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Optical Sensing to Determine N Needs of Rainfed Corn in the Northern CornBelt: The Future

Optical Sensing to Determine N Needs of Rainfed Corn in the Northern CornBelt: The Future. Gyles Randall Univ. of Minnesota 2007 NUE Workshop Monmouth, IL. Our Experience at Waseca. Number of field studies where NDVI measurements were made on N rate studies for corn. General Findings.

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Optical Sensing to Determine N Needs of Rainfed Corn in the Northern CornBelt: The Future

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  1. Optical Sensing to Determine N Needs of Rainfed Corn in the Northern CornBelt: The Future Gyles Randall Univ. of Minnesota 2007 NUE Workshop Monmouth, IL

  2. Our Experience at Waseca Number of field studies where NDVI measurements were made on N rate studies for corn.

  3. General Findings • Grain yield: preplant N generally > split N • for both CC & C-Sb • especially when split has a low rate of preplant N or SD N is applied after V8 • NUE: not consistently improved with split N • NDVI: For CC, V6-V12 distinguished among N rates w/V7-V11 best. • For C-Sb, V7-V11 sometimes distinguished between 0-lb vs greater N rates. • delta NDVI is small, does not distinguish between 30 & 150 lb N rates.

  4. Support Data 2005, Cont. Corn, N rate = 160 lb/A

  5. Support Data 2006, C-Sb, N rate = 90 lb/A

  6. Support Data 2006, Cont. Corn

  7. Soil Properties • Higher OM soils (>3%) • Soils frozen over winter • greater supply of mineralized N early in season • In IA, MN, and WI, 70 to 80% of total N taken up by corn after soybean is from the soil.

  8. Effect of Rainfall on Soil Moisture 2007, May-July rainfall = 9.9” or 2.8” below normal

  9. Factors Affecting Adoption of Optical Sensing for N Rate Guidance • Little interest among dealers, farmers, and consultants • fall and preplant application • workload (post-herbicides, insecticides & fungicides) • extra level of management • risk • cost (equipment, labor, time) • absence of research documenting the rewards/returns

  10. What is the Future? - Jury is still out - Dismal - Futile Are there options to the approach we have been taking?

  11. Research Opportunities • Apply swine manure at a rate that meets the P requirement and then supplement w/N at V10+ based on simultaneous NDVI measurements and N-rich strips • will NDVI differences be (1) predominantly related to N status (2) sufficiently robust to differentiate application rates • will these “later” N applications be efficient • acceptance is likely to be scale-dependent • system needs extra management • Higher altitude hyperspectral imaging

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