Reading and Understanding Soil Test Results: Why Get a Soil Test?

Reading a Soil Test

Taking it from the top, the first line below "Element" is Exchange Capacity. Exchange Capacity or "EC" is a measure of the cation (pronounced cat-eye-on) nutrient holding ability of your soil. Cations are positively charged + ions. Sand has a low exchange capacity, most clays and organic matter have a high exchange capacity. How much water a soil will hold is a good analogy. This number will range from a low of around 5 to a high of around 40.

Next line down is pH. Most of us are familiar with pH; it is a measure of the acidity or alkalinity of your soil. This soil's pH is 5.9, a little too acid for most crops. 6.0-6.5 is ideal.

The third item is the percentage of organic matter in your soil. Many soil scientists say that 4-5% organic matter is ideal, but that depends on the climate. In a cool, rainy climate 10% organic matter may be common.

Anions

Next we come to a couple of Anions, Sulfur and Phosphorus. Anions are negatively charged atoms. They are designated by the - minus symbol. Sulfur is important for many life processes including formation of protein. Most soils in high rainfall areas are deficient in Sulfur as Sulfur is easily leached away in water. Onions, Garlic, and members of the cabbage family all require a lot of Sulfur to grow well. At 13ppm, this soil is far too low in Sulfur.

Large amounts of Phosphorus are needed by all living things. Plants use Phosphorus to make sugars. Animals use Phosphorus to make bones and teeth, and to generate energy in the body cells. An apple or watermelon that looks perfect but isn't sweet was likely grown in a Phosphorus deficient soil. This soil has a good level of Phosphorus.

Cations
(pronounced cat-eye-ons)

The cation elements are the most critical nutrients for a healthy soil. If they are missing or out of balance nothing will grow really well. Cations are bases: that means they have a + charge, and the Exchange Capacity of your soil is a measure of the amount of cation elements it can hold. Base saturation is a measure of how much of the EC is filled by each element. On this soil test 64.58% of the EC is filled by Calcium, just about the perfect amount.

The critical importance of the cation nutrients is poorly understood by many gardeners. A really fertile soil contains more Calcium than all of the other mineral nutrients combined! A soil with the right amount of Calcium will remain loose and workable. Calcium is the major transporter of other minerals and nutrients, including sugars.

An atom of Magnesium is at the center of each molecule of chlorophyll that plants use to convert sunlight into food and fiber. The Calcium to Magnesium ratio should be about 7:1 by weight in most soils. Magnesium and Calcium are necessary for proper nerve and muscle function in animals.

Potassium is a powerful growth stimulant for plants and is needed in large quantities by animals too, but unfortunately it is too often overused. Large amounts of Potassium will encourage lush growth but the plants will be weak. Note that you never need more than 5% base saturation of Potassium.

Sodium is also an essential nutrient for plants and animals, and one that is frequently in short supply in high-rainfall areas.

Hydrogen in the soil is not considered a nutrient. It is more of a place-holder. Plant roots and soil microorganisms exchange Hydrogen for nutrient cations. The higher the level of exchangeable Hydrogen, the more acid the soil.

The Minor elements

These are only "minor" in the amounts required compared to other minerals. They must be available and in balance for truly healthy soil, plants, animals, and people.

Boron is needed in tiny amounts in order for plants and animals to properly utilize Calcium. For each thousand pounds of Calcium only about one pound of Boron is necessary. Boron can easily reach toxic levels if it is over-applied. 3-4 parts per million is all that is needed even in a high Calcium soil.

Iron is needed by plants and animals. Our blood contains an atom of Iron at the center of each hemoglobin molecule. The 196ppm of Iron in this soil is plenty.

Manganese is needed for a plant to set fertile seeds and is also an essential nutrient for animals.

Copper and Zinc work together and need to be in a balance of about 1 part Copper to 2 parts Zinc. They are both essential for hundreds of life processes. In this soil they are out of balance, as there is 6 times as much Zinc as Copper.

Aluminum is the second most abundant mineral on Earth, and it is found in all soils. High Aluminum levels are usually only found in very acid soils. Anything under 2000ppm is normal.

For more examples of soil tests and recommendations click HERE.

To see the prices for soil tests and the procedure for taking a soil sample, click HERE.

