Potting mix considerations

I have been doing a lot of thinking and reading about potting mix recently. For one thing, it is only four months till we start seedlings for 2016! (And only a month or so before we winter plant seed for perennials.) For another thing, I am thinking about using lots of wicking planters for greens in the upcoming year to improve their survival in our dry climate. Finally, a movable greenhouse has many benefits. I have been considering making our hoop house on the Littleton farm moveable. That way, we could start hardy spring greens, and then, once they were going and the weather was a bit more moderate, I could slide it away and start summer seedlings on the new site. Right now, spring plants languish in the increasing heat in the house, while delaying the summer tomatoes and peppers, and the tomatoes keep out the Fall kale and lettuce. However, a movable greenhouse is a big investment, and it might be better to just plant everything in containers, and then move and swap those. An unproven idea that we might try.

Anyway, there are lots of reasons for me to be considering potting mix strategies right now. For the past ten years or so, I have been using compost/ peat/ perlite type potting mixes. They are a logical extension to my organic gardening philosophy of feeding the soil, not the plant. However, I just now did some research and found a forum thread where a member was advocating a bark/ peat/ perlite mix, with the ratios being 5 1 1, very light and airy. They then add some commercial slow release inorganic fertilizer. The reasoning behind this is that a pot of fine grained potting mix contains a perched water table, where the natural attraction of the water to the soil particles is greater then gravitational pull. This zone becomes airless and is off limits to roots. So, some advocate separating the two functions of potting mix; structural support, and the provisions of nutrients.  Of course, this is just what conventional farmers do; they view the soil as an inert medium for holding plant roots, and then douse the soil with chemical fertilizer. However, since the pot is already an artificial growing area with different conditions then the soil, it makes sense that a different approach might be warranted. As an organic gardener, I would use organic slow release fertilizer, or a liquid fish/ kelp product if I switch over to a coarse grained medium.

I may do some experiments to compare the two approaches.

I also may include a small pot or bag of worm castings in larger, long term pots, which would provide fertilization without gumming up the whole pot.

Here is a link to the forum thread that got me interested in this: http://forums2.gardenweb.com/discussions/2842847/container-soils-water-movement-and-retention-xxii?n=329


notes from the work meeting, March 15th

We got one length of the wire fence up, which runs across the width of the property. It should keep out rabbits and groundhogs, and, with the addition of an electric wire, it will help keep out raccoons and squirrels. We still need to deconstruct and replace the fencing on the other three sides.
The fruit trees have now been ordered. They should arrive in the first week of April.
We got a lot of work done on the next set of planting beds. These will be hugelkulture/ raised beds. We are digging down about six inches, and then piling on lots of sticks, putting the dirt and sod on top of them, and layering on leaves, manure and wood chips. It will basically be a big thick sheet mulch. Since they are being built on a slope, we will edge the downhill side with rocks to form a sort of terrace. Unlike our last hugelkulture, it will not have a deep trench in the center, and it will be under two feet deep.
We are still removing trees and brush along the bottom of the property, generating firewood, and piles of sticks for hugelkultures.
There are two problems with our greenhouse. The beds tend to dry out too fast, so the batch of lettuce we planted germinated erratically. We will be solving this with a combination of more watering, clay seed balls, and self watering planters. And the entrance does not close well. So we will be attaching weights to the bottom of the flap door, and installing a PVC pipe and clamps along the vertical edge. However, it is much warmer inside than out, and the automatic vent seems to be working well.

notes from the work day March 12th

At this work day we removed and cut back cotton wood trees along the ditch and fence line. We want to get this done before our new fence is build. The fence project will start at the next meeting. We will use the sticks from the trees to make a large hugelkulture, and we will use sections of the trunks to stabilize a slope.

We discussed our fruit trees, which we will be ordering soon. And we found that it is difficult keeping surface planted seeds such as lettuce moist in the greenhouse, since we are not on the site every day to water. So we will be constructing self watering planters out of salvaged five gallon buckets, starting seeds in them, and then transplanting the seedlings into the beds. This way the surface layer drying out will not be quite such a concern.