Soil testing critical after a drought year
Expect soil nutrient values — particularly residual nitrate — to be more variable this fall than in recent years from field to field, and within fields. The only way to know the availability of soil nutrients is to soil test. Fertilizer costs can easily exceed $100/acre for irrigated corn. Nitrogen prices currently range from about $0.50 to $0.70/lb N, depending on the fertilizer source. Phosphorus prices range from $0.45 to $0.80/lb P205, depending on P source and the price of N fertilizer. Thus, an irrigated corn field requiring 180 lb N/acre at $0.60/lb, and 60 lb P205 at $0.60/lb, will have a fertilizer cost of $148/acre. Making accurate estimates of profitable fertilizer rates for next year will require accurate soil test information. Guidelines for soil testing are available in two Extension publications — Guidelines for Soil Sampling (G1740) and Soil Sampling for Precision Agriculture (EC154).
While there should be plenty of time for soil sampling this fall due to an early harvest, consider sampling next spring instead. Dry conditions this fall may make sampling difficult, and spring sampling may result in a more accurate prediction of nitrate-N availability, depending on weather conditions this winter. Nebraska is fortunate to have several good analytical labs where growers can have soil samples tested. Contact any of these Nebraska soil testing labs for information on current pricing and how to ship samples.