Soil sampling is not a difficult process. The most important issue to be remembered is to provide the sample to be taken represent the field as required.
It is possible that soil of a farm is very similar to the soil of another farm while there may be divisions in the same farm showing different characteristics. These different characteristics are: Color (the dark or light color deriving from the organic materials and iron compounds), bending and elevation texture (sandy, loamy, clay): Depth (deep, mid or shallow ), crop difference (the sections where different kinds or amounts of crops are gathered), different fertilization or liming (the sections where different fertilizers are used more or less or the sections where no fertilizer is applied or the sections where liming is performed or not) and the soil cultivation is different (such as different irrigation techniques and etc.). In other words, some part of a farm soil may be light colored while the other part of the same farm field may be dark or some part of the farm soil may be flat while some other part of the same farm field is inclined. Based on that, according to the soil depth, the farm soil may be deeper at the flat sections while shallow at the inclined sections. Other than that, farming may have been performed on the same farm field during the previous years and because of that different soil cultivation techniques may have been applied.
Before performing soil sampling process, the field where the sample is to be taken is divided into homogenous sections by taking the above-mentioned issues into consideration. In other words, the sections showing important changes are accepted as separate sections of the same farm field. Separate mixed (composite) samples are taken from each of these sections. The section where the mixed sample is to be taken should not be larger than 40 decades. Even if the soil is very homogenous, separate mixed samples are taken for each 40 decades of a field.
At the same time, it is recommended to mention the places where the soil samples will be taken on an informative document.
The composite (mixed) soil sample is a sample formed by mixing the samples taken from 8 or 10 points of the farm field in accordance with the size of the farm field. If the field where the soil sample will be taken is a farm field, it is started sampling from a point of the section to be sampled and as it is shown in the figure, 20 cm deep and V formed pits are dug by making zig zags as shown in the figure. Then from the smooth part of the soil, a 3 – 4 cm of soil section is taken by means of a trowel or a spade and taken on a shovel. The soil taken on the shovel is smoothed by clearing the excessive parts from the right and left parts of the shovel. The important issue to be taken into consideration here is not to throw away the soil section that represents the upper part of the farm field that is close to the handle of the shovel. The soil taken in accordance with the above mention way is taken in a bucket and the same process is repeated at 8 or 10 sections of the farm field. At the end, the soil gathered on a cloth or in a bucket is mixed well by hand, lumps are dissolved and the found stone and plant root parts are thrown away. After that process, the well-mixed soil in the bucket is taken by hand or a spoon and put into a 1 kg of a bag. Two copies of soil information labels are filled in and one copy is put into that bag while the other copy is tied to the bag or stuck on it. If the bag where the soil sample is put into is cloth, it should be washed well. If the bag is nylon, it should be new and should not be used before. The information form that is put into and stuck onto the bag should be written by a pencil. Because the letters written by a copy pen or an ink pen are damaged because of humidity and become unreadable.
The soil samples should not be taken through a straight line, they should be taken through a zig-zag line.
V formed pit is dug while taking soil samples. Then 3 – 4 cm wide, 18 – 20 cm long soil slice is taken from the smooth section of the pit.
If it is required to detect the micro food material content of soils, the sampling should be performed by using the tools manufactured from the materials that the micro food materials can not be involved (plastic, wood or stainless steel).
The samples prepared by that way can be directly delivered to the Soil Analysis Lab while they can be sent by means of email or local agricultural associations.
The depth and time of soil sampling
Although it is mostly based on the climate, the soil sample is taken one and a half or two months before the planting or fertilization. Soil sampling is not performed during the days of frost or while the soil is muddy.
The sampling depth varies in accordance with the plough and cultivation depths of soil. According to fertilization, mostly the cultivation side is related to our scope. Because most of the farm plants acquire their food materials from that part. While taking productivity samples, the sampling tools should not be steeped in the lower hard part. The depth of samples that are taken for fertilization purposes is usually 15 – 20 cm. From the wineries and orchards, the mixed (composite) soil samples are taken from 0 – 20, 20 – 40, 40 – 60 cm of depths. These depths levels can be increased in accordance with the kind and age of the tree. From this point of view, if it is required, it will be advantageous to take the recommendations of the authorized personnel in the lab who give fertilization advice in accordance with the soil analysis.
If the soil is not very wet or dry, the soil probe is preferred for the soil sampling process. If there is not any soil probe or auger, it is possible to perform soil sampling by means of a trowel or a spade.
