Soil nutrients and pollution in our garden soils
Recently we sent out soil samples to the UMass Soil and Plant Tissue Testing Laboratory for analysis of nutrients and other metals, such as lead. In addition, I measured dry weight % organic matter at University of Pittsburgh by burning a known mass of dehydrated garden soil at 550 C for four hours, and weighing it again to measure the mass lost (which is equivalent to organic matter %). It’s interesting to see the patterns that are apparent between the garden at my house versus Todd’s house. To characterize Todd’s and my garden, I took a sample from my two main garden plots, and sampled soil from Bed’s ‘A’ and ‘E’ in Todd’s garden. These two site were chosen because Bed A contains a layer of garden soil imported from AgRecycle, whereas Bed E contains soil largely in place prior to gardening. The data is plotted below.
Macronutrients appear to be high at each site.
And micronutrients appear to be at adequate levels.
Overall we have basic soils. Higher soil pH appears to correlate (R^2 = 0.86) with higher available calcium concentrations found in the macronutrient graph.
Organic matter concentrations are much higher at Todd’s. This is probably because people have been adding mulch to the soils at Todd’s garden over the last couple years and Bed A is composed of imported soil with mulch. The garden soil history at my garden is poorly known. The area was definitely a garden sometime in the recent past, and even possibly over the duration of the 103 year lifespan of the house I am living in. This year I pulled out weeds that were definitely growing for over a year prior to me moving in to the house. Overall, after digging around a bit, the back garden at my house appears to have the best soils (darker, less minerogenic, less coal ash), which do appear to correspond to higher organic matter concentrations.
Available lead and aluminum, which are toxic humans and plants, appear to be at low levels.