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Today’s producers are confronted with squeezing more yield from increasingly expensive and scarce resources. They are also challenged to do that while maintaining good stewardship of the land and water resources that provide their living. The key to these challenges is to balance the soil fertility and allocate soil amendments to maximize yield. Soil sampling is the most cost-effective tool to accomplish this goal.
Unbalanced fertility has a number of potentially undesirable affects. Low levels of one or more nutrients limit the potential yield; they become the “limiting factor” regardless of other nutrient levels in the soil. Extremely high levels of nutrients impact the environment and put to waste those fertility resources. Soil fertility analysis shows the amount of each nutrient needed to obtain desired yield goals. Ultimately, proper fertilizer application results in the best yields, saves time and money and is environmentally correct.
How to Sample Soil
The biggest and most common mistake is taking too few samples per field to adequately represent that field. Take the soil samples with a soil probe, trowel or spade. The soil probe is the best tool for this job because each core will be of the same size and depth. Standard depth of sampling is 6 inches regardless of tillage practices. For mobile nutrients, such as Nitrate-Nitrogen, a 6-24 inch sample is suggested to capture movement of the nutrient. In no-till fields, a 2-inch surface sample can be taken to determine excessive nutrient stratification. Several cores should be taken to represent one area or one grid. For whole field composite sampling, collect 15 samples to represent the field, mix thoroughly in a bucket and fill sample bag about half full. For grid or management zone sampling, collect six samples to represent the area sampled, mix thoroughly in a bucket and fill sample bag about half full.
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Sampling Methods
The traditional method of Soil Sampling is whole field composite sampling. While this method is quick and inexpensive, it is not preferred to detect nutrient variation within a field.
Management zone sampling can be used to detect nutrient variation within a field. Topography, yield monitor data, soil type, satellite imagery, and/or electrical conductivity data are used to create soil sampling management zones.
Another soil sampling method to detect nutrient variation within a field is grid sampling. Depending on field uniformity and economics, divide it into 2.5 to 10-acre grid sections. The 2.5 acre grid is recommended. This gives an adequate sample number for the field size.
Uniformity is a must in sampling soil. To ensure accuracy and consistency, you must take the sample from the same location and the same depth — usually at a depth of 7 inches.
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When to Sample – Time of Year
Sampling can be done at any time during the year, although sampling when the soil temperature is below 50oF will result in a more accurate analysis of soil nitrate and sulfur. If initial sampling was done in the spring, then chose spring for resampling. Do not sample after recent fertilizer or lime applications.
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Submitting the Soil Sample
Place the cores in a paper bag and label the bag with the field and sample ID. When submitting the bags to the lab, please submit either the order online form or a completed paper form.
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