The soil of the place where the soil sample is to be taken should be dry and tempered as it does not cling onto your foot. If the taken sample is a little bit wet, it should be dried under a shade without any interference. It is not a right process to dry the wet sample on a stove or a central heating system. If the sample is put in a wet bag, some kind of plant food materials can be absorbed by the cloth bag. If the sample is dried over a stove or a central heating system, some kinds of food materials can be vaporized. Therefore, no correct results are taken from both of these analyses.
At the same time, it is a right action to take a sample from an average part of the soil sampling section in order to learn the situation of the soil layer at 20 – 40 cm depth.
The places that are inconvenient for soil sampling
As it is mentioned before, the soil samples should be taken from the places that can represent the whole section where they are taken. Soil sampling is not performed from any random place of the farm.
The places those are inconvenient for soil sampling areas in the following:
- The places where used to stack fertilizer
- The places where animal fertilizers are located
- Threshing floors or the places where animals lie
- The places where stems, roots, and weeds are burned.
- The small bumped points of the farm field or the pits because of water accumulation.
- Under the trees
- For the crops that the line fertilized planting, the upper parts of the lines.
- The parts of the farm field that is close to a stream, forest, channel, water ditch, fence, and roads.
At the same time, if there is a small sandy place in the farm field, a sample should be taken from here but that sample should not be mixed with the other samples. Because it is required to fertilize that point separately from the other sections of the farm, a separate mixed (composite) soil sample should be taken from that point.
Sending Samples to the Soil Analysis Laboratories
The informative form is filled in with a pencil for each different farm or sections where the mixed soil samples are taken and put into the sample bag.
Also, a label is tied or stuck to the sample bag. A copy of the same label is put into the bag.
The soil sample that is prepared by that way is delivered to the closest soil analysis laboratory by the farmer or by means of the Provincial or District Directorates of Agricultural Affairs.
Analysis of soil samples and preparing the required fertilization recommendations can only be possible at least a week or ten days after the soil samples are delivered to the laboratory. It is required to add several days to the above-mentioned period during the autumn times because so many soil samples are sent to the analysis laboratories during that season. This process is required for a sensitive soil analysis and a good fertilization recommendation. Because of that reason, the soil samples should be taken in accordance with the procedure and by taking the planting time into consideration. The analysis results and fertilization recommendations of the samples that are sent only by that way can be delivered by the farmer before the seed – time.
Soil Sampling for Detecting and Amending the Problematic Sections
In order to detect and amend the various soil problems that have a negative impact on the growth of plants, it is very important to take the soil samples from the sections where these problems are seen.
It is certainly impossible to determine the number and depths of samples to be taken from these problematic sections. It can only be determined by field – analysis of the problematic section on – site and by means of the required laboratory pre-studies.
The samples from different textures and depths are taken in order to research the eliminate the actual causes of several soil problems deriving from the situations such as salinity, alkalinity, excessive limeness, the toxicity of food materials, texture, water permeability and groundwater. It is mostly required to take profile samples from these kinds of problematic sections. The deep profile pits are dug and samples from different soil layers are taken in order to identify the problems exactly at these kinds of problematic sections. If groundwater emerges from the pits to be opened, these pits are not dug deeper. Also, the groundwater samples from the waters emerging from these opened pits are taken for analysis.
Soil Sampling for Some Physical Analysis
Soil sampling is performed in different ways for some physical analysis of the soil. For example, the samples that are undistributed according to bulk density indication are taken for irrigation of soil. This kind of soil sampling is preferred because it damages the natural condition of the farm soil at a minimum level. The brass 100 cm3 special sampling containers with a blade at its opening are used for taking undisturbed soil sampling.
The other issues related to the soil samples
- For soil sampling, it is possible to use a trowel or spade as mentioned at above as well as some tools that are developed for that purpose. If the soil is not very wet or dry, the most useful one of these tools is the soil probe. These can be obtained from the agricultural associations or it can be learned from these associations to where to obtain them. The soil probe or auger especially provides soil sampling from the deeper layers of soil such as 20 – 40 and 40 – 60 cm of depths.
- The samples from two resembling farms should not be mixed and made a single sample. Even if the farm fields are small, they should be sampled separately.
Provided that conforming with all issues mentioned under that section, the farmers who take soil samples in accordance with the procedure and make these samples analyzed duly and apply the fertilization recommendations based on these analyses, perform balanced and conscious fertilization and provide important contribution both to themselves and the economy of the country by using their farm fields at optimum level.
Soil Fertility Analysis
pH (1:2 suspension)
EC (dS/m) (1:2 soil-water)
Lime (%) (Calcimetric)
Organic matter (%) (Walkley Black)
Texture (%) (Bouyoucos)
Available phosphorous (ppm) (Olsen-Spectrophotometer)
Available Potassium (ppm) (Amonium Acetate-Flamephotometer/ICP-OES)