More snow yesterday—a lot more snow—means that it is still too early to be thinking about starting any work on the garden outside. At this rate of snowstorms, we won’t be digging out until March.
That is just as well because there are still a few items from last year to recap. Most notably, there are the results of the soil testing that arrived at the end of October (2013) but which I have not had a chance to discuss.
Based on the previous year’s testing, I was not expecting any startling new information for the east and west planters (see October 19, 2013, part 2). Sure enough, the reports confirmed my expectations. The all-important pH of the soil remains within the sweet spot (6.20 to 6.80) for vegetable gardens with the east planter at 6.57 and the west planter a tad more acidic at 6.23.
Interestingly, the soil pH of the east planter increased slightly (from 6.31 in 2012) while the soil pH of the west planter decreased (it was 6.78 in 2012). The soil in the east planter is now squarely within the preferred range but the soil in the west planter is bouncing from endpoint to endpoint. Both are perfectly fine, however, and we will not have to make pH adjustment to either.
Similarly, the macro- (Ca, K, Mg and P) and micronutrient (B, Cu, Fe, Mn and Zn) concentrations in the east and west planters are close to each other, a result, I think, of at least three factors. First, we treat the planters identically; neither has received any amendments (other than a top dressing of compost at the beginning of the season) or more fertilizer than the other.
Second, we have been rotating crops back and forth between the planters. Therefore, their soils have been depleted (or replenished) by more or less the same amount. Third, the age of the soil in each planter is more than two years. I assume that given their consistent treatment, both soils are converging on the same steady state.
For the most part, the micronutrient levels in the west planter decreased when compared to last year (i.e., 2012). This is not too surprising, again considering that we don’t heavily fertilize or otherwise modify our soil during the growing season (I think of it as time smoothing the soil’s rough edges). Micronutrient levels in the east planter are mostly the same as 2012 (its soil is older and smoother).
What I didn’t expect is that in both planters, the concentration of Calcium increased by almost 50 percent. We did not add lime, bone meal or any other source of the micronutrient so I have no idea from where the additional Calcium comes.
So much for the well-established planters. On to the ground level soil, where we planted squash and cucumbers last season.
For starters, the pH of this soil is too high at 7.10 (the soil is slightly alkaline). We’ve learned from both of the growing seasons prior to last that this can have a very detrimental effect on plant performance. And I learned from this year’s experiments with seed starting mix that the culprit is probably not the very acidic peat moss, of which the ground level soil is roughly half. The other half is compost (mainly cow manure) which tends to be more alkaline.
When we dig new pits for the squash and cucumbers this year, we will have to increase the proportion of peat moss to manure and perhaps add some elemental Sulfur to bring the pH down. Otherwise, the ground soil profile resembles that of the planters. The macro- and micronutrient concentrations are very close, including—somewhat mysteriously—the high concentration of Calcium.
This is a bit ironic because the summer squash plants experienced a high rate of blossom end rot last season, a condition that is usually associated with Calcium deficiency. I think this is what the testing lab was alluding to when they called me in the fall (see October 24, 2013). The testing methods based on acid extraction indicate a high concentration of Calcium but it is not, apparently, in a form that plants can readily use. I’ll have to look into this one further.
The reports list lots of numbers, not all of them obviously meaningful. So, what does it all mean? The bottom line is that our planters’ soil is doing fine and that with minor modification the soil in the ground will come into line as well. That’s good—if not exciting—news.
garden engineer 
I’m sure if I had the smarts like you I’d have a MUCH more efficient garden. I’ve never had my soil tested! And basically just guess. An LOL escaped me when I saw your planters looking buried and tiny (and I know they are large!) in the snow. I would think the minerals from the snow melt would be good for the garden, something we know nothing of in Los Angeles, and rain is almost as rare.
I don’t know how smart it is but the testing and its results are definitely interesting. After three years of it, I’ve concluded that knowing the soil’s pH is the most important thing and I will be looking into easier, quicker (and cheaper) ways to monitor it. I often makes guesses, too—it is the way of gardening—and hope that by checking the outcomes of guessing, my judgment will eventually improve. Thanks (and I hope LA gets a nice, long, soaking rain at the end of the week).