As clean fresh water becomes ever scarcer and more valuable (and expensive), conservation becomes critical. In some areas this could mean the difference between having a garden and not having one. Here are some ways to reduce water consumption (taken together they can save a lot of water).
• You can cut down on water use by working a smaller number of beds very intensively.
• Mulching is one of the most important water conserving techniques and can reduce water consumption by as much as a third. It not only shades the soil from direct sunlight and by but also reduces weed competition (see Mulching.)
• Up until there is at least 20% leaf cover, the soil loses more water by evaporation than is used by the plants. Never leave the soil bare for any longer than necessary, cover with mulch or row covers to minimize evaporation. Keeping seed beds covered not only reduces water use, but also the frequency with which you have to water.
• Put plants with similar water needs in the same bed. You can then have a bed for moisture loving plants and a separate bed for more drought tolerant crops. This enables you to more easily adjust your watering to the crop.
• The way you irrigate affects water consumption. The most water conserving methods are the drip systems, the most wasteful are overhead ones. Hand watering, with a can or wand, is also very efficient, but labor intensive.
• The soil is a water storage medium and one of the best ways to conserve water is to add organic matter to the soil. When a soil is high in organic matter it absorbs water like a sponge and any the water that falls on it in will be absorbed and held.
• In row gardens, where the soil is bare for much of the time, the top couple of inches of soil was often cultivated to create a dust mulch, in the belief this would reduce evaporation. It has been found that the top couple of inches of soil tend to dry out naturally, so it really isn’t necessary to cultivate. In fact cultivation may actually increase water loss.
• Raised beds lose more water than flat beds because they have more surface area. In hot, dry climates the beds should only be slightly raised, or even flat to reduce evaporative losses. In extremely arid areas they may even be sunken.
• If water is very scarce don’t use cover crops or green manures. These can take a lot of water from the soil even before you plant your crop (you should use a mulch instead). Remove old crops when they start to decline, otherwise they will continue to use water.
• Dry winds can take a lot of moisture from the soil, so make sure the garden has an efficient windbreak (a mulch will help also).
• Another useful strategy for saving water is to only water your plants at critical growth times (during germination, after transplanting and when the food part is sizing up). If you only give plants water when they need it most, you can get the highest productivity for the least consumption of water. You may get 60% of the yield, using only 10% of the water.
• Don’t deprive plants of the water they need for proper growth. It’s much better to grow a few plants well than a lot of plants badly.
• Starting plants inside, rather than direct sowing, can also save water.
• A few crops are so drought tolerant (watermelons, tomatoes) that they can be grown without irrigation, even in areas with rainless summers. They simply need to be planted further apart, to give each plant access to a larger volume of soil. In the arid southwest, Native Americans grew corn without irrigation by planting the hills 6 feet apart. Yields are lower when grown in this way, but the fruit is sweeter and better flavored. If you have plenty of space, but not much water, you may want to investigate this further.
• If your hose connections drip, then fix them.
• Don’t let rainwater run away down storm drains. Make use of it by storing as much as you can, either in the soil or in containers. See Rainwater for more on this.
• Get the maximum use of your household water by using it twice. Once in the house and a second time in the garden. See Gray Water for more on this.
• In areas with wet winters and dry summers you might try growing your main crops in spring, while there is still plenty of water in the ground from winter rains.