Soil Testing at Texas A&M: 2026 West Texas Glossary

TL;DR

The Texas A&M Soil, Water and Forage Testing Laboratory has been analyzing soil samples since 1946 and remains the go-to resource for Texas homeowners, farmers, and arborists. West Texas soils are almost always alkaline (pH 7.5 to 8.5+), which locks up iron, phosphorus, and zinc, making professional soil testing essential rather than optional. This glossary breaks down every term you’ll encounter on a TAMU soil test report, explains what the numbers mean for Lubbock-area landscapes and trees, and helps you decide when to call in a professional.

What Is the Texas A&M Soil Testing Laboratory?

The Soil, Water and Forage Testing Laboratory is operated by the Department of Soil and Crop Sciences within Texas A&M AgriLife Extension Service. It began operations in 1946 primarily as a soil testing laboratory. Over the following decades, the lab added irrigation water testing, plant and forage analysis, and other services. Today it provides research-based analyses for Texans and customers throughout the continental United States.

The lab is located in College Station, Texas, and is open 8 a.m. to 5 p.m., Monday through Friday, following the Texas A&M University holiday calendar. Soil testing at Texas A&M focuses on nutrient levels, pH, salinity, and soil texture, all with the goal of maintaining or improving plant growth.

For West Texas homeowners, understanding this lab matters because the soils around Lubbock, sitting on the Llano Estacado, behave very differently from soils in East or Central Texas. The TAMU lab provides calibrated recommendations based on the extraction methods best suited to your soil type.

If you want to understand how soil test data connects to tree nutrition and irrigation decisions,our soil testing guide walks through the full process for West Texas properties.

The Lab and Its Services

AgriLife Extension Service

The broader university outreach system that houses the soil testing lab. AgriLife Extension operates through county offices across Texas, and each county extension agent can help you interpret TAMU results. For Lubbock residents, the Lubbock County Extension office is a free local resource.

Routine Analysis

The least expensive and most common test. It reports levels of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, sodium, boron, conductivity, and pH. For most homeowners maintaining lawns, gardens, or landscape beds, this is the right starting point. As of 2025, boron via the Mehlich III extract has become a standard component of the routine test, replacing the older hot water-soluble boron method.

Micronutrient Analysis

An add-on that tests zinc, iron, copper, and manganese. In West Texas, this test is particularly valuable because high pH locks up micronutrients, especially iron. If your trees show yellowing leaves with green veins, a micronutrient panel can confirm whether iron deficiency is the problem.

Detailed Salinity Analysis

Costs $37 when bundled with the routine test. It uses a saturated paste extract to measure calcium, magnesium, potassium, sodium, conductivity, pH, and the sodium adsorption ratio (SAR). Given that well water in West Texas often contains elevated sodium levels that home soil tests cannot detect, this analysis is worth the extra cost for properties on well water.

Complete/Comprehensive Analysis

The most thorough option, combining routine testing with micronutrient, organic matter, detailed salinity, and textural analysis. TAMU describes this suite as providing the most comprehensive data needed for troubleshooting most plant and soil growing issues. Pricing is valid through December 31, 2026. Note that organic matter analysis is currently delayed due to supply chain issues, though the lab continues processing all other analyses.

Plant Tissue Testing

A separate analysis that examines nutrient concentrations in leaf tissue rather than soil. Approximately one pint of semi-compacted leaves is needed. For trees, the most fully developed leaves from the mid-third of the canopy are preferred. Plant tissue analyses will not directly indicate the cause of plant death. They detect nutrient toxicities or deficiencies only in living, yet sickened, plant tissues. This distinction matters: if a tree is already dead, tissue testing won’t tell you why. If it’s struggling but alive, tissue testing can reveal exactly which nutrients are lacking.

Texas Plant Disease Diagnostic Lab (TPDDL)

A separate facility from the soil testing lab. The TPDDL identifies plant disease problems for extension personnel, homeowners, arborists, and consultants. At peak time (spring through fall), routine diagnoses take 11 to 21 days. Specimens requiring specialized testing need more time. Oak wilt testing, for example, takes a minimum of 21 days.

