Crop production linked to regional changes in climate


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Corn and soy plants can cool the climate on a regional level, but intensified conventional agriculture can harm water and soil quality. (Lana/flickr)

Jenna Ladd | February 14, 2018

A new study by researchers at Massachusetts Institute of Technology and Dartmouth College detail the way intensive agriculture has influenced precipitation and temperature patterns in the midwest.

During the second half of the 20th century, corn production in the midwest increased by 400 percent and soybean yields doubled due to more intensive agricultural practices. The study, which was published in Geophysical Research Letters, found that the midwest also saw significantly more precipitation and lower temperatures during the summer months over the same period of time. They concluded that the changes were not merely correlated, but that the land use change actually caused the regional climate changes.

The authors explain that each time plants take in carbon dioxide, they release moisture into the atmosphere through pore-like structures called stoma. With more plentiful and robust plants due to intensive agriculture, the amount of moisture corn and soy crops collectively release into the atmosphere has increased in the midwest since the 1950’s. This extra moisture, the study found, has caused summer air to cool and more precipitation to fall. In the last fifty years, average summertime rainfall in the midwest has increased by 15 percent and average summer temperatures have dropped by 0.5 degrees Celsius.

Roger Pielke Sr., a senior researcher at the University of Colorado at Boulder commented on the study, he said, “This is a really important, excellent study. The leadership of the climate science community has not yet accepted that human land management is at least as important on regional and local climate as the addition of carbon dioxide and other greenhouse gases into the atmosphere by human activities.”

Since completing the study, the researchers have developed a formula that accounts for the causative relationship between plants and regional climate changes that can be entered into U.S. regional climate models. It correctly predicted those changes that have been observed in the midwest over the last 50 years.

The study opens the door for further research into land use changes and how they can affect local climate.

As global temperatures rise, future of agriculture uncertain


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Soybean yields could decrease by as much as 40 percent due to rising temperatures. (United Soybean Board/flickr)

 Jenna Ladd | January 20, 2017

Without further action to curb greenhouse gas emissions, global temperatures are expected to rise as much as 6.1 degrees Fahrenheit above pre-industrial averages, which may meaningfully impact agricultural outputs.

According to a recent study by the the Potsdam Institute for Climate Impact Research and the University of Chicago, rising temperatures could significantly reduce U.S. grain harvests. Using a set of computer simulations, the researchers found that yield reduction could reach 40 percent for soybeans and almost 50 percent for corn by the end of the century if carbon emissions are not cut drastically. Wheat would fare slightly better, with its yields decreasing by an estimated 20 percent.

The researchers said, “The effects go far beyond the U.S., one of the largest crop exporters. World market crop prices might increase, which is an issue for food security in poor countries.”

A report by the European Union’s Joint Research Centre came to a different conclusion. They found that wheat may actually benefit from higher concentrations of carbon-dioxide in the atmosphere, while corn yields would decrease.

Although the global temperature has reached record highs for three consecutive years, U.S. corn and soybean yields were seemingly unaffected. Thanks in part to genetically modified seed, which can have adverse environmental impacts, corn and soybean output was higher than ever in 2016.

However, the extreme drought of 2012 serves as a reminder that agricultural productivity is vulnerable to a changing climate. That year, U.S. corn harvests decreased considerably and caused global corn prices to skyrocket.

EnvIowa Podcast: Soybean crops found to contribute to nitrate levels in Iowa’s waterways


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Jenna Ladd | November 4, 2016

On episode three of EnvIowa, we sit down with Dr. Chris Jones, IIHR Research Engineer, to discuss his recent research, which looks at the effects of soybean crops on water quality in Iowa. Much of the research over the last 40 years has been focused on corn, given that corn plants require more fertilizer than soybean plants. However, studies in 2009 and 2016, both of which Dr. Jones co-authored, suggest that soybeans play a larger role than previously understood.

Dr. Jones helps us understand why nutrient pollution has increased steadily as more and more farmers have integrated soybeans into crop rotation, replacing smaller grains and cover-crops, and what it will take to turn this science into water quality policies that benefit Iowans.

The EnvIowa podcast can also be found on iTunes and soundclound. For a complete archive of past episodes, click on the EnvIowa Podcast tab at the top of this page.

Soybeans may play bigger role in nitrate levels than previously thought


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IIHR’s water-quality monitoring network has generated interesting data that contradicts some widely-held beliefs regarding corn and soybeans and their impact on nitrate in Iowa’s streams. (IIHR)
Jake Slobe | September 28, 2016

New research shows that soybeans may play a key role in the transport of nitrate from farmed fields to the stream network.

As Iowa farmers have planted more acres of corn to meet the increasing demand, many models predicted that nitrate concentrations in Iowa streams would increase as a consequence. However, a new study conducted by the UI’s IIHR-Hydroscience & Engineering group and the Iowa Soybean Association, published in the Journal of Soil and Water Conservation, challenges many of these predictions.

As the amount of corn planted increased and the amount of soybeans decreased, fertilizer application increased by 24 percent in the watershed. Surprisingly, the nitrate levels in the river saw no increase and in some cases saw slight decreases.

