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.
Sampling can be done anytime. To maximize the benefits of sampling
and have enough time to apply fertilizers 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.
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 to avoid metal contamination. Make sure the bucket was not
previously used with lime or fertilizers.
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 those 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.
In turf and other shallow rooted crops, sample the top three inches
of 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,
bermudagrass, sorghum and cotton, take a separate sample of 7 to
24 inches in addition to tillage sample.
Use a zigzag random approach when taking samples and subdivide non-uniform
fields into smaller, more uniform areas.
Taking soil samples at random locations throughout your field is
important to get a good representative picture of your soil conditions.
One way to ensure this is to use a zigzag pattern across the entire
area.
Don't take all of your samples:
- from one side of the field
- only from the corners of the field
- from the same spot on each side of the field
Random sampling ensures "non-bias" in your soil sample.
This results in a sample that is representative of your entire field.
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