Does Soil Biology Influence Soil Chemistry? Yes, It Does!

Johnson-Landview property

By Betsy Ross

Working with landowners in Texas, we’ve found that soil biology amendments can “shift” or alter nutrient values on a soil chemistry test. The following case study provides details on site conditions, the sequence of soil sampling and biology treatments, and soil test data.

Our company, Sustainable Growth Texas, LLC, uses bio-spray field treatments to help restore life in the soil.  Many of our clients are rural landowners in Texas with pasture lands.  Our motto is “better soil, better life”.

Project Site: The site had sandy loam soil and was located in Gonzales County, Texas.  The landowners had signed up for an EQUIP program from their local NRCS office.  They had just finished clearing heavy understory brush among Post Oak trees.


Here is the sequence of events:

1. Fall 2006.  Two areas were cleared of heavy brush and trees. Pasture 4 (P4) was sloped, rocky, and loaded with iron pebble. Pasture 6 (P6) was flat with deep sand.

2. April 1, 2007.  Soil samples were collected by NRCS. (These never came back from the Texas A&M Soil Lab, so NRCS didn’t make fertility recommendations.)

3. April 10-11, 2007.  Landowners planted Tifton 85 bermuda on land that had been lightly disced and harrowed, but not ploughed up.  No herbicides were applied.  (Landowners had gotten some rain so they went ahead and planted.  They told NRCS they were going organic and were going to use SGTx’s soil biology program.)

4. April 13, 2007.  Soil samples were collected again by NRCS, then analyzed at Texas A&M (TAMU).

For P4, TAMU recommended:  80 lbs N/acre; 50 lbs of  P2O5/acre; and 75 lbs of K20/acre.

For P6, TAMU recommended:  90 lbs of N/acre; 60 lbs of P2O5/acre,  and split applications of 90 lbs of K2O/acre; plus an additional 70 lbs N/acre for each subsequent heavy graze down.

Note:  The owners did not apply recommended fertilizers.  Instead they relied on the SGTx bio-spray field treatments.


Table:  Soil Chemistry Results, Six Months Apart, Comparing Before and After Two Treatments of a Liquid Compost Extract-based Bio-Spray Blend

Texas A&M Soil Lab Pasture 4
April 13, 2007
Pasture 4
Sept 17, 2007
Pasture 6
April 13, 2007
Pasture 6
Sept 17, 2007
pH 5.9 5.7 5.9 8.6
Conductivity 74 117 38 138
Nitrate-N 10 ppm (ExLow) 1  (ExLow) 3 (ExLow) 7 (ExLow)
Phosphorus 14 ppm (Low) 16 (Low) 6 (VLow) 46 (Mod)
Potassium 73 ppm (Low) 100 (Med) 59 (Low) 402 (VHigh)
Calcium 691 ppm (CL) 1,660 (CL) 451 (CL) 3,926 (High)
Magnesium 97 ppm (CL) 180 (CL) 51 (CL) 371 (High)
Sulfur 13 ppm (CL) 14 (CL) 8 (Mod) 21 (High)
Sodium 116 ppm (Low) 127 (Low) 98 (Low) 147 (Low)
Iron 37 ppm (High)
Zinc 2.02 ppm (High)
Manganese 20 ppm (VHigh)
Copper 0.20 ppm (CL)
CL = Critical Level 
CL is the point which no additional nutrient is recommended (excluding NO-3). The Critical Level lies between Moderate and High.
ppm = parts per million All nutrients in ppm

5. May 19, 2007.  SGTx collected soil samples and sent them to Soil Foodweb Inc-NY Lab for soil biology analysis.  The microbial biomass readings for Total Bacteria (297 ug/g) and Total Fungi (287 ug/g) were sufficient, in our estimation, to respond to soil biology treatments.

6. June 2, 2007.  SGTx applied the 1st application of Liquid Biological Amendment (LBA) at 20 gallons per acre.  The LBA was a bacterial dominated Liquid Compost Extract (LCE) with kelp, humic acid and molasses added as microbial food sources.

7. June 31, 2007.  Landowners mowed the bermuda grass stand.

8. July 3, 2007.   SGTx applied the 2nd application of LBA at 20 gallons per acre. This was, likewise, a bacterial dominated LCE with increased amounts of  kelp, humic acid and molasses added to help mitigate summer heat stress; Pasture 4 received an extra heavy dose for bio-stimulation.

9. Sept 13, 2007.  Soil samples were collected by NRCS.  When NRCS drove up to check the planting, they remarked,  “This is the best looking new Tifton 85 pasture in the county.  Did you apply our soil fertility recommendations?”  The owners replied, “No, as we explained, we are using Liquid Compost Extract.”

When the Texas A&M lab tests came back from the September sampling date, NRCS recommended they spread chicken litter as an organic source of nitrogen.

The landowners applied chicken litter in 2008.  The pasture grass was well established and cattle were brought in for grazing.  No further biological applications have been made to the site.

Based on the Texas A&M soil chemistry tests, it is clear that many of the nutrient levels changed in the soil. The only soil treatment made to the site was Liquid Compost Extract amended with microbial food sources.

So back to the question posed in the title of this case study: Can soil biology amendments “shift”, “alter”, or “improve” soil nutrients on a soil chemistry test? Yes, it does!  This is one example of many sites in Texas where we’ve seen this happen.

Liquid Compost Extract contains billions of living micro-organisms from diverse microbial groups.  When LCE is applied to land in the form of a fortified bio-spray, the microbes colonize soil and root surfaces.  When nutrients are needed by the plant, microorganisms living in the rhizosphere interact with soil particles and the clay-humus matrix and thereby make plant nutrients available to plants for growth.

Dung Beetles at Work!

And look what else came back to the site after soil life was replenished:  Dung beetles!

Sustainable Growth Texas, LLC is an agriculture company with headquarters in Granger, Texas.  Working premises is that natural systems, driven by the soil food web, are as effective as chemical, synthetically driven systems. December 2008 ©.

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