The study evaluated 7,000 water samples in the Raccoon River Watershed from 1999- 2014 and had access to fertilization data for 700 fields in the watershed. The result from the study has led researchers to believe that nitrate levels are less dependent on corn production than previously thought.

IIHR —Hydroscience & Engineering researcher Chris Jones says that clues to the reduction in nitrate levels can be found in the differences between corn and soybean  growth, soil chemistry, and the decay of other crop residues. Conversely, the dead and decomposing soybean plants can increase the amount of nitrate in the soil vulnerable to loss.

“We know we can’t just focus on fertilization of corn. We need a systems approach to improve water quality. It also demonstrates the power of monitoring water quality. Without this data, we could easily have missed this important and counter-intuitive conclusion.” 

As a result, Jones says he believes that declining amount of soybeans planted may have reduced the cropped areas most susceptible to nitrate loss, more than compensating for the increased fertilizer inputs on corn production.

 

On The Radio – China agrees to purchase $5.3B in soybeans from U.S.


A soybean field near Williamsburg, Iowa. (Chris Yunker)
A soybean field near Williamsburg, Iowa. (Chris Yunker)
November 2, 2015

This week’s On The Radio segment looks at a recent agreement China made with the United States to purchase more than $5 billion worth of soybeans from American farmers.

Transcript: China agrees to purchase $5.3B in soybeans from U.S.

Chinese leaders signed an agreement to purchase more than 5-billion-dollars worth of soybeans from American farmers during a recent visit to the United States.

This is the Iowa Environmental Focus.

Last month a 49-member Chinese delegation signed a deal with U.S. officials to purchase roughly 13 million metric tons of soybeans – or approximately 484 million bushels. The agreement was reached during a recent trip Chinese President Xi Jinping made to Seattle. This deal accounts for roughly half of China’s annual soybean purchases.

Iowa governor Terry Branstad traveled to Seattle to meet with President Xi Jinping. Branstad said roughly 30 percent of the soybeans China imports come from Iowa. Iowa farmers are expected to harvest about 525 million bushels of soybeans this year.

During his visit, President Xi Jinping also announced that beginning in 2017, China will implement initiatives to reduce greenhouse gas emissions and utilize more renewable sources for generating electricity.

For more information about the agreement, visit Iowa-Environmental-Focus-dot org.

From the UI Center for Global and Regional Environmental Research, I’m Betsy Stone.

 

Wet conditions hamper fieldwork in May


Fall crops and standing water from rains in 2009 in Polk County (Carl Wycoff / Flickr)
Fall crops and standing water from rains in 2009 in Polk County (Carl Wycoff / Flickr)
KC McGinnis | June 2, 2015

Rain, cool temperatures and standing water halted Iowa farmers for parts of last month, slowing crop progress by limiting suitable days in the field.

The USDA’s National Agricultural Statistics Service reports that in the last week of May just 2.3 days were suitable for fieldwork across the state, with only 1.7 suitable days for southwest Iowa. Topsoil moisture was rated at above surplus for 50% of southwest and south central Iowa, and 22% across the state. That’s compared to last year, when only 7% of Iowa topsoil was at surplus moisture.

This excess moisture has made it difficult for farmers to get in their fields, leading to lags in soybean planting and alfalfa hay first cutting, which was only at about half the five-year average. Some operators reported standing water in their fields, and some fields will need to be replanted due to the excess water. The moisture also prevented spraying, and led to concerns over muddy feedlots.

While 92% of soybeans were planted by the end of May last year, this year’s numbers were at 50% or less for parts of the state, with southwest Iowa reaching only 37%.

Iowa faced a similar situation last year, with consistent heavy rains in June and July leading to less than three suitable field days for three consecutive weeks. “We just came through three of our most challenging years, as far as weather goes,” noted northeast Iowa farmer Travis Holthaus in a recent CGRER documentary. Heavy rains, flash flooding and challenging droughts continue to lead to increased unpredictability for Iowa farmers. These producers may need to prepare for decreased field days in the next week as well, with more storms predicted later this week.

Iowa fields are eroding at an unsustainable rate, study says


Agricultural runoff in Iowa (Lynn Betts/Flickr)
Agricultural runoff in Iowa (Lynn Betts/Flickr)

The rate of soil runoff from Iowa fields may be many times higher than previous estimates, according to a recent study.

The report, released by Environmental Working Group, shows that Iowa fields are eroding at unacceptable rates, depleting Iowa’s rich topsoil and sending sediment and chemicals into streams and rivers. Between 2002 and 2010, many fields consistently lost more than the sustainable rate of five tons of soil per acre from storms and other erosion events. A single storm in May of 2007 eroded up to 100 tons of soil per acre.

Much of the soil is carried away by gullies that are increasingly appearing in Iowa fields. These low channels are a telltale sign of high erosion, and are often refilled with soil only to be emptied again with the next storm.

High erosion creates high agricultural and environmental risks by carrying away Iowa’s rich topsoil and by polluting waterways with sediment and chemicals. An effective means of curbing this is to plant grass and trees along the edges of fields and in areas where gullies are likely to form. A series of buffers implemented in various fields reduced sediment, nitrogen and phosphorus by more than 90 percent in 2009.