It takes a lot of water to grow food: approximately an inch every week in hot weather. In Southeastern Idaho, we average just over 12 inches of precipitation in a year. And most of it comes in winter and spring, leaving the prime growing months of July and August very dry.
A dry climate is not all bad. Fungal infections are rare, intense sun and high daytime temperatures help heat-loving plants thrive, and slugs and snails are not usually a problem. But moisture-loving, cool-weather crops like arugula, radishes, spinach, and even lettuce become stunted and bitter from the heat of our summers.
A responsibly irrigated garden, even in hot, dry climates, likely reduces your total ecological impact. But since water is a scarce resource, I try to use as little as possible. Here’s how to use less water while growing a phenomenal vegetable garden.
Grow during the spring and fall when possible. Crops grown in cool weather don’t loose as much water to evaporation (and may get some moisture from actual rainfall, unlike those grown here during the summer months). Start in early spring and keep growing through the fagetsll. A hoop house might help you grow through the winter while needing very little water in cold regions.
Use drip irrigation instead of sprinklers. Dripping water directly onto the soil instead of the leaves lets plants use more of the water before it evaporates. Drip systems can deliver water directly to your garden beds or rows instead of soaking paths, making weed control easier in addition to lowering water consumption. And longer, less frequent watering with drip irrigation encourages roots to grow deeper and become more resilient to dry spells at the surface of the soil.
While drip irrigation is ideal for established plants, it doesn’t moisten the soil’s surface evenly enough for seed germination and young seedlings. Make sure you sprinkle newly-planted beds frequently instead of relying on drip irrigation alone.
There are many options for drip systems. I use a system like this one with pressure-regulated ‘drips’ at 6 inch intervals. It is easy to assemble, easy to repair, available from my local home improvement store, and attaches to a garden hose. You can customize it to fit your garden beds perfectly, and you can even turn sections on or off so that you don’t have to water when there’s nothing growing there. An automatic timer like this one makes it easy to schedule watering times.
Mulch with straw. Straw prevents water loss and insulates the soil. I use straw to keep the soil warm in the winter and cool and damp in the summer. Before planting a new bed, I pull off the winter’s straw, add compost, and loosen the soil with a garden fork. After a month or two, when the soil has had a chance to warm up, I layer new straw around my larger plants to keep the soil wet during the hottest part of the summer. Mulching is more effective on top of a drip system than underneath sprinklers, where water has trouble penetrating the straw to reach the roots. Compact straw bales are often available in the fall from plant nurseries.
Feel your soil before watering, or check it periodically if using an automatic timer to water. The surface doesn’t need to be wet once your plants are established, but soil should be damp about an inch down.
Water in the evening or early morning. Morning is best if you have trouble with fungi or slugs, since they prefer soil that stays wet overnight. An automatic timer like the one described above lets you water just before dawn without disturbing your sleep or morning routine.
Consider adding rain barrels to collect rain from your roof. We installed four 50-gallon rain barrels. These quickly overflow in the spring and then sit empty most of the summer, but they help water our fruit trees. Rain barrels may be a great option if you get consistent rain through the summer or have room for really large barrels.
These simple practices will help your garden flourish without a wasteful splash.