I have a very small planting area that cannot be expanded at the moment & I'd like to plant in spring, summer & fall, then let it rest in the winter. So my goal is 3 separate plantings.

I'm going to limit heavy feeders to 1 part of the space for 1 planting only & the rest will be legumes & light feeders.

Can anyone share their experience with such an approach?

I've done this for three years now and haven't seen any problems. I do rotate crops to help reduce the chance of disease. The best advice I ever heard was to feed your soil and it will feed you. Good luck!

For me, staggered plantings of the arugula and turnips make sense, because i want to eat them in a few meals every week, but because the peas will provide a continuous harvest over a longer period - because we're harvesting the fruit, and not the whole plant - I would put in that row all at the same time, and in another bed put in a second row a few weeks later, or establish a succession by planting a variety with a different maturation period.

The arugula MAY provide multiple harvests, depending on your method, and will be available first. It is also least tolerant of heat, so will benefit from being shaded by the peas as the season progresses. Because it will see the most attention, I would plant it at the outside of my bed, where it is easiest to reach. The turnips, being root crops, will cause some disturbance when they are harvested, so I will make sure that they are not too closely spaced, to the other turnips, but also to the other crops in the bed. The peas will be comparatively tall when they are ready to harvest, so the shade that they produce will need to be accounted for in the layout of the bed - not only in terms of North-South-East-West, but if the row is in the middle, with other crops on either side, or on one edge, where the effect of shading is reduced.

Assuming 70 days for the peas to mature, and perhaps 2 weeks of harvest, it's possible that you could have the entire bed emptied and ready to plant on 3 months, but that would mean a significant amount of space was being underutilized where the arugula and turnips were removed. You could choose to reseed those areas with your second crop, but it would be more time-efficient to transplant. In the interest of rotation, and taking into account the season, you might put in cucumbers, to climb the trellis soon to be vacated by the peas, or eggplant, or squash. Broccoli would work, but it's a heavy feeder, and it's related to turnips, so less ideal. Greens could work, but you're getting into the warmest part of the season, so kale would be a better choice than spinach. And ideally you want whatever you plant to be ripe and ready in time to get a third crop into the ground - and ripe - before winter sets in, so maturity dates become even more important as you do your planning later in the season. Otherwise, you'll get to the end of the growing season, and unless you have some kind of season-extension tactics, the only thing able to grow to maturity in your garden will be 25-day radishes, and really, how many of those do you want to eat?

Another consideration is how you will deal with the harvest. If you are growing only to have fresh vegetables for the length of the growing season, successions are the way to go. But if you want to freeze pesto or can tomato sauce or make pickles, you want a large harvest all at once so that you can efficiently process your produce. Personally, I don't want to be stuck in a hot kitchen on August, so I schedule some of my plantings so that the canning can take place, as much as possible, in the cooler months, and the foods that can be enjoyed raw are coming ripe in summer. That means not only making choices about crops, but about varieties - slicing tomatoes to ripen early, but plum tomatoes in September, or Hakuri turnips to eat in summer, and purple-tops, which taste better cooked, for fall.

As you can see, the process of multiple cropping is wonderfully complex. This is just one example, with only a few crops, and doesn't fully incorporate the varying needs of water, nutrients, and sunlight that a detailed plan should include. Short maturity crops like radishes and salad greens can often simply be tucked in wherever space and time allow without much planning, and having seedlings always on hand to transplant will provide you with a denser harvest schedule, but a successful plan for multiple harvests is a multi-dimensional puzzle, involving space, time, species, cultural requirements, season, and use.

Personally, I enjoy the complexity, it's like a game of chess, or planning a perfect heist, but for some people it can seem daunting. It is probably best, in the beginning, to follow one simple rule - plant something every week, and when you harvest one crop, renew the soil (I add lots of compost, and nothing more) and plant again.

Lastly (for now), although you are growing in the same space, it is never the same soil. It is important to renew the soil regularly, to replace all of the nutrients that multiple cropping removes. Lots of compost, and fertilizer when needed, will go a long way towards providing a good succession.

So my biggest concern is the renewal of the soil to prevent disease/pests from happening. It looks like compost will be my best option, since I'm going all organic.

How much compost should I be adding? 1 inch, 2 inches?

In my big garden, which also has some beds that are in use year round, I carefully rotate crops. But in this small space I just try to remember a bit where things were, and adjust accordingly. It's like a smorgasborg (sp?) all the time, and very pretty. It also gets a lot more renewal with compost than the rest of the garden (It's in the front yard, so I want it to look decorative -- hence the different treatment.)

If you can get 2 inches of compost, great. I figure soil in nature doesn't rest. I always think of the quote "Nature abhors bare ground" It will grow weeds if we try to let it rest without mulch! So if you continually renew it, I see no reason why you can't continually use it, especially in zone 7b.

After pulling the tomatoes in July I let the beds sit until September when I plant a crop of bush beans and start planting lettuce, arugula, and Swiss chard for a fall/winter crop. I plant English peas in December for an early spring crop. By mid March I'll start transplanting tomatoes and peppers. Most of the lettuce/arugula will have started to go to seed by then. With this warm winter we're having I'm surprised they haven't already.