UNDERSTANDINGA SOIL TEST

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Ammonium Level Result 0.00 – 3.0 Low

3.1 – 30 OK

30+ High

PHOSPHATES

Phosphorous is very important for all root and trunk growth. The levels are dependent upon the crop being grown.

Level Crop Types 0 – 10 None

12 – 20 Grazing Pastures only

25 – 40 Dairy Pastures and Grain Crops on Non red soils

50 – 80 Grain on red soil and all fruit trees and small crops

100+ Too high will cause tie ups

Phosphorous when over 100ppm will tie up Boron and Zinc

THE CATIONS

The Cations are Calcium, Magnesium, Potassium, Sodium, Aluminium, Ammonium, Nitrogen and Protons (H) or acid. Of these, we only consider the first five in the calculations for balancing the soil. To work out if the cations are in balance we must convert from parts per million (ppm) to milli equivalents per 100grams (Meq/100g). This second set of units takes into account the electronic charge on the cations.

Cations Conversion Factor Calcium 200

Magnesium 121.56

Potassium 391.02

Sodium 230

Aluminium 90

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The cation level is divided by its Factor to Meq/100g from the ppm. The sum of all the Meq/100g is called the Cation Exchange Capacity (CEC).

To balance to CEC, obtain the percentages of each of cations to each other. When soil is in balance the following levels will be found.

Manganese Mn

Boron B

Electrical Conductivity E C

Sodium Na

pH (Water)

Ph (CaCl2)

Nitrate Nitrogen NO 3

Nitrite Nitrogen NO 2

Phosphorous P

Iron Fe

Zinc Zn

Copper Cu

Aluminium Al

Magnesium Mg

Calcium Ca

Sulphates SO 4

Potassium K

Chloride Cl

Alkalinity ALK

Cation Exchange Capacity CEC

Cation Percentage Calcium 65 – 80%

Magnesium 12 – 20%

Potassium 3 – 6%

Sodium <4%

Aluminium <2%

If levels are just below or above by a few % then it is only slightly out. If more, than will be low or high (e.g. Calcium 55% is low).

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TRACE ELEMENTS

The trace elements play a very important role in the growth of plants. All have different levels to represent the availability.

Manganese should be over 0.5ppm but less than 10.00ppm with 11 to 25ppm as slightly high for Grain Crops and high for Pome fruit.

Iron should be 0.5 to 5.0 and not less than one tenth of the Manganese level.

Zinc should be 0.6 to 5.0. Note: Will be affected by Phosphorous if Phosphorous is >100+

Copper should be 0.6 to 5.0

Boron should be 0/25 to 0.5 for most crops; But 0.50 to 1.00 for all sensitive crops. Also, Boron is affected by Phosphorous if Phosphorous is >100+

Molybdenumn (not tested in the soil; best test is through the tissue analysis).

Sulphate S. Sulphate Sulphur is essential for normal plant growth. The levels below can be used as a guide:

Sulphate Level Result <8 Low

8 – 15 Marginal

15+ OK

50+ High

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GUIDE LINE LEVELS FOR SOIL

pH

The range for pH is dependent on the crop to be grown or that is growing in the soil. i.e. If the crop is bananas then the pH will range from 5.0 to 7.0. But for tomatoes the pH will range from 6.0 to 7.0.

Electrical Conductivity

Depend on the salt tolerance of the plant to be grown or that is grown. For example, if a low salt tolerant plant is needed then the range is 20 – 200 micro S/cm.

Tolerance Range Low 20 – 200

Medium 200 – 600

High 600+

Nitrate Nitrogen

For all non legumes the level of nitrate nitrogen should be at least 8.0ppm in the soil. All legumes need to have very little nitrate nitrogen in the soil. This will make them work at fixing nitrogen out of the air. So nitrate nitrogen level for legumes should be <8.0ppm.

Cations: Calcium, Magnesium, Potassium, Sodium and Aluminium

To find the guidelines for all of the cations we need to calculate the levels in Meq/100g from the percentages need in the Guides.

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Sodium <4% 230

Aluminium <2% 90

Note: When CEC is greater than 10.0 Meq/100g then potassium range is 120 – 240ppm.

So now we must find the percent of the cation of the CEC. To do so, multiply it by its Conversion Factor.

i.e.

Calcium 65% x CEC x 200/100 = Ca Minimum

Calcium 80% x CEC x 200/100 = Ca Maximum

Magnesium 12% x CEC x 121.56/100 = Mg Minimum

Magnesium 20% x CEC x 121.56/100 = Mg Maximum

Potassium 3% x CEC x 391/100 = K Minimum

Potassium 6% x CEC x 391/100 = K Maximum

Sodium 4% x CEC x 230/100 = Na Maximum

Aluminium 2% x CEC x 200/100 = Al Maximum

Note: For CEC’s over 10.0 Meq/100g Potassium minimum level is 120ppm. While the Potassium Maximum level is 240ppm

Conversion Factor Cation Percentage Calcium 65 – 80% 200

Magnesium 12 – 20% 121.56

Potassium 3 – 6% 391

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TRACE ELEMENTS

Nutrient Range Sulphates 15 – 25

Copper 0.6 – 5.00

Iron 0.6 – 5.00

Manganese 0.6 – 10.00

Zinc 0.6 – 5.00

Boron 0.5 – 1.00

Note: Boron at 0.25ppm is Marginal.

Chloride

Chloride will work with the tolerance of the plants

Salt Tolerance Range Low <200

Medium 100 – 300

High 300+