Garden water demands and irrigation scheduling are the result of complex interactions between climate, weather, soil type, plant species, and irrigation practices. This means that there is no one recipe that is suitable for all gardens. Taking the time to learn about proper irrigation in your own situation will pay dividends. There are a few general principles that will help guide your decision on how best to irrigate your vegetable garden.
Once the plants approach full size, typical water use for most vegetables will be ¼ inch (meaning that if you put a can under the sprinkler, the water inside would be ¼ inch deep at the end of the irrigation) per day. This means a summer garden will need around 2 inches of water per week. Because most soils will not hold this much water, plan to irrigate twice each week with the total being about two inches. In the spring when weather is cool and plants are small, they may use less than half this amount of water. In the fall, when plants start to mature, water use will also decline.
Plants use the same amount of water regardless of soil type. However, sandy soils hold less water and plants will use the water very quickly and then become stressed. So, if your soil is sandy, change your irrigation practices to water more frequently but put less water on during each irrigation event.
Sprinkler irrigation is a simple method for making uniform applications of water to the vegetable garden. However, sprinklers wet the leaves and encourage disease development and they also splash dirt on leaves that may add some “grit” to your meals. If these are problems in your garden, consider using a bottom up irrigation method such as soaker hoses or a drip system.