Soil Chemistry Tests
(Go Back to Bioretention Home)

Soil is a mixture of minerals, organic matter, water, and air.  It has a definite structure and composition, and forms on the surface of land.  Many soils have three major layers: top soil, subsoil, and parent matter.  These layers make up the soil profile.  The soil profile represents the succession of distinctive soil layers from the surface down to the unchanged parent material beneath it. 

We are mainly concerned here with the top soil since it is here that the living and nonliving link together to support the plants in the bioretention system.  High quality top soil is usually dark brown, dark gray, or black because of the humus it contains.  Humus is the highly decomposed plant and animal residue that makes up much of the organic nutrients composing the soil.  Because of its texture, a good topsoil will hold adequate moisture and allow air to circulate, which are required for photosynthesis to take place in plants.  Decomposers break down humus to free the nitrates, phosphates, and potassium that are required by plants.  Fertile soils contain and are able to supply a complete set of nutrients required by growing plants. 

The major essential nutrient elements supplied through soil are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.  Soil pH is an important property since it affects the availability of nutrients to plants. The nutrients described above tend to be less available to plants in soils with low pH. Other major nutrients like carbon, hydrogen, and oxygen come from water and atmospheric carbon.  Nitrogen, phosphorus, and potassium are of particular interest to farmers and other plant growers since plants require relatively large quantities of these elements.  When plant materials are harvested over and over from the same area, the soils are quickly depleted of these elements.  This is why the main components of fertilizers are nitrogen, phosphorus, and potassium.  However, excess amounts of these three components in water systems can be detrimental and lead to the premature aging of ponds and lakes (eutrophication). For more information on soil please visit the University of Missouri Soil and Plant Testing Laboratory website, the How Stuff Works website on fertilizers, and the North Carolina Dept of Agriculture website. For more information on lead in soil please visit the UMass Soil Testing Site and the CDCs site on the Impacts of Lead Exposure.

Acceptable Readings
Soil Texture
A mixture of Sand, Silt, & Clay
pH
5.5 - 7.8
Potassium
120 - 420 lb/a
Phosphorus
15 - 90 lb/a
Nitrogen
20 - 200 lb/a
Lead

Normal Levels ~50 ppm
If >300ppm pregnant women and childred should avoid contact


Data 09/11/07
Data 04/16/08
Data 11/19/08

Data 04/16/09
Data 11/09/09

Soil Tests Performed on November 9, 2009
Test
Cell 1
Cell 2

Cell 3

Prairie
Soil Texture

47% Sand

40% Silt

13% Clay

27% Sand

47% Silt

26% Clay

30 % Sand

13 % Silt

56 % Clay

80 % Sand

20 % Silt

0 % Clay

pH
6.75
6.5
7.25
7.0
Potassium
260 lb/a
300 lb/a
400 lb/a
300 lb/a
Phosphorus
200 lb/a
100 lb/a
175 lb/a
100 lb/a
Nitrogen
10 lb/a
10 lb/a
10 lb/a
10 lb/a
Water %
19.4 %
30.0 %
20.9 %
14.6 %
Lead Presence?
>100 ppm
>100 ppm
> 100 ppm
> 100 ppm
Recent Climate Data
11/09
11/08
11/07
11/06
11/05
Temp Hi/Lo
         
Precip (in)
         

 


Soil Tests Performed on April 16, 2009
Test
Cell 1
Cell 2

Cell 3

Soil Texture

13 % Sand

40 % Silt

47 % Clay

33.3 % Sand

60 % Silt

6.6 % Clay

18 % Sand

44 % Silt

38 % Clay

pH
6.5
7.5
7
Potassium
350 lb/a
300 lb/a
400 lb/a
Phosphorus
200 lb/a
200 lb/a
180 lb/a
Nitrogen
10 lb/a
10 lb/a
10 lb/a
Water %
31.0 %
20.2 %
21.1 %
Recent Climate Data
04/16/09
04/15/09
04/14/09
04/13/09
04/12/09
Temp Hi/Lo
62/39
63/35
47/42
53/45
54/37
Precip (in)
0
0
0
0.09
.41

Soil Tests Performed on November 19, 2008
Test
Cell 1
Cell 2

Cell 3

Soil Texture

76.5 % Sand

8 % Silt

15.5 % Clay

14.2 % Sand

80.2 % Silt

5.6 % Clay

26.5 % Sand

48 % Silt

25.5 % Clay

pH
6
7.25
7.25
Potassium
240 lb/a
300 lb/a
400 lb/a
Phosphorus
237.5 lb/a
75 lb/a
200 lb/a
Nitrogen
15 lb/a
15 lb/a
25 lb/a
Water %
29.2 %
26.3 %
22.3 %
Recent Climate Data
11/19/08
11/18/08
11/17/08
11/16/08
11/15/08
Temp Hi/Lo
55/30
38/25
44/32
56/30
45/35
Precip (in)
0
0
0
0
.01

 

Soil Tests Performed on April 16, 2008
Test
Cell 1
Cell 2

Cell 3

Soil Texture

39.5% Sand

58% Silt

2.5% Clay

31.5% Sand

38.3% Silt

30% Clay

36% Sand

49.5% Silt

15.5% Clay

pH
6
6.5
7
Potassium
332 lb/a
300 lb/a
360 lb/a
Phosphorus
137.5 lb/a
125 lb/a
175 lb/a
Nitrogen
20 lb/a
27.5 lb/a
17.5 lb/a
Water %
22.4%
21.3%
21.5%
Recent Climate Data
04/16/08
04/15/08
04/14/08
04/13/08
04/12/08
Temp Hi/Lo
72/42
60/29
50/33
43/36
46/37
Precip (in)
0
0
0
.07
.07

Soil Tests Performed on Sept 11, 2007
Test
Cell 1
Cell 2

Cell 3

Soil Texture

66.7% Sand

43.3% Silt

0% Clay

73% Sand

27% Silt

0% Clay

13% Sand

70% Silt

17% Clay

pH
6.5
7
8
Potassium
400 lb/a
400 lb/a
350 lb/a
Phosphorus
200 lb/a
150 lb/a
150 lb/a
Nitrogen
10 lb/a
10 lb/a
15 lb/a
Water %
19.2%
26.3%
29.6%
Recent Climate Data
09/11/07
09/10/07
09/09/07
09/08/07
09/07/07
Temp Hi/Lo
77/49
87/62
86/64
79/71
82/71
Precip (in)
0
0.02
0
.17
.72