Up here in the Fourth Corner, we get plentiful rain in the winter and sometimes we have quite a bit of water standing in the fields until late spring. Some farmers have had to wait until late June to even get out to their fields in past years (and maybe this year). We also have drought conditions in summer, so irrigation is necessary. Building up organic matter in the soil only goes so far in regulating soil moisure, so I am going to take a page from ancient agriculture and try chinampas this year. Chinampas were an intensive cultivation system used by the Aztecs on Lake Tenochtitlan. When Cortez and his men saw them in 1519, they referred to them as "floating gardens," but they were actually raised beds recovered from lake and marsh areas. Chinampas are still used in Mexico City to this day, usually for growing flowers. The typical chinampa was 15-30 feet wide and 300 feet long. They were constructed by digging trenches on the side or bringing muck and dropping it in a marked-out area. When the chinampa was finished, the Aztecs planted willow trees around the perimeter to anchor the soil. They also used an early version of soil blocks for plant starts - an aid in maximum plant survival to harvest versus direct seeding. There are three main requirements in intensive agriculture; irrigation, fertilization, and labor. The structure of the chinampas maximized soil moisture and additional water was available in the ditches/canals next to the chinampas. Fertilization was provided by the muck (similar to the Nile flooding, by the way), and human labor was plentiful for the Aztecs.
My idea is to take the chinampa idea, add some insights from the old Irish "lazy beds," and adapt them to Whatcom County. The lazy beds of pre-famine Ireland were usually four feet wide and the seed potatoes were laid on the ground. Ditches were dug on the side using the loy, or turf cutter, and the overturned sod laid on top of the potatoes. Hilling up later in the season was done by digging deeper in the ditches. I have tried growing potatoes under mulch and it worked well. I don't do this now because it is more labor intensive than row cropping using a tiller and I grow a lot of potatoes. So, combining the chinampas and the lazy beds, I am going to lay out a grid with 4 foot wide raised beds and the soil will be provided by digging an 18" wide ditch on each side. The 18" is the width of my cultivating tiller, but I could actually go 2 feet wide since there will be some "roll-down" from the raised beds. A 4 foot wide raised bed allows me to reach 2 feet in from either ditch, so that is optimal. Right now my salad mix beds are 30" wide and I can straddle them if needed. However, if I dig my ditches deep enough, I can actually stand in the ditch and weed and harvest without bending over too much. Soil moisture should not be a problem and I can actually do some ditch irrigation if needed. This will certainly be cheaper than drip irrigation and should use less water than an impact sprinkler. I will also throw the biomass from weeding, cabbage leaves, stalks, etc. into the ditch to decompose. If I am tilling the ditch and there is plentiful soil moisture, the composting process in the ditches should be speeded up. An added benefit of raised beds is to gain an extra degree in soil temperature for each inch you have above the surrounding soil, so this system could actually allow earlier planting because of dryness AND warmer soil temps.
I am looking forward to testing out this idea. The fly in the ointment is the labor requirements. I already have access to more land for this experiment, and I might pitch it to a local high school for one of their projects. I could come out and help set up the markers, show the students how to dig efficiently and let them have at it. They could grow potatoes or any number of crops. Then, next year, we could see if we could get out on the chinampas a couple of weeks earlier than normal.