Sampling Terms You Should Know

Composite Sample

Rather than testing one scoop of dirt, TAMU wants you to collect 8 to 10 cores from across the area being tested, mix them thoroughly, and submit the blend. This composite approach gives an accurate average rather than a single random snapshot. Cut each core or divot 6 inches deep. Remove roots, mix well, and fill a quart-sized resealable freezer bag half to three-quarters full.

Sampling Depth

Texas A&M AgriLife bases recommendations on soil test calibrations for 6-inch soil samples. This is the standard for lawns, gardens, and most landscape applications. Dr. Calvin Trostle, Extension Agronomist at TAMU Lubbock, notes that consultants and producers in the Texas High Plains report they are generally able to sample to 18 inches without much difficulty when deeper profiles are needed for agronomic crops.

Air Drying

You can air dry samples before shipping, but do not use heat. Oven-drying or microwaving alters the chemical properties the lab is trying to measure.

Sample Contamination

Do not put your sample in a galvanized bucket. Galvanized metal contains zinc, which will skew micronutrient results. Any sturdy zip-closure bag with sample identification written on it is acceptable. Special bags are not required.

Urban vs. Agricultural Submittal Forms

The urban soil submittal form covers small-area landscapes, lawns, gardens, and simpler-sized areas. It is the form most Lubbock homeowners should use. The agricultural form handles larger landscapes, agronomic-sized fields, pastures, and forage systems. One third-party guide author noted visiting the A&M soil test website more than 20 times before discovering the online payment option, so take your time navigating the forms.

Soil Chemistry Terms: Reading Your Report

pH

A scale measuring acidity or alkalinity on a range from 0 to 14, with 7.0 being neutral. West, Central, and South Texas generally exhibit alkaline soil with pH often ranging from 7.5 to 8.5 or higher. Soils of the Llano Estacado hover around a pH of about 7.8. This single number drives nearly every other recommendation on the report. As one experienced member of The Lawn Forum put it when discussing soil testing at Texas A&M: what matters most is “Primarily: pH, pH, pH.”

Electrical Conductivity (EC)

Measures dissolved salts in the soil. Expressed in units like dS/m (deciSiemens per meter). High EC indicates salinity problems, which are becoming an increasing concern in West Texas due to excessive use of nitrogen fertilizers and irrigation. If your report shows elevated conductivity, adjusting your irrigation approach becomes a priority.

Mehlich III Extraction

The specific chemical method TAMU uses to estimate plant-available nutrients. Phosphorus, potassium, calcium, magnesium, sodium, sulfur, and boron are all extracted using the Mehlich III extractant and measured by ICP (inductively coupled plasma) spectroscopy. Forum users sometimes debate extraction methods between labs. The consensus among knowledgeable practitioners on The Lawn Forum is clear: more important than the lab itself is selecting the proper extraction method for the soil being tested, and TAMU uses the right one for Texas soils. As one experienced member concluded, “TAMU is a fine Lab.”

Critical Level (CL)

The threshold concentration above which no additional nutrient is recommended. Your TAMU report lists each nutrient concentration alongside its critical level. If your phosphorus reading is above the CL, you do not need to add more phosphorus. Simple as that. This is one of the most practical numbers on the entire report, yet most homeowners skip right past it.

Macronutrients (N-P-K)

Nitrogen (N), phosphorus (P), and potassium (K) are the primary nutrients plants need in the largest quantities. These are the three numbers on any fertilizer bag. One forum poster admitted that for years he “just followed the fertilizer bag instructions and applied whatever fertilizer I had bought,” and soil testing at Texas A&M revealed specific deficiencies he had been missing entirely.

Secondary Nutrients

Calcium, magnesium, and sulfur. In West Texas, calcium is almost never deficient (it is the main component of caliche). Sulfur, on the other hand, can run low. TAMU’s routine analysis covers all three.

Micronutrients

Zinc, iron, copper, manganese, and boron. Required in small amounts, but their absence causes visible problems. Iron deficiency is the most common micronutrient issue in alkaline West Texas soils because high pH makes iron unavailable to roots even when it is physically present in the ground. Practitioners on lawn care forums consistently note that with high soil pH, foliar iron application will have better success than soil-applied iron.

