Turn back time a half century, to my Cooperative Extension career as a dairy and field crops agent. I tried to get farmers to mentally break down their businesses into three parts: cows, heifers and crops. Perhaps an oversimplification, but this approach helped them home in on possible “weak links” in their farm operation.
In more recent years, I’ve gotten a little fancier, just targeting crop programs. There I see four basic categories of inputs required for successful crop production. They are solar radiation, moisture, warmth (soil and air) and soil nutrients. One can argue that they are all equally important, because if any one of these is seriously limiting, crop production rapidly derails.
Crops generally demand that these components be presented to them uniformly. For instance, our country’s most universal crop, field corn, demands that warmth be delivered quite steadily. With a baseline temperature of 50º, the most commonly used unit for assaying usable warmth sought by plants is growing degree days (GDDs). A day with average temperature of 70º would have accrued 20 GDDs. Two consecutive days with an average temperature of 70º would have accrued 40 GDDs.
If that same field had an average temperature one day of 60º and the next day an average temperature of 80º, total accrued heat units would be 40 GDDs. What the corn does not “appreciate” is when one day amasses 10 GDDs, followed by a day amassing 30 GDDs.
Another vital item demanded by crops is sunshine – solar radiation. The most commonly used unit of solar radiation is the Langley (Ly), which is defined thusly: a unit of heat transmission, especially used to express the rate of solar radiation (or insolation – which is an abbreviation of incoming solar radiation) received by the earth.
More precisely, a Ly is defined as “a unit of solar radiation equivalent to one gram calorie per square centimeter of irradiated surface.”
Chinese scientists addressed this subject in a paper titled “Quantitative Relationship Between Solar Radiation and Grain Filling Parameters of Maize.” It was authored by Yushan Yang, Ph.D., et al., and appeared in Frontiers in Plant Science in June 2022. That research was conducted at the College of Agronomy in Shihezi, China. Following is a summary of that paper:
Workers stressed the need to understand the factors driving changes in corn grain filling as being essential for effective prioritization of increasing maize yield. “Grain filling is a significant stage in maize yield formation,” they wrote. “Solar radiation is the energy source for grain filling, which is the ultimate driving factor for final grain weight and grain filling capacity that determines maize yield. Here we first confirmed the quantitative relationships between grain filling parameters and photosynthetically active radiation (PAR) by conducting field experiments using different shading and plant density conditions and cultivars in 2019 and 2020 in Xinjiang, China.
“Relative changes in PAR were significantly and positively correlated with relative changes in yield and average grain filling rate (Gave). With every 1% change in PAR, yield and Gave changed by 1.16% and 0.17%, respectively. These workers also believe that with increased likelihood of factors continuing to decrease PAR, plant geneticists should place more emphasis on developing corn strains that are less susceptible to erosion of effective solar radiation.”
At the peak of the Canadian wildfire gray-out two years ago, Cristen Hemingway Jaynes, on June 25, 2023, penned an article for Ecowatch titled “Smoke from Canada’s Wildfires Interfered with Solar Power Generation.” Jaynes, a great-granddaughter of Ernest Hemingway, wrote that when the smoke from the Canadian wildfires drifted into the Eastern and Midwestern U.S. the week before, creating super-abundant orange haze, it not only diminished air quality, it caused another problem – it reduced solar power generation by making it more difficult for solar panels to absorb sunlight.
At that time the electricity coming from New England solar farms was 56% less during peak times compared to the previous week, according to Bloomberg News.
Jaynes wrote that in the Mid-Atlantic and Midwest, solar power generation was reduced by 25%. Solar energy production in New York State, one of the areas most affected by Canadian smoke, was reduced by 1,466 megawatts (MW) during June 6 – 7, compared to month-earlier readings. (One MW produces enough electricity to power 800 – 1,000 homes.)
At the height of the 2023 wildfire smoke-out, I talked to Certified Crop Advisor Tom Kilcer regarding the impact of reduced insolation on crops. He was more concerned about what smog-induced sunshine shortage does to perennials, rather than how it hurts yield and quality of corn. He said that much like the way that solar panels are short-changed (in their attempt to create megawattage), forages, particularly alfalfa, need that insolation to form sugars – a process which is very time sensitive and fundamental to quality.
Kilcer explained the main reason that insolation is so critical. The early dry-down is driven by photosynthesis. This is where the plant takes water and carbon dioxide to make carbohydrates, liberating oxygen for animals (and people) to breathe. When more of the plant is exposed to sun, the faster it dries, as photosynthesis is operating and using plant moisture. Moisture is also leaving through the stomates, where carbon dioxide comes in and oxygen exits.
Online sleuthing revealed the following: Whether wildfire smoke will significantly affect crops in New York State during 2025 depends on several factors, including the severity and duration of smoke events. Heavy and prolonged exposure to wildfire smoke, such as the event on July 15, when Canadian wildfire smoke affected most of New York, is more likely to impact crops. Less intense smoke events, or smoke that remains aloft and doesn’t significantly impact ground-level air quality, will likely have less impact.
The timing of smoke events during crops’ development is crucial – severe stalk rot and lodging are often observed in association with prolonged periods of low solar radiation during grain fill.
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