General Raised Bed Questions
1. Is the ground supposed to be prepared first beneath the raised bed? Are you supposed to remove all the grass first and then put down your ground cover and then soil, and so on? Or do you just throw the black plastic and lumber on the ground and go for it?
Ground preparation under a raised bed could be a whole topic for a post but here are some general thoughts. You don't want grass growing up through your raised bed. I've had that happen and Bermuda grass is hard to remove. I don't use plastic under my raised beds. It doesn't allow them to drain. I use thick layers of newspaper or cardboard. These break down over time which feeds the soil but by the time they are gone so is the grass and weeds that were there. When I say thick I mean multiple sheets. One sheet of newspaper will not do. Thick and overlapping layers will effectively kill off the sod without the need for chemicals or digging.
2. I have a wonderful raised bed. It was great the first 2 years I planted my spinach and Swiss chard. Now, this past summer I wasn't able to grow anything but flowers. I guess I need to re-nourish it but need some guidance in this area. Do you have any suggestions?
My number one suggestion is always compost! A fresh dressing of compost multiple times per year can do wonders but there are other options. There are quite a few organic ingredients you could use in your beds to add nutrients including bonemeal, bloodmeal, kelp meal, alfafa meal, bat guano, and too many others to list! (at least in this post). A good option is to look for a quality organic fertilizer. If you read the packaging it should say OMRI approved on it somewhere. This means that the ingredients in the fertilizer are on the lists of the Organic Materials Review Institute which publishes and reviews organic products. Espoma and Jobe are two companies that have some good products that are easy to find. I've also found that John and Bob's (my review) as well as Winchester Gardens have some good products too. Both companies have sent me samples to test and try out which I've found effective in my garden. There are many formulations of products out there so read the labels and make sure they will do what you want them too. Make sure that the nitrogen number (the first one where it says NPK) is not too high. It promotes growth of stems and foliage. A 10 foot tall tomato plant with no tomatoes is not what you desire. Sure it's pretty but a tomato plant has to have tomatoes!
Make sure you use mulch which will break down over time to feed the soil and when you aren't gardening plant a cover crop. Legumes like beans, peas, and clover put nitrogen back into the soil as they decay.
Questions on constructing a metal raised bed.
3) Were you screwing in your deck screws at an angle? Any special tools needed?
Yes I was screwing in at angles! To put the frames together the way I did angle holes were necessary for the deck screws. No special tools are needed but there are kits that make it easier to drill at angles. A pocket hole kit would make some nice finished holes but since I was putting this in my backyard I didn't go that route. In this case I started the drill hole going straight, just enough to create a small indention. Then I changed the angle of my drill to match the angle I wanted. The small indention kept the drill bit in place while I made my angle hole. If I hadn't done that the drill could easily have slid away and caused me a bit of frustration.
4) What did you use to cut your metal?
I used a pair of metal snips which you can find in any hardware department. My dad and I used them for multiple areas when building my shed (Youtube Video). The key here is make sure you wear thick gloves when cutting the metal. Otherwise you will get some nasty cuts. Metal is sharp when cut. The cut ends are in inaccessible areas of the raised bed so it shouldn't cause any issues with cuts or injuries.
5) Do you think using painted roofing will mitigate the reaction between the metal and the treated wood?
Maybe. The paint may act as a protective layer but you will have to drill holes in it somewhere which will expose the metal to the wood. Also there may be some issues with the paint eventually breaking down and releasing chemicals. If you're concerned about the reaction try looking for cedar or redwood as naturally rot resistant wood materials or consider composite woods used for decking. They would be heavier but are very long lasting.
6) Do you think that much straw bale on the bottom will rob your fruits and veg of nitrogen, and if so, what will you supplement with?
Many people have tried and experienced success with straw bale gardening. Essentially the gardener adds compost and soil to the bales to encourage the breakdown of the materials. A balanced approach shouldn't do any harm to the plants. That's why sheet composting works so well. A garden that has been sheet composted (Lasagna Gardening) has very balanced ratio of brown (carbon) to green (nitrogen) and it doesn't adversely effect plants. Sheet composting involves alternating layers of green and brown materials like cardboard, leaves, grass clippings, coffee ground, kitchen scraps, and a lot of other ingredients to build a garden that composts in place.
I'll supplement with organic materials I mentioned in the question 2.
7) Will the metal conduct too much heat in the summer for the plants?
That's a possibility but I think it can be managed. If cucumber plants or other vining plants are allowed to hang off the east and south sides they will reduce that impact a lot. I also think the the increased soil capacity will hold more moisture in the bed and reduce the impact of high heat. In addition the added heat could be an advantage where it will warm up the soil earlier and keep it warm longer which may extend the growing season. I'll report on my findings but your thoughts could certainly prove valid.
Did any of these questions help you? If not, send me your questions!