Modifications to the Cropping System

Recommendations for nitrogen use often center around the “four Rs”: applying the right source of nitrogen, at the right place, at the right time, and at the right rate. While this is a useful framework for optimizing nitrogen use, Frankenberger noted that incentives to maximize yield and profit mean that the nitrogen application rate that is “right” or economically optimal for farmers is likely not optimal for reducing nitrogen loss, creating a tension that is at the heart of the nitrogen problem.

Many solutions to reduce nitrogen inputs focus on improving the ability for growers to “spoon-feed” nitrogen to their crops. Rod Weimer, Fagerberg Farms, reported that adopting drip irrigation on his onion farm allowed better control over nitrogen application with far less runoff, reducing water use by 30 percent and reducing nitrogen fertilizer use by up to 40 percent while maintaining a high-quality crop and yield. However, he noted that installing a drip irrigation system can be costly and may not be feasible for many farms without government support.

Altering the mix of plants on the field can reduce the amount of nitrogen that leaves the farm. Alejandro Plastina, Iowa State University, discussed how cover crops, which cover the soil between plantings of annual cash crops, can improve water quality and soil health, reduce erosion, and potentially reduce nitrogen losses. Despite these benefits, however, only a tiny fraction of Midwestern farms use cover crops, largely because they are not profitable for most farmers in crop-only production agriculture. Hoffman noted that farmers are becoming more amenable to incorporating cover crops and growing a more diverse mix of crops overall (e.g., growing barley in addition to corn and soybeans) as they become more concerned about soil health and more willing to experiment to find cover crops or small grains that work in their rotations and in their geographic environments. Several participants noted that the reintegration of crop and cattle production would help make cover crops more economically feasible by replacing some feed costs with cover crop forage and also reduce the need for nitrogen inputs.

Another option is to farm perennial crops. As an example, Steve Culman, The Ohio State University, described Kernza, a perennial wheatgrass that produces edible seed, could be used as forage, and can be grown with far less nitrogen fertilizer than annual wheat.¹⁰ It has a much deeper and more extensive root system than wheat and therefore captures more nitrogen. However, adoption of Kernza is limited at this time, largely due to low yields, a decline in productivity over time, and a lack of markets.

Lisa Schulte Moore, Iowa State University, discussed how prairie strips, sections of diverse perennial vegetation situated between crop fields, can substantially reduce nitrogen losses where shallow groundwater interacts with the prairie root zone. Prairie strips can also reduce erosion and support beneficial fauna such as pollinators and, at roughly $7 per treated acre, represent one of the most cost-effective conservation practices, especially when they are created on unprofitable regions of a farm.¹¹

Another option is to replace traditional synthetic nitrogen fertilizer with alternative sources of nitrogen. Daniel Nocera, Harvard University, discussed how his team effectively turned microbes into a slow-release fertilizer that directly injects nitrogen into the root system while also sequestering carbon. Once the microbial system is established in the soil, it can be maintained with drip irrigation and dramatically cuts the need for synthetic fertilizer. Leif Fixen and Ben Wickerham, The Nature Conservancy, discussed opportunities to develop a market value for livestock manure to better integrate livestock and crop production systems, particularly in the Midwest. Emerging technological approaches can improve the nutrient balance, remove water, allow for easy storage, and support precision application of manure-based fertilizer, though Fixen said further refinements to the supply chain are needed to overcome challenges such as the cost of storage and transportation to make this approach economically viable on an ongoing basis.

Modifications to the Drainage System

Controlling drainage water can reduce the amount of nitrogen that flows downstream.¹² For example, Frankenberger described how adjustable water control structures can be placed in the drainage system to reduce the amount of water drained during times of the growing cycle when drainage is less important. However, she noted that this strategy incurs installation costs and requires time for operation and maintenance. A more hands-off approach is to reduce the drainage intensity by spacing drainage pipes farther apart or placing them closer to the soil surface. This may not be an attractive option in areas where climate change is expected to bring increased precipitation, however, as growers in these areas are likely to increase their emphasis on ensuring adequate drainage.

