Does anyone know approximately how much water per square foot a mulched vegetable garden would need per day in the Phoenix area? I am planning to install rain gutters and we have a nice sized roof to collect rainwater to supplement the garden. We are going to start with 550 gallons of storage capacity for now and keep the garden bed small.
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Janet, how are you distributing the water onto your garden soil? Are you using a garden hose attached to your rain barrel?
The problem with using gravity-fed systems for irrigation is that you never get the required pressure required for landscape irrigation equipment - even drip components. Rainbird drip emitters are meant to operate at 15-30 psi. One psi is equal to 2.31 feet of head. So to get 15 psi out of your rain barrel, it would have to be almost 35 feet above ground. Beth - that's why your drip emitters don't work as well as you'd like (Unless I misunderstood and you're using metered water - in that case you need larger flow emitters - like 4 GPH). Even the Rainbird Landscape Dripline (which is what I'd recommend for row gardening) requires 8 psi to operate. So hand watering is really your only option, unless you install a pump. Soaker hoses are an option, but they clog easily and can rot in a few years; and you'll never really know how much water you're applying.
If you're using a hose, you can just count the time it takes to fill a gallon or 5-gallon bucket, and use that time to determine the flow rate of your garden hose at your low pressure.
As far as how much water to use per square foot - that depends on what you're growing, the sun and wind conditions where your garden is located, and what time of year it is.
PS - Be prepared to want to add to your water tank. You say you have a 'nice size' roof. A 2,000 sf roof will collect over 550 gallons of rainwater from just a half-inch of rain. The great thing about water tanks is that they can be added to by linking them with hoses or pipe at the bottom. I haven't met anyone yet who installed a rainwater harvesting tank who hasn't wished they'd gone bigger.
Congratulations to you for conserving a precious and scarce natural resource!
I just hooked up a drip system for my sqaure foot garden, I thought each square foot would only need about a gallon a day which would be about right if I was using the hose or watering can.
It seems with a drip emitter I need much more because it drips so slowly that it doesn't spread around. Tomato plants need more water than most of my other veggies. For your system I would guess about a gallon per day or every other day per square, but if you are hand watering its probably less than that.
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The problem with using gravity-fed systems for irrigation is that you never get the required pressure required for landscape irrigation equipment - even drip components. Rainbird drip emitters are meant to operate at 15-30 psi. One psi is equal to 2.31 feet of head. So to get 15 psi out of your rain barrel, it would have to be almost 35 feet above ground. Beth - that's why your drip emitters don't work as well as you'd like (Unless I misunderstood and you're using metered water - in that case you need larger flow emitters - like 4 GPH). Even the Rainbird Landscape Dripline (which is what I'd recommend for row gardening) requires 8 psi to operate. So hand watering is really your only option, unless you install a pump. Soaker hoses are an option, but they clog easily and can rot in a few years; and you'll never really know how much water you're applying.
If you're using a hose, you can just count the time it takes to fill a gallon or 5-gallon bucket, and use that time to determine the flow rate of your garden hose at your low pressure.
As far as how much water to use per square foot - that depends on what you're growing, the sun and wind conditions where your garden is located, and what time of year it is.
PS - Be prepared to want to add to your water tank. You say you have a 'nice size' roof. A 2,000 sf roof will collect over 550 gallons of rainwater from just a half-inch of rain. The great thing about water tanks is that they can be added to by linking them with hoses or pipe at the bottom. I haven't met anyone yet who installed a rainwater harvesting tank who hasn't wished they'd gone bigger.
Congratulations to you for conserving a precious and scarce natural resource!
It seems with a drip emitter I need much more because it drips so slowly that it doesn't spread around. Tomato plants need more water than most of my other veggies. For your system I would guess about a gallon per day or every other day per square, but if you are hand watering its probably less than that.