Patti,

Six inches is fine as long as there is soil beneath the raised bed and not concrete. : ) If you have concrete (hey, I have seen people build raised beds on top of patios and driveways), by chance, I'd go with a minimum of 12-18".

I have used square foot gardening and it works fine for me, although since I use lots of cages and trellises to raise plants higher off the ground and use less ground space, it is more cubed-foot gardening than square foot. Either works well here.

Dripworks offers very high quality materials and their service is second to none. I would recommend them. They have a design service and will help you design your layout free of charge, so by all means, let them! They will help you every way they can and you have the benefit of their knowledge and experience.

For the really long run you can use driptape with emitters or plain old soaker hoses. Your choice. If your 70' long bed is level and doesn't have complicated elevation changes, I'd probably use soaker hoses placed under mulch so that the soaker hoses would last longer (since exposure to UV rays breaks them down more quickly). Soaker hoses would give you even moisture distribution all along the bed.

I tend to side with your DH if the device you're talking about is the magnetic water thingy they sell. I don't remember its name. To me, the magnetic device is unproven junk science and independent research studies do not seem to back up the theory or anecdotal reports about how such systems work. I'm not an expert, though, by any means.

You will neeed some sort of filter and they sell them and can recommend the best one for your circumstances. You might want to onsider adding the fertigation device to make it easier to feed your plants, especially if you are not going to garden organically. I garden organically and let the soil feed the plants, but I'd fertigate if I wasn't organic and thought my plants needed to be fed. (Some organic gardeners do fertigate using organic products, but I haven't fed it necessary in well-enriched soil that has adequate amounts of organic matter.)

What we have done right with regards to irrigation, whether by soaker hose or dripline, is to watch the soil closely and understand how quickly it dries out in different conditions. You can't just install a system, set it on a timer, and walk away from it and never change it throughout the entire growing season. You have to pay attention to how fast or slow your soil drains as well as the water needs of your various plants. Very large plants in 95 degree weather have entirely different water needs than small plants in 70 degree weather, for example. Also, if rain is falling and your system is on a timer, shut off the timer if adequate rainfall is occurring. Otherwise, you can overwater. Plants will suck up a lot more water in July than in May, so don't assume that the amount of irrigation that kept them happy in May will keep them happy in July.

When I plant, I zone plants together....plants that need little if any irrigation are together in beds and plants that guzzle lots of water are together in other beds. If you mix water guzzling plants together with plants that prefer low water in the same rows or beds, you'll never be able to keep both types happy. So, before you lay out your driptape, know exactly what plants will be planted where.

I use both drip irrigation and soaker hoses and am happy with both. I've even used drip irrigation to water the hanging baskets of flowers on the wraparound porch. However, they are not perfect. Emitters clog and you have to watch and pay attention to your system.

Also, there is no way to water "by formula". Often, people who are new to soaker hose and dripline irrigation want to be given a formula like "water twice a week for 30 minutes" and there is just no formula that works like that because rainfall and evaporation rates vary so much as does the ability of soil to hold moisture and plants to take up moisture. You just need to learn to water your plants when they need moisture and don't water them when they don't. It sounds simple, but lots of folks overwater to the detriment of their plants. After a whole growing season with your new raised beds, you'll have a good understanding of how quickly the beds' soil dries out in various conditions as well as how quickly or slowly the plant roots take up the water and how much evaporation and wind dry out the soil. That experience will enable you to confidently set a timer and use it most of the time while making adjustments depending on the variables in weather conditions.

Dawn