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In-Season N Management: Minnesota Perspective

In-Season N Management: Minnesota Perspective. 2010 Nitrogen Algorithm Workshop Aug. 3 and 4 th Stillwater, OK Jeff Vetsch and Gyles Randall Univ. of Minnesota Southern Research and Outreach Center. Research questions (answers).

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In-Season N Management: Minnesota Perspective

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  1. In-Season N Management:Minnesota Perspective 2010 Nitrogen Algorithm Workshop Aug. 3 and 4th Stillwater, OK Jeff Vetsch and Gyles Randall Univ. of Minnesota Southern Research and Outreach Center

  2. Research questions (answers) • Performance of mid- to late-season N applications for corn in MN • Sensor response vs crop response in corn after soybean and corn after corn • Sulfur deficient corn vs N deficient corn: Can sensors delineate? • Wet fields in Northern Corn Belt: Sensor based supplemental N recommendations.

  3. Corn yield responses to mid to late sidedress N

  4. Corn yield responses to mid to late sidedress N 1 of 23 sites gave a positive yield response to sidedress N at V6 8 of 23 sites gave a negative yield response (averaged 16 bu./ac.) 14 of 23 sites had no response - similar yields

  5. Summary: Performance of mid-season N applications in Minnesota • In 35% of comparisons split application of N yielded less than a single application. • Because of the risk of a yield penalty with mid-season N applications on dry land corn, Univ. of Minnesota recommends all sidedress N be applied no later than V6.

  6. Corn yield response to sidedress UAN application 2006-08 avg., corn after soybean at Waseca

  7. Summary: Split N applications of UAN • No differences in NDVI at V7 and V9 were found among the 90 and 180 lb/A N applied at V2 and 30+60 lb/A (V2+V7) treatments. • Very small differences in NDVI were found between the zero N control and 180 lb N/A, this would make algorithm calibration difficult. • Appling a small amount of starter N (15 lb N/A) at V2 and then delaying N application to V7 or V12 decreased yield, N uptake and NUE, compared with 90 lb N/A at V2 and 30+60 lb N/A at V2+V7.

  8. Effect of crop rotation on corn response to preplant vs split N: NDVI, yield and NUE. 2007-09 avg., Port Byron sil, SE MN

  9. Observations: Effect of crop rotation • Corn following soybean • Response index (RI) = 1.06 for NDVI at V8; RI = 1.34 for grain yield. • Corn after corn • RI = 1.18 for NDVI at V7-8; RI = 2.51 for grain yield (very responsive site).

  10. The effect of sulfur on early growth of corn and relative leaf chlorophyll content at R1 at Waseca. Funding provided by AFREC & FFF

  11. Sulfur responses in corn documented on medium and fine textured soil in MN. • Corn fertilized with S was 7% taller, had 17% more dry matter, and was a darker green color than the untreated control. • Implications for in-season sensing for N: • Sensors unlikely to delineate between N & S • Sulfur deficient corn frequently shows symptoms of N deficiency as well, especially later in the season. • Sulfur responses are more common in corn after corn with high residue (reduced tillage).

  12. Nafziger recommends applying nitrogen to corn in low, wet areas only after the water is gone and plants start to green up, which indicates they are getting some oxygen. If plants are stunted and far behind the rest of the field, applying nitrogen may not help. "I don't recall seeing severely stunted, deficient plants standing in saturated soils come back to produce much yield," he said. "That's not proof it can't happen, but the deck is stacked against these plants. Applying more inputs may be a demonstration of more hope than is justified."

  13. “Realize that the areas showing nitrogen deficiency have also lost some yield potential, so a full-rate application is likely not the best alternative, simply because the plant won't be able to use all that nitrogen to make yield. The sooner you apply nitrogen, the better response you are likely to see.” “… areas needing a rescue nitrogen application are most often patchy, so targeted applications rather than even applications across the field are key to minimizing cost and potential nitrogen loss to the environment and to increasing return on investment.” “Aerial photographs can be converted into variable nitrogen rate maps to guide a variable rate applicator.” Fabián G. Fernández

  14. Appropriate Strategy? Compromise Strategy Application Rate NDVI “Feed the Rich” “Starve the Rich” Application Rate Application Rate NDVI NDVI Multiple Factors + N Limiting Yield RI =1.5 RI = 2.0 Application Rate NDVI Raun et al., 2007

  15. Are sensor based algorithms designed for these extreme conditions (rescue N applications) and are they effective? • No reference strip in most fields • What does one use for a reference? • What if much of field has reached NDVI saturation? Red-edge? • Can sensors delineate between sufficient and deficient areas of fields near NDVI saturation? Mid-row sensing?

  16. Questions Jeffrey Vetsch jvetsch@umn.edu http://sroc.cfans.umn.edu/ http://sroc.cfans.umn.edu/People/Staff/JeffreyVetsch/index.htm 507-837-5654 Univ. of Minnesota Southern Research and Outreach Center

  17. No Starter or S Broadcast S, no N ATS Only Starter N Photo courtesy of Dan Kaiser, 2009

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