Guest essay by David Archibald

Readers may recall a previous WUWT article where I examined growing conditions experienced in the Corn Belt over the last 30 years with Growing Degree Days (GDD), using Whitestown, Indiana as a data point. This article revisits and updates those calculations.

It is the time of the year that farmers in the Corn Belt start thinking about getting their crop in. Conditions for planting are less than ideal at the moment though with a lot of ground frozen or waterlogged:

Figure 1: April 3rd in North Iowa

Figure 2: Rain-soaked fields behind afternoon storms in East-Central Illinois

And models are predicting another blizzard to come through:

Figure 3: ECMWF Model of 850 millibar wind speed, showing a strong low pressure center advecting cold air from Canada into the central USA.

Figure 3 is from Ryan Maue who notes on Twitter:

“So, does winter end anytime soon? ECMWF 12z has a massive blizzard that would make January jealous in the upper Midwest in 9-days. Of course, that’s too far away for accurate prediction but worth highlighting that winter isn’t done — at all.”

Now that the Modern Warm Period is over and we are going back to levels of solar activity typical of the 19^th century, it is apposite to look at what the climate was like then and how a return to 19^th century-type climate will impact on agriculture.

Figure 4: Whitestown, Indiana Average Daily Minima for Decades 1900 – 1910 and 2000 to 2010

What Figure 4 shows is that a century ago daily temperature minima during the planting season were three weeks behind what farmers experienced last decade. What is also interesting is that in the 1900 to 1910 decade there was a pronounced dip in temperatures in February. Last decade the dip was reduced and came forward by a fortnight.

Figure 5: Whitestown, Indiana Cumulative GDD from 27th April to First Frost

Corn growth responds to heat. The concept of Growing Degree Days (GDD) captures that by taking 50°F from the average daily temperature. For example a daily maximum of 76°F with a minimum of 54°F produces an average of 65°F. Take 50°F from 65°F gives a result of 15 GDD for that day. Corn varieties have been bred to maximise productivity from recent climatic conditions and require 2,500 GDD to reach maturity.

Figure 5 shows that last decade corn crops could get to 2,500 GDD by mid to late August. A century ago maturity mightn’t be reached until the end of September. Normal first frost date for Whitestown is 10^th October but 110 years ago the first frost was on 3^rd September, ending growth for the season. Last decade averaged 177 days between the last spring frost and the first fall frost. In the first decade of the 20^th century, the average number of days between these frost events was 147.

Figure 6: Crop Progress and Condition for Corn in Indiana

The USDA provides a wonderful service following the state of crops in the Corn Belt, by state. If planting is delayed by waterlogged fields then farmers may elect to plant a lower-yielding crop that requires fewer GDD to reach maturity. If planting is so delayed that corn is out of consideration, then the fields may be left fallow or a short-growing-season crop such as rye might be substituted.

This year another factor has entered into farmers’ decision-making with China announcing a 25% tariff on US soybeans.

Figure 7: US and Brazilian Soybean Exports and Chinese Imports 1964 – 2017

Processed through China’s 400 million pigs, that country’s soybean imports provide 20% of their minimum protein requirement. As Figure 7 shows, China’s soybean imports take most of combined US and Brazilian exports. For US growers there is a price and fertiliser cost trade-off between growing corn and growing soybeans. The Chinese tariff would encourage a switch from soybeans to corn, if they can get a crop into the ground.

David Archibald is the author of American Gripen: The Solution to the F-35 Nightmare.