Sodium Adsorption Ratio (SAR)

A calculated ratio indicating how much sodium is present relative to calcium and magnesium. High SAR means sodium dominates, which degrades soil structure, reduces drainage, and harms roots. Well water in West Texas often carries enough sodium to push SAR into problematic ranges. The detailed salinity test from TAMU includes this number. If your landscape has drainage problems, a high SAR could be contributing.

Cation Exchange Capacity (CEC)

The soil’s ability to hold and release positively charged nutrients like potassium, calcium, and magnesium. Sandy soils have low CEC; clay soils have higher CEC. TAMU does not always list CEC directly on the report, but forum experts calculate it from the data provided. One Lawn Forum member calculated a CEC of 2 from TAMU results and called it “dismal,” explaining that with very low CEC, you should “spoonfeed, like a half application every 2-3 weeks instead of a full application every 4-6 weeks.” This is practical advice for sandy West Texas soils.

Organic Matter

The percentage of decomposed organic material in the soil. West Texas soils are naturally deficient in organic matter due to low rainfall and limited vegetation decay. Higher organic matter improves water retention, nutrient availability, and microbial activity. TAMU’s organic matter testing is currently experiencing delays due to supply chain issues, but the data remains valuable when available.

West Texas Soil Terms

Alkaline Soil

Any soil with a pH above 7.0. The Texas Panhandle region consists of a wide range of soil types from caliche to clay to sandy, but nearly all of it is alkaline, typically between 7 and 8.5 on the pH scale. The lack of precipitation and presence of underlying limestone and caliche drive these basic conditions. Understanding soil testing at Texas A&M starts with accepting that your West Texas soil is almost certainly alkaline, and that fact shapes every fertilizer and amendment decision.

Caliche

A hardened layer of calcium carbonate common in arid Texas soils. Caliche makes the soil highly alkaline and locks up essential nutrients like iron, phosphorus, and zinc, making them unavailable to plants even when present. If your TAMU textural analysis reveals a caliche layer, amending with sulfur or acidifying fertilizers may help marginally, but the underlying chemistry is difficult to change permanently.

Iron Chlorosis

Yellowing leaves with green veins, a hallmark symptom of iron deficiency caused by high-pH soil. The iron is often physically present in the ground, but the alkaline conditions prevent roots from absorbing it. This is called nutrient lockup. Soil testing at Texas A&M can confirm whether iron is truly deficient or just unavailable, which determines whether you should apply iron to the soil, spray it on the foliage, or address the pH itself.

If your trees are showing these symptoms, a certified arborist evaluation can determine whether iron chlorosis or another condition is the root cause.

Nutrient Lockup

When high pH prevents plants from absorbing nutrients that are physically present in the soil. This is the defining challenge of West Texas horticulture. Your TAMU report might show adequate iron levels, yet your trees display classic iron deficiency symptoms. The soil test provides the chemistry; an arborist or agronomist provides the interpretation.

Salinity

Salt accumulation from irrigation water, fertilizer runoff, or natural mineral deposits. Soil salinity is becoming an increasing problem in West Texas. The choice between drip and spray irrigation can affect how salts accumulate near root zones, making salinity data from your TAMU report directly relevant to irrigation decisions.

Understanding Your TAMU Soil Test Results

How the Report Is Formatted

TAMU provides nutrient concentrations alongside recommendations. For each nutrient tested, the report reveals concentrations that you can compare to the critical level. If a nutrient falls below the CL, the report will typically suggest a specific amount of fertilizer to apply.

The Urban Fertilizer Management Calculator

TAMU offers an online calculator to help translate soil test recommendations into actual fertilizer application rates. This tool bridges the gap between “your soil needs 1.5 pounds of nitrogen per 1,000 square feet” and “how much of this particular fertilizer bag do I actually spread?”

Turnaround Time

Expect results within 5 to 10 business days after the lab receives your sample. Practitioners on forums report that the report typically arrives about 10 days after receipt, though some have received results in as few as 5 to 7 business days. Several days may pass between receipt and data entry, so do not panic if you do not see immediate confirmation.