Drainage water can also be captured and recycled in order to re-apply lost nitrogen to the same field later in the growing season, allowing farmers to achieve the same yield while applying less nitrogen overall. In tile-drained systems, this requires taking land out of production in order to construct a reservoir, which can create hurdles in terms of cost. Jim Schepers, University of Nebraska–Lincoln, discussed how in-field irrigation strategies are being leveraged to reduce nitrogen waste and loss in Nebraska. Where excess nitrogen flows into aquifers and then stays near the top of the water, it is possible to irrigate with the nitrogen-rich water at the top of the aquifer. However, for this approach to be feasible, he noted that farmers need better sensors to determine when the crop is close to needing more nitrogen.

Edge-of-Field Practices

Frankenberger described a variety of approaches implemented at the edge of the field that can help to reduce the amount of nitrogen that leaves the farm. Although most of these strategies require taking land out of production and many have no yield benefit, for some farms it is feasible to convert areas that are not profitable anyway, helping to mitigate cost barriers. Constructed wetlands, two-stage ditches,¹³ and saturated buffers¹⁴ are options that can not only increase denitrification but also reduce drain flow and increase plant uptake of nitrogen. Denitrifying woodchip bioreactors, simple trenches filled with woodchips, can enhance the natural biological process of denitrification.

Precision Approaches to Farming and Conservation

Several speakers discussed emerging technological solutions that could help growers manage nitrogen inputs and implement conservation measures in a way that is responsive to the on-the-ground reality of their farm. Bruno Basso, Michigan State University, described how sensors and digital tools can be used to precisely characterize how particular areas of a farm perform over time. Such tools can help growers apply the right amount of nitrogen to the areas where it will have the biggest payoff, or alternatively, inform conservation measures in areas that are more vulnerable to nitrogen surplus or that are unprofitable to farm.

Kit Franklin, Harper Adams University, described how high-resolution surveys of soil texture can be combined with lower-resolution information on soil chemistry and yield maps to understand baseline conditions on a farm, while in-growth sensing approaches based on spectral analysis (using satellite data, drones, or tractor-mounted sensors) can deliver insights into plant health and nitrogen needs in real time. David Lee, Booz Allen Hamilton, discussed how the U.S. Department of Energy's SMARTFARM program¹⁵ aims to model nitric oxide and other greenhouse gases using technologies such as in-field microneedles for nitrogen monitoring. Ana Arias, University of California, Berkeley, described her team's work to develop biodegradable sensors that could be spread across a field for continuous monitoring of nitrogen, water, and other variables. Karl Rockne, National Science Foundation, spoke of advances in using plants as sensors to better understand the bioavailability of nitrogen in soil.

Motivating Change

Participants discussed what is needed for growers to adopt conservation practices, in terms of both willingness and feasibility. Linda Prokopy, Purdue University, said that background factors are an important starting place and include characteristics of the farmer, characteristics of the farm, and contextual factors like climate, commodity prices, and policies. These factors, combined with the characteristics of a given conservation practice, influence farmers' perceptions and in turn feed into attitudes and norms—heavily influenced by the trusted individuals in a farmer's orbit—and farmers' perceived level of control over the actions required to adopt the practice. The intention to adopt a practice influences behavior but is mediated by the farmer's actual level of control over the practice. Other factors, such as financial incentives and knowledge, are often a necessary part of the pipeline from awareness to action but are not in and of themselves sufficient to drive change, Prokopy noted. While the drivers of behavior are reasonably well understood up to the point of adoption, she said further research is needed to understand what motivates a farmer to continue using the practice in the future, especially after any initial incentives are terminated.

Farmers are not merely motivated by economic gain; many are intrinsically motivated to support a healthy environment. Rochelle Krusemark, Krusemark Farms, said that in her experience, farmers see themselves as stewards of the land and have a strong drive to retain and improve their soil and efficiencies in order to pass productive farms on to the next generation. Healthy, well-maintained soils, she noted, produce higher yields and better quality products while retaining nutrients better, thus requiring fewer inputs. The increasing adoption of no-till and low-till practices, nutrient and water management strategies, and precision technology for more efficient use of inputs speaks to many farmers' desire to make U.S. agriculture a global leader in sustainability, she said. Economic drivers are important, as well. Richard Wilkins, Delaware Farm Bureau, pointed to a tension between consumer perceptions and the realities of today's agricultural sector. While some consumers have expressed a desire for less “science” in the food production system (exemplified in the criticism of advanced plant breeding methods and the use of synthetic pesticides and fertilizers), applying the latest scientific advances is critical, in his view, to the ability to optimize food production and allow farmers to minimize the resources required for each unit of production. He cautioned that increasing regulation in agriculture could lead to even more consolidation and vertical integration in the food and agriculture system.

External motivators can be used to overcome barriers. Kurt Waldman, Indiana University, discussed how certification and supply chain standards can motivate change by rewarding producers for desired practices. This began in the 1970s with a proliferation of “eco-friendly” certifications and expanded to scorecards and public campaigns in the 1980s. More recent years have brought an emphasis on multistakeholder initiatives focused on continuous improvement toward more sustainable practices (e.g., by giving farmers tools for analyzing the environmental outcomes of their practices compared to industry averages). The idea behind all of these efforts is to create a de facto rule to drive the adoption of certain practices through consumer demand for products that comply with them. However, several factors limit the likely impact of these approaches in the context of nitrogen use. One is that demonstrating compliance depends on the ability to collect high-quality, farm-level data and then transmit them all the way through the supply chain. This is especially challenging given that some of the major crops that contribute to nitrogen contamination, such as corn and soybeans, are often consumed indirectly as part of processed food or animal products and are therefore “invisible” in the end product that the consumer encounters, Waldman noted.¹⁶ Plastina pointed out that food labels and certifications can be confusing to consumers and may not truly increase demand, especially given that there are already so many. Another key issue is a lack of incentives; Waldman said many farmers and retailers are reticent to undertake the work required to implement, document, and communicate about their practices unless there is a clear reward for doing so, or a clear cost for not doing so.

Paying for Change

Most nitrogen-conserving practices impose some cost. Wendy Graham, University of Florida, said that ultimately the consumer will need to pay more for food in order to support the changes required to make the agriculture system more sustainable; other participants argued that this is not generally seen as a viable option. Schulte Moore suggested that a nationwide “willingness to pay” study could shed light on the degree to which the public is willing to pay for environmental benefits that farms could provide to society, whether through increased food prices or government subsidies. If a price increase for consumers is not an option, it is necessary to find other opportunities to make a business case for adopting changes, said Jenny Ahlen, Environmental Defense Fund (EDF). Where farmers have a direct relationship with buyers, buyers can incentivize change. She pointed to corporate initiatives by Walmart, Smithfield Foods, Campbell Soup Company, and others as examples of supply chain–based efforts to reduce agricultural inputs and emissions. While the EDF has focused on how to get funding and incentives into the right hands, she noted that many of its efforts have failed due to a lack of economic viability. She suggested the farming community should advocate for the programs and funding that will make implementing changes more feasible for producers.

Another option is to pay producers directly for implementing desired practices. Leah Palm-Forster, University of Delaware, described how conservation auctions can be an efficient approach for connecting land managers with buyers willing to pay them to implement certain management practices. Buyers can be private individuals or groups, regulated entities, or government. Growers can be paid for either practices or outcomes. In theory, auctions provide a platform for reducing the cost of conservation by creating competition among land managers and selecting who can provide the most value per dollar spent. In practice, however, transaction costs can make auctions less cost-effective, particularly if participation is low. They require a significant amount of organization and education, and evaluating their benefits also requires time and resources, Palm-Forster noted.

Rockne noted that farmers are in a good position to provide ecosystem services, such as habitat for pollinators and game species. So far such services have been undervalued economically, but they provide a possibility to compensate farmers for a product that addresses the nitrogen problem and provides environmental and recreational benefits.

It is also possible to focus rewards and incentives related to the end of the pipeline by focusing on water quality. Kurt Stephenson, Virginia Polytechnic Institute and State University, discussed how a water quality trading system could provide a way to achieve this but cautioned that this approach would make only a trivial impact under the current circumstances. The degree to which such a system actually reduces nitrogen contamination depends on the ability to set a nitrogen cap below current levels. It also depends on the balance of entities that are regulated and thus motivated to adopt changes (or trade credits for others to do so) versus entities that are not regulated and not willing to adopt practices in exchange for some reward. To make a dent, Stephenson said such systems would need to incentivize trading among a large and diverse array of nitrogen contributors including agricultural entities that are not currently regulated as point sources, urban stormwater systems, and others.

Lessons from Policies and Programs

Most government efforts to control pollution fall into two main categories: incentives and regulations. Steven Wallander, U.S. Department of Agriculture's Economic Research Service, discussed federal programs seeking to incentivize nitrogen conservation, focusing on two in particular: the Environmental Quality Incentives Program and the Conservation Stewardship Program. While a broad range of policy approaches can potentially have an impact, Wallander stressed that the success of any program is highly dependent on its ability to target the farmers, places, and practices where it can make the most difference. This can be challenging, however, as uptake depends not only on the eligibility rules and design for a particular program, but also on the decisions and behaviors of all of the stakeholders involved. Kling commented that federal and state policies are largely not well targeted or designed to address the scale and breadth of the problem. Overall, Wallander said that federal funding has mostly been devoted to programs that encourage cover crops, nutrient management, and conservation tillage, while less funding has gone to programs that promote riparian buffers, manure management, and other strategies. To design effective policies that link payments to outcomes, he said it is important to consider additionality (the degree to which farmers would adopt the practice irrespective of subsidies), direct impacts of the practices, and the degree to which the adoption of a given practice leads to the joint adoption of other practices or decisions.

Schepers noted that Nebraska's natural resources districts have taxing authority, and the funds are used to improve on-farm water management. Farmers pay $3 an acre, which supports the purchase of equipment such as soil-water sensors, buried pipelines, and drip irrigation. One district also has the authority to restrict fall fertilizer application and require annual reports of soil and water testing, amount of nitrogen applied, irrigation amount, and yield. Schepers suggested this model could be a possibility for supporting programs to improve nitrogen management.

Mark Lubell, University of California, Davis, discussed the option of regulating nitrogen contamination from farms as point-source pollution. Three programs represent examples of this approach: California's Irrigated Lands Regulatory Program (ILRP), the Everglades' Agricultural Area Best Management Practices program, and the European Union's Nitrates Directive. California's ILRP takes a hybrid approach combining collaboration and regulation. Under this program, farmers must join coalition groups or register individually with the regional water board and submit documentation such as a farm evaluation plan for protecting surface and groundwater, their plan for irrigation and nitrogen application, and their actual yearly amount of nitrogen applied. It also requires producers to monitor nitrates in domestic wells on irrigated parcels and inform residents of exceedances. While the program currently does not impose nitrogen limits, it lays the groundwork to potentially do so in the future. Studies of farmer adoption of nitrogen-conserving practices since the program started reveal that cost and uncertainty—primarily regarding impacts to yield and return on investment—are important barriers to adoption.

Many programs have used collaborative approaches to increase farmers' access to critical information they need to adopt nitrogen-conserving practices. Carrie Vollmer-Sanders, The Nature Conservancy, shared how the 4R Nutrient Stewardship Certification Program¹⁷ increased the adoption of these practices by certifying crop advisers—who have direct relationships and established rapport with farmers—to assist farmers with implementation. Because the “right” source, place, time, and rate of nitrogen application varies from place to place, she stressed that standards for 4R guidance should be location specific. She also urged a holistic approach that not only focuses on direct fertilizer application but also incorporates conservation practices such as reduced tillage, buffer strips, and cover crops. Greg La-Barge, The Ohio State University, discussed opportunities for improving the information sources farmers use to assess when nitrogen fertilizer is needed, including tools for calculating the optimal nitrogen application rate,¹⁸ extension services that connect farmers with specialists, and approaches to quantify water quality impacts of their practices. While farmers have many potential sources of information for monitoring the health of plants and soils, he noted that consistency among them is important to influence decision making. Several participants stressed the need for improved nitrogen monitoring capabilities in order to address the role of risk and uncertainty as a barrier to practice adoption. Better data could provide feedback to show farmers the impact of their actions and also potentially allow programs to offer guarantees as an insurance policy in case a practice does not have the expected impact. Cassman suggested a collaborative approach to giving farmers greater access to useful data, such as through a large, anonymized database that enables farmers to compare their performance to others with similar conditions. Such a system could also act as a collection of “thousands of field experiments” running each year, helping to build the evidence base for which practices yield the best payoff under given land, climate, and market conditions.

The Floridan Aquifer Collaborative Engagement for Sustainability project,¹⁹ presented by Graham, focuses on increasing the adoption of best management practices, which have been shown to allow farmers to reduce nitrogen application by about one-third without affecting yield. The project uses biophysical models to shed light on tradeoffs involved in different practices. The researchers are also developing economic modeling tools to help farmers balance environmental benefit with economic feasibility. The project uses a participatory modeling process to keep its research grounded in the growers' needs and priorities and to facilitate stakeholder engagement. Building on this theme of collaboration, Roger Wolf, Iowa Soybean Association, described how the Iowa Soybean Association has advanced conservation goals and best practices to improve water quality at the watershed scale in Iowa using a coalition-based approach. Examples include the Middle Cedar Partnership Program, which connects upstream and downstream stakeholders in the Cedar River watershed to address community priorities such as flooding, and the Agriculture's Clean Water Alliance, which brings agriculture retailers together around a shared mission to reduce nutrient loss, build healthier soils, and improve water quality in the Raccoon River and Des Moines River watersheds. To build successful coalitions, he said it is essential to have leadership, supportive policies and programs, and associated funding. It is also important to build on shared resources and values while using research, tools, and processes to derive measurable outcomes and impactful results.

Several speakers suggested that the nitrogen problem simply cannot be addressed by incremental fixes to the existing food and agriculture system, but instead will most likely be driven by disruptive changes, such as transformative shifts in consumer preferences, revolutionary new technologies, or the overhaul of current policy structures. Thomas Hertel, Purdue University, reminded participants that interventions to change behavior need to be designed beyond just the local scale. The nitrogen problem is influenced by policies and programs related to biofuels, crop insurance, and trade, among others. Tweaking the application of nitrogen will not mitigate the problem in a meaningful way if the fundamental economic drivers of the current production system are not considered. Frankenberger noted that a lack of accountability for externalities, such as environmental and public health consequences, within the agricultural system perpetuate unsustainable practices. To increase accountability, however, will require a clearer understanding of the benefits that can be derived from various practices, she noted.

The nitrogen problem is also inextricably linked to other issues, including climate change and phosphorous pollution, which may help drive some sweeping changes that address multiple issues, several speakers noted. Rockne and Hoffman both emphasized the need for a systems approach that integrates the management of nitrogen with that of phosphorus and carbon. Hoffman suggested that nitrogen-conserving practices could be paired with emerging carbon credit systems to drive the adoption of practices that bring multiple environmental benefits. To do this effectively, he stressed that a systems approach is needed to understand the full picture of how various practices affect both nitrogen use efficiency and greenhouse gas emissions because it is possible that some nitrogen-conserving practices could reduce nitrogen leaching while potentially increasing the emissions of nitrous oxide, a greenhouse gas.