and drip systems also make tempting targets for thirsty rabbits or squirrels. On the plus side, burying drip tubes in shallow trenches or under mulch seems to be effective in mitigating this sort of damage.
If you are considering installing a drip system, putting it on an automatic timer is recommended. An automatic timer provides a consistent watering schedule. With a timer, you provide the exact amount of water you want and there is no forgetting to turn the system on or off.
Something else to consider when planning a drip system is planting zones. Simply put, this means that the same valve should service plants with similar watering needs. You wouldn't want a drip line that waters a vegetable garden to also serve a cactus garden, because their water needs are so different. A simple, inexpensive pressure regulator is also necessary because drip systems require far less water pressure than normal house pressure. Most emitters cannot withstand pressures greater than 40psi and micro-sprinklers cannot function below 10psi (psi stands for “pounds per square inch,” the measurement standard for water pressure).
Many retailers offer how-to pamphlets that provide further information on drip irrigation components and installation.
Schwankl, Larry, and Terry Prichard. Drip Irrigation in the Home Landscape. Oakland, CA: U of California, Division of Agriculture and Natural Resources, Communications Services—Publications, 1999.
By Brent McGhie, Butte County Master Gardener, February 7, 2014
Since this is shaping up to be one of the driest years in California history, it's appropriate to look at ways to conserve water in the home garden. A good starting point is the garden soil itself. Sandy soils tend to drain too rapidly, while heavier clay soils may drain poorly and not provide sufficient oxygen for plant roots. Adding organic compost to the soil will help rectify both of these situations. Organic material increases the water-holding ability of sandy soils and loosens clay soils, so that they are better aerated.
A lawn is normally the single greatest water-user in the home landscape, so unless it serves a specific purpose, such as entertainment, or a play area for pets or children, you might consider replacing it. Lawn substitutes can include planters, ground covers, mulches or hardscape features such as decks or patios. If you choose to have a lawn, the type of turf will affect water use. Warm season grasses such as Bermuda grass, St. Augustine grass, or zoysia grass typically require about 20 percent less water than cool season grasses like tall fescues or bluegrass. Water only when necessary. If you step on the lawn and it springs back when you move your foot, it doesn't need water. Aerating the lawn will maximize water penetration and the duration of watering should be timed so that excess water does not run off of the lawn due to saturated soil. Adjust sprinklers so that water does not end up on concrete or gutters where it is wasted. For lawns and all landscape plants, watering in the early morning hours when wind and temperatures tend to be low means less water will be lost to evaporation.
If you are deciding what to plant, California natives from our climate zone are a good choice. They will need regular watering at first, but can often survive with little more water than they receive from average rainfall after they are established. Try to limit the use of plants that require frequent irrigation and, for efficiency, group them in areas where they can be watered together.
All plants should be watered only when necessary. Check on soil moisture and adjust your watering schedule frequently to reflect seasonal variations in temperature, wind and rainfall. Any plants with similar watering requirements should be grouped and watered with separate valves. Although sprinklers are the best way to water lawns, the most efficient way to water other plants is with drip or soaker hoses. This minimizes water loss through evaporation or runoff. Infrequent, deep watering results in deeper root growth, which in turn allows plants to develop greater tolerance for hot, dry weather. It is important to maintain your irrigation system, checking for leaks, broken sprinkler heads, clogged drip emitters and other problems that could result in wasted water or stressed plants.
A drought year is not the time to engage in excessive pruning. Such pruning can lead to heavy plant growth and a resulting increased demand for water. Light pruning during the winter can shape a plant without stimulating excess growth. And early summer pruning reduces vigor, leaf area and water demand without stimulating excessive growth.
Over-fertilizing can also result in excess plant growth and extra water consumption.
There are several advantages to mowing lawns slightly higher during hot weather. Their growth rate is slowed (reducing water demand) and deeper root growth is encouraged. Taller grass also shades the soil, which lowers evaporation and reduces weed seed germination.
Finally, think twice before running water. Indoors, for example, flush the toilet only when necessary. Turn off the tap while brushing your teeth. Capture water in a bucket or a large pot while the shower or the dishwater is warming up and use it to water garden plants. Using a broom instead of the hose to clean a driveway can save hundreds of gallons of water. Leaving the hose running while washing a car can waste 150 gallons of water; instead, re-fill a bucket with water as needed, and turn off the hose. It's often just a matter of common sense.
Geisel, Pamela M. "Pub. 8036 Water Conservation Tips for the Home Lawn and Garden." Anrcatalog.ucdavis.edu. UCANR, n.d. Web. http://anrcatalog.ucdavis.edu/pdf/8036.pdf
"Water Conservation in Your Garden & Landscape Checklist." Colusa County Farm Bureau. UCCE, n.d. Web. http://cecolusa.ucanr.edu/files/65442.pdf
Kim, Dohee. "Questions and Answers about Water Conservation." UC Cooperative Extension Connection. UCANR, n.d. Web. http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=5356
Water Conservation Suggestions for Your Home Vegetable Garden." UCCE Master Gardeners of Trinity County, n.d. Web. http://cetrinity.ucanr.edu/files/180197.pdf