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Introduction:

This test was performed to investigate whether the addition of SoilTech to various soils can support the claim "aerates soil". Many users claim that SoilTech improves lawn drainage and makes zoysia grass and bermuda grass care easy.

It is widely accepted that soils with poor structure break down to a mud as the amount of water is increased thereby reducing the amount of oxygen available to the plant roots. Air components such as oxygen and nitrogen diffuse through the soil profile. When water is added much less air diffuses through the thick water films.

Question:

Does SoilTech increase the soil respiration rate of treated soils versus non-treated soils?

Purpose:

Soil respiration (aeration) is directly affected by the amount of moisture contained within the soil. Soils will reach a point of saturation, which is the level when aeration or the diffusion of air ceases. At this point plant growth is affected and can be detrimental if the soil remains saturated for a period of time. This test explores the potential of soils that have been treated with SoilTech, to increase the amount of moisture contained before reaching saturation, and increasing aeration at lower moisture levels.

Materials and Methods:

Soil respiration rate is measured by the production of carbon dioxide (CO2) as an indicator of aerobic microorganism activity, live roots, and soil organisms. Soil respiration is essential for the establishment and maintenance of a healthy plant community therefore is considered a positive indicator of soil quality.

The accessibility of oxygen to live plant roots in soil in the various amounts of water is measured by the technique of Webley, Quastel et al., described in detail in the J. Agr. Sci. 37, 257 , (1947). Yeast was substituted for the plant roots and the oxygen uptake by the yeast is measured by a manometric method. The carbon dioxide evolved (respiration) in the metabolic process is absorbed by potassium hydroxide in a center well so that the change in gas volume is caused by the utilization of oxygen by the yeast and the soil microorganisms.

Ten replications of each soil type at four soil moisture % levels were performed to achieve an average result. Three selected topsoils were air-dried, pulverized, and screened to pass a one mm sieve. Each topsoil was then equally divided into ten 100 gm portions. (30 portions total-10 of each topsoil type). Then five 100 gm portions of each of the three topsoils were treated with 40 ml of water. Then the remaining topsoil samples (five of each soil type) were treated with a water solution containing 2.5% SoilTech. Each of the wet soil samples were then broken up, and allowed to air dry. Then each sample was broken up further to pass a 4 mm sieve. Crumbs 4mm or less were collected for each sample. These crumbs were then used in each flask for the evaluation of soil respiration.

Test Results:

Respiration Rate and Soil Moisture %

Soil Types

% SoilTech

Soil Moisture %

25%

37.5%

50%

62.5%

OK Chandler Clay

None

77

43

16

0

2.5

110

97

52

12

Bixby Sandy Loam

None

112

91

51

6

2.5

134

120

68

22

Black Gumbo (KS)

None

89

50

23

0

2.5

102

76

39

8

Interpretation:

The respiration rate measured by the Warburg apparatus should be as high as possible in the presence of the maximum soil moisture levels. All soils become saturated if enough water is added thereby preventing access of air. In this condition, the respiration rate of the soil cannot be measured therefore the result shown in the above chart is "0". As the soil moisture % increases the respiration rate decreases until the soil becomes saturated and further growth of the yeast stops.

Conclusion:

Soils with good aggregate stability retain their porous crumb structure in the presence of large amounts of water. The yeast suspension in water is spread over a large surface and oxygen can diffuse through relatively thin films of water. This increases oxygen uptake by the yeast, thereby increasing the soil respiration rate. Soils with poor structure break down to a mud as the amount of water are increased and much less oxygen diffuses through these thick water films. Thus the oxygen uptake by yeast in this type of soil is much lower.

SoilTech in all three soils demonstrated an increase in the respiration rate at all tested soil moisture levels. This supports the claim that SoilTech "aerates soil".