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Soil Testing and Analysis

Organic Matter

Organic Matter is a measurement of fully decomposed humus and not recently-plowed-in organic matter, which will be part of future measurements as it decomposes. Grower's Source OVERHAUL stimulates biological activity to break this down and increase humus for a higher organic reading.

Note: An increase of 1% in topsoil organic matter will increase each acre's capacity to hold water by 10,000 gallons. Higher organic soils are more tolerant of drought conditions and can go longer between watering.

Phosphorus (P)

  • P1 is the measure of readily available phosphorus for immediate plant use.
  • P2 is P1 plus the non-available phosphorus in reserve.
  • Bicarbonate: This test measures the readily available phosphorus in basic soils (higher pH over 7.0) as some readings can be neutralized in soil with free lime.

Biological activity is critical in the conversion of P1 to P2. We have 3 products to help (REVAMP, OVERHAUL and W.A.M.), depending on soil compaction and alkalinity. Most soil fertility manuals give the required phosphorus and this amount is often sold to growers.

We suggest subtracting the available amount, helping the conversion process of the unavailable, and buying only what is needed for the specific crop. Anything else increases input costs and does nothing for yield.

Potassium (K)

Higher levels are needed of Potassium for optimum performance in clay and high organic matter soils. Light soils should have reading of 120-175 ppm while heavy soils do best with 100-250 ppm. Extra potassium may be needed in soils exceeding 20% in magnesium base saturation. Potassium in base saturation should always exceed Sodium levels for maximum yield.

Magnesium (Mg) & Calcium (Ca)

Magnesium and Calcium should be in proper balance for maximum yield. These elements are closely related to soil pH. Both calcium and magnesium are generally higher in high pH soil.

Note: Many books state that calcium is rarely deficient in adequate pH soil. This can be misleading. Both magnesium and calcium are positive cations. You can get good pH readings where magnesium and/or sodium are much too high and calcium too low. High magnesium concentrations are associated with compaction. (They use magnesium to make bricks) In compacted soil, many elements are locked up and unavailable to the plant.

Sodium (Na)

Too much sodium can kill plants, and high sodium soil is often referred to as alkali soil. Excessive exchangeable sodium must be replaced by calcium or magnesium or removed by leaching. Sodium often is high as a natural occurrence or where irrigation and evaporation are present. Over 2.5% exchangeable sodium will damage plants and over 5% will require sodium tolerant plants.

Note: If your sodium is higher than your potassium, you have a problem.

Since sodium and potassium are neighbors on the chemical chart and closely associated (both +1), the plant can readily take up excess sodium. This often causes cell eruption opening the plant to disease and attracting harmful insects. A specific function of Grower's Source OVERHAUL is to ameliorate sodium damage.

Soil pH

A pH of 7.0 is neutral. Soils over 7 are alkaline and under 7 are acidic. The most desirable range to work with is 6.0 to 7.0 with highly organic soils often a little lower.

Buffer Index

The buffer index is used to show the amount of lime necessary to raise low pH soil.

Hydrogen (H)

Hydrogen contributes to soil acidity and will not be present in soil above 7.0 pH.

Cation Exchange Capacity (CEC)

CEC is the ability of the soil to hold nutrients. Calcium, magnesium, potassium and trace minerals with a positive charge are attracted to the negative soil colloid. Heavy soils have a high CEC, while light sandy soils have a low CEC. Low CEC soils often need to be spoon fed, as the soil cannot retain elements. High CEC soils hold more nutrients, but are harder to correct when they are out of balance. Microbial activity helps break down unavailable elements into their base form, which can attach to a soil colloid and is readily available to the plant. Use Grower's Source OVERHAUL to maximize availability.

Percent Base Saturation

This is a critical area to understand soil balance.

  • Potassium (K) should be 3-7%.
  • Magnesium 12-18%.
  • Calcium 65-75%.
  • Sodium should be 0.5-1%

Note: Sodium should be added to the magnesium saturation to determine if overall mineral salt content is too high.

Hydrogen is only present in pH below 7.0. There will be virtually no hydrogen in Alkali high pH soil colloids. This weak cation is driven off by stronger elements. Add what you need to be in balance if you have substantial hydrogen.

Trace Elements PPM

An acre of topsoil 6 inches deep weighs about 2 million pounds. To convert ppm to pounds per acre, multiply by 2. Use this to determine how many additional pounds per acre may be needed. Don't buy it if you don't need it. Most of the elements will not remain available in the soil.

Nitrate (NO3-N)

This nitrate-nitrogen (NO3-N) is the readily available nitrogen. Both high organic matter and microbiological activity increase nitrogen and other trace mineral availability. Overuse of nitrogen can harm the environment and will not stay in the soil. Check your crop manual for what you need, and subtract what you have before applying.

Sulfur (S)

The need for sulfur increases in low CEC soils, low pH soils, and heavily nitrogen fertilized fields. Optimum levels depend on organic content. This measures the readily available sulfate sulfur. Since sulfur will combine with any positive cation that is in excess, it is often used to balance soil through its combination with other minerals to form soluble and highly movable sulfates.

Note: A high reading of sulfur is indicative of a compaction problem.

Since sulfur combines to make soluble sulfates that translocate, it should not be high. We have successfully recommended sulfur surface applications where it was listed as "High" on the charts. It simply could not do its job because of compaction. A better course is to solve the compaction problem. We suggest Grower's Source W.A.M.

Zinc (Zn)

Zinc can interact with soil phosphates and pH to significantly alter rate recommendations. Optimum range is 1.8-2.5 ppm. Zinc is necessary for plant function, especially in reproduction. Residual effects of zinc can last several years, so broadcast application should be used when applying a heavy application.

Manganese (Mn)


Optimum 14-22 ppm in DTPA extraction method. (3-6 ppm in 0.1 N HCI extraction). Manganese quickly reverts to unavailable forms shortly after application so band treatments or foliar application is recommended. REVAMP, W.A.M. and OVERHAUL can help with availability.

Iron (Fe)

Optimum 12-22 ppm in DTPA extraction method. (20-30 ppm in 0.1 N HCI extraction). Chelated forms of iron are best as iron quickly reacts with other elements and can become unavailable for the plant. Again, biological activity keeps iron more readily available.

Copper (Cu)

Optimum 1-1.8 ppm. High organic matter, high soil pH and high nitrogen and phosphorus applications can create copper deficiencies. Still, soil applications of copper can be effective for several years.

Boron (B)

Boron deficiencies are most common on sandy, low organic and high pH soil. Reading should be 1-1.5 ppm.

Note: Toxicity range and deficiency range is narrow. Take care not to under- or over-apply boron.

Excess Lime

This is a visual test of free lime. Too much lime inhibits availability of elements. Elemental sulfur or acid forming fertilizer will be recommended.

Soluble Salts

Excessive salts may cause wilting or death. We suggest immediate application of OVERHAUL when stress is visible because of salt or chemical damage. This product has saved many damaged crops since its formulation. Salt deposits can occur naturally, with irrigation or through chemical wastes.

Special Tests

If a grower has requested special tests, the results will be in this section.

Call Grower's Source 

Call Grower's Source, LLC at 1-903-303-5445 for a free evaluation of your soil test.

If you did not do your soil test through us, please email your soil test to This email address is being protected from spambots. You need JavaScript enabled to view it. so we can better serve you.


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