Published on Wednesday, 30 November -0001 00:00
By Dan Martens,
U of M Extension
I attended a crop insurance workshop in Mankato in the middle of September where Elwynn Taylor, well know climate specialist and agronomist at Iowa State, offered some discussion about the weather, climate, and crop trends.
One of the weather patterns Taylor talked about was based on corn yields recorded since 1866 that show about 19 years of fairly stable yields alternating with about 25 years of more volatile yields, meaning wider variations from year to year. He showed that we're coming out of one of the 19 year periods with more stable yields and he suggested that we are moving into 25 years with more variable weather and yields. That would mean having a strategy for managing risk from year to year and over longer periods of time continues to be important.
He also noted that U.S. corn yields have increased at a rate of about 2 bushels per year over the last 30 years; and Minnesota's corn crop has increased about 2.5 bushels per year during this time. Taylor also cautioned us with the idea that we are as sensitive to the weather as we ever have been - even though we have better genetics in crop varieties and we have learned some things about other crop production practices. You might think about it like this. Unfavorable weather conditions 40 year might have resulted in half a crop or less. We can still have weather conditions that could deal us half a crop or less. 40 years ago, half a crop might have been
50 bushels of an expected 100 bushel yield. Today it might mean 70 bushels of an expected 140 bushel yield, but it's still half a crop. Economically, it might not serve us much better than half a crop did 40 years ago. It is more feed.
Taylor said that along with getting less rain, the corn crop in the southern part of the corn belt suffered because of warmer than normal night temperatures. Minnesota did better this year partly because being farther north, night temperatures were not as excessive. He said that if overnight temperatures from pollination to grain maturity are 4 degrees above normal, this can reduce yields by 20 percent. I found that interesting because I've heard the comment many times over the years that "these warm nights are gonna' make corn."
Taylor explained that crops store energy and manufacture dry matter material through the process of photosynthesis during the day. Respiration goes on 24 hours a day and this is where plants use energy. When night temperatures are too high, through respiration, the plant burns off more of the energy it captures during the day. Taylor said if we stay with warmer weather patterns, Minnesota might have an advantage over other Corn Belt states more often in the future.
I asked Jeff Coulter, our Minnesota Extension Corn agronomist about this recently and he agreed with Taylor. Coulter commented that warm temperatures during the vegetative phases aren't usually a big deal because this just increases GDD (Growing Degree Day) accumulation and growth rate; and temperature is usually not high enough during this time in MN to hurt anything. (I'd add that 1988 might be an exception to that.) But, during grain fill it is different because the sugars from photosynthesis are wasted on respiration rather than for storage in kernels when nighttime temperatures are too hot.
Coulter said some of the highest corn yield environments in the U.S. are the irrigated desert regions-small acreages in Arizona, New Mexico, etc. where it is warm and sunny during the days (upper 80s), and then cool in the evenings. Minnesota will gain market share in U.S. corn production and yield ranking while the I-states (IL, IN, IA) will continue to struggle if the weather becomes more extreme and variable. Coulter noted that hot temps (greater than 86 at normal to low soil moisture or greater than about 90-92 F with adequate to abundant soil moisture) during the two weeks before and after silking are the worst because they affect pollination and more importantly kernel abortion following pollination. However, soil moisture levels during these critical 4 weeks are more important than air temperatures.
So, if you're a weather buff, watching crops from year to year, you can think about how that plays out with your experience. In the end, the task seems to be the same, we try to do the best with the cards that are dealt, and we can be thankful for the harvest we have this year.