Scott Irwin Profile picture
May 18, 2020 10 tweets 4 min read Read on X
1. My next thread deals with the yield impact of late corn planting. We looked at three approaches to estimating impact on US avg corn yield in a #FDD article last week farmdocdaily.illinois.edu/2020/05/the-im… Image
2. The first method simply regressed trend deviation for US avg corn yield on the measure of late planting. Slope is -0.2, or decline of 2bpa for each 10% increase in late planting. Notice how well that fit the obs for 2019. Image
3. The explanatory power for this regression is low because we took trend out and only included one variable---late planting. Did not account for any weather impacts. Could result in a biased regression coefficient estimate due to "omitted variable bias." Image
4. So, we also estimate a crop weather regression model for US avg corn yield. Included trend, late planting, and monthly precip and temp variables. The full enchilada. coefficient estimate was -0.22, almost same as simple one variable model.
5. Final approach was different. Rather than using time-series data we used a cross-section of states for 2019. Idea is that variation in late planting and yields across major Corn Belt states is another way to identify the relationship. Image
6. Despite the extreme simplicity of this cross sectional approach, we get a very comparable estimate of -0.17. For each 10% increase in late planting across these 10 states in 2019, state corn yield dropped 1.7bpa. Image
7. In sum, all three methods yield an estimate very close to -0.2, implying that a good rule of thumb is a loss of 2bpa for every 10% that planting on May 20th is above the long run average of 17.7%. Good to know.
8. A real asymmetry in late planting impacts on yield that can be missed. Gain for early planting (0 late planting) is about +3.5bpa above trend but loss from late planting can be much larger, such as almost 7bpa in 2019.
9. Finally, the kind of late planting impacts discussed in this thread and in the article are related but different than those in agronomic planting date trials. Apples and oranges. Not directly comparable.
10. Here is the link to the #FDD with all the details farmdocdaily.illinois.edu/2020/05/the-im… Up next later this week---late planting and soybean yield.

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More from @ScottIrwinUI

Jul 12
1. We keep getting rain around here. About a half an inch last night. We are pushing 7 inches this week in Champaign County. I went out to what I call the Field of Dreams to walk our dog this morning and it is still hard to believe how good the corn and beans look. But, call me paranoid, this got me thinking about whether we were starting to get too much rain this month?
2. So, you know me, I ran back to my computer and starting digging out the data to check out the relationship between July precip and corn yields. I was relieved to see that, no, we are not in the territory of too much July precip. Image
3. Note that the y-axis is deviation from a simple linear trend over 1980-2023 for the Illinois state average yield. Precip is the average for the state too. The data scatter shows that there is no real dip in trend deviations all the way out to about 8 inches. I know the quadratic regression I used shows the yield deviation turning down above six inches of July precip but that is more the result of forcing this functional form on the data, which probably is better modeled by a linear function up to around 5 inches and then going flat.Image
Read 5 tweets
Jul 8
1. Man, I really hate to do this tonight after a day like this in the grain market. But we gotta start talking about the potential scale of financial losses for producing corn and soybeans in 2024. This is an updated budget from this FDD: farmdocdaily.illinois.edu/2024/06/revise…
Image
2. I am going to use the following yield/price combinations just to get the convo started. Corn: 240 bu./$3.70. Soybeans: 75 bu./$10.30. I use higher yield expectations based on the expectation that Beryl rains will go a long ways to improving prospects. Mr. Market sure thinks so. Without taking into account LDP and crop insurance proceeds, this results in estimated farmer returns of -$244/acre for corn and -$98/acre for soybeans. For farms with 50/50 rotations that results in average farmer returns for all acres of -$171 per acre.Image
3. We are getting close to where 85% crop insurance policies will trigger based on price alone. Feb price was $4.66. For the 85% policy, Dec 24 futures have to drop to $3.96 to trigger payments at APH yields. With the increased yields I used, looks like still aways to seeing insurance payments. But need to wait for my colleagues who are much more expert in this regard to chime in. My sense is that crop insurance right now is not likely to help much. I am not sure about ARC/PLC payments. Maybe more help there.
Read 5 tweets
Mar 20
1. I guess today is the day to talk about corn yields. Just received an email from @aaea announcing a new Choices article "A Slowdown in US Crop Yield Growth" by David Boussios. Here is the link: choicesmagazine.org/choices-magazi…
2. The author of the Choices article argues: "The statistical evidence of a productivity slowdown in crop yield growth builds each year. The linear yield growth trends since 2013 for corn, soybeans, and wheat are all statistically lower than one starting in 1988. Models, forecasts, market participants, and policy makers should consider that yields in the future will probably be lower than forecasted by the USDA and that extrapolating trends into the future without revision is problematic."
3. This argument is especially interesting because I have seen similar arguments in the grain trade in the last few years. We can all agree that the US average corn yield has been relatively flat since around 2013. That is obvious looking at a chart of corn yields. But one has to be extremely careful in then leaping to the conclusion that productivity growth in corn yields has also slowed. The reason is that runs of poor or good weather can mask the true underlying trend in small samples of years.
Read 7 tweets
Nov 1, 2023
1. Recommended Reading for the Day: Fascinating new FDD from my colleagues on the farmdoc team, led by Carl Zulauf. Long-term look at real crop prices. farmdocdaily.illinois.edu/2023/10/the-po…
2. It has long been a staple of economic thinking that real (inflation adjusted) commodity prices have a strong tendency to decline over time. Probably the most famous example of in this regard is the bet about real commodity prices between Julian Simon and Paul Ehrlich in 1980. See the details here:
3. Carl and team put together the data for a USDA index of real crop prices going back to 1912. This is the chart shown below. Lots of interesting history here, but the 30 year period of stable real crop prices that began around 1990 is unmistakable. The question is whether this is a pause in a very long run downward trend or something new.
Image
Read 8 tweets
Sep 28, 2023
1. Excited to announce that the band is back together! Actually, talked Darrel Good into coming out of retirement to work on this FDD: "The New Era of Crop Prices: A 15-Year Review." farmdocdaily.illinois.edu/2023/09/the-ne…
2. When crop prices started to take off in 2006-07, a huge question was whether this was just another spike like we had seen so many other times, or was this the beginning of a permanent jump in the level of average prices, like in 1973. Image
3. For some reason (temporary insanity?), Darrel and I decided to stick our necks out and predict that a new era in crop prices was afoot AND make specific predictions for the average price and trading range in the new era. As this chart shows, we did not have much data to go on.
Image
Read 8 tweets
Jun 1, 2023
1. Ok, I have hopefully convinced you that the RIN cliff scenario is a logical possibility. Now what are the chances of it actually happening? The first step is to estimate QM in the graph below. Turns out the proposed RVOs released by EPA last December are the place to start. Image
2. We can use the proposed RVOs to come up with a defensible estimate of the maximum demand for biomass-based diesel (BBD) for 2023, 2024, and 2025. We can do this because we know mandates are and will be binding. Image
3. I will leave the details of the computations to the article. Suffice it to say that under the EPA's preliminary rulemaking, the max amount of BBD needed is about 4BG each year. That is national demand for sum of RD and BD. Image
Read 11 tweets

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