Matthew Liebman, this week’s Food Hero, is a Professor of Agronomy and Wallace Chair for Sustainable Agriculture at Iowa State University. Liebman is a graduate of Harvard University and obtained his Ph.D. from the University of California, Berkeley. His research team focuses on cropping system diversification, soil amendments, and weed ecology and management. Included within the scope of his work are experiments involving crop rotations, cover crops, green manures, intercrops, conservation strips, animal manures, composts, and insects and rodents that consume weed seeds. Liebman’s team also conducts research examining the environmental impacts of using new crops and native perennial species for biofuel production.
Food Tank had the opportunity to question Liebman about his research, and what it can offer to experts working in the field of sustainable agriculture.
How did you become interested in the field of farming, and sustainable agriculture?
Agriculture has always fascinated me, and I’ve been growing horticultural and agronomic crops since I was a teenager. I have a memory of sitting on the back steps one afternoon when I was about 17, thinking I wanted to be an agronomist. I didn’t grow up on a farm, but farming has never been that far away. My first professional job was a few miles from the farm where one of my grandmothers grew up – my great uncle continued to operate a horse business there, which his son runs now. One of my brothers also pursued a career in agricultural science.
I started to study the intersection between agriculture and ecology in college and received some outstanding guidance. When I graduated, I worked for the University of California as a technician in an integrated pest management program and began to think about the impacts of pesticides and alternatives to their use. After that, I went back to school and pursued my interests in agronomy, ecology, and pest management, and I was fortunate to learn from some of the scientists who laid the foundations for agricultural ecology and sustainable agriculture. My academic supervisors were wise and generous, and showed me that scientific discovery could be immensely interesting and satisfying. I’ve also enjoyed working with and learning from farmers. Several of them have completely reoriented my path in science.
Why and how is growing important for improving soil and water quality, and for wildlife conservation? What has your research found?
Perennial plants perform many key ecological functions more effectively than annuals, including: (1) regulating the flow and storage of water, (2) reducing soil erosion, (3) storing and cycling nutrients and carbon, and (4) providing a habitat for natural enemies of crop pests and for native plants and animals of conservation concern. Where I live in Iowa, deep rooted, perennial prairie plants were a major factor in the formation of the rich, productive soils that are now used for corn and soybean production, wetland perennials filtered the water and promoted huge waterfowl populations, and forests along streams and rivers kept the soil in place served as corridors for wildlife.
The research projects I’ve been engaged in have shown that (1) diversification of the dominant corn–soybean system with small grains and perennial forage legumes like red clover and alfalfa can permit substantial reductions in agrichemical and fossil hydrocarbon use without compromising yields or profitability; (2) conversion of small amounts of corn and soybean fields to prairie buffer strips can provide disproportionately large improvements in soil and water conservation, nutrient retention, and densities of native plants and birds; and (3) native prairie species can generate large amounts of biofuel feedstocks and offer large environmental benefits relative to corn- and soybean-based systems, including greater carbon inputs to soil and large reductions in nitrogen emissions to drainage water.
How would you define diversified cropping systems? Why is it important?
Diversified cropping has spatial, temporal, and genetic components. Spatial diversification can occur when farmers plant different crops together within a single field as intercrops or agroforestry mixtures, or when they create a matrix across the landscape by planting strips and patches of different crops. Temporal diversification can occur when farmers plant rotation sequences in the field, such as a five-year rotation of corn-soybean-oat plus alfalfa-alfalfa-alfalfa. Genetic diversity occurs when different genotypes of a single crop are sown together in a single field, in neighboring fields, or in sequence over time.
Diversification is important for regulating populations of weeds, insect pests, and pathogens; for protecting and improving soil fertility; for conserving soil and reducing erosion; for creating opportunities to reduce reliance on synthetic fertilizers, pesticides, and fossil fuels; and for maintaining or improving yields. It can also be an important component of limiting risks related to food security and income that arise from unpredictable pests, weather conditions, and markets.
Why are non-food crop biofuels important? How can mass production of biofuel agriculture be sustained?
The food versus fuel debate has been framed the wrong way. American farmers are never going to produce enough material to replace the 140 billion gallons of gasoline that are consumed each year. So the appropriate question is not, ‘What can agriculture do for the energy sector?’ but rather, ‘What can the energy sector do for agriculture and the environment?’ The key point to start from is that the status quo of dominance of the landscape by annual crops like corn, soybean, and wheat is incurring high environmental costs like water pollution, soil erosion, loss of soil carbon, and loss of wildlife.
If we want to maintain the productivity of fields used for annual crops, and if we want to reduce the environmental impacts incurred by annual crops, we need to see whether perennial plants used for biofuel, like switchgrass, Miscanthus, prairie communities and trees, can provide not just fuel but conservation benefits. A desirable bioenergy scenario is one in which perennial vegetation can be harvested as a source of energy and cash for the farm and surrounding community while still providing conservation benefits like keeping soil in place, decreasing water and nutrient runoff, filtering water, and providing wildlife habitat. A number of research groups are showing that that scenario may be quite feasible.
What are the primary goals that you hope to accomplish through your teaching and research?
I’m interested in working with farmers and students to develop ecologically based solutions to farming problems. I want to see conservation practices put in place across the landscape now and further developed by the next generation of scientists and farmers.
What are other areas of agriculture that you find important to research in order to create a more sustainable future?
We need to learn how to retain nutrients on farmland more effectively, both as a means of improving economic efficiency and as a key component of protecting water quality. We need to reduce the use of toxic pesticides by developing multi-tactic ecologically based strategies that reduce selection pressures for resistance and that better protect environmental quality and human health. We need to gain more insights into what constitutes healthy soil and we need to develop soil management strategies that increase crop water use efficiency; in particular, we need to know much more about soil microbial communities and soil organic matter dynamics. We need to develop agricultural machinery that increases the labor efficiency and reduces the physical burdens of small- and medium-scale farmers – weed control machinery is especially important in this regard. We need to renew public plant breeding programs to make high quality germplasm widely available at reasonable cost, and we need to develop new crops, both annual and perennial, that are better able to deal with a changing climate and new and evolving pest complexes. We need to better understand the effects of spatial, temporal, and genetic diversification of cropping systems, and we need to study the ecological, energetic, and economic efficiencies integrated crop-livestock systems. Overall, we need to develop scientific and economic assessment tools that allow us to evaluate systems that produce multiple goods and services, rather than large quantities of just one or a few commodities.