Geology & Soil Analysis

In addition to performing a soil analysis (below), I have done some research on the soils in my area. British Geological Survey maps show the geological bedrock to be alluvium. Sitting on top of the alluvium are “Loamey and Clayey soils with naturally high groundwater” (National Soils Resources Institute), or more scientifically “Dry Clay Loams, or Gleyo Eutric Fluvisols” (European Union Survey).

I took several pH measurements around the garden, thus:

Area	pH	Number on Map
Lawn (next to fruit bushes)	7.0	1
Vegetable plot	6.5	2
Orchard (centre, away from trees)	7.1	3
Nettle Stand	7.1	4
Compost Heap	7.0	5
Ash from recent fire	7.1	6

The 'Number on Map' column refers to the numbers visible on the Topology, Pedology Samples & Hydrology Contours map, in lime green. I made observations of soil samples from three of the areas above (the other two are not as functionally important to me):

Area	Description
1. Lawn (next to fruit bushes)	Very dark brown to black in colour. Clumps of soil. Grey appearance. Greasey smear mark on glass (forma 5- 10 cm clumps). Much undecomposed material; small twigs, and root- like.
2. Vegetable plot	More friable than above. Less clumped together. Some lumps, circa 1- 2 cm across. Light grease marks on side of glass. Loamy appearance, little undecomposed material. Intermediate in colour between sample 1 and sample 3. Dark brown.
3. Orchard (centre, away from trees)	Lighter brown in colour. Some undecomposed material; rootlets, blades of grass, etc. More clumps than sample 2 about 1-2 cm across. One larger clump c 10cm. No reasemarks on glass. Examination with a x 10 handlens reveals occasional grains of sand, which are absent with sample 1.

 

The results in all cases are indicative of clay loams. All samples have virtually no silt, but varying degrees of sand and mostly clay. Samples 1 and 3 have the largest fraction of clay, and a modicum of sand (10- 20%). Sample 2 (from the vegetable plot) however, has a larger proportion of sand (circa 40%), and also a lower pH (the standout value of 6.5 from the table above). This is not so surprising when we consider the vegetable plot has been used historically, and was used in recent years to grow vegetables following a hiatus for an unknown period of time. I delivered a topping of manure to the plot about a year ago, which may account for the lower pH (plus the sandier condition of the plot). Samples 1 and 3 are more akin to the ‘natural’ state of the soil. I would hazard a guess that the area which floods (sample 1) which is more clay- like than any of the other samples, and accounts for a slight hollow in the lawn, has had a layer of topsoil removed which was transported to the vegetable plot. This would make sense. The bungalow was built in the inter- war period. Self sufficiency and vegetable growing was much more prevalent than today, and the homeowner no doubt needed to extract as much productivity from the thin soils as possible in their vegetable plot, and could afford to sacrifice a bit of lawn, although the seasonal flooding may have come as a surprise. All of this is conjecture, but explains the nature of the soils I have analysed.  

From left to right: soil jar test samples from the lawn, vegetable plots, and orchard respectively.