How to Take Good Soil Samples
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KEY POINTS:
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Note: This
web help page is for general guidance only. Contact
your county Extension agent or land grant university
for more specific information on soil sampling. |
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Why
Sample your soil?
Soil testing is essential in order to check the levels
of nutrients, pH, and other factors that affect your soil's
ability to support plants. The most important factor
in testing is to carefully remove samples from your soil.
A good representative soil sample will help
you decide whether you need to take such actions as applying
lime or fertilizer. If the sample is not representative
of your soil, you run the risk of inaccurate test results,
inappropriate recommendations, and yield losses.
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What
do you need to do your own soil sampling?
To sample soil, you'll need a sampler or trowel to collect
the sample; a notepad and pen to record locations; a marking
pen to mark the subsample containers; a clean plastic bucket
for collecting and mixing samples; and plastic bags or
wax paper sacks to hold your subsamples for testing. Do
not use metal buckets, or plastic buckets previously used
to hold fertilizer of lime, to prevent possible contamination
of your sample.
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When
do you take soil samples?
Sampling can be done anytime. To maximize the benefits
of sampling and have enough time to apply fertilizes and
lime, we recommend that you do your sampling in the fall.
Fields with cultivated crops may be sampled
anytime after harvest and before planting. It's best to
sample fields with non-cultivated crops during the dormant
season.
Samples may be taken after planting if you
suspect soil conditions such as salt concentration is the
cause of poor stand establishment. Take the sample from
the area around the roots of the seedlings.
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| Record locations and sample numbers for future use. |
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Where
do you take soil samples?
If the soil is uniform across your field, take 15 to 20
samples from random locations throughout the field. Combine
these samples into one sample by mixing them in a plastic
bucket. If the soil is highly variable from one part of
the field to the other, divide the field into smaller uniform
areas and treat each of these areas as a separate field.
Take 15 to 20 samples from each area. Combine
these as suggested above. Test each combined sample from
each area separately. Separate test results will allow
you to appropriately remedy the deficiencies of each subdivision
within your field.
Indicators of variable soil include differences
in soil appearance, texture, wetness or salt content. Avoid
sampling close to lime or manure piles, animal droppings,
freshly fertilized rows, low spots, fences, and roads.
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| Break the field into smaller areas with similar soil
conditions, then randomly sample each area. |
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How
deep do you sample?
In turf and other shallow rooted crops, sample the top
three inches of the soil. In ornamentals and other deeper-rooted
cultivated crops, sample the tillage layer (the top six
inches). A shallow sample taken with a garden trowel may
be acceptable if it's taken immediately after tillage,
since most tillage operations mix the tillage layer thoroughly.
In non-cultivated crops, samples should be
taken from a depth of six to eight inches. In deep-rooted
non-legumes such as wheat, corn, Bermuda grass, sorghum
and cotton, take a separate sample of seven inches to 24
inches in addition to the tillage sample.
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| Don't sample too close to fence rows. |
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- Always use clean tools and containers
- Remove samples at the correct depth for your
plants
- Split non-uniform subdivisions. Sample each subdivision
separately..
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- Sample near lime, manure piles or animal droppings.
- Sample too soon after lime or fertilizer applications.
- Sample too close to fences or roads.
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