By monitoring crops through machine learning and satellite data, Stanford scientists have found farms that till the soil less can increase yields of corn and soybeans and improve the health of the soil – a win-win for meeting growing food needs worldwide.

Agriculture degrades over 24 million acres of fertile soil every year, raising concerns about meeting the rising global demand for food. But a simple farming practice born from the 1930’s Dust Bowl could provide a solution, according to new Stanford research. The study, published Dec. 6 in Environmental Research Letters, shows that Midwest farmers who reduced how much they overturned the soil – known as tilling – increased corn and soybean yields while also nurturing healthier soils and lowering production costs.

“Reduced tillage is a win-win for agriculture across the Corn Belt,” said study lead author Jillian Deines, a postdoctoral scholar at Stanford’s Center on Food Security and the Environment. “Worries that it can hurt crop yields have prevented some farmers from switching practices, but we found it typically leads to increased yields.”

The U.S. – the largest producer of corn and soybeans worldwide – grows a majority of these two crops in the Midwest. Farmers plucked about 367 million metric tons of corn and 108 million metric tons of soybeans from American soil this past growing season, providing key food, oil, feedstock, ethanol and export value.

Monitoring farming from space

Farmers generally till the soil prior to planting corn or soybeans – a practice known to control weeds, mix nutrients, break up compacted dirt and ultimately increase food production over the short term. However, over time this method degrades soil. A 2015 report from the Food and Agriculture Organization of the United Nations found that in the past 40 years the world has lost a third of food-producing land to diminished soil. The demise of once fertile land poses a serious challenge for food production, especially with mounting pressures on agriculture to feed a growing global population.

In contrast, reduced tillage – also known as conservation tillage – promotes healthier soil management, reduces erosion and runoff and improves water retention and drainage. It involves leaving the previous year’s crop residue (such as corn stalks) on the ground when planting the next crop, with little or no mechanical tillage. The practice is used globally on over 370 million acres, mostly in South America, Oceania and North America. However, many farmers fear the method could reduce yields and profits. Past studies of yield effects have been limited to local experiments, often at research stations, that don’t fully reflect production-scale practices.

The Stanford team turned to machine learning and satellite datasets to address this knowledge gap. First, they identified areas of reduced and conventional tilling from previously published data outlining annual U.S. practices for 2005 to 2016. Using satellite-based crop yield models – which take into account variables such as climate and crop life-cycles – they also reviewed corn and soybean yields during this time. To quantify the impact of reduced tillage on crop yields, the researchers trained a comput

Average impacts on corn yields from conservation tillage across the U.S. Corn Belt from 2008 to 2017. Red colors indicate increased yields under conservation tillage, blue colors indicate yield declines.

Improved yields

The researchers calculated corn yields improved an average of 3.3 percent and soybeans by 0.74 percent across fields managed with long-term conservation tillage practices in the nine states sampled. Yields from the additional tonnage rank in the top 15 worldwide for both crops. For corn, this totals approximately 11 million additional metric tons matching the 2018 country output of South Africa, Indonesia, Russia or Nigeria. For soybeans, the added 800,000 metric tons ranks in between Indonesia and South Africa’s country totals.

Some areas experienced up to an 8.1 percent increase for corn and 5.8 percent for soybeans. In other fields, negative yields of 1.3 percent for corn and 4.7 for soybeans occurred. Water within the soil and seasonal temperatures were the most influential factors in yield differences, especially in drier, warmer regions. Wet conditions were also found favorable to crops except during the early season where water-logged soils benefit from conventional tillage that in turn dries and aerates.

“Figuring out when and where reduced tillage works best could help maximize the benefits of the technology and guide farmers into the future,” said study senior author David Lobell, a professor of Earth system science in the School of Earth, Energy & Environmental Sciences and the Gloria and Richard Kushel Director of the Center on Food Security and the Environment.

It takes time to see the benefits from reduced tillage, as it works best under continuous implementation. According to the researchers’ calculations, corn farmers won’t see the full benefits for the first 11 years, and soybeans take twice as long for full yields to materialize. However, the approach also results in lower costs due to reduced need for labor, fuel and farming equipment while also sustaining fertile lands for continuous food production. The study does show a small positive gain even during the first year of implementation, with higher gains accruing over time as soil health improves. According to a 2017 Agricultural Censuses report, farmers appear to be getting on board with the long-term investment and close to 35 percent of cropland in the U.S. is now managed with reduced tillage.

“One of the big challenges in agriculture is achieving the best crop yields today without comprising future production. This research demonstrates that reduced tillage can be a solution for long-term crop productivity,” Deines said.

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David Lobell is also the William Wrigley Senior Fellow at the Stanford Woods Institute for the Environment, a senior fellow at the Freeman Spogli Institute for International Studies and the Stanford Institute for Economic Policy and Research. Graduate student Sherrie Wang is also a co-author. Research was funded by NASA Harvest.

The recently launched Stanford Alumni in Food & Ag group aims to bring together Stanford graduates with a background or interest in food and agriculture issues. Tannis Thorlakson, one of the group’s creators, works as the environmental lead for Driscoll’s in the U.S. and Canada, and recently earned her Ph.D. from Stanford’s E-IPER program. She hopes the group will help alumni stay connected with cutting-edge research and stay up-to-date on news within the food and agriculture space. Thorlakson sat down with FSE to chat about the group and upcoming launch event taking place at the O'Donohue Family Stanford Educational Farm later this month.

Q: What inspired you to create the group and who else was involved?
Thorlakson: It has been exciting to see the increasing enthusiasm for agriculture and food around Stanford's campus during my time there. Between the newly expanded Stanford Farm and the buzz around ag tech, more and more students are interested in careers in food and agriculture. My cofounders Manuel Waenke, Anthony Atlas and I wanted to harness some of this enthusiasm to bring alumni together.

Q: Who is eligible to join?
Thorlakson: At this point, we are focused only on Stanford alumni, but will build collaborations with student groups over time. 

Q: What are your goals or focus areas?
Thorlakson: We have two primary goals; to connect alumni to share insights and opportunities in the food and agriculture space; and to keep alumni connected to campus through events and sharing of cutting-edge Stanford research. 

Q: You have your first event on Oct. 26. What are you hoping to accomplish, who can come, and how can people learn more?
Thorlakson: All alumni and faculty are invited to join. This will be a chance to connect with fellow alumni and learn a bit more about the club. More information here: https://www.stanfordfoodag.com/events.

Q: Anything else you’d like to let others know about?
Thorlakson: We're just getting started, so if you have ideas on how to make this group more relevant to you, please reach out to us at mwaenke@stanford.edu. 

The rising level of carbon dioxide in the atmosphere means that crops are becoming less nutritious, and that change could lead to higher rates of malnutrition that predispose people to various diseases.

That conclusion comes from an analysis published Tuesday in the journal PLOS Medicine, which also examined how the risk could be alleviated. In the end, cutting emissions, and not public health initiatives, may be the best response, according to the paper's authors.

Research has already shown that crops like wheat and rice produce lower levels of essential nutrients when exposed to higher levels of carbon dioxide, thanks to experiments that artificially increased CO2 concentrations in agricultural fields. While plants grew bigger, they also had lower concentrations of minerals like iron and zinc.

Read the entire story at NPR.