How to Read a Soil Test

Knowledge is the key to success in any Endeavour. The more you know about what you’re working with, the more successful you will be and the less stress you will encounter as you put the job together and complete it. When working with the soil, revegetating any area is a tough job when working without any knowledge of what mineral levels exist in the materials which have been piled up and graded for you to grow something on. What if the PH is so low (acid) that no roots will establish? What is causing the low PH? OR, what can I add to help nullify the high PH so that my project will be successful? AND what minerals do I need to add to make that happen and how much. A soil test will provide these answers and it actually works as insurance for success. A soil test will point out when Sodium is a problem (destroys cell function in plants) while the pH may read OK at the same time. A soil test will show the need or not for fertilizer (NPK) amendments (save input $’s using lesser amounts when good organic matter is already available). A soil test on your work area is just as important as the initial blood “workup” the Dr. does when you go for your yearly checkup! When the numbers are available, analysis can be done, answers can be given and preventative medicine will be prescribed. The cost of soil testing is not usually figured into the cost of a job. The value of soil testing is understood quickly when the revegetating project is a failure and it’s painfully obvious that the problem is in the soil and probably could have been prevented. So, spend money wisely and increase your chances of success. Don’t spend it doing the same job twice with no soil information.
Soil Report

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1 - Organic Matter

This is a measurement of fully decomposed humus and not recently plowed in organic matter. They will be part of future measurements as it decomposes. Hydro VG 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.


2 - 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, (Renew, Reclaim and AIM) 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.

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3 - Potassium (K)
Higher levels are needed for optimum performance in clay and high organic matter soils. Light soils should have reading of 150-175 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.

4 - 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.

5 - 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.


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 AgPro Reclaim is to ameliorate sodium damage.

6 - Soil pH
A pH of 7.0 is neutral. Over 7 is 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.

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

8 - 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 AgPro RENEW to maximize availability.

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9 - 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.

10 - Trace Elements PPM
An acre of topsoil 6 inches deep weigh 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.

NOTE: for Potassium (K) multiply ppm by 2.4. For elemental available Phosphorus (P1) use 2x factor. However for unavailable Phosphorus (P205) multiply by 4.6.

11 - 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.

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12 - 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.


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 AgPro AIM.

13 - Zinc (Zn)
Zinc can interact with soil phosphates and pH to significantly alter rate recommendations. Optimum ranges 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.

14 - 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. RENEW, AIM and RECLAIM can help with availability.

15 - 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.

16 - 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.

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17 - 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.

18 - 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.

19 - Soluble Salts
Excessive salts may cause wilting or death. We suggest immediate application of HYDRO-RX 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.

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Products of biotechnology offer the greatest potential for growers to achieve minimum inputs and maximum yields by enabling them to better manage the factors that drive input costs up as well as those that limit production.

There are three proven keys to creating a balanced soil for a profitable growing program.

  • Life in the soil including the microorganisms in the soil, which is the foundation for the second and third keys;
  • Physical which include tillage, planting, crop rotation, irrigation, etc.;
  • Chemical which include fertilizers, herbicides, insecticides, etc.

The following are recognized benefits of a healthy, balanced soil:

  • More friable soil requiring less energy in cultivation
  • Softer top soil causing less stress and damage to sprouting plants
  • Faster and more complete seed germination frequently requiring less seed per acre
  • Better decomposition of organic matter
  • Better soil aeration and release of CO2 produced by microbial action in the soil organic matter
  • More efficient use of soil moisture often reducing costs of irrigation
  • Greater drought resistance
  • More rapid water penetration and less erosion
  • More effective use of plant nutrients present in the soil by increasing organic conversion to plant available forms
  • Faster, larger, healthier root formations, and better nutrient absorption
  • More efficient use of plant nutrients with an increased fertilizer and chemical efficiency
  • Release of nutrients that otherwise would not be available to the plant
  • Less loss of nutrients by leaching
  • Soluble plant available nutrients are held in the root zone
  • Yield increases, often 20% or more
  • Quality increase by escalating carbohydrates (sugars and starches), oils and proteins
  • Often greater resistance to insect and fungus damage due to healthier, less susceptible plants
  • Less weeds
  • Less toxicity

Soil fertility cannot be reduced to a simple formula of N-P-K. The microbial life in the soil is responsible for reaching and maintaining a complete balance of minerals in the form of plant nutrients, readily available for the plant’s uptake. When there is a true (available) nutrient balance within the soil, the plants are able to feed as fast as their needs require. This reduces the stress that often inhibit the plant’s growth. This balance also cuts the number of days until harvest, improving the quality of yields in the process.

In recent years the breakdown of the structure of the surface layers of soil under continuous cultivation and the paralleling decline in their productivity has been a matter of increasing concern.

This decline in production from soils which require constantly increasing expenditures for tillage and water represents ever greater economic problems for the farmer and the nation. Increased usage of chemical fertilizers and inorganic soil conditioners, while serving other beneficial purposes, has not alleviated the problem of deteriorating soil structures, loss of organic matter, and the wastage of water and fertilizers. In many cases perhaps the chemicals used have aggravated the situation.

A productive soil is characterized not necessarily by the mere presence of large quantities of plant nutrients, but by the rapidity with which the soil microbes make these nutrients available to the higher plants. The processes that take place within the soil are, for the most part, dependent first upon the activities of living organisms; and hence, the existence of higher plants depends on the activities of the soil microbes. Dr. S. A. Waksman stated in 1952, “The humus content, plus active microorganisms, is equivalent to a high degree of fertility.”

