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Corn Harvest Quality Report 2015/2016

Contents

  1. Harvest Quality Highlights
  2. Introduction
  3. Quality Test Results
  4. Moisture
  5. Chemical Composition
  6. Physical Factors
  7. Mycotoxins
  8. Crop and Weather Conditions
  9. Planting and Early Growth Conditions - Spring (March - May)
  10. Pollination and Grain Fill Conditions - Summer (June - August)
  11. Harvest Conditions (September - October +)
  12. Comparison of the 2015 Average to the 2014, 2013, and 4YA
  13. Corn Production, Usage, and Outlook
  14. U.S. Corn Use and Ending Stocks
  15. Outlook
  16. Survey and Statistical Analysis Methods
  17. Survey Design and Sampling
  18. Statistical Analysis
  19. Testing Analysis Methods
  20. Corn Grading Factors
  21. Moisture
  22. Chemical Composition
  23. Physical Factors
  24. Mycotoxin Testing
  25. U.S. Corn Grades and Conversions
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VI. SURVEY AND STATISTICAL ANALYSIS METHODS

A. Overview

The key points for the survey design and sampling and statistical analysis for this 2015/2016 Harvest Report are as follows:

  • Following the methodology developed for the previous four Harvest Reports, the samples were proportionately stratified according to Agricultural Statistical Districts (ASDs) across 12 key corn-producing states representing 98% of U.S. corn exports.
  • A total of 600 samples collected from the 12 states were targeted to achieve a maximum ±10% relative margin of error (Relative ME) at the 95% confdence level.
  • A total of 620 unblended corn samples pulled from inbound farm-originated trucks were received from local elevators from September 23 through November 23, 2015, and tested.
  • A proportionate stratified sampling technique was used for the mycotoxin testing across the ASDs in the 12 states surveyed for the other quality factors. This sampling resulted in 185 samples being tested for aflatoxins and DON.
  • Weighted averages and standard deviations following standard statistical techniques for proportionate stratified sampling were calculated for the U.S. Aggregate and the three Export Catchment Areas (ECAs).
  • To evaluate the statistical validity of the samples, the Relative ME was calculated for each of the quality attributes at the U.S. Aggregate and the three ECA levels. The Relative ME for the quality factor results was less than ±10% except for three attributes – total damage, stress cracks and stress crack index (SCI). While the lower level of precision for these quality factors is less than desired, these levels of Relative ME do not invalidate the estimates.
  • Two-tailed t-tests at the 95% confdence level were calculated to measure statistical differences between the 2015 and 2014, and the 2015 and 2013 quality factor averages.