Element		Results	Reading a Soil Test Taking it from the top, the first line below "Element" is Exchange Capacity. Exchange Capacity or "EC" is a measure of the *cation* (pronounced cat-eye-on) nutrient holding ability of your soil. Cations are positively charged + ions. Sand has a low exchange capacity, most clays and organic matter have a high exchange capacity. How much water a soil will hold is a good analogy. This number will range from a low of around 5 to a high of around 40. Next line down is pH. Most of us are familiar with pH; it is a measure of the acidity or alkalinity of your soil. This soil's pH is 5.9, a little too acid for most crops. 6.0-6.5 is ideal. The third item is the percentage of organic matter in your soil. Many soil scientists say that 4-5% organic matter is ideal, but that depends on the climate. In a cool, rainy climate 10% organic matter may be common. Anions Next we come to a couple of Anions, Sulfur and Phosphorus. Anions are negatively charged atoms. They are designated by the - minus symbol. Sulfur is important for many life processes including formation of protein. Most soils in high rainfall areas are deficient in Sulfur as Sulfur is easily leached away in water. Onions, Garlic, and members of the cabbage family all require a lot of Sulfur to grow well. At 13ppm, this soil is far too low in Sulfur. Large amounts of Phosphorus are needed by all living things. Plants use Phosphorus to make sugars. Animals use Phosphorus to make bones and teeth, and to generate energy in the body cells. An apple or watermelon that looks perfect but isn't sweet was likely grown in a Phosphorus deficient soil. This soil has a good level of Phosphorus. Cations (pronounced cat-eye-ons) The cation elements are the most critical nutrients for a healthy soil. If they are missing or out of balance nothing will grow really well. Cations are bases: that means they have a + charge, and the Exchange Capacity of your soil is a measure of the amount of cation elements it can hold. Base saturation is a measure of how much of the EC is filled by each element. On this soil test 64.58% of the EC is filled by Calcium, just about the perfect amount. The critical importance of the cation nutrients is poorly understood by many gardeners. A really fertile soil contains more Calcium than all of the other mineral nutrients combined! A soil with the right amount of Calcium will remain loose and workable. Calcium is the major transporter of other minerals and nutrients, including sugars. An atom of Magnesium is at the center of each molecule of chlorophyll that plants use to convert sunlight into food and fiber. The Calcium to Magnesium ratio should be about 7:1 by weight in most soils. Magnesium and Calcium are necessary for proper nerve and muscle function in animals. Potassium is a powerful growth stimulant for plants and is needed in large quantities by animals too, but unfortunately it is too often overused. Large amounts of Potassium will encourage lush growth but the plants will be weak. Note that you never need more than 5% base saturation of Potassium. Sodium is also an essential nutrient for plants and animals, and one that is frequently in short supply in high-rainfall areas. Hydrogen in the soil is not considered a nutrient. It is more of a place-holder. Plant roots and soil microorganisms exchange Hydrogen for nutrient cations. The higher the level of exchangeable Hydrogen, the more acid the soil. The Minor elements These are only "minor" in the amounts required compared to other minerals. They must be available and in balance for truly healthy soil, plants, animals, and people. Boron is needed in tiny amounts in order for plants and animals to properly utilize Calcium. For each thousand pounds of Calcium only about one pound of Boron is necessary. Boron can easily reach toxic levels if it is over-applied. 3-4 parts per million is all that is needed even in a high Calcium soil. Iron is needed by plants and animals. Our blood contains an atom of Iron at the center of each hemoglobin molecule. The 196ppm of Iron in this soil is plenty. Manganese is needed for a plant to set fertile seeds and is also an essential nutrient for animals. Copper and Zinc work together and need to be in a balance of about 1 part Copper to 2 parts Zinc. They are both essential for hundreds of life processes. In this soil they are out of balance, as there is 6 times as much Zinc as Copper. Aluminum is the second most abundant mineral on Earth, and it is found in all soils. High Aluminum levels are usually only found in very acid soils. Anything under 2000ppm is normal. For more examples of soil tests and recommendations click HERE. To see the prices for soil tests and the procedure for taking a soil sample, click HERE.
Exchange Capacity		9.72
pH of soil sample		5.90
Organic Matter %		10.24

Anions
Sulfur- (parts per million)		13
Phosphorus- as P2O5 (lbs per acre)		955

Cations
Calcium Ca++ lbs per acre	Desired Found Deficit	2643 2510 -133
Calcium base saturation	60 to 70%	64.58%
Magnesium Mg++ lbs per acre	Desired Found Deficit	279 212 -67
Magnesium base saturation	10 to 20%	9.09%
Potassium K+ lbs per acre	Desired Found Deficit	303 156 -147
Potassium base saturation	2 to 5%	2.06%
Sodium Na+ lbs per acre		31
Sodium base saturation	.5 to 3%	.70%
Other Bases (Fe,Mn,Cu,Zn etc)		5.60%
Exchangeable Hydrogen H+	10 to 15%	18.00%

Minor Elements (parts per million)
Boron B		0.51
Iron Fe+		196
Manganese Mn+		43
Copper Cu+		1.05
Zinc Zn+		6.25
Aluminum Al+		1545