Wednesday, April 20, 2011

Soil test in garden box

My wife found a soil test kit similar to the one shown at the right. She wanted to see if all of the amendments which we have put into our garden box is at the right levels. We have added quite a few things, so we felt that it should be doing fairly well across the board. We knew that our soil is really alkaline, so that is one of the first things that we looked at. Here are our findings:
  1. pH: Adding a lot of organic matter in a raised bed is going to mean that you are avoiding many of the problem in the natural soil. In our case, the test showed that the pH is essentially neutral, unlike most of the surrounding soil. This was a good validation!
  2. Nitrogen: It was surprising that the Nitrogen levels of this garden box were extremely low. This is after adding six bags of manure and some blood meal, which is high in Nitrogen. The only thing that I can think of is that there is probably a lot of high-Carbon organic matter mixed into the soil that hasn't decomposed completely. This will tie up much of the available Nitrogen. I was hoping that this wouldn't be the case, but it looks like it is a problem. I suppose that I could top-dress the soil with more aged manure, since we have already planted a lot of peas and lettuce (which hasn't sprouted, by the way) or we could call those seeds a loss and add a bunch more fertilizer and till it in. (We'll have to decide.)
  3. Phosphorus: This test showed that the soil sample was moderately high in Phosphorus. With all of the amendments this was expected. No need for further amendments here.
  4. Potassium (Potash): This test showed that the soil sample was high in Potassium.
Once we overcome the problem with the Nitrogen, all of the other tests showed that we have good levels in the other measurable levels. The Nitrogen problem may even be the cause of the seeds not sprouting. (It is nice to have some reason behind failures, even if not all of the evidence is known.)

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