Soils may hold the key to our future
By Miriam Rich, Office of International Research, Education, and Development
For Michael Mulvaney, Virginia Tech soil scientist, a handful of dirt tells a powerful story. Soil organic carbon, bulk density, organic matter fractions — these are not just scientific terms. They speak to a much larger narrative: the ability of human beings to recalibrate our relationship with the Earth, to help feed people in food-insecure countries, and to help address the challenge of global warming.
Mulvaney is assistant program director of a five-year, multimillion-dollar program funded by the U.S. Agency for International Development to improve the livelihoods of smallholder farmers in the developing world. The Office of International Research, Education, and Development manages the program. In addition to helping oversee the overall program — the Sustainable Agriculture and Natural Resource Management Collaborative Research Support Program (SANREM CRSP) — Mulvaney is also the lead project investigator of an initiative that cuts across each of five component projects to look at soil.
By studying soil, Mulvaney and his team hope to learn the answer to this question: Can conservation agriculture in developing countries increase soil organic carbon and soil fertility, compared to conventional practices? Conservation agriculture is a system of minimum soil disturbance and environmental impact. The work has two thrusts: One is to measure soil organic carbon changes over time, and the other is to measure carbon dioxide flux of soil.
Good-quality soils underpin productive agriculture. Yet in the developing world, where most people depend on agriculture to make a living, they are farming on land that is of poor quality. Population pressures have forced people to cultivate increasingly marginal land, farther up mountainous slopes, or in places that are left over after the premium land has been taken. Farmers are working parcels of land that have been divided and subdivided. Erosion and development have taken a toll.
In this environment, if soils could be improved, two things could happen. One: People could grow more food on the same soil. Two: If the soil carbon content could be increased, this carbon could be used for carbon credits in a warming world where such things may be traded between nations as a commodity. Rich, organic soils will then be valuable in more ways than one. "Having organic matter is like having money in the bank," says Adrian Ares, director of the SANREM CRSP, and himself a soil scientist as well as an advisor to the soil carbon and soil quality study.
Conservation agriculture, the system that the project is promoting, is composed of three major facets: minimal tillage, permanent soil cover, and crop rotation.
In a sense, this is how agriculture used to be done thousands of years ago. A farmer poked a hole in the ground with a stick, put in some fish for fertilizer, and then added the seed. "Now we call this precision agriculture," says Mulvaney.
What we now call intercropping isn't new, either. "They put in a corn seed, a bean, and squash seed — the three sisters." The bean would climb up the corn plant and provide nitrogen to the soil, the squash would cover the soil and protect it from erosion, and all three plants would produce food.
"During most of human history, we've done conservation agriculture," says Mulvaney. "We're trying to get back to an improved version of that." Modern "plow-based" agriculture uses significant amounts of chemical fertilizers. These modern fertilizers, curiously enough, were a byproduct of military bomb-making research done during World War II. While modern farming methods have been a boon, they can also degrade soil quality through nutrient mining — the removal of nutrients from the soil. Fertilizer alone, Mulvaney cautions, will not solve this problem.
If another way to improve soil can be found — perhaps through conservation agriculture — then the "money in the bank" of rich, organic matter can grow. "You need to be able to intensify productivity sustainably," Mulvaney says. "That's the challenge of our age. We're going to have to use resources, like soil and water, in a much more sustainable fashion."
Mulvaney, who is also an adjunct professor in the Department of Crop and Soil Environmental Sciences, speaks about soil the way one would a trusted, respected friend. "Soil has amazing resilience. It can resist change, and it can also overcome change."
In one component of the research, Mulvaney and his team are measuring soil organic carbon change over time. He hopes to quantify the amount of short-term carbon that is increased by conservation agriculture. Such carbon is useful because it is easily broken down by micro-fauna and cycled back into the nutrient stream for plant uptake.
To chart the change, Mulvaney is collecting soil samples from Bolivia, Cambodia, Ecuador, Ghana, Haiti, India, Kenya, Lesotho, Mali, Mozambique, Nepal, the Philippines, and Uganda — the countries where the project is located. These time-zero samples are shipped back to the United States, where Mulvaney and his team conduct a suite of soil fertility tests on them. The soil samples then comprise a soils library that is kept under lock and key on Virginia Tech property.
