Laboratory tests often check for plant nutrients in three categories:
Major nutrients: nitrogen (N), phosphorus (P), and potassium (K)
Secondary nutrients: sulfur, calcium, magnesium
Minor nutrients: iron, manganese, copper, zinc, boron, molybdenum, chlorine
Do-it-yourself kits usually only test for the three "major nutrients", and for soil acidity or pH level. Do-it-yourself kits ar
e often sold at farming cooperatives, university labs, private labs, and some hardware and gardening stores. Electrical meters that measure pH, water content, and sometimes nutrient content of the soil are also available at many hardware stores. Laboratory tests are more accurate than tests with do-it-yourself kits and electrical meters. Here is an example soil sample report from one laboratory. Soil testing is used to facilitate fertilizer composition and dosage selection for land employed in both agricultural and horticultural industries. Prepaid mail-in kits for soil and ground water testing are available to facilitate the packaging and delivery of samples to a laboratory. Similarly, in 2004, laboratories began providing fertilizer recommendations along with the soil composition report. Lab tests are more accurate, though both types are useful. In addition, lab tests frequently include professional interpretation of results and recommendations. Always refer to all proviso statements included in a lab report as they may outline any anomalies, exceptions, and shortcomings in the sampling and/or analytical process/results. Some laboratories analyze for all 13 mineral nutrients and a dozen non-essential, potentially toxic minerals utilizing the "universal soil extractant" (ammonium bicarbonate DTPA).[2]
Record test
A record test is a test of soil taken for disturbed and undisturbed samples. Record tests are taken only in a soil testing laboratory.[citation needed]
Soil
Grain size
Moisture
Specific gravity
Liquid limit
Plastic limit
Shrinkage limit
Compaction
Direct Shear
Permeability
Murum
Grain size
Moisture content
Specific gravity
Compaction
Direct Shear
Permeability
Shear test are taken on two machines:
Small shear machine - Hearting material and for casing material if particle size is less than 4.75mm
Large shear machine - Casing material if particle size is more than 4.75mm
Permeability test - For hearting material permeability between 10-6 to 10-7
Permeability test - For casing material permeability between 10-4 to 10-5
Soil contaminants
Common mineral soil contaminants include arsenic, barium, cadmium, copper, mercury, lead, and zinc. Lead is a particularly dangerous soil component. The following table from the University of Minnesota categorizes typical soil concentration levels and their associated health risks.[3]
Children and pregnant women should avoid contact with soil estimated total lead levels above 300 ppm Lead Level Extracted lead (ppm) Estimated total lead (ppm)
Low 3000
Six gardening practices to reduce the lead risk
Locate gardens away from old painted structures and heavily traveled roads
Give planting preferences to fruiting crops (tomatoes, squash, peas, sunflowers, corn, etc.) Incorporate organic materials such as finished compost, humus, and peat moss
Lime soil as recommended by soil test (pH 6.5 minimizes lead availability)
Discard old and outer leaves before eating leafy vegetables; peel root crops; wash all produce
Keep dust to a minimum by maintaining a mulched and/or moist soil surface