Another noted microbiologist, Dr. Stanley E. Wedberg, University of Connecticut, went further in stating, “The fertility of the soil is in direct proportion to the number and activity of soil microorganisms.”

As you can see there is correlation or an association to humus content and high microbial activity in the soil; but, where does the humus come from?

Organic matter is the source of energy and food supply for the soil organisms and microorganisms. As organic matter is returned to the soil, it is digested by the microbes. The resulting cellular material is mixed with the living and dead bodies of bacteria, fungi, actinomycetes and other microscopic forms of life. Also, together with certain excretory materials produced during their life cycles, they form a dynamic, ever-changing, organic material called HUMUS.

HUMUS is the major storehouse of plant nutrients in the soil. It is literally the “fat of the land.”

Soil microorganisms are involved in many beneficial activities in the soil. These are decomposition of crop residues, mineralization of soil organic matter, synthesis of soil organic matter, nitrification, fixation of nitrogen, immobilization of mineral nutrients and formation of organic substances which may be both stimulative and toxic to plant growth, depending upon the concentration. Organic substances formed by microorganisms influence soil structure stabilization, binding particles of soil together to permit better water penetration and reduce erosion.

Many cropping and tillage practices that a farmer uses are effective in crop production because of their influence on microbial activity. For example, when the soil is tilled, aeration may be improved and aeration is favorable for the growth of the nitrogen, sulfur and iron oxidizing organisms. When the soil lacks oxygen, it is unfavorable as an environment for many plants and organisms.

Every practice or management system influences microbial activity, which in turn influences the decomposition of plant residues, the availability of nutrients and the soil structure. These all influence crop growth, and the growth of crops determines the soil cover and the ultimate organic matter. This influences the balance between the various types of microorganisms whose actions play a major role in the carbon, nitrogen and mineral cycles and thus govern to a great extent the fertility of the soil.

Each spoonful of mellow soil contains billions of living microscopic organisms. Multiply this by the number of spoonfuls of soil in an acre and you have figures that are astronomical. In fact, the living bacteria alone in an acre of soil of average fertility would weight as much as a medium size cow.

This seething mass of microorganisms constitutes a crop of three to five tons per acre foot of soil that the farmer sustains beneath the soil surface, in addition to the crop that he grows above the ground. If the crop of microorganisms beneath the surface does not have adequate food, the crop above ground will suffer from competition for mineral nutrients and be more susceptible to disease.

“Microorganisms eat at the first table. They are in contact with almost every particle of soil. Plant roots are not. Without micro-organic life, soil, the dynamic perpetual system that sustains terrestrial life, would become an inert mass incapable of providing food. Microorganisms decompose organic material and release elements and organic food for repeated use,” states Dr. T. M. McCalla, Research Microbiologists, University of Nebraska.

Microorganisms need three things: Air, Water and an Energy Source starting with organic matter. John Box, Extension Agronomist, Texas A & M has written, “Mike,” the microbe is your best friend and may be the most important livestock you produce. Microbes live in the surface layers of soil in fantastic numbers. Since we cannot see them, we often neglect them. Mike and his cousins can perform chemical miracles that man has not yet learned to duplicate. Treat him well and give him the raw material with which to work, and he will keep your soils in top production.”

In addition to a food supply, you can help by preventing soil compaction. Compaction reduces air supplies, limiting the ability of microbes to perform. Compaction has an adverse effect on root development and the soil’s ability to absorb and hold water.

Without active soil microorganisms, man would long ago have been covered up by his own waste or would have had to find a way of putting his refuse on the moon or elsewhere; but, thanks to Mike and his cousins, these waste materials are recycled and made into compounds that can be reused over and over.

How alive is your soil? A good microscope could show you, or you could use a visible friend to tell you…the earthworm. Earthworms are one of the best indicators of a well-balanced soil. If you don’t have them in great numbers, then you can be reasonably sure that all is not as well in your soil as it should be. On the other hand, if they are very numerous you can know that in most years your soil will be most productive.

Jack Denton Scott, writing in the August/September, 1968 National Wildlife says about the earthworm, “As a soil chemist he has few equals. The earthworm churns the earth into rich topsoil by blending in vegetable matter from the surface into the ground below, and by bringing mineral-rich subsoil up where plants can use it. He drags leaves down into his burrow where bacteria can work on them. What he eats emerges in little clumps of dirt called Castings which are extremely rich in plant nutrients.

Passing through the worm’s digestive tract, both alkalis and acids become more neutralized. Earth minerals and chemicals are broken down, enriching the soil with particle nutrients that plants and seedlings can more easily assimilate. Experimenters comparing the top six-inch layer of the soil with the castings contained in a form that plants can use found there are five times as much nitrate, twice as much calcium, two and a half times as much magnesium, seven times as much phosphorous and eleven times more potassium. Subsequently, scientists found that the soils content of actinomycetes organisms that play a significant role in decomposing all organic matter into humus multiply seven times as it passes through the earthworm.

Our amazing friend is as energetic as he is talented. Each mature earthworm casts up about half a pound of humus a year. Since a population of 50,000 earthworms in an acre of normal ground is common (seven million have been found), you can figure conservatively that earthworms are producing twelve and a half tons of topsoil a year in each acre of good garden-type soil.

As our knowledge of the soil microbes grows, we will learn ways of increasing those species which are needed to overcome problems which we have reacted by changing the natural environment, or problems which existed before, but which have grown out of hand, such as the various fungal diseases. Certainly the time is here for a deeper look into our soils and the problems that limit their production.

If you have a problem soil, i.e., hardpans, compacted soils, low water holding capacity, excessive toxic salts, poor water penetration or just low productivity from tied up plant food, then look to Mike and his cousins…they can help.

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