Interpreting Soil Test Results

The primary goal of soil testing is to inform efficient and effective resource management. Soil testing is the most accurate way to determine lime and nutrient needs. Soil testing is also useful for identifying contaminated sites

Testing the soil yourself

You also need to prepare your soil by checking its nutrient and chemical contents. Take a simple soil test of your soil to know how to amend it. Purchase an inexpensive soil test kit online or contact your local extension office and ask about local soil testing services.


Check the soil’s pH

Soil testing will tell you the soil’s pH. You can use a simple pH test kit to determine the pH in your tomato patch. If you’re planting a large number of tomatoes, then test several areas across the planting area. A neutral pH level is 7.0. Numbers lower than 7.0 indicate acidic soil – the lower the number, the more acidic the soil. Numbers higher than 7.0 indicate alkaline soil – the higher the number, the more alkaline the soil. Tomatoes grow best in slightly acidic soil with a pH level between 6.0 and 7.0 – optimum is between 6.5 and 7.0. If your soil’s pH isn’t within that range, make proper adjustments.

To lower your soil’s pH, work sulfur into the soil. 

To raise your soil’s pH, work lime into the soil.

An appropriate pH is an important component to preparing the soil for planting tomatoes.

Evaluate nutrients

Check soil test results for an even balance between nitrogen, phosphorus, and potassium, all necessary for strong tomato production. Evaluating nutrients will go a long way in preparing your soil because you will know what you need to add.


Nitrogen helps your tomatoes maintain healthy, green leaves. Yellowed older leaves  and slowed growth indicate nitrogen deficiency. But when you apply too much  nitrogen before fruit is set, stems become quite large, leaves are deep green and  soft, and there are few if any flowers. Tomatoes need about 300 – 500 grams of  nitrogen per 45m² feet. Incorporate nitrogen into soil just before planting.

Good organic fertilizer sources of nitrogen:

alfalfa meal, blood meal, compost, feather meal, fish meal

Good inorganic nitrogen sources:

ammonium nitrate  ammonium sulfate  anhydrous ammonia  calcium nitrate  potassium nitrate  sodium nitrate  urea




Phosphorus helps your tomatoes develop strong root systems, build disease resistance, and cultivate fruit and seed formation. Slow, stunted growth and reddening stems and foliage indicate a phosphorus deficiency. Incorporate phosphorus-containing fertilizers into the soil before planting, rather than sprinkling them on the surface.

Good organic fertilizer sources of phosphorus : bone meal compost

Good inorganic phosphorus sources : rock phosphate  super phosphate


Potassium helps promote growth and disease resistance in your tomato plants. Weak plants and slow growth indicate a potassium deficiency. In more severe cases, leaf edges will brown. An easy way to amend the soil is to add wood ash, which is 5% potassium. Best rate is about 10-15 pounds to a 300 square foot bed. Work in wood ash in the fall or winter.

Good organic fertilizer sources of potassium : wood ash granite dust (also called rock potash) – slow-releasing leaf mold

Good inorganic potassium sources : potassium sulfate rock sand

Laboratory testing


  • Iron  (Fe)
  • Manganese (Mn)
  • Boron(Bo)
  • Zinc (Zi)
  • Molybdenum (Mo) Copper  (Cu)
  • Silicon (Si)                                                                                                                                                         

Fertilizers are salts

  • cations and anions cannot live separately, but will attract each other like a magnet because of the difference in electrical load, and will form molecules, or salts.(+ and – ) = neutral. Salts are neutral in load.
  • But elements has different load values…

Elements and its load


  • NH4+
  • K +
  • Na +
  • Ca2+
  • Mg2+
  • NO3
  • Cl
  • SO4 2-
  • HCO3
  • PO43-

Try to make fertilizers by  combining elements

positive negative   salt  fertilizer name
NH4+    NO3      NH4 NO3 Ammonium Nitrate
K +       K +          

K + H2+  






K +        

NO3–     SO42-



NO3–      Cl      SO42-

NO3–      Cl          






Ca Cl2  




Potassium Nitrate/ Multi-  K

Potassium Sulphate

Mono Potassium

Phosphate (MPK)

Calcium Nitrate

Calcium Chloride

Magnesium Sulphate

Magnesium Nitrate

Potassium Chloride


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