Are U.S. crop conditions as good as ratings suggest?

CHICAGO - If anything is ruining the presumed narrative of troubled U.S. corn and soybean crops, it is the crop condition scores. On Monday, the U.S. Department of Agriculture's (USDA) statistics agency upped the ratings on the world's largest co...

Agweek file photo.

CHICAGO - If anything is ruining the presumed narrative of troubled U.S. corn and soybean crops, it is the crop condition scores.

On Monday, the U.S. Department of Agriculture's (USDA) statistics agency upped the ratings on the world's largest corn and soybean crops by one percentage point apiece in its weekly crop progress report.

The new figures place 76 percent of U.S. corn and 71 percent of soybeans in good to excellent condition.

Soybeans conditions are among the top four best of the past 30 years and corn conditions are the best since 1999. Both crops are doing better at this point than each respective record-yielding year, 2014 for corn and 2015 for soybeans.

Such promising condition scores have caused some traders and analysts to push their final yield estimates up over USDA's trendline yields of 168 and 46.7 bushels per acre on corn and soybeans, respectively.


But recent weather has not been entirely favorable, and simply following these ratings could lead to trouble since actual conditions may not be as good as meet the eye.



The problem with crop conditions is that they mask the fact that the weather this season thus far has certainly been different than the previous two.

June is an important month for the development of corn and soybeans as it sets up both crops for their pollination periods later on in the summer.

Collectively across the U.S. growing region, this year was one of the drier and warmer Junes in recent memory. This is in stark contrast to the past two years, particularly with rainfall. ( )

Between now and the end of August, nighttime is critical for corn because the warmer the overnight low temperatures become, the greater the potential for kernel density to shrink. Although there so far have been a few cool July days, the second half of the month looks to be downright hot and much warmer than the previous two banner crops. ( )

But not all problems may be visible right now. Going back to when the corn crop was planted in April and May, soils were generally wet. Some states had near record wet soil moisture at this time, including parts of Iowa and Nebraska, which are two leading corn producers. ( )


The problem with soils being wet at planting and then warm during development in June is that the corn's roots may not have gotten as thick or gone as deep as they normally should. What this could mean is that while the plants look good now, they may struggle to draw in sufficient moisture and nutrients later on when the corn is undergoing grain fill.

This is less of a problem with soybeans since they are not as fussy as corn is with the weather. Since soybeans will not start setting and filling pods until August, it is a bit difficult to assess soybean weather in the same way as corn right now, but a hot July could diminish moisture which is soybeans' number one desire.

The latest drought monitor suggests that moisture at this same point in the year is not as sufficient as it was last year at the same time. If this trend continues or gets worse, soybeans could have some issues down the road. ( )



Vegetation density implied by satellite imagery should be one of the best ways to corroborate the high crop condition scores, but the imagery has identified some obvious problem areas.

The eastern corn belt, particularly Ohio and Michigan, are struggling the most. Vegetation is much less green than it should be at this time of year, but these two states together only account for 7 percent and 10 percent of the corn and soybean crop, respectively. ( )

The vegetation in bigger producers Illinois and Indiana is not as lush as 2015 although it is very close to normal, which props up crop conditions as a whole across the eastern belt. Similarly, the western belt is supported by heavy hitters Iowa and Minnesota, where vegetation density is equal to or better than last year. ( )


But the Plains states, including Nebraska and South Dakota, have been battling some weather issues lately and vegetation density falls short of average as a result. The weather only looks to become more challenging for these states as next week will bring in temperatures that could break the century mark for several days in a row.

The VIIRS Vegetation Health Index is an imagery product offered by the U.S. National Atmospheric and Oceanic Administration and it compares vegetation health by the week. Taking a look at a map of conditions from the first week in July, the prime corn and soybean growing states appear to be in worse health now as compared to one year ago. ( )

Both views of satellite imagery together with this summer's weather trends indicate that U.S. corn and soybean condition ratings might be artificially high at the moment, and that precautions should be taken when using them, particularly after the heat moves in next week.

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