Soil sampling refers to the act of taking or obtaining small quantities (samples) of soil from different parts of the field and taking to the laboratory for analysis.
Aims of soil sampling
To know the pH of the soil.
To know the organic matter content of the soil.
To know the moisture content of the soil.
To know the type of fertilizer to apply to the soil.
To know the type of crop to be grown in the soil.
To know the amount of air in the soil.
To determine the drainage and water retention capacity of the soil.
To know the capillarity of the soil.
To know the structure and texture of the soil.
To know the nutrient level of the soil.
To find out the presence of living organisms in the soil.
To fairly estimate how much increase in crop yields expected after applying a certain fertilizer.
After analysis, appropriate recommendations are made as to how the farmer can improve his soil by either applying fertilizers or other good farming practices.
Methods of soil sampling
Zigzag/ random method
In this method, the samples are taken from sites that are selected to run diagonally from one corner to another as shown below.
Zigzag/ random method
In this method, the samples are taken from sites which are randomly chosen in a zig zag format.
Procedures for obtaning a soil sample
Clear the vegetation around the area from which you are going to get the soil sample.
Make a vertical cut into the soil to a depth of 15-25 cm for crop land and 5 cm for pasture land.
Take a slice from the vertical cut made or use a soil auger to scoop out the soil.
Collect the soil from many points or sites usually 15 to 20 on average.
Mix the soil thoroughly to get a representative or composite sample.
Put the representative sample in a container e.g. soil tube or bag.
Label the container using a tag from both inside and outside with the following information:
Name and address of the sender.
Plot of field number.
Place of .location.
Date of sampling
Areas to avoid while getting soil for sampling
- Ant hills
- Old house sites
- Manure heaps
- Road embankments
- Where vegetation has been burnt
- Very wet areas
- Pig sties
NB: samples of soil from these areas give a misleading result therefore the areas should be avoided.
Tools used in soil sampling
- Hand trowel: to cut very thin slices of soil
- Soil auger: to tell the depth of sampling
- Hand hoe
- Shovel and spade: used as trowel
- Wheel barrow
- Panga or knife
Diagrams of tools used in soil sampling