Farming 101Instructional MaterialvaMudhumeni

Soil sampling

by Albert Makendenge

Easiest Methods Of Soil Sampling

Soil sampling is the process of taking a small sample of soil, which is then sent to a lab to determine and test for the chemical, physical and biological properties which are critical to plant nutrition. The two most common methods, zone-based sampling and grid sampling are explained in greater detail below.

  1.  Zone soil sampling is a form of sampling that uses management zones to gain a better understanding of soil fertility. The field is divided into zones with similar soil or crop characteristics such as drainage and soil texture. The more variable the soil, the smaller the zones need to be to accurately map soil fertility patterns. For zone sampling, collect a composite sample from each zone. Larger zones require more samples than smaller zones. As a rule of thumb, 2 subsamples per acre in a zone are normally recommended. This method has a big advantage in that it acknowledges the differences in soil that exists within a particular field or piece of land
  2. Grid sampling, which is most commonly used by many producers and farm service providers, involves taking samples at locations spaced in a uniform pattern. Typical grid sizes range from 1 to 5 acres, with smaller grids (2.5 acres or less) providing the best results. For one-acre grid cell, collect at least five subsamples and for grid cells between 2.5 acres and 5 acres, collect between 8 and 10 subsamples. Although grid sampling may be inefficient in that it does not target areas of known variation in a field, it is very easy to implement and provides improved spatial information over whole-field soil sampling. Conclusively, the goal of sampling is to get a sample representative of the typical soil in the field and therefore these should be distributed (most commonly by the zigzag method) across the entire field.

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