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Using yield data correctly
By Jeremy Dirks
Pioneer Hi-Bred agronomist
Using yield comparison data when selecting hybrids and varieties: For decades on-farm comparisons have helped growers measure performance and plan for the next year's crop needs. Yield data from one side-by-side or plot comparison is important, but a decision should not be made from this alone. An on-farm hybrid or variety test plot provides valuable information about how products perform at that location during that growing season only. Comparisons of hybrids or varieties should include at least 10 different locations in order to make a prediction about how that product may perform in the future. It is very important to look at yield data over a two- or three-year period, if possible, and plant a package of hybrids or varieties that fits your individual farming operation. Consult with your Pioneer representative for yield results in your area.
Fall fertility management: Preparation for next year's cropping season can start as soon as harvest is completed, if the weather cooperates. Fall soil testing and fertilizing can give you a nice head start on the next year's crop. Soil testing is the most accurate way to determine if nutrient levels are going to be a limiting factor in your fields. As always, accuracy is imperative. Good sampling procedures done by you or a reliable consultant or retailer are a must.
Whether or not to apply nitrogen in the fall is a perennial question. It is a practice that has both associated risk and potential benefits. The risk is, of course, the loss of nitrogen, and the benefits are primarily in timesaving and spreading of workload. If you are considering nitrogen applications this fall, use anhydrous ammonia. When applied to the soil, anhydrous ammonia is quickly converted to ammonium, which is positively charged and adheres to soil clays and organic matter. Anhydrous ammonia also has the advantage of being placed in a narrow zone in the soil, also making it less available to losses than other nitrogen sources.
Soil temperatures should be 50 degrees or less at a 4-inch depth to limit the conversion of ammonium to nitrate. Nitrification inhibitors slow the nitrification process and may be beneficial for fall-applied anhydrous applications. Fall nitrogen applications will have more risk on soils prone to ponding. Do not make fall nitrogen applications on sandy soils or in sensitive groundwater areas. If you are considering fall-applied nitrogen, limit your potential risk by doing so on only some your fields going to corn and choose fields that are less prone to waterlogged conditions. Producers need to weigh the risks and benefits with their own farming practices to come up with a nitrogen-management strategy that fits their operations.
Applying fertilizer to meet crop removal rates will maintain soil test levels at current levels. If it is necessary to raise soil test levels, apply for crop removal plus a buildup rate. It takes approximately 9 pounds P2O5 per acre and 4 pounds K20 per acre to raise the P and K tests by 1 pound per acre respectively. Some labs report soil test values in pounds per acre and others in parts per million (ppm). Remember that 1 ppm equals 2 pounds per acre. Therefore a K test of 150 ppm is equal to 300 pounds per acre.
Editor's note: Crop Talk is brought to you by agronomists serving your community to keep you informed about current growing conditions and crop-management issues affecting the crops in your area. Jeremy Dirks, Kearney, Neb., is an agronomist with Pioneer Hi-Bred International, Inc.
Date: 10/20/04
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