Web-Based Nitrogen Recommendation Tool For Corn Grain In Nebraska.pdf

1. This publication edition provides information about a newly developed web-based nitrogen (N) recommendation tool for corn grain, adopted from our previous N recommendation equation. The N recommendations are based on expected yield, soil nutrient availability, residual nitrate, soil type, soil organic matter, water use, fertilizer cost, and time of application. Rec-ommendation information for phosphorus, potassium, sulfur, iron, zinc, and lime remains unchanged from the previous edition.

2. Crop production in Nebraska typically requires nitrogen (N) fertilization to supplement what is available from the soil. After N, phosphorus (P) is the nutrient most likely to be deficient for profitable corn production. Criteria for other nutrients are given, but the need varies across the state.

3. We highly encourage accounting for residual nitrate in fields to fine-tune N fertilizer recommendations to enhance profitability and minimize nitrogen losses. Deep core soil sampling is especially encouraged where elevated residual nitrate concentration might occur with recent manure applications, large fall or late season fertilization and subsequent above normal-precipitation, drought damage, hail damage, and compromised crops due to pests or other mishaps.

4. Soil nitrate sampling generally is not needed for corn grown after soybean or other legume unless the fields have a recent manure history. Sampling to 4 ft for residual nitrate will provide the most accurate recommendations, but a minimum sample depth of 2 ft is acceptable.

5. To determine P, potassium (K) and micronutrient needs, and soil organic matter content, collect soil samples from a depth of 0 to 8 inches every three to five years in the fall. Most Nebraska soils supply adequate amounts of potassium, sulfur, zinc, and iron, but on some soils, the corn crop will benefit from applying one or more of these nutrients.

6. Calcium, magnesium, boron, chlorine, copper, manganese, and molybdenum are seldom, if ever, deficient for corn production in Nebraska and toxicities may occur with overapplication. The complete University of Nebraska–Lincoln nutrient recommendations for all crops are available at http://extensionpubs.unl.edu/publication/9000016363764/nutrient-management-for-agronomic-crops-in-nebraska/ and up-to-date nutrient management information at https://cropwatch.unl.edu/tags/nutrient-management.

7. Our recommendations for fertilizer N are based on expected yield, the amount of residual soil nitrate-N (NO3-N), soil organic matter, other nitrogen credits (previous legume crop, manure, other organic material applied, irrigation water N), timing of application, and price of fertilizer and corn. These N recommendations remain a valuable option in planning and financial budgeting.

8. Alternative N management is suggested to improve fertilizer use efficiency, maintain or increase profit, and minimize environmental nitrogen losses. The fertilizer N recommendations for corn grain are available in a web-based digital nitrogen recommendation tool provided on the link https://cropwatch.unl.edu/nitrogen-tool.

9. N rate varies by year and application of about 60 percent of the fertilizer N in-season in response to crop needs should be considered on sandy soils. The expected yield should be about 105 percent of the five-year yield average. A higher yield goal may be appropriate if management improvements are expected to result in increased yield.

10. The N recommendation equation for corn silage (lb/ac) = [35 + (7.5 × EYS) – (8 × NO3-N ppm) – (0.85 × EYS × OM) – other N credits] × Priceadj × Timingadj. Optimal N rates are sensitive to wide fluctuations in fertilizer and corn prices.

11. Research conducted from 2002 to 2004 provides the basis for economic adjustments to the N recommendation equation, and is summarized in papers available at https://agronomy.unl.edu/nitrogen. The price factor in the N equation (Priceadj Price adjustment factor = 0.263 + (0.1256Corn:N) – (0.00421(Corn:N)2) is based on the diminishing effect of increasing N rate on corn yields.

12. If soil samples indicate greater than 15 ppm in the top 2 ft, it is recommended to adjust the N rate.