At the end of the project cycle, three to four years later, the team will take soil samples from the same fields, conduct the same suite of soil analyses, and then be able to say whether their hypothesis was correct — that rain-fed smallhold farms in the developing world can increase soil organic carbon, and hence soil fertility, by the adoption of conservation agriculture.
In another research thrust, Mulvaney and his team are looking at measuring greenhouse gas fluxes from traditional versus conservation agriculture systems. In other words, they are looking at how much a given plot of land breathes.
Most ecosystems, Mulvaney explains, are in a starvation environment. "If you add biomass, as with conservation agriculture, you are making a more nutrient-rich environment." Soil that is more nutrient-rich, and therefore healthier, will respire more. This carbon-rich soil has the potential to offset man-made carbon emissions, and may become useful for carbon sequestration payments.
But how does one measure soil respiration? It turns out there is a device called an automated soil carbon dioxide exchange unit that was designed just to track how much CO2 a given area emits. The unit can also collect data on soil moisture at four depths, and it can track six temperature inputs and photosynthetically active radiation. It can take measurements continuously for 28 days at a stretch, operating off a battery. At $11,000 apiece, the ACE Continuous Soil CO2 unit is not standard lab equipment, and must first be shipped to Virginia Tech for testing from England, where the units are made. Mulvaney expects to purchase six of these to be deployed in one country at a time. Use of the ACE units began in March 2012 in Kenya.
Mulvaney collaborates with local researchers at each site, depending on them for data collection. "Everything is done with intimate involvement with our in-country partners," he says. "We couldn't do it without them." But assuring uniform protocols and accurate data collection in distant locations can be difficult.
Organizational partners include nongovernment organizations, such as Zanmi Agrikol in Haiti; Instituto Nacional Autónomo de Investigaciones Agropecuarias in Ecuador; Project to Support Agricultural Development in Cambodia; and Local Initiatives for Biodiversity, Research, and Development in Nepal, among many others. Mulvaney also works with researchers at Virginia Tech and collaborating scientists at Auburn University, the University of Georgia, and the University of Florida.
The research spans disciplines as well as countries: Sociologists, economists, and gender specialists all contribute their expertise. Sociologists assist with on-farm research trials; economists look at the profitability of conservation agriculture; gender specialists ensure that women's special knowledge about soil is not overlooked.
The input of these peer scientists is critical, according to Mulvaney. "The agronomic questions are easy in many ways; the socio-economic questions are difficult and arguably more important." Mulvaney points out that this kind of crosscutting research is not usually found in other research programs. Because aspects of farming, such as sowing seed and weeding, are considered women's work in some of the project countries, "we're fortunate that we have a gender specialist that we can team up with," Mulvaney says.
He also works with men and women agricultural extension agents, suppliers, farmers, and students. Each brings their own set of questions and contributions to the project. "I feel very lucky to be part of this project," says Ryan Stewart, a graduate student working on his master of science degree in the Department of Crop and Soil Environmental Science. "What I am working on may directly help smallholder farmers in the Central Plateau of Haiti. There hasn't been much work done on characterizing the soils in this region, so I feel I am doing something worthwhile."
As if straddling time zones, traveling in remote rural areas, unraveling language confusions (Mulvaney speaks Spanish, which helps him in Latin America), and sorting through customs regulations were not enough, Mulvaney must also work within time constraints imposed by the funding agency. "Soil-forming is a geologic process. And yet we're looking at improving it within five years!"
Not that he is complaining. Mulvaney is clear that he is lucky to get to do this kind of research. "It's rare in a researcher's life that you can have this kind of impact," he says.
In fact, the work by Mulvaney has achieved such notice that he was invited to serve as the program co-chair at the Second International Conservation Agriculture Workshop and Conference in Southeast Asia in Phnom Penh, Cambodia, in 2011. In the same year, he also presented papers at conservation agriculture conferences in Long Beach, Calif.; San Antonio, Texas; and Brisbane, Australia.
If all goes as planned, the CO2 flux units and the soil samples will show that soil cultivated under conservation agriculture has higher fertility. This will be good news for Mulvaney and the farmers who decide to try conservation agriculture. But it will also be good news for all of us who depend on that handful of dirt to grow our food.