How to Sample Soils for Pesticides & Herbicides
For best results for your garden, soil testing is recommended. Soil testing can provide useful information such as pH and nutrient content. These measurements can guide plant selection decisions. It can also supply information regarding past use of the land and environmental impacts from nonpoint source pollution (NSP). NSP is pollution from runoff such as from agricultural fields. Even if you don't use chemicals, NSP can bring unwanted pesticides and herbicides onto your soil. Areas in the watershed of farms and development are most vulnerable. Does this Spark an idea?
Things You'll Need
- Bucket
- Shovel
- Containers for samples
- Soil test kit
- Newspapers
- Soil auger or soil core sampler (optional)
Instructions
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Gather and clean materials to collect the soil sample. All tools and containers must be thoroughly cleaned to prevent contamination and provide an accurate reading.
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Dig several holes in the planting area to gather a representative sample, placing soil in a clean bucket. Pesticides and herbicides can be mobile in the environment, using the same transport methods of NSP that brought the contaminants to the soil in the first place.
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Alternatively, use a soil auger to collect undisturbed soil samples. A soil auger is a long tube that bores into the soil. The advantage of using a soil auger or core sampler is the ease of collection. It also collects a more complete soil profile. Pesticides and herbicides can percolate down into the soil over time. A soil auger can collect a sample deeper into the soil.
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Place soil samples in sterile containers for testing. When emptying the soil auger, try to keep the sample intact for an accurate soil profile. Some augers may come with plastic liners for collection.
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Place soil samples in a bucket and mix, if collecting samples from dug holes. Since the soil is disturbed, a soil profile is not possible. However, it is still possible to gather information regarding the presence of pesticides and herbicides.
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Empty the bucket contents onto newspaper. Allow the soil to dry. Collect a sample for testing. Your local agricultural extension office will be able to assist you either by doing the testing or directing you to another agency. Some agencies may provide collection containers. Results take a few weeks.
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Purchase a soil test kit for immediate results. Soil test kits are available at garden and home improvement centers. While they cannot detect specific pesticides, they can provide other indicators of contamination such as acidic pH and high nitrogen or phosphorus levels. The latter may indicate excessive residual fertilizers in the soil.
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Tips & Warnings
Test soils in early spring or late fall to give you plenty of time to correct any issues.
Always test soils before planting any edible plants for possible pesticide contamination.
References
Resources
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