Soil Sampling
WHAT
Soil sampling can refer to any kind of soil investigation or analysis. The most common (and the type required every 3 years by the VT Required Agricultural Practices) is a chemical fertility analysis. This tells farmers things like pH, organic matter, phosphorus, potassium, and several other key nutrients. The Cornell Soil Health Test is a more comprehensive and intensive option that measures the soil's biological and physical health in addition to chemical. Besides these two tests there are many other ways for farmers to understand their soils better - from bringing out an NRCS or Extension Soils Scientist to simply slowing and digging around to observe more on their own.
WHY
Soil sampling helps a farmer understand how the soil's current chemistry, biology and structure align with the needs of their crops. Soil sampling can:
Improve water quality: Fields that have a high level of phosphorus need to be managed to keep that phosphorus in the field, make it available to crops, and prevent further phosphorus build-up.
Improve crop yields & soil health: Soil sampling gives farmers a road map for how to meet the immediate and long-term needs of their soil and their crops, guiding applications to adjust pH, provide macronutrients like NPK, or boost particular micronutrients. Farmers can also understand how their soil's organic matter measures up - which is important for both holding water and releasing it (like a sponge) and for making nutrients available to plants. Low organic matter levels might lead a farmer to grow a high-biomass cover crop and till it in, or make other significant management changes.
Save money by using manure and fertilizer effectively: Fertilizer is expensive, and it's often expensive to transport manure to where it's needed most. Regular soil sampling helps farmers invest in exactly how much fertilizer they need to optimize their crop's growth, and nothing extra to wash into waterways.
Meet a requirement of VT's Required Agricultural Practices: In 2016 VT required all farms to write, use, and keep-updated a Nutrient Management Plan, and as part of that plan to take soil samples every three years for all fields where manure or fertilizer is mechanically spread.
HOW
It's easy to take your own soil tests. If you wish, contact your local Conservation District or UVM Extension office and they can typically at least lend you a soil probe, if not come out in the field to help. If you need a Nutrient Management Plan or help updating your Nutrient Management Plan, definitely contact your Conservation District or Extension staff - they'll be glad to help and may be able to give you a discount on your GoCrop renewal.
How to take a soil sample (adapted from UVM's flyer)
The reliability of a soil test is only as good as the sample you submit. The small amount of soil in the sample bag you send to the Agricultural Testing Lab must represent the entire area to be fertilized. Avoid unusual areas such as those where fertilizer or lime has spilled. Take samples before lime, fertilizer, or manure are added. Use only clean equipment for collecting soil samples.
Where to sample: The area to be sampled should be as uniform as possible in terms of soil type and cropping and fertilizing history. For practical purposes it should be an area you expect to fertilize as a unit. This means separate samples for annual mixed vegetables and a strawberry patch, for golf green and fairway, and for different major crops in a commercial nursery or vegetable operation. If you have a problem on part of a lawn, garden, or commercial production field, you may wish to determine if soil fertility is the cause by taking one sample to represent the “good” and the other to represent the “poor” area.
Take a good sample: Collect a number of cores or slices by walking in a zig-zag pattern over the area. Mix cores thoroughly in a clean pail for a composite lab sample. The greater the number of collected cores mixed together, the better the sample will represent the average condition of the sampled area. Consider 10 cores as the minimum for home gardens and lawns up to 10,000 square feet in size. Larger areas should be represented by at least 15 to 20 samples. Choose one of the following tools:
Soil Probe or Auger – A soil probe or auger, available from mail order catalogs and garden or farm supply outlets, is the best tool for sampling. An auger will be needed if the soil is very stony or gravelly. Simply push the probe (or push and turn the auger) into the soil to the desired depth, lift up to remove the core, and place it in the clean pail. Sampling depth should be 4 to 6 inches deep for lawns, turf, or other perennial sod, or tillage depth (usually 6-10 inches) for annually tilled crops.
Garden Trowel or Shovel – If a soil probe or auger is not available, collect your sample by pushing the blade of a garden trowel, shovel, or spade into the soil to the desired depth. Cut out a triangular wedge of soil and set it aside (to be replaced after sampling). Now slide your blade into the soil again taking a thin (half inch) slice from one side of the hole. With a knife, trim the slice to about a 1-inch strip of soil down the center of the spade – top to bottom. Save this “core” as part of your composite lab sample.
Mix the sample and fill the sample bag: Make sure that all the cores are thoroughly mixed together. Your soil test mailer contains a plastic bag intended for one lab sample, or you can use any clean, plastic sealable bag. Fill plastic bag with approximately 1 cup of the mixed sample. Print and fill out the sample submission form available at the UVM lab's website. If submitting multiple samples, include one check for total being tested.
Follow the nutrient recommendations, and take tests again in three years. Try to take your samples at roughly the same time of year each year.
COSTS
The lab fee for a basic fertility analysis at UVM's lab costs $15 per sample. For Nutrient Management Plans, each sample can represent no more than 20 acres and should represent either a single field or fields that are nearby and managed the same way.
ASSOCIATED & COMPLIMENTARY PRACTICES
Nutrient Management
RESOURCES
Your local Conservation District
Your fertilizer dealer or contracted Technical Services Provider