A successful fertility program starts with understanding what is already in your soil. Regular soil testing provides valuable information about nutrient availability, soil pH and overall fertility, helping growers make informed decisions about fertilizer applications and soil amendments.
Why Soil Testing Matters
Regular soil testing helps growers:
- Make informed fertilizer decisions: Identify nutrient requirements and develop fertility programs based on actual soil conditions.
- Optimize input costs: Avoid unnecessary fertilizer applications while addressing nutrient deficiencies that could limit crop performance.
- Reduce environmental impacts: Minimize the risk of nutrient losses and potential contamination of surrounding water resources.
When Is the Best Time to Test Your Soil?
For general soil fertility testing, early spring before fertilizer application or late fall are commonly recommended sampling periods. However, the ideal timing and sampling depth depend on the crop, type of test and information required.
For routine fertility monitoring, soil testing every one to three years is generally recommended, depending on cropping intensity and management practices.
Common Soil Tests and Sampling Guidelines
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| Soil Test | Recommended Timing | Sampling Depth | Purpose |
|---|---|---|---|
| Soil Fertility Test (Basic or Detailed) | Early spring, before fieldwork or fertilizer application, or late fall | 0–15 cm (6") | Assess soil nutrient levels, identify deficiencies and guide fertilizer applications. |
| Post-Harvest Nitrate Test (PHNT) | Early fall (September–November), after harvest and before significant nitrate leaching | 0–30 cm (12") | Measure residual soil nitrate to help guide nitrogen management for the following growing season. |
Sampling recommendations may vary depending on the crop, region and specific test requirements. For BC growers, consult the Government of BC's soil sampling timing and depth guidelines.
Important Considerations
Be consistent. Sample at the same time each year to accurately track nutrient trends.
Plan ahead. Fall sampling allows time to address fertility needs before spring planting.
Use the correct depth. Follow recommended sampling depths for accurate, comparable results.
Monitor soil pH. Soil pH affects nutrient availability and crop performance. TerraLink offers lime to raise pH and elemental sulphur to lower it.
How to Collect a Representative Soil Sample
Even the most detailed laboratory analysis is only as reliable as the sample submitted. Poor sampling practices can produce misleading results, potentially leading to incorrect fertilizer recommendations.
Before heading into the field, take some time to plan your sampling process. Consider the characteristics of your field, including soil type, cropping history, previous fertilizer applications and management practices.
Step 1: Identify Your Sampling Zones
- Divide fields into separate sampling zones where significant differences exist. For example, areas with different soil textures, cropping systems or management histories may require separate samples.
- Areas showing unusual crop growth or suspected nutrient deficiencies should also be sampled independently when investigating specific problems.
- Keep it simple where possible: If the entire field is relatively uniform, you may be able to sample it as one zone.
Step 2: Choose Your Sampling Method
Two common approaches to collecting soil samples are grid sampling and transect sampling.
- Grid sampling divides a field into smaller, evenly spaced sections. Multiple subsamples are collected within each grid to evaluate variations in soil properties across the field. This approach is useful for larger or more variable fields.
- Transect sampling is for relatively uniform fields. Subsamples can be collected along a planned route, such as a diagonal line or a series of transects across the sampling zone.
- The subsamples are then combined and thoroughly mixed to create a representative composite sample for that zone.
Avoid non-representative areas: Do not collect samples from fertilizer or manure storage areas, low spots or depressions, or areas near fences, roads, and drainage ditches. These locations may not reflect the overall field conditions.
Step 3: Collect Your Soil Samples
- As a general guideline, collect 15–20 subsamples from representative locations throughout the field.
- Ensure that each sub-sample is collected from the appropriate depth that is either 0-15 cm (6 inches) or 0-30 cm (12 inches) according to the test type required.
- Combine the subsamples from each zone to create one representative composite sample.
For more detailed information, including crop-specific recommendations, refer to the Government of BC's soil sampling methods and tools guidelines.
Step 4: Prepare and Label Your Samples
Proper sample handling is just as important as collecting soil from the correct locations.
- Use the right equipment. A soil probe or auger, clean plastic bucket, sample bags and permanent marker are the basic tools required.
- Prepare a representative sample. Remove foreign material such as grass, rocks and plant debris. Thoroughly mix the subsamples collected from each sampling zone before transferring the required amount into a sample bag.
- Approximately 450 g (1 lb), or two cups of soil, is generally sufficient for analysis, although laboratory requirements may vary.
- Label samples clearly. Include a unique identifier, such as the grower's name, field identification or sampling zone. Accurate labelling ensures laboratory results can be matched to the correct field or management area.
Turning Soil Test Results into Better Crop Decisions
Collecting a representative soil sample is the first step. The real value comes from understanding the results and using them to make informed fertility decisions.
Soil test results help identify existing nutrient levels, potential deficiencies and soil conditions that may affect nutrient availability. When considered alongside crop requirements, previous management practices and production goals, this information provides a foundation for developing an effective fertilizer program.
From selecting appropriate fertilizers to addressing soil pH and nutrient imbalances, our goal is to help growers make informed decisions that support crop productivity and efficient nutrient use.
Contact your TerraLink representative to discuss your soil test results and fertilizer requirements.
Written by: Mehakpreet Kaur