Volume Discounts

Discounts are available when groups of eight or more samples are submitted at the same time for the same test. If you are testing multiple zones on a large property, this can add up.

When to Retest

Every 2 to 3 years for general maintenance. More frequently after major amendments, new plantings, or if you have changed irrigation sources. Dr. Calvin Trostle of TAMU’s Lubbock office emphasizes: “Soil testing does not cost, it pays!”

Where to Mail Samples

USPS: Texas A&M AgriLife Extension Service Soil Testing Laboratory, 2478 TAMU, College Station, TX 77843-2478. Courier (FedEx/UPS): 2610 F&B Road, College Station, TX 77845.

When Soil Testing Connects to Tree and Landscape Health

Soil testing at Texas A&M is not just for lawns and crops. Arborists use the same lab to diagnose tree health problems. A tree displaying chlorotic leaves, stunted growth, or die-back may need a soil test, a plant tissue test, or both, and knowing which to request saves time and money.

The key distinction: soil testing tells you what is happening in the ground. Plant tissue testing tells you what the plant has actually absorbed. Disease diagnostics at the TPDDL tell you whether a pathogen is involved. These are three separate services addressing three different questions.

Irrigation practices directly affect soil chemistry. Overwatering can leach nutrients from sandy soils with low CEC. Under-watering concentrates salts. Using sodium-heavy well water without knowing your SAR can slowly poison root zones. This is where soil testing, irrigation management, and tree care intersect. To understand how these systems work together, see our guide on coordinating irrigation with tree health.

M&M Sprinkler and Tree Services employs certified arborists who partner with the TAMU lab for soil and tissue diagnostics as part of their tree care process. The value is straightforward: you can collect and mail your own samples, but a certified arborist knows how to interpret the data and act on it for your specific trees and soil conditions.

If your trees are showing signs that warrant professional attention, a soil test through TAMU is often the first diagnostic step.

Frequently Asked Questions

How much does soil testing at Texas A&M cost?

The routine analysis is the least expensive option and covers pH, macronutrients, sulfur, sodium, conductivity, and boron. Adding detailed salinity brings the cost to $37. The comprehensive analysis (routine plus micronutrients, organic matter, salinity, and texture) costs more but provides the most complete picture. Current pricing is valid through December 31, 2026.

Do I need special bags or containers to submit soil samples?

No. Any sturdy zip-closure bag works. Just write your sample ID on the bag so it matches the ID on your submittal form. Do not use galvanized metal buckets, which contaminate samples with zinc.

How deep should I dig when collecting soil samples?

Six inches is the standard. TAMU calibrates all its fertilizer recommendations to 6-inch soil samples. Take 8 to 10 cores from across the area, mix them, and fill a quart-sized bag half to three-quarters full.

How long does it take to get results back from the TAMU lab?

Most people receive results within 5 to 10 business days after the lab receives the sample. There may be a delay of a few days between when the lab receives your sample and when it is entered into the system.

What extraction method does the TAMU lab use?

TAMU uses the Mehlich III extraction method, which is well-suited for the range of soil types found across Texas, including alkaline West Texas soils. Nutrients are measured using ICP spectroscopy.

Why is my soil pH so high in Lubbock?

Lubbock sits on the Llano Estacado, where soils are slightly alkaline at around pH 7.8, often higher. The combination of low rainfall, underlying limestone, and caliche deposits keeps the soil basic. Amending pH is possible but difficult to sustain long-term at scale.

Should I get the detailed salinity test?

If you irrigate with well water, yes. West Texas well water frequently contains elevated sodium that home test kits miss. The detailed salinity analysis gives you SAR and conductivity data that are critical for making informed irrigation decisions.

When should I hire a professional to interpret my soil test results?

If your report shows high SAR, extremely low CEC, or micronutrient levels below critical thresholds, especially when trees or expensive landscape plants are involved, professional interpretation pays for itself. A certified arborist or extension agronomist can translate the numbers into a specific treatment plan rather than a guessing game with fertilizer bags.

Contact M&M’s certified arborists for help interpreting TAMU soil test results and building a nutrition plan for your West Texas landscape.