Though the USDA in its October crop production report hiked the 2017 U.S. corn yield by 1.9 bushels per acre to 171.8 bpa and lowered the national soybean yield by 0.4 to 49.5 bpa for a corn/soybean yield ratio of 3.47 vs. 3.36 a year ago the trend in the corn-soybean ratio has actually been opposite.
Based on enhanced seed genetics, higher yielding shorter season varieties and more precise planting and harvesting technology and equipment, soybean yields have risen on a relative basis to those of corn even as soybean planted acreage has expanded at a faster rate than corn over the past number of years.
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A look at the 20 year trend shows the ratio in 1998 at 3.70 trending down to 3.47 by 2017. In light of this we decided to look at the corn/soybean yield trend for the top 15 producing states of both crops as this graphic shows the 2017 results and both the five and 20 year averages.
Looking at the data 10 of the 15 states have seen soybean yields increase on ratio basis relative to corn over the past few years with some states seeing dramatic gains. For instance in Kansas back in 1998 corn yielded 4.9 times as much bushels as soybeans yet last year corn yields were less than three times that of soybeans with the five year average of 3.53 well below the 20 year average of 4.11 with this year’s ratio at 3.27. The same pattern though to a lesser degree is seen in the states of Kentucky, Nebraska, South Dakota and Tennessee as soybean yields seem to have gained on corn yields more in the Plains and Delta states than in the core Midwest region.
Perhaps this trend may reverse for during the big ethanol boom farmers were constantly planting continuous corn with the resultant 10% yield drag so should crop rotations return where they were in the past corn yields may improve vis-à-vis those of soybeans.
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