Raised beds and the how to's are the topic of this latest TreeYo EDU article. It's a staple earthwork when contextually and climactically appropriate but has great advantages when applied and managed appropriately. some nice tips on how to maintain are in there so enjoy the read.

https://treeyopermacultureedu.wordpress.com/chapter-9-earth-working-and-earth-resources/raised-beds/

Excerpt:
Written by Doug Crouch

To extrude upward the earth for creating favorable growing conditions is the action and intent behind creating a raised bed. While a very common feature in a permaculture landscape, we must check, as always, that they are climate and context appropriate. If so, this common gardening earthwork comes in many forms and fashions from a few square meters to kilometer long lines for tree crops. They are easy to build and with a few tips, relatively easy to maintain. Their advantages of improving drainage and warming soil temperatures earleir in the season make them a great season extender and general earthwork. This is especially true in more humid climates, poor draining soils, or at specific times of the year in other climates where humidity is seasonal (i.e. Mediterranean). Their fertility can be maintained in numerous ways including chicken tractors, their construction can be with or without boards or logs along the side, and they can be straight line beds in zone 3 or curvy waves of a mandala garden in Zone 2. They can also be dramatically raised in boxes so the needs of the elderly and handicapped are met thus meeting the important function of social inclusion. With raised beds exposed edge, again, they do dry out and warm up quicker, which is a plus in some climates, but in others it creates a painful watering habitat. So be sure this is the right earthwork for your soil type, for the right time of the year, and for the climate.

Why Raised Beds?

Building raised beds is a northern European technique, in general, where humidity persists throughout the year. They have short growing seasons, especially for summer crops like Tomatoes or Peppers whose origins are in Central America. The water table is often quite high and soils can be heavy and quite poor draining. So as you can see the obvious response is to elevate the growing space to deal with such factors. Imagine climates and contexts like England, Holland, and Belgium and from there the tendency to make raised beds makes sense.

Moreover, spring rains are a blessing for our cool season crops as they can deal with the temperature fluctuation of spring and thrive in this cooler and wetter environment. As the days get longer, especially around the time of the spring equinox, the daylight hours grow rapidly and the plants awaken and take off as well. This daylight lengthening impulse spurs growth but our soil conditions are vital at this time of the year. If the water table is too high, or soils drain too slowly, anaerobic conditions can persist thus causing plant pathogens to build up and cause rot. This can be disastorous for the farmer immediately and for future fertility. The raised bed acts as the mountain in this case as it sheds water while the valleys, or the paths, collect more of the moisture. These spring rains are often accompanied by cold breezes and the rain itself is quite cold. This lowers soil temperatures, which is a huge factor for plant growth at this time of year. As the water drains and the edge is exposed to sunlight the beds can warm up and cool season crops can begin to grow sooner. Also it allows the farmer to put summer crops in earlier, which really need the right soil temperature or they simply stunt from going dormant due to cold soils.

A note on this was working with the campesinos in the Dominican Republic back in 2012-2013. This area broders the subtropics and tropics especially on the north shore where I was farming, teaching, and learning. In the winter months of the Northern Hemisphere, even there amongst papaya and moringa, the landscape experiences a slow down of growth, which I found odd but true. Each day I was encouraged to feel the soil and its true the cooler soils were there in January and early February. However, over time I could feel them warm and you could see the subsequent plant growth as the days got longer and hotter. Furthermore in the Mediterranean climates, where I have farmed in three different continents, I can highly recommend sunken beds especially for summer crops. However raised beds in the winter months will have all of these advantages and allow for year round food production in most regions. This is especially true, again, in areas with heavy clay soils and high water tables. When the rains are waining and its time for warm season crops, switch to sunken beds as to take advantage of the conditions given by that earthwork.

How to Build

While there is tractor implements that build such beds for tree crops and large scale row crop production, I will be referring more to the hand built ones. While I am not opposed to these mechanical implements for initial installment, the process is little more than marking out their initial layout and driving parallel to that. Similarily for the hand-built type, you will also want to do this but you can do it more personal sized. First, most people will orientate the beds east to west to optimize sun exposure. However slope and working with beds on contour may indeed change all of that as each site is unique especially as it pertains to topography, aspect, and access to water. Second, the earthwork itself in terms of dimensions depends a bit on the user. A tall person of over 2 meters may have different sized beds than say the person 1.4 m. Their arm reach is dramatically different. Like any bed, but particularly important in raised beds, stepping on the beds is very counter productive. Thus size the bed appropriately for comfortable arm reach into the bed so you never have to step on it. So take a rope, stick, stone or anything really and put it where you think you would want your pathway. Put your feet behind that and reach comfortably into the area where you will want the raised bed to be. Put a stick there where your hand touches the earth. Remember to only reach comfortability and not everstretch because this is very straining on the body and will eventually cause you to step into the bed. Furthermore, come around to the other side of the bed and stand where you think the next pathway will go. Reach out and if you can comfortably touch the position on the ground where the stick is then place another marker at the front of your foot. Then delineate the lines or shapes of the pathways. If you don’t want straight row beds or have some other context like a perennial crop of Jerusalem Artichokes, you make elect for stepping stones and make the bed bigger. Of course keyholes allow you to increase access in a raised bed system, especially those that are more free form.