Vegetables are made up of about 90% water, and because of this require sufficient moisture to grow. Water is also essential because it allows plants to take nutrients from the soil. The minerals in the soil dissolve in this moisture so that the roots of the plant can absorb them to help the plant grow. If your soil doesn’t have enough moisture it can accumulate high amounts of harmful salts, rendering it inhabitable.
Amount of Water
Soil receives water naturally through rainfall or by irrigation. During heavy rain, gravity pulls the water down into the ground filling up all the pore spaces between soil particles. This is an ideal condition allowing plants to grow to their fullest without stress due to a lack of moisture. The soil will continue to lose water through two mechanisms. The plants will gradually soak up moisture from the soil through their roots to obtain nutrients. The ground also loses water through evaporation at the surface of the soil, which is one of the main reasons for mulching.
A typical garden requires at least an inch of water a week, which should leave the soil soaked about 5-6 inches deep. Keep in mind that sandy soils, which have low water retention, may require significantly more water. It may be helpful to put a rain gauge or a coffee can in the garden to keep track of how much rainfall your garden receives each week. If ten days or more go by without rainfall, it’s time to get out the gardening hose. Too little water can cause plants to develop shallow roots that can become scorched in hot, dry weather, often killing the plant.
So how much water does my garden need?
The answer to this question is a lot! While an inch of rain doesn’t sound like much, an inch of rainfall covering a garden that is 20’ x 10’ (200 square feet) is equivalent to approximately 125 gallons of water. For a rough estimate of how much water your garden requires, use 5 gallons of water per 8 square feet.
Due to gravity, water tends to flow down into the soil. The better the soil structure, (particle size and pore space), the easier it will be for the water to move through the soil. Heavy clay soils have tiny clay particles that clog quickly, causing water to run off without penetrating. Sandy soils lose water rapidly because the water tends to flow through the large pore spaces with nothing to hold on to. Both types of soils can be improved in their ability to retain water by adding generous quantities of organic matter annually. When organic matter is added to clay soil, it acts like a glue, making larger particles out of the small particles and thus increasing pore space for added water retention. In sandy soil, organic matter fills the large pore spaces and enables the earth to retain more water.
When to Water
There are two times during the growing season when your garden must receive adequate moisture: When the seeds are germinating and just before harvest. Wilting is an indication that your plants aren’t getting enough moisture from the soil. When a plant begins to wilt it needs water immediately. Ensuring your plants receive sufficient amounts of water each week will enable the roots of the plants to grow deep where they can access additional moisture. Deep roots also make for a healthy and sturdy plant that is less likely to be damaged by wind.
You can water your vegetable plants at any time. Contrary to common belief, the leaves will not scorch from the sun if you water them in the heat of the day, although you will lose some moisture through evaporation. If time permits, it’s best to water plants is in the morning, as they are already wet from the morning dew. This allows them to dry off as they would naturally, and keeps the time they are soaked to a minimum. Some plants are more susceptible to disease if left wet for prolonged periods, as could be the case if watered late in the day.
How to Water
The most water conservative method of irrigation is a soil soaker system, which consists of a special hose that allows water to seep into the soil with minimal runoff. Sprinklers are easier and cheaper, and can be set up to cover vast areas. Those who are conservative with their water can collect rainwater from their gutters in barrels to use as a water source for the garden.