Appalachian Laboratory

Seeking sustainable agriculture

UMCES researchers work toward universal grading system for a healthier environment

Too much of something isn’t always a good thing.

Farmers who use nitrogen fertilizer to increase crop yield are helping to nourish more people while making farming economically viable, but there’s a trade-off to that growth and it’s hurting our environment.

Some of the nitrogen lingers long after the crops are plucked from the land, finding new life as a pollutant that contributes to climate change and poses health risks.

That problem may never go away completely, but two scientists with the University of Maryland Center for Environmental Science believe nitrogen can be used more efficiently and agriculture as a whole can be more sustainable while still meeting growing demand for food.

Xin Zhang works in the field. She always had a passion for the environment and later developed an interest for agriculture.

Xin Zhang and Eric Davidson of UMCES’ Appalachian Laboratory will soon lead a team of experts on a global research project to establish a universal grading system that will offer a comprehensive evaluation of each country’s performance of agriculture and its environmental, economic, and social impacts. Over time, the data in their Sustainable Agriculture Matrix (SAM) also could help influence policy recommendations for how countries and the private sector can move forward to meet food production targets with minimal impact on the environment.

“On any sort of quantitative indicator—whether it’s your grade-point average in school or your checking book balance—you want to look at it over time and see if it’s going in the right direction,” said Davidson, a biogeochemist and director of the Frostburg-based Appalachian Laboratory.

The idea for this project arose from the United Nations' Sustainable Development Goals, which include zero hunger and sustainable agriculture among its list of 17 “goals to transform our world.”

However, there’s a need to better assess the progress in sustainable agriculture, said Zhang, an assistant professor and researcher. Simply measuring what percentage of a country’s agriculture follows vaguely defined “sustainable” practices leaves too much room for discrepancy.


“There is no well agreed upon definition of what constitutes sustainable agriculture, so we can expect countries to adopt varying definitions of sustainability when estimating the percentage of their agricultural land under sustainable management,” Davidson said. “But if every country has a different definition of what it thinks is sustainable, how do we make comparisons across countries and across regions?”

Independent and transparent measurements of countries’ performance in agricultural production would offer one method of holding countries accountable for their commitment to sustainable agriculture. Zhang and Davidson will lead a group of collaborators to gather those measurements.

Neither are new to the concept of nitrogen-use efficiency.

The two teamed up last year for a report that inspects the 50-year footprint of agricultural nitrogen use around the world and weighs the value of technology and the shift in socioeconomic conditions in finding a solution to protect the environment without limiting food production. 

Increased use of nitrogen fertilizer stems from the early 20th-century invention of the Haber-Bosch process. The Haber-Bosch process synthetically converts nitrogen from the air to create a chemical fertilizer that helps farmers significantly boost their crop output.

While nitrogen fertilizer has enabled tremendous progress in human nutrition, a portion of the nitrogen in the fertilizer remains in the soil, leaches into groundwater and surface areas, or enters the atmosphere as ammonia, nitrous oxide, or other gases.

Inputs to agriculture are shown as blue arrows and harvest output as a green arrow. NUE is defined as the ratio of outputs (green) to inputs (blue) (i.e. NUE = Nyield/Ninput).
Curves moving towards the lower right indicate that those countries are achieving yield increases by sacrificing nitrogen-use efficiency (NUE).
Over-application of herbicides and pesticides on farm fields can result in excess toxins and nutrients reaching the waterways. Photo by Jane Hawkey, Integration and Application Network, University of Maryland Center for Environmental Science

Too much nitrogen can create harmful algal blooms, including species of algae that produce toxins harmful to fish and humans, or increase nitrate levels in the groundwater, an issue linked to drinking water quality and growing evidence of possible links to certain kinds of birth defects and cancers.  

“Nitrogen is a very wicked problem. You can’t have too little and you can’t have too much,” Zhang said.

There are some technological developments that make it possible for farmers to use the product more efficiently. For example, there are slow-release fertilizers and precision farming—a technique that helps a farmer determine more precisely how much fertilizer a crop needs for optimal growth. Some of these solutions, however, are expensive or stray from the traditional techniques farmers use and aren’t as widely adopted yet as they could be, Davidson said.

“It’s not just a problem of coming up with better fertilizers or fertilizer spreaders or purely technical solutions like that,” he said. “It also has to do with understanding how farmers make decisions and what technologies they’re willing to adopt, how they respond to economic signals, and how their background or culture dictates the way they make decisions.”

Change needs to come at the national level, too. For example, some governments, such as in China and India, provide subsidies for nitrogen fertilizer. That move intended to increase crop production and food security, but has led to excessive application of nitrogen fertilizer, often exceeding standard application rates in North America and Europe.  

Years of research helped Zhang and Davidson, among others, to see food security and pollution are interconnected, which motivates their latest endeavor.

“It’s not a black-and-white issue,” Zhang said. “Even though we are interested in protecting the environment, we cannot do that in a vacuum.”

Growing food demands also need to be met in sustainable ways, Davidson said.

“The human population is growing, and we want them to be well nourished, which means we need food, which means the demand for fertilizer and manure in agriculture is growing, which means some of that leaks out into places we don’t want it like the Chesapeake Bay, like the Gulf of Mexico, like the air,” he said.

He likened the Sustainable Agriculture Matrix to a report card that could give countries and farmers a grade of their agricultural sustainability based on data they collect. Ideally, he said, that grade would galvanize communities to seek changes necessary to score better.

Building that matrix, however, will take a team of experts from a range of backgrounds, including experts in agronomy, economics, sociology, and ecology.

“The goal is to construct an integrated matrix to evaluate a country’s performance in agricultural production, and the performance would be measured from three different dimensions: environment, economics, and social perspectives,” Zhang said.

Zhang and Davidson received funding through the National Socio-Environmental Synthesis Center (SESYNC) to get them started.

They are currently building their team for a workshop next summer designed to further define the project. From there, they would seek more funding to carry out their plan. Ultimately, their goal is to build a suite of biophysical and socioeconomic indicators that can be used to more adequately measure sustainable agriculture on local and global levels.

“There hasn’t been research like this before at this scale,” Zhang said. “I’m pretty excited about putting a team to work on this subject.”