With increased early spring rain events followed by periods of drought and extreme heat, farmers across the U.S. were significantly challenged this past growing season. While there are different points of view on how we got here, it’s hard to ignore the fact that our weather is changing.
Scientists are using datasets of weather and climate in their research to identify ways to help mitigate their impact on crop production. It’s important to note that climate and weather are not the same thing. According to the United Nations World Meteorological Organization (WMO), weather describes short term natural events such as rain, snow, wind and thunderstorms occurring at a specific place and time. Climate, on the other hand, is defined by the WMO as these same events over a span of 30 years.
With continued speculation of global warming and the impact of climate change, is there anything that can actually help farms deal with the impact of evolving weather patterns? Austin Pearson, agriculture and natural resource educator and climatologist at the Midwestern Climate Research Center, and Hans Schmitz, Agriculture and Natural Resources director and lead cropping agronomist at Purdue University Extension, were part of the program addressing “Smart Agriculture Practices” at the Indiana Small Farm Conference.
“Climate change isn’t always an easy topic to talk about,” Pearson began. “When we’re talking about climate and developing climatology for certain regions, we’re actually looking at an accumulation of weather events over a period of time. Weather is the day-to-day variations in the earth’s atmosphere.”
He explained how the numeric “normal” is reached for weather forecasts. It is defined by the 30-year average for climate variables such as temperature and precipitation. A meteorologist’s report, for example, may indicate that the day’s high temperature was six degrees Fahrenheit above normal for that day.
Pearson said that while single year extremes don’t actually correspond to climate change individually, collective evidence of this for longer time periods typically does. He pointed out that temperatures, especially in the Midwest, are rising. He explained how Indiana is getting warmer with an annual temperature increase of 1.2º over the last century. Of concern, their findings show that the cycle of warming during the entire previous 100-year period was at a much lower rate than from 1960 to today. “What we’re seeing is longer frost-free seasons, fewer cold days and significantly warmer temperatures overnight,” he said.
Growing Degree Days
Growing degree days (GDDs), the measurement of the growth and development of plants and insects during the growing season, are being impacted by these changes. “We have some crop tools looking primarily at row crops, but some of those applications could be looked at for diversified farms,” Pearson said. Based off of the research and climatological data, these tools are further evaluating GDDs for crops. “Given certain times of the year and the certain number of growing units or heat units that accumulate, we would expect the physiological maturity of crops to be at a certain stage,” he said.
With Indiana annual precipitation over the last century increasing by 5.6 inches, farms are experiencing heavy rainfall that is not only more intense but also more frequent. Pearson indicated that there is a 42% increase in the amount of rain falling during these heavy downpours with a projected pattern of a 6% – 8% increase in annual rainfall by mid-century.
“When it comes to precipitation, even though the spring/fall projected rainfall is at an increase, all of that is occurring when precipitation is already falling,” he said. The result is more intense rain events during those time periods. Unfortunately, despite the increased numbers in spring and autumn rains, the summer months are showing a slight decline in precipitation.
Orchards are experiencing a change in chilling hours needed for fruit production. Schmitz pointed out the significance of a decrease in chilling hours available to help fruit trees initiate bud and bloom growth in spring. “Changes in chilling hours will change the types of fruit trees or varieties that we can grow,” he warned. Also, the increase in heat stress is mainly due to increases in overnight temperatures, especially when the low temperature does not get below 68º or 70º. “That increases heat stress for humans and increases heat stress on plants,” Schmitz said.
Autumn fertilizer applications are also affected by temperature fluctuations. “If it’s hitting 50º soil temperatures in February, how much fall-applied nitrogen are we still going to have when it comes time to plant crops in the spring?” he queried. While autumn nitrogen fertilizer application continues to be popular because of equipment availability, better soil conditions and competing springtime field activities, scientists are evaluating the elimination of autumn nitrogen applications due to earlier warm soil temperatures.
In closing, Schmitz offered, “We can manage for change and adapt our farm to not only be able to keep profitability and what we are producing, but provide some mitigatory aspects to our system so that it can be more profitable under a changing climate. Or we can do nothing and have no clue long-term exactly what those outcomes might be.”
As a farm is first starting to think about what it might need to look at concerning changing climates, the USDA Adaptation in Agriculture workbook gives ways to think about what your priorities might be.
The workbook’s first strategy addresses maintaining and improving soil health. It recommends minimizing soil disturbance by avoiding or reducing tillage, utilizing cover crops, increasing soil organic matter and diversifying with crop rotations. Windbreaks for soil erosion and subsurface drainage are also suggested.
A second strategy is how to reduce risks from warmer and drier conditions by including a selection of longer growing season or drought-resistant crop varieties and improving efficiency of any irrigation systems. The adjustment of the timing of planting to earlier dates would also help avoid heat stress during critical periods of plant development.
For more information, the workbook resource is available free online at climatehubs.usda.gov/sites/default/files/AdaptationResourcesForAgriculture.pdf.
Perhaps the beloved Dr. Seuss character the Lorax said it best: “Unless someone like you cares a whole awful lot, nothing is going to get better, it’s not.”
by Gail March Yerke