Soils need to be tested properly to obtain accurate results. You need to prepare them correctly for proper sampling.
Right Sampling Time
Before you start any landscaping project, collect a soil sample from several different locations. You may need to wait until after you’ve applied the inputs for the first time to see if they change the pH.
Established lawns, trees, shrubs, and other perennial plants need to be sampled once every three or four seasons. Pick a good season for sampling according to your crops.
If soil testing is important for agriculture, then so is it for construction.
If an established area shows any signs of abnormality, take a soil sample immediately. You may be able to send matching plants or separate soil specimens for nematode assay, but avoid the areas recently limbed or fertilized for up to six to eight weeks.
Take Soil Samples For Analysis – Step-by-step Guide
Divide The Field To Collect The Samples
For routine soil fertility tests, first, traverse the fields to be tested. Note any differences in slope, color, texture, cropping patterns, and land use. Divide these areas into equal-sized sections. Then collect representative soil cores from each section.
Do not Sample Unusual Area
Avoid areas recently fertilized, old bunds, marshes near tree roots, compost heaps, etc.
Use Proper Sampling Tools
To get satisfactory results, you can use any number of methods including a soil tube auger, trowel, kauri, or pick axe. Make sure your equipment is completely free from fertilizers. Cleaning your implements should also be included. Other items include buckets, plastic sheets, bags, or tarps.
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Soil Samples Collection Process
Before starting your work, make sure you know what you’re doing. Digging holes without knowing how deep they should go can damage your plants.
A good rule of thumb is to dig no deeper than the diameter of your root ball. For example, if you’ve planted an Iris, then digging a hole that’s only 1″ deep is fine; however, if you were planting a tree, you’d probably want to dig a hole 2″-3″.
1. Soil quality (10cm) 2. Soil salinity & alkalinity (1 meter) 3. Garden establishment (2 meters) 4. Soil survey profile (1 – 1.5 meters)
Record the areas that were tested and keep a sketch map for future use.
Handling and Dispatch of Samples to Laboratories
Once you’ve collected all the samples, you’ll need to prepare them for lab testing. To do so, follow these guidelines.
- Drying
- Grinding
- Sieving
- Mixing
- Partitioning
- Weighing
- Storing
- Labeling
After collection, you must first let the soil air dry. Then you will have to grind them into powder using a wooden mortar and pestle. However, you can avoid contamination by using a wooden mortar and a pestle instead of a plastic one.
After crushing, you need to sift through the soil using a 20-80 mesh screen. Then mix all soil together by spreading them out on a piece of cloth or newspaper.
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From this bulk soil, you’ll need to take one representative soil from the quartering technique. Approximately 250 to 500 grams of the soil is enough for analysis. It must be stored in dry and clean plastic bags, screw-top containers, or cardboard boxes with appropriate labels.
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