Soil Testing - Do It Now!

Posted: December 4, 2012

Did you now that 20% of crop fields lack a current soil test? Del Voight discusses the importance of taking a test and how to properly sample a field.

Here are some soil testing ideas:

With the mild weather we have an ideal time to gather soil test information. With 20% of the fields in Pa not having a current soil test, I’d like to focus on that issue. Corn grain yields in Pennsylvanian range from less than 100 bu/acre to more than 250 bu/acre. With high yields the nutrients contained in the soil are depleted (200 bu corn crop pulls (80lbs of P and 60lbs of K) and it is important to get a bench mark as to what remains. Soil test kits are available at the local Extension Office for 9 dollars and are the best way to measure the relative amounts of nutrients available for crop growth.

A kit is nothing more than a bag and paper. Errors occur when the sample is taken without regard to ensuring it represents the area to be tested. Some growers try to stretch a sample to more than 10 acres and that reduces the confidence that the test is accurate. I have seen yellow corn and soybeans, stalk rot, and mycotoxins from low potassium (K) levels. Low levels of Phosphorus (P) can cause purple corn leaves and numerous ear malformations. All of these could have been avoided with a simple test! Don’t forget those no-till fields need a surface pH as well to get a handle on any acid roof that might form over repeated N applications in this reduced tillage system.

1. Getting the sample now.

a. You need to ensure that the 10-15 acres that one bag is designed to represent does just that: - represent the soil profile in that field.

b. By and large the plant food (fertilizer) industry has offered the service of pulling the soil test for the farmer, but it is still up to you to ensure that the sample comes from the correct field. Each sample should represent the same soil type and therefore, the field may need to be split into several sub-samples. A typical 200 acre farm would cost about $180.00 in testing fees and just a few hours to sample . If this is too much, then 1/3 of the farm each year, as sample results are good for three growing seasons.

c. Take samples yourself or be sure a consultant with proper training is collecting them. Order enough kits to cover the fields that are due for testing.

d.Plan a day to gather the samples. Frozen soil slows the process down. With ATV’s other devices It should be a fairly speedy process. Label the bags first get them in a box in order and then go get them!

2. Overall planning

a. Have a plan! Determine a method for your farm that allows for timely three year testing or shorter. See if grid sampling applies (this could mean testing on a five year plan). Avoid “rented ground syndrome” where some farmers (turned miners) forget the building blocks for maintaining yields. Soil test, work with landowners, find solutions to providing the needs and not mining the soil. By the way, research indicates that depleted soils may take much more money to bring back fertility than adequately maintained soils.

b. Plan to sample by rotations. Many growers I work with will pull soil samples from soybeans then fertilize (P and K) either from manure or commercial sources in the fall for both a corn and soybean crop. Thus, in the crop season, only N requirements are needed and it eliminates the following year’s application. Remember P and K do not move in the soil and can be stockpiled for a season or more.

3. pH issues

a. Lime ¼ to 1/3 of your farm each year. This eliminates the tremendous bill and ensures that pH is maintained for the whole farm.

b. On no-till ground, turf areas, pastures, and alfalfa pull a 2 inch soil sample and test for pH. This can be done with a simple at home testing kit. I recommend the Cornell PH test kit. This might be the most important aspect of your fertility plan.

It’s that time of year to gather the tests. Get a plan, get the kits and get it done. Watch for future articles on tips to interpret and use your soil test for top yields.

Contact Information

Del G. Voight, M.S
  • Senior Extension Educator - Agronomy
Phone: 717-270-4391