Death comes to us all. Life's but a walking shadow | I've been listening to the "back & forth" for a few weeks now and I think it's time to remind everybody that: "They don't call it rain-fed agriculture for nothing." For example, over the past 120 years, Iowa has averaged 3.86 " in July. Last year it was 5.92", in 2015 it was 5.51", 1&1/2 to 2 inches more than average. In 2012 it was 1.17 in.
Why is this important? We know from all sorts of experience that July rainfall is the single most important parameter for corn yield. For example, the Jewison Westcott weather adjusted yield model has five weather related parameters, mid-May planting progress, June precipitation shortfall,and July temperature deviation, July precipitation deviation and July precipitation squared. In the model, the July precipitation squared parameter only become significant given excess precipitation. By far the most important parameter is July precipitation at +/- 13.8 bu per inch of rainfall up or down from the average. The next most important parameter is the June precipitation shortfall at -9.5 bu/inch. Now this model was developed to cover the 8 most important corn producing states but since Iowa is such a large part of this area there's no reason to believe that the model parameters won't apply generally to Iowa alone.
We already know that Iowa has experienced a -1.22 inch shortfall in June. Iowa could have easily lost 10 bu. from trend last month. Now, we won't know Iowa's July precip. for another eleven days but if you look at the CPC's gauge based rainfall % of normal map for the past 7 days and the past 30days you can see that a significant area of Iowa, maybe even as much as a 1/3 to 1/2 is between 25-50% of normal. Well, 50% of 3.86 " is 1.93 ".
Well, if half of Iowa is 2 " short and remains 2" short thru the end of the month that's -2" x 13.8 bu/in x 50% area or maybe as much as -14 averaged over all of Iowa. This suggests that Iowa corn yields could possibly be 20 bu off trend where Iowa trend is somewhere around 184-185 bpa making 165 bpa Iowa's 2017 corn yield in neighborhood of 165 bpa.
In conclusion, if you've knocked 20 bpa off Iowa in addition to all the problems in the Dakotas, Indiana and Ohio to say nothing of the spots in Illinois, that's sobering thought.
PS: Iowa's yield in 2012 was 137 bpa trend would have been about 176 bpa or -39 bpa.
Edited by 1234 7/20/2017 15:02
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I've been listening to the "back & forth" for ....
