Wheat planting is just around the corner in Kansas, so now is the time to get your soil sampling done to have good information on which to base your fertilizer inputs. This is particularly important after drought and lower-than-expected yields for the previous crops in parts of the state.
The most important tests and nutrients to focus on this year depend in part on where you are located, the choices you make when applying nitrogen, and your tillage system.
The nutrients for which wheat is most likely to show responses statewide are nitrogen (N) and phosphorus (P). Wheat is the most P-responsive crop we grow in Kansas, and while P removal with wheat may be less than with corn or soybeans, the relative yield response is often the highest. Therefore, knowledge of P soil test levels and fertilizer needs will be valuable
A standard 0-6 inch surface sample is normally used to test for pH and the non-mobile nutrients such as P and potassium (K). Growers might also want to check for the micronutrient of zinc (Zn). Zinc is not a nutrient commonly found deficient in wheat production. However, it is important for corn and grain sorghum. Thus including it in your sample package would be helpful for planning for these rotation crops.
Soil organic matter (SOM) is an important source of nutrients such as N and sulfur (S). When calculating the fertilizer needs for both these nutrients, SOM is taken into consideration. For wheat production, 10 pounds of available N and 2.5 pounds of S are credited for every 1% SOM in the soil.
In addition to pH, SOM, P, K, and Zn -- all of which are non-mobile in soils and accumulate in the surface – the mobile nutrients N, S, and chloride can provide significant yield responses when deficient in soils. Since all three of these nutrients are mobile in soils and tend to accumulate in the subsoil, it is strongly recommended to use a 24-inch profile soil sample prior to growing wheat, corn, or grain sorghum.
In summary, wheat producers in Kansas should consider soil testing to help in making accurate fertilizer decisions. Accurate decisions are especially important during years with falling grain prices and tight budgets. Furthermore, after variable conditions and yield levels across the state, fertilizer needs may require adjustments based on soil tests. Wheat producers specifically, should use surface 0-6 inch samples to determine the need for lime on low pH soils, P, K, Zn, and soil organic matter. They also should be using 24-inch profile soil tests for N, S, and Cl. Now is the time to get those samples taken, to ensure there will be enough time to consider those test results when planning your fall fertilizer programs.
For more information on soil sampling and submitting samples to the K-State Soil Testing Laboratory, visit their website at http://www.agronomy.k-state.edu/services/soiltesting/ or stop into the Cottonwood District offices in Great Bend and Hays. We have soil sample probes to loan out and can mail off your soil samples and help you with interpreting the results and recommendations.
Stacy Campbell is an Agriculture and Natural Resources agent for Cottonwood Extension District. Email him at scampbel@ksu.eduor call the Hays office, 785-628-9430.
