As faithful readers may recall, we highly recommend soil testing at the SACG. We tested our soil when we started in 2009, in no small part to avoid lead and other toxic pollutants from finding their way into our produce from the soil. (Rumor has it that lead can get into the soil when buildings with old lead paint are demolished on the site and the construction debris is left behind – like it was at the SACG). Soil testing also determines whether the soil has the correct pH to grow vegetables and fruits. Since we started in 2009, we have greatly improved our soil with approximately 4 inches of compost and soil acidifier (i.e., peat moss and aluminum sulfate). This time, we had our soil tested for $15 by CLC Labs in Westerville (which, unlike the University of Massachusetts at Amherst, does not test for lead for the same low price).
By way of comparison, in 2009, our soil was very alkaline (i.e., 7.7 pH). In 2011, we now have a neutral pH of 7.0 from adding lots of compost (from Kurtz Brothers and Com-Til Plus), peat moss and soil acidifier. Ideally, I’m aiming for a pH of 6.8.
Our soil still is over-the-top in nutrients. We are in surplus for Phosphorus, Potassium and Magnesium. We had 200+ pounds per acre (PPA) for Phosphorus, 939 PPA for Potassium and 969 PPA for Magnesium. We are "high" for the Base Saturation Percentage for Potassium (6.6) and Magnesium (22). We are “medium” for Calcium (5156) and for the Base Saturation Percentage for Calcium (71). Finally, we were rated “high” for fertilizer maintenance level with nitrogen rates of 3.0 to 4.0. In other words, if we feel the need to add any more fertilizer, it should just be something rated 4-0-0. If you’ve seen our garden, however, you know that we are not hurting for nitrogen.
The SACG has greatly benefitted from great soil, a great location for sun exposure (i.e., no buildings to our immediate east or west) and a slight incline (for good drainage). Of course, we have at least a ten-foot barrier between the garden and any pavement to prevent run-off into the stormwater sewers which empty into Alum Creek.
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