Advantages and Disadvantages of the Various Types of Tests for Soil Properties

Laboratory Testing

• Soil tests done in a laboratory require that the soil be removed from its natural state. Tests done in the laboratory have the advantage of being easier to perform and with predictability. The disadvantage to soil testing done in a laboratory is that these tests, despite the best efforts of the researcher, cannot duplicate the conditions of the soil in its natural state. The act of sampling the soil introduces other factors to the soil. These other factors are changes in the structure of the soil, its moisture content and relationship to the soil. The information gathered through laboratory testing also has the disadvantage of not being as accurate as testing the soil directly in the field.

Particle Size Determination

• One of the most important tests for classifying a soil is determining its texture, which is based on the amount of different sized particles in the soil. Testing a soil for its exact texture has the advantage of providing vital information about a soil's capacity to absorb and retain water, how suitable it is for certain crops and whether it is possible to build a road or structure on it. The disadvantage of soil's particle size test is that it is only accurate if the soil particles are spherical. Thus, the test is generally not very accurate as most sand, silt or clay particles are not spherical.

Saturated Solution

• Many tests for soil fertility and salt content require making a saturated soil solution. The advantage of these types of tests is that they allow important compounds to dissolve, which enables you to measure soil nutrients and salt levels. The disadvantage of these types of soil tests is that they change the soil's natural state and in doing so might introduce chemical reactions that would enhance the level of nutrients in the test. This would result in a higher tested level of nutrients than are actually in the undisturbed soil.

Organic Matter

• Testing for the quantity of organic matter in soil has the advantage of providing numerical information on the levels of plant nutrients in the soil. However, many common tests use toxic chemicals in the process of testing. These chemicals make the tests expensive, more complicated to run and potentially hazardous.