Natural Solutions for Agricultural Productivity

Sustainable nutrition outlook

Many agricultural researchers are now look- ing to a set of practices known as sustainable intensification. The specifics vary depending on the setting, but a growing number of exam- ples from around the world highlight the pos- sibility of a second green revolution — one that might better live up to its name.

Many roads to sustainability The concept of sustainable intensification was popularized2 in 1997 by Jules Pretty, an environmental scientist at the University of Essex in Colchester, UK. His goal was to challenge the idea that increasing yield is inherently incom- patible with environmental health, with an agricultural philosophy that encompasses parameters such as biodiversity and water quality as well as the social and economic welfare of farmers. Researchers have defined the scope of sustainable intensification in different ways, but the big picture, says Pretty, entails recognizing that agriculture is inexo- rably connected with the environment and designing cultivation strategies accordingly. “Components of sustainable systems tend to be multifunctional,” he says. “You want a diverse

system that provides support to pollinators, UK INK LTD. FOR AFRICA/ICIPE/ GREEN AGRICULTURE SUSTAINABLE CLIMATE-SMART, SYSTEM: FARMING THE ‘PUSH–PULL’ A farmer inspects her maize crop, grown using a ‘push–pull’ approach. fixes nitrogen and provides a break against insects.” Advocates of sustainable intensification recognize that global agriculture can’t be reinvented in one fell swoop and that progress Natural solutions for will come from incremental steps that improve efficiency, as well as more-dramatic measures that redesign the farming landscape. agricultural productivity Lucas Garibaldi, an agroecologist at the National University of Río Negro in Bariloche, Argentina, has focused on pollinators as a Scientists are pursuing sustainability strategies for crucial component of what he calls ecological intensification. “Crop yield depends not intensifying production to tackle food security and only on the count of pollinators, but also on environmental crises. By Michael Eisenstein the biodiversity of pollinators,” says Garibaldi. “Millions of honeybees alone will not replace the function of diverse species of wild bees n paper, the global agriculture sector “Globally, we have to increase food production and butterflies and birds.” He notes that dif- has done an admirable job of keep- by 60%, and in some areas we have to increase ferent bees pollinate different crops, but also ing pace with a growing population. by 100%,” says P. V. Vara Prasad, a crop ecophys- allow more efficient pollination for some plant According to the United Nations’ Food iologist at Kansas State University, Manhattan. species. To create a haven for these airborne and Agriculture Organization, agricul- Over the past 50 years, producers increased assistants, Garibaldi advocates minimizing Otural output per person has increased by 50% agricultural output in much of the world pesticide use and including non-agricultural since 1960 — impressive, considering the num- through the ‘green revolution’. But this revolu- zones in farmland. These could be wild-plant ber of mouths to feed has more than doubled. tion has been environmentally harmful, relying borders that surround fields or just hedge- But the reality is messier. Many people, heavily on chemical pesticides and fertilizers row-like strips of flowers that are appealing to including those in high-income nations, lack that have inflicted lasting damage on the soil the bees that traverse them. reliable access to nutritious food. And food and water supply. Natural biodiversity has Growing a mix of crops can have many bene- security is an ongoing struggle for people in been sacrificed to create vast monoculture fits, including attracting pollinators. Conven- poorer regions. Even transient disruptions can fields. And in many low-income nations, sur- tional monoculture leaves soil exposed for have far-reaching consequences. One article1 vival depends on coaxing greater productivity much of the year, Garibaldi says. This creates described the global food supply as being “on a from existing plots as more and more people opportunities for weeds to grow — necessi- razor’s edge” — weather events or natural disas- scramble for limited resources, says Bernard tating herbicides — or leaves soil susceptible ters in one part of the world can cause the price Vanlauwe, a soil scientist based in Nairobi at the to erosion. With multiple crops or rotation of grain everywhere to spike by more than 50%. International Institute of Tropical Agriculture. throughout the year, more durable root

systems that densely and extensively perme- are concerned that the approach is untested ate the ground can be established, reinforcing and unproven. Last year, Panjab Singh, presi- the soil and preventing the nutrient depletion dent of the National Academy of Agricultural associated with long-term monoculture. Sciences in Delhi, told the newspaper The Diversity can also eliminate the need for Hindu, “We are worried about the impact on pesticides. Pretty says around 180,000 farm- farmers’ income, as well as food security.” ers in Kenya, Uganda and Tanzania now use Smith concurs. “It was a political move, not a push–pull cropping practices when growing scientific move,” she says, adding that the nat- maize. They plant grasses around the edges of ural farming approach has “not been properly maize plots that produce chemicals that ‘pull’ a trialled”. To assess the technique, she and her common pest, the maize stalk borer (Busseola colleagues modelled the long-term impact fusca), away from crops, while the maize itself of ZBNF on soil health. They found that the attracts parasitic wasps that prey on the stalk approach could meaningfully and sustaina- borer. The farmers also intersperse legumes bly improve nitrogen levels for low-yield lands, of the genus Desmodium with the maize that but that it would offer little benefit to farms 6 CHRIS GOMERSALL/2020VISION/NATUREPL.COM enrich the soil with nitrogen, and produce already achieving high yields . They concluded compounds that ‘push’ away pests and kill off Crops rely on pollinators such as bees. that a more targeted implementation of ZBNF a genus of invasive weed known as Striga. is needed to protect overall national food secu- Sustainable soil management is a thorny forest management, pest management and rity. Smith remains largely positive about ZBNF, issue, particularly in resource-limited settings. water,” says Pretty. By partnering with these which has been gaining momentum among Vanlauwe notes that nutrient depletion is one groups, researchers can design programmes farmers. “There’s a lot of good things about it, of the greatest threats to yield for African farm- that are more likely to be compatible with but it needs more science,” she says. ers, making a hard-line approach to sustainabil- social, cultural and environmental conditions, Outside national initiatives, smallholder sus- ity unrealistic. “People who say you can trigger and establish local networks of collaborators tainable intensive farming requires targeted agricultural development in Africa without to facilitate the dissemination of information. investment and efforts to support social and fertilizer do not have on the ground experi- Some governments are also taking a more economic stability. Vanlauwe contends that, in ence,” he says. But there are environmentally active role. Ethiopia, for example, has focused many parts of sub-Saharan Africa, environmen- friendly ways to feed the soil. Jo Smith, a soil on aspects of ecological repair by establishing tal and political conditions mean that many scientist at the University of Aberdeen, UK, has ‘exclosure’ areas for depleted soils. “Areas are farmers will continue to struggle at the margins been equipping farmers in Africa and Asia with fenced off, and after about ten years the land for the foreseeable future. Still, he sees a path anaerobic digesters — simple systems that use starts to recover,” Smith says. towards economic mobility. “Give them access microbes to convert animal manure into biogas In China, Fusuo Zhang, a plant-nutrition to credit they pay back over time, and invest in for fuel and leave a nutrient-rich bioslurry. “It’s specialist at the China Agricultural University integration and value-chains so they can get rid like giving them a little fertilizer factory — it in Beijing, and his colleagues are working with of or sell excess produce,” he says. “It’s about gives you available ammonium that the crop government officials to mobilize an effort to creating incentives and access systems.” can take up quickly,” she says. The biogas is also help smallholder farmers across the nation But durable change also requires building less harmful than conventional fuels, reducing transition to more evidence-based, sustaina- local expertise in crop and soil research, and in household air pollution and improving quality ble cultivation. This includes selecting seed ecosystems. Many specialists in these areas are of life, Smith adds. varieties that are suited to a given plot, using also involved with international education and Much of the world’s farming takes place modelling techniques to guide planting based training. For example, as director of the Feed on smallholder plots. One study3 estimated on levels of sunlight, water and nutrients, and the Future Innovation Lab for Collaborative that one-third of the global food supply is optimizing the timing and density of seed Research on Sustainable Intensification, Prasad produced on farms of less than two hectares. planting. “We sent faculty members and groups has helped to coordinate undergraduate- and This fragmentation can make it challenging of students to live among the farmers in the vil- graduate-level agriculture programmes in to introduce sustainable intensification prac- lages, and work with them to try to change their places such as Senegal, Cambodia and Bang- tices. “Smallholder production systems are management,” says Zhengxia Dou, an agricul- ladesh. Normally, these programmes take on absolutely risk-averse,” says Vanlauwe. “Falling tural scientist at the University of Pennsylvania a few dozen students at a time, but the shift to from earning US$100 to $50 a month can be in Philadelphia, who collaborated with Zhang’s online training as a result of the coronavirus the difference between being not-hungry and team. By 2015, the effort had grown to include pandemic could prove to be a long-term gain being hungry.” nearly 21 million farmers across China, who, for capacity building. “We are now talking to Close collaboration with individual farmers on average, achieved a more than 10% boost about 500 or even 1,000 students,” he says. is needed, but this is difficult to achieve at scale. in yield while using around 15% less fertilizer Fortunately, smallholders are increasingly par- and reducing their greenhouse-gas output5. Michael Eisenstein is a science journalist in ticipating in collectives that can accelerate Many farmers in India are embracing a Philadelphia, Pennsylvania. information sharing and reduce the risk associ- national programme known as zero-budget ated with adopting new cultivation strategies. natural farming (ZBNF). This cultivation strat- 1. Cassman, K. G. & Grassini, P. Nature Sustain. 3, 262–268 4 (2020). In August , Pretty and his colleagues reported egy involves using soil microbes and mulch 2. Pretty, J. M. Natural Res. Forum 21, 247–256 (1997). that, worldwide, around 8 million such groups rather than synthetic fertilizers to enrich lands. 3. Ricciardi, V. Glob. Food Security 17, 64–72 (2018). have formed over the past two decades. “That’s Farmers in several Indian states are pursuing 4. Pretty, J. et al. Glob. Sustain. 3, e23 (2020). 5. Cui, Z. et al. Nature 555, 363–366 (2018). about 240 million people working in collec- the approach, including around half a million 6. Smith, J., Yeluripati, J., Smith, P. & Nayak, D. R. Nature tive-action efforts around areas like irrigation, farmers in Andhra Pradesh. But some scientists Sustain. 3, 247–252 (2020).