Week 3: Soil Sampling

Your soil results will only be as accurate as your sample taken.  Be sure to take random samples to get a good representation of your plot’s soil requirements.  When using a spade shovel dig a V-shaped hole approximately 6 inches deep, cut a slice from the side of the hole for your sub-sample (sub-samples make up a core sample, core sample is a representation of the entire plot area and the sample that will be sent to the laboratory for analysis).  Try to spread 10-15 sub-samples per acre to achieve a good core sample of the area, mix sub-samples together in your collection pale or bucket.  There needs to be enough sub-samples so that the core sample fills the soil sample bag to the line.  Make sure to label your core sample bag, so that it is not confused with other plot samples.  Another sampling tip to keep in mind is to always sample your soil the same time each year (sample every fall, if taken in the fall, every spring if taken in the spring). This will aid in obtaining accurate nutrient levels, as they can change during the growing season.  Once you’ve labeled and collected your core sample(s), your farm service center can assist you with filling out a soil sample information sheet.

Understanding Soil Test Results:
Unless you’re totally into soil science, a results sheet can look pretty intimidating with all the information and values listed on the document.  So let’s simplify your results and concentrate on the important values that are directly related to food plotting:

Soil pH: is a measurement of active soil acidity or alkalinity in the soil.  If the pH value is below 7, the soil is considered acid and if the value is above 7, the soil is considered alkaline.  The most desirable pH range for the majority of crops grown is between 6.0 and 7.0.  Although, many crops will grow at a lower pH value the closer the soil is to the optimum range the better the crop output.
Building your soil pH to optimum range takes time, so don’t let an acidic value discourage you from planting that area, unless it’s really extreme.  Acceptable ranges can be 5.3 to 7, depending on crop to be grown.

Lime:  Liming is directly related to soil pH, the purpose of applying lime to your food plot is to reduce acidity in the soil allowing nutrients to become readily available for plant uptake.  You can apply a ton of fertilizer to a food plot with little effect if the soil pH is not in an acceptable range. If lime is needed to reach your crop’s target pH, it will be listed under this category. There are 3 types of lime that can be applied to the soil to reduce acidity, Ag Lime, Pellet lime and Rapid Lime (NP Wildlife Products liquid lime). 

AG lime has the longest effect of maintaining and adjusting soil pH, it also takes the longest to become active in the soil.  One ton of AG lime can raise the soil pH a full point, although it takes 6 months to take effect.  AG lime is more difficult to apply and requires an AG applicator; there is however some new ATV applicator implements on the market.  On the NP Test Farm we apply AG lime every 2 years, according to soil test requirements.

Pellet lime is more expensive than AG lime; it works faster in the soil and will begin adjusting soil pH within a couple of weeks after applying.  Pellet lime is a quick fix for the season raising soil pH anywhere from 0.5 to a full point; it should be applied every year according to soil test requirements.

Rapid Lime (for more information on this product, check out the NP web page)

Soil Fertility Guidelines- Your soil test report is a guide to applying the correct amount of primary nutrients (N-P-K) needed for a crop response (potential growth and output). The crop to be grown and units of fertilizer are listed in this section of the report.  The unit values are given in lbs/acre or lbs/1000 sq ft.  The requirements of N-P-K are listed in lbs of actual nutrient; a farm service center can convert this information into a fertilizer analysis.  What you commonly see as 10-10-10, 6-24-24 etc.  Your local fertilizer dealer will tell you how many lbs of the analysis to apply per acre matching your soil test requirements.