I can't tell you how large a planting area you need but a 1200sf garden should be able to grow a LOT of produce, especially if you do succession plantings of fast crops likes greens and peas. I grew up with a much smaller dedicated vegetable garden than that and my folks canned and froze a lot of what we grew. There were 6 of us in my family. You might want to look into 'square foot gardening' for intensive planting in a smaller area.

How much soil/compost you will need will depend entirely on how large the garden area is you decide upon. You will have to determine that before you know how much to add. If doing raised beds, it's pretty easy to calculate the volume each will contain (multiply the length x width x depth). If open beds, you'll need at least 6" of soil, more if you want to grow any root crops. Remember to keep the units the same - 6" = .5'. If you were going with the 30'x40' garden area again to a depth of 6", you'd need 600 cubic feet of soil or about 22.5 cubic yards. That's assuming you have no existing soil at your disposal.

Here is a link that might be useful: square foot gardening

g'day tinyelvis,

how much garden space a bit like how long is a piece of string, what i would suggest is allocate what space you can initially. then have room to add more gardens until you reach the optimum, which of course you may or may not do depending on available space. most of us in suburbia just have to do what we can with limited space.

your location of gardens will depend on that part of you yard that gets the sun the most, for you i would suggest the eastern to southern sides, and no big shade trees near by.

i find the best size for each bed to be 1 meter wide and up to 6 or 8 meters long. you will need to have a starting depth of organic matter of around 6" to 8"s.

anyhow we invite you to look at our pic's on how we do our raised beds there may be some hints there for you?

len

Here is a link that might be useful: lens garden page

Much easier to build, make into good, healthy soil, and maintain would be a series of 4 x 4 planting beds as in Square Foot Gardening, especially if you are creating new beds by covering the sod you have with newspaper. What you need to do is add organic matter to the soil you have and you need about 5 percent OM in that soil so you need to add as much as it takes to get there. Spending your money on something called "topsoil" is simply a waste because what you would get might be something with about 95 percent of what you already have, the mineral portion of the soil mix, and maybe if the seller adds some 5 percent of what you need, organic matter.

For question 1, I would say that it is a matter of what you can work. I would increase my garden size a bit each year based on what amount of time I am spending in my garden now. If you currently spend 8 hours a week with garden upkeep and you have 16 hours to put into it then you can double your garden size. Everybody that I have read about or talked to that have followed the guides for how much garden space per family member has said that none of the formulas match their situation well. It is a bit of trial and adjustment per family.

For question 2, where do you live? In warmer climates we go through a lot more compost than those in cooler climates. The microbes are active for a larger portion of the year and there are more of them or their metabolisms are running at a higher rate during our warmer summers. I am up to about 3 inches of compost per year and I don not think it is quite enough.

I also agree with kimmsr that some sort of formal or informal beds are easier to maintain and, with dense planting (square foot is one example) get more produce out of.

Steve

A couple of things to think about. Have you ever canned before? Canning can be quite a chore. The start up equipment can be expensive but worth it.

Are any of your children/hubby old enough to help? You can do it all yourself but makes for very grumpy person. Apparently you already have a garden area is there anyway to increase the harvest without making a bigger area. Such as increasing the density as suggested by Steve.

I find that some veggies, especially corn and potatoes take up too much space in my small garden to be economical. Except for new potatoes it is cheaper to purchase from another grower than grow myself. Think of other things that your family may only eat once or twice a summer that could be purchased vs space and time. Devote your time to things that go well with your family and add one or two new things each year.

With regards to the methods that are being prescribed, you did not mention your access to irrigation. If you are planning now on doing a 30x40 area of intensive beds (i.e. square foot) you are going to need a LOT of water. If you are fortunate enough, nature will provide it. However, if you are in a dry, hotter climate...

For instance, to provide one inch of water to 1000 square feet requires 623 gallons of water. With intensive beds, mulched, in a hot climate, you may need to apply 1-1.5 inches every 4-7 days (depending on temp., sunshine, rainfall, etc.). If you cannot reliably provide 500-700 gallons every week and a half, you might run into some serious problems.

Because of the description in your question I would add: consider edible landscaping. Look around and see where you have room for a tree, and plant a self-fruitful fruit tree. Bushes? A bush cherry, thornless black berry, blueberries, etc. Flower garden? use flowering bushes that fruit or maybe even currants or gooseberries. A patio? trellis some grapes. Yes, it takes a few years for them to produce fruit, but they will feed your family tirelessly for a lifetime.