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Category: Blog
Texas Plant and Soil Lab has been testing soil since 1938, using a superior form of extraction method that mimics the way plant’s roots take up nutrients from the soil. Along the way, prominent TP&S Lab owner K. Chandler set the stage for our plant nutrition monitoring program, “Ask the Plant”. And since the late […]
Mon, 09 Mar 2015 18:43:55 +0000

Category: Blog, Lab News
Another PDF installment of Lab News from Texas Plant and Soil Lab! TPSL LAB NEWS FEBRUARY 2015
Thu, 05 Mar 2015 01:51:16 +0000

Category: Uncategorized, Farm Ranch and Dairy Magazine, Potato, Soil
TP&S Lab’s own Larry Zibilske, Ph.D., and Noel Garcia, C.C.A. penned the lead cover-story in the current edition of Western Farm, Ranch & Dairy Magazine. To order a physical copy you can contact them here: where you can also view all of their periodicals online: including our featured copy here:
Tue, 17 Feb 2015 21:40:34 +0000

Category: Blog, soil lab, soil testing
Texas Plant and Soil Lab has been testing soil for farmers and growers since 1938. And while technology advances and some tools become fancier and quicker, the process of testing soil remains largely the same. And while our nutritional standards are updated and refined each year based off last seasons success and ongoing environmental changes, […]
Thu, 12 Feb 2015 20:42:05 +0000

Compost Testing

Order Compost Testing Online
You can now order Compost Testing online. Ordering your compost testing online streamlines the process and provides online order status tracking.

Compost Testing Online Category Page
For the entire Compost Testing Category Page Click Here.

Compost Test Direct Links
To Click Through directly to the Compost Test you wish to order, choose from the list below:

Compost Testing Forms Download Links
To Download and Print forms for ordering Compost Testing, choose from the list below:

U.S. Composting Council

TP&S Lab is the 11th approved US Composting Council Seal of Testing Assurance ( USCC STA ) laboratory for all participating STA composters in the U.S. and Canada! You can find us listed at

Compost Testing and Organic Mix Testing

Composting testing is important for characterizing the beneficial physical and chemical properties of a compost as well as for identifying potential problems with compost use. TP&S Lab employs testing procedures from the U.S. Compost Council’s Test Methods for the Examination of Composting and Composts as well as some proprietary testing methodology that is also essential to measure the quality of your compost.

For example, TP&S Lab measures the humus fraction of the compost as well as the total organic matter to verify that the compost is fully mature. An indicator of compost maturity is high OM (humus) and Nitrate (NO3) > 30 ppm which indicates well matured (cured) compost by biologically active microbes releasing Nitrate (NO3). High OM (humus) and Nitrate (NO3) < 10 ppm indicates a very active to moderately active (curing stage) compost. Adjusting C : N ratio with fertilizer N or biologically with energy (molasses, fish, vegetable meals, etc.) will aid maturity. Just like a conventional fertilizer bag that comes with a guaranteed analysis and a label rate, we must also know the guaranteed analysis of composts to make sure that we apply safe rates to avoid accumulation of excessive mineral salts over time.

See Explanation of Soil Organic Matter here.

General Guidelines of Compost Testing and Organic Mix Testing

pH is a measure of active acidity in the feedstock or compost. Most finished composts will have pH values in the range of 5.0 to 8.5. Ideal pH depends on compost use. A lower pH is preferred for certain ornamental plants while a neutral pH is suitable for most applications. pH is not a measure of the total acidity or alkalinity and cannnot be used to predict the compost effect on soil pH.

Soluble salts are determined by measuring Electrical Conducity (EC) in a 1:5 (compost:water, weight ratio) slurry. Electrical Conducity (EC) is related to the total soluble salts dissolved in the slurry and is measured in units of millimhos/cm (mmho/cm). Composts typically range from 1 to 10 mmhos/cm. High salinity may be toxic to plants. Ideal soluble salt levels will depend on the end use of the compost. Final compost blends with soil or container media/potting mixes should be tested for soluble salts.

The ideal moisture content for composting will depend on the water holding capacity of the materials being composted. In general, high organic matter materials have a high water holding capacity and a higher ideal moisture content. A typical starting compost mix will have an ideal 65-45 % mositure. Finished compost should have a 50-40 % moisture.

Compost Testing Protocols

Review our Online Ordering Page for Compost Testing for a complete list of test descriptions and protocols.

Please contact us today at 956-383-0739 and speak with us
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Ask the Plant
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TP&S Lab is proud to be a member of the Texas Ag Industries Association.
Texas Wine & Grape Growers Association
TP&S Lab is proud to be a member of the Texas Wine and Grape Growers Association.
US Composting Council
TP&S Lab is proud to be an approved Lab by the U.S. Composting Council for Seal of Testing Assurance.
TP&S Lab is proud to be a member of the American Society for
Enology and Viticulture.
American Society for Enology and Viticulture
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