Farm Talk

October 30, 2012

Fall is a good time to do some soil testing

by Scott Gordon
CNHI

Parsons, Kansas — Fall is a good time to soil test fields that will be planted to crops next spring. So once you have the beans, milo and corn out of the fields and the wheat put in the ground, take a little time and pull some soil samples on your fields. You can also make weather-related harvest or planting delays productive by going out and pulling a soil sample or two. The soil doesn’t have to be completely dry for a routine sample, but of course you have to be able to at least walk across the field.

Soil testing can also save you money. If you guess on the amount of fertilizer to apply you could be costing yourself money, especially with phosphorus and potassium applications. Under estimating what you need to apply can result in reduced yields—reducing potential income. While over estimating your needed fertilizer application simply cost you extra out-of-pocket expense in excess fertilizer.

Knowing your soil pH and lime requirement is also important. When a soil pH drops to around 6.0 and lower you could be costing yourself production, especially if legume crops are in the rotation. Over applying lime is also costly, not only in increased out-of-pocket expense for the lime but potential crop damage if the resulting pH is much above 7.0. Many herbicides are not labeled for use on high pH soils. Potential problems in this situation are direct damage to the growing crop and/or carryover problems to the next crop. To prevent possible problems you need to know the pH of the soil in your field and read all pesticide labels carefully.

Accurate test results start with taking a good representative sample. Results can be no better than the sample taken from the field. To take a sample for a routine soil fertility test you need a sampling tube, auger or spade, a clean pail, sample containers and notepad. Almost anything will work for a sample container, as long as it is clean and will hold about a pint of soil. People use small plastic bags, cans, paper sacks, etc. We also have soil sample bags available at no charge in the Extension Office.

Take 20 to 30 cores or slices from across the field, mix thoroughly in a pail and place about one pint of this mixture in a soil sample container. Be sure to label the soil container and keep a record of the identification names that you used for each sample. Sample cropland to a depth of about six inches and permanent sod (pastures, lawns, etc.) to a depth of four inches. Avoid pulling cores from unusual or problem areas in the filed. If you want information on a problem area, obtain a separate sample for that section.

Bring your samples to the Extension Office and we will send them to the Soil Testing Laboratory at Kansas State University for analysis. There is a small charge of approximately $7 for each routine fertility sample sent to the lab. When you come in, we will ask you for field identification names, previous crop, intended crop, and if it is an upland or bottomland soil series.

We usually receive the results back in a week or so. I will then make recommendations for lime (if needed), nitrogen, phosphorous and potassium. The recommendations are based on the intended crop, previous crop, soil series and the soil test results. We then send you the test results and recommendations. We also keep a copy in the office. This allows us to use this test to make recommendations for different crops at a later date, if you want us to. However, we recommend that fields be retested at least every three years.

Other special soil test are also available. These include profile nitrogen, zinc, iron, organic matter, and salt-alkali. There is an additional fee for each of these test and some require a different sampling method.

Regular soil testing is an easy area of crop production management that can save you money and/or help improve productivity. For more information on soil testing please feel free to contact Wildcat Extension District agent Scott Gordon in Independence by calling 620-331- 2690 or by email at sgordon@ksu.edu. You may also contact Keith Martin in Altamont by calling 620-784-5337 or by email at rkmartin@ksu.edu. We also offer programs in Family Consumer Science, 4-H and Youth, and horticulture. Program information and additional contacts can be found on our website www.wildcatdistrict.ksu.edu. £