Agricultural Pollution Fertilizer Figure 1. Green Tides along the Coast of Qingdao, China Source: © STR / AFP / Getty Images (left). © Dongyan Liu (right). Note: Since 2007, vast algal blooms (covering nearly 29,000 km2 in 2013) have blanketed the Yellow Sea, bringing annual green tides to China’s coast (left). A green tide is seen engulfing an Olympic stadium in 2008 (right). Why Care about Fertilizer Pollution? both indispensable for food production and thought to Over the past 50–60 years, unbridled growth in glob- be swiftly approaching peak supply (as early as 2035). al fertilizer use to boost and maintain crop yields has polluted natural and agricultural systems, leading to a Nature and Magnitude of the Problem range of harmful outcomes. The abundant and ineffi- Several practices lie at the heart of this global problem. cient application of fertilizer is a leading cause of water Fertilizer is often applied in significant excess of what pollution, as well as a contributor to greenhouse gases plants can use, and in some instances, the poor timing of and the deterioration of air and soil quality. This, in fertilizer applications increases the amount that is washed turn, has adverse consequences for public health, the cli- away by irrigation or rainwater. Fertilizer use and losses mate, wildlife, and business—including tourism, agri- are notably concentrated in areas where intensive irriga- business, commercial fishing, and farming. Although its tion is practiced. Another problematic practice in certain use, in combination with other Green Revolution tech- contexts is the use of the wrong fertilizer blends relative nologies, is credited for feeding the world and averting to plant requirements, because the mismatch leaves more a more dramatic expansion of agriculture into natural fertilizer unmetabolized and free to escape. This has both landscapes, today’s fertilizer use is considered to be environmental and economic costs. pushing the planet’s biogeochemical boundaries. In 2015, the world used more than 180 million metric Some nutrient losses are to be expected as the biolog- tons of fertilizer, or about six times more than it did 55 ically available or “reactive” form of nitrogen in fertiliz- years prior (see Figure 2). In developing countries, fertil- er is particularly mobile, while fertilizer’s phosphorus izer consumption increased by a factor of 34. This growth and potassium minerals travel with the soil particles to pattern generally tracks the intensification of agriculture which they bind (see Box 1). Yet it is common for some and rise in crop output witnessed over this period, over 50–75 percent of fertilizer, that is, the vast majority of which global cereal output, for instance, more than tri- it, to volatilize, gasify, leach into the soil, or wash away pled. Much of the increase in fertilizer use occurred first unused by plants after it is applied. Fertilizer is by far in today’s high-income countries, and later in parts of the largest anthropogenic source of reactive nitrogen in South and East Asia, and South America. Today, China which the world is awash; and the same can be said of is the largest consumer of fertilizer in absolute terms, fol- phosophorus, a mined, nonrenewable resource that is lowed by India, the United States, the European Union, This note was written by Emilie Cassou. Full references and acknowledgments are available online. Agricultural Pollution Fertilizer Figure 2: Fertilizer Consumption by Region, 1961–2015 Box 1: What is Index, 1961=100 Fertilizer? 6,000 Fertilizers enhance plant growth by providing them nutrients, and 5,000 in some cases, by improving soil properties (for example, water 4,000 retention, aeration). The three primary components of fertilizer are the macronutrients nitrogen 3,000 (N, which promotes leaf growth), phosphorus (P, which promotes root, 2,000 flower, seed, fruit development), and potassium (K, which aids stem growth, water movement, flowering, 1,000 and fruiting). Three secondary macronutrients commonly found in 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 fertilizer are calcium (Ca), magnesium (Mg), and sulphur (S). Fertilizer also ■ South Asia ■ West Asia ■ Latin America and the Caribbean ■ East Asia ■ Africa provides a variety of micronutrients, ■ World ■ North America ■ Eastern Europe and Central Asia ■ Western and Central Europe including copper (Cu), iron (Fe), Source: Based on International Fertilizer Industry Association (IFA) data. manganese (Mn), molybdenum (Mo), Note: Accounts for nitrogen, phosphate, and potash nutrients. zinc (Zn), boron (B), and others. Brazil, and Indonesia. When it comes to per hectare in- linked to cancers of the digestive track as well as infant tensity, Gulf countries, New Zealand, Egypt, Ireland, and methaemoglobinaemia, also known as blue baby syn- China have been among the largest users over the past drome. Cleaning up polluted bodies of water, meanwhile, decade. Growth in global fertilizer use shows no signs of can be tremendously costly. slowing, in part due to the high rates of growth projected At the same time, nitrogenous fertilizer is volatile and for Latin America and South Asia, and to a lesser extent its use contributes to local air pollution in the form of fine in Middle East and North Africa. particulate matter and ground-level ozone, which are known causes of cardiovascular and respiratory disease. Impacts In particular, fertilizer is second only to cattle as a source When an overabundance of fertilizer leaches into the of emitted ammonia, a form of nitrogen which plays a sig- soil, or deposits onto it in the form of ammonia,1 this can nificant role in particulate matter formation. Meanwhile, create an imbalance of nutrients that leads to soil acidi- by exponentially increasing soil emissions of nitrous ox- fication, and even to a loss of soil organic carbon, affect- ide, a greenhouse gas 300 times more powerful than car- ing crop yields over time. This, along with the expense bon dioxide, fertilizer application also contributes to glob- of wasted fertilizer, is costly to farmers and can detract from agricultural sector competitiveness. When fertilizer Figure 3: Dead Zone in the Gulf of Mexico finds its way into surface water, an abundance of nitro- gen and phosphorus can fuel an overgrowth of algae and seagrasses, a phenomenon known as eutrophication. This not only mars bodies of water but also depletes dissolved oxygen levels over time, killing native flaura and fauna, and in severe cases, resulting in hypoxic dead zones in which almost nothing can live. Fertilizer runoff has been a leading contributor to vast dead zones, such as those which stretch over tens of thousands of square kilome- ters in the Gulf of Mexico and the Baltic Sea (see Figure 3). In humans, exposure to toxic algae from recreational water use and the consumption of inadequately treated water can lead to liver damage. And high concentrations of nitrates (plant-available nitrogen) in drinking water are Source: National Aeronautics and Space Administration (NASA). Note: Globally, an area roughly the size of the United 1 Emitted ammonia (NH3) returns to the earth’s surface Kingdom is hypoxic (approximately 240,000 km2 of waterways, mainly in the form of dry deposition of NH3 and wet deposi- of which 30 percent are inland and the remainder along tion of ammonium NH4+. coasts). Agricultural Pollution Fertilizer al climate change—and its carbon footprint is larger if es. In such instances, the heavy use of fertilizer can reflect one factors in its energy-intensive manufacturing process. limitations of knowledge, information, and technology, and result from a lack of tools to understand and provide Drivers for plants’ specific nutrient needs. Farmers often lack ac- While agricultural intensification and the rise in agricul- cess to or undervalue (at least from a social perspective) tural output provide essential context, they do not fully aids such as diagnostic tests, agronomic training that explain why fertilizer use has risen to the counter-pro- would enable them to know when “less is more,” well- ductive levels often observed today. Fertilizer misuse is dosed fertilizer blends (or formula fertilizer), or fertilizer better understood by examining farmers’ economic in- products, planning tools, and irrigation or other technol- centives, and the influences of policy and technology. One ogies designed to deliver fertilizer efficiently. That is not factor that is central to today’s fertilizer pollution problem systematically the case, however, and behavioral factors is the fact that its market price to farmers does not account are almost certainly at play where farmer incentives, for the full environmental and social costs of its use. As awareness, and access to information and technology do a result, the abundant use of fertilizer can simply make not fully explain their actions. It may be the case, for in- economic sense from farmers’ perspective, particularly if stance, that the quantity of fertilizer in a standard pack- they highly value near-term results. Farmers may believe age has an influence over the amount that is applied, even that its heavy use is a cost-effective means to overcome though that quantity has no relation to soil-crop needs. low or declining soil fertility, even when fertilizer overuse is part of the problem.2 In comparison to the perceived What Can Be Done? benefits of such strategies, the potential for damaging the Two major avenues exist to limit fertilizer pollution. land and shared water resources over time, or for contrib- The first involves reducing the amount of fertilizer that uting to climate change, can seem a distant concern. farmers use in the first place. Many opportunities exist This proclivity to discount future gains, and to only to curb the use of fertilizer without compromising crop focus on private ones (real or perceived), is sometimes en- yields or food security. In China, for example, nitrogen couraged by agricultural policies more bent on promot- use was cut by roughly 4 percent to 14 percent in maize, ing production than environmental responsibility. Fertil- rice, and wheat system field trials while boosting yields izer subsidies in many countries further insulate farmers by 18 percent to 35 percent, thanks to a knowledge-inten- from the full cost of fertilizer, leading them to apply it sive approach to farming known as integrated soil-crop more heavily, and less according to agronomic needs. system management or ISSM (Chen et al. 2014). Similarly, policy incentives that favor the expansion of A second avenue to mitigate fertilizer pollution in- farmland and irrigation, irrespective of their adverse ef- volves limiting the amount that runs off unused by fects, also invite fertilizer use to expand; and the result- plants, including by recycling nutrients that are already ing erosion and runoff exacerbate fertilizer use inefficien- present in the environment. From a technical perspec- cy by carrying nutrients off the field. Such scenarios are tive, this can be achieved through changes in dosing, particularly pronounced where