Product Code Database
A soil test is a laboratory or In situ analysis to determine the chemical, physical or biological characteristics of a soil. Possibly the most widely conducted soil tests are those performed to estimate the plant-available concentrations of nutrients in order to provide fertilizer recommendations in agriculture. In geotechnical engineering, soil tests can be used to determine the current physical state of the soil, the seepage properties, the shear strength and the deformation properties of the soil. Other soil tests may be used in geochemical or ecological investigations.
Labs, such as those at Iowa State and Colorado State University, recommend that a soil test contains 10-20 sample points for every of field. Tap water or chemicals can change the composition of the soil, and may need to be tested separately. As soil nutrients vary with depth and soil components change with time, the depth and timing of a sample may also affect results.
Composite sampling can be performed by combining soil from several locations prior to analysis. This is a common procedure, but should be used judiciously to avoid skewing results. This procedure must be done so that government sampling requirements are met. A reference map should be created to record the location and quantity of field samples in order to properly interpret test results.
For example, in the United States corn and soybean growing regions a grid distribution with a resolution of 2.5 acres per grid (one sample for each 2.5 acre grid) is offered by many precision agriculture soil test service providers. This is generally referred to as grid soil testing.
The amount of plant-available phosphorus is most often measured with a chemical extraction method, and different countries have different standard methods. Just in Europe, more than 10 different soil phosphorus tests are currently in use and the results from these different tests are not directly comparable.
Do-it-yourself kits usually only test for the three "major nutrients", and for soil acidity or pH level. Do-it-yourself kits are often sold at farming cooperatives, university labs, private labs, and some hardware and gardening stores. 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. An example soil sample report is provided for reference by Wallace Laboratories LLC.
In order to avoid complex and expensive analytical techniques, prediction based on regression equations relating to more easily measurable parameters can be provided by pedotransfer functions. For instance, soil bulk density can be predicted using easily measured soil properties such as soil texture, pH and organic matter.
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 and often utilize very precise flow injection technology (or Near InfraRed (NIR) scanning On-the-spot, real-time and affordable soil testing technology is enhancing the agricultural value chain in Uganda. On-the-spot, easy and affordable soil testing for Kenyan smallholder farmers). In addition, lab tests frequently include professional interpretation of results and recommendations. Provisory statements included in a lab report may outline any anomalies, exceptions, and shortcomings in the sampling, analytical process or 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).
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.
| + 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) |
| <500 |
| 500-1000 |
| 1000-3000 |
| >3000 |
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