How to Take a Soil Sample for Field Crops

Why take Soil Samples?

Routine Soil Analysis

Introduction

We are specialists in soil fertility management and developing fertilizer programs for farmers.  We carry out fast and affordable soil analysis in our laboratory, and we use the results to make the right recommendations for your farm. We are independent and don't sell any farm input products and we only offer you the best advice.

Soil testing is essential for building sustainable soil fertility and fertilizer management programs for your farm, to increase your crop yields and reduce your input costs.   Accurate sampling is absolutely critical to a successful soil management plan as all recommendations are based on the samples submitted to the lab.

How to take a soil sample in a field crop

Equipment Needed

1.Sample bags(we can supply at no charge)

2.  Auger or shovel

3.  Bucket

4.  Sample submission forms (please request these from us)

5.  Field logbook

6. Labels or marker pens

SelectingSample Areas

When you are selecting areas to sample you must remember that there is no set size but we don’t recommend single sampling areas of>20 Ha.The actual size of the sample area is determined by certain factors.Areas that differ in any of the following should be sampled separately: 

  1. Soil type.
  2. Soil colour.
  3. Previous cropping history.
  4. Previous lime or fertilizer applications.
  5. Slope.
  6. Drainage.

For example, eleven samples have been taken from the area below:-

Where very large areas of land are uniform, divide the land into areas that would be treated as a unit (i.e.one field),and sample these areas individually.One sample should not represent more than one field,as individual fields will have had different treatments in the past.As mentioned ,it is recommended that one soil sample should not represent more than 20 hectares regardless of apparent field uniformity.This is because non-uniformity is usually difficult to assess over broad areas of landscape. Large fields can be divided for sampling purposes into two or three smaller sections. 

Make a map of your fields and always label the field with the same name – this way you can follow your field’s soil health historically.

Sampling depth

Depth of sampling is critical because tillage and nutrient mobility in the soil can influence nutrient levels in different soil zones.Sampling depth depends on the:

  1. Crop.
  2. Cultural practices.
  3. Tillage depth.
  4. Nutrients to be analyzed.

Plant roots,biological activity and nutrient levels occur mainly in the top soil (0-25 cm) hence most of the soil samples are collected within this layer.For tree crops and other deep rooted crops,samples from the sub soil (25–50 cm) should also be collected.

Sampling Procedure

Procedure

  1. One sample should consist of about 20 cores taken from the set area.It is recommended that the cores be taken from the area in a zig zag pattern as shown below:
  2. Scrape away surface litter and crop residues and sample the whole core from the true soil surface to 25 cm depth.
  3. Put the soil cores in a bucket and mix thoroughly. 
  4. Label the bag carefully with your company name,farm name,field name,sample depth and date, and crop to be grown. Fill the soil bag half full (500g), from this mixed representative sample.
  5. Different tools such as a soil sampling tube,soil auger,or spade may be used to take soil samples.Do not use galvanized,soft steel or brass equipment if trace metal analyses are desired.  Clean all tools between sampling.
  6. Avoid taking samples from areas such as lime piles, fertilizer spills, ant hills,  gate areas,livestock congregation areas,poorly drained areas,dead furrows,fertilizer bands,old fence rows,or any other unusual areas.

The quality of any analysis is directly related to how well the sample is collected.


N Fertilizer Recommendations

Our lab analysis determines the amount of available nitrogen in your soils and we give you calculated nitrogen fertilizer recommendation based on the results.  This is based on your yield target, nitrogen removal, organic matter and nitrogen efficiency of your soil type. 


Soil Health Care Program

Our Soil Health Care Program is a complete service package for growers who want to sustain farms profits, through building and maintaining high levels of soil fertility in each of their fields.

The service includes:

  •          On farm per field sampling by our technician before each crop
  •          Full Soil Health Audit and Soil Fertility Analysis in our Laboratory
  •          Detailed lab report including full Soil Fertility Correction & Fertilizer Recommendations
  •          Farm visit every 6 months by our Soil Health Advisors to monitor the program and advise on additional soil health practices such as crop rotations and green manure crops


Soil Life Test

Soil and plants interact in the search for and supply of nutrients. Soil provides the environment for plant growth while plants participate in building and sustaining soils by releasing exudates and leaving behind their own residues. This dynamic cycle is best described as the soil-plant system. In the process, humus is formed and carbon dioxide (CO2) is released due to microbial activity. The relationship between these processes is an important indicator of soil fertility. Declining rates of CO2 respiration are associated with intensive tilling, compaction and over fertilizing. These soil practices are potentially destructive and inhibit the soil’s ability to sustain its humus content, the natural reservoir of organic nutrients and soil life. As soil declines, microbes starve for food and the rate of CO2 respiration decreases, indicating deteriorated soil quality. Being able to evaluate the turnover of organic matter via CO2 respiration is important for a number of reasons:

  • •       Indicator of soil health – The rates of CO2 release is generally regarded as an indicator of Soil Health and is favorably improved with practices such as cover cropping, where the quality of soil is improved by building the organic matter through accumulation and decay of roots and plant litter.
  • •       Indicator of soil nutrients – Measure and evaluate the rate of carbon exchange, to estimate potential release of nutrients such as nitrogen and phosphorus that are components of humus.

Sample handling and dispatch to lab

  1. If possible soil samples that are moist should be air dried on site away from dust contamination and not in direct sunlight
  2. Samples from outside Kenya require an import permit.  Please contact us to get the neccessary documents.

Routine Soil Analysis Packages

Code Analysis Name Description Days
CNSA022 Complete Soil Analysis pH, EC, %OM, %N, P, K, Ca, Mg, Na, S, Fe, Mn, Cu, B, Zn, CEC, Ca:Mg ratio, %Ca, %Mg, %K, %Na, %OB, %H with Full Recommendations 7
CNSA104 Available Soil Nitrogen Available Soil Nitrogen kg/Ha (Top soil + Sub soil) 7
CNSA040 Soil Life Test Soil Biota Respiration Test (indicator of soil health) 7
CNSA090 Exchangeable Acidity (Hp) Hp 7
CNSA050 Soil Texture Analysis % Sand, % Silt, % Clay (Texture Class) 10
CNSA091 Heavy Metals As, B, Cd, Co, Cr, Cu, Pb, Ni, Zn.  7

For more information please contact us through:

Office Mobiles: +254 (0)720 639933 / +254 (0)736 839933

Location: Cooper Centre, Kaptagat Rd, Loresho, Nairobi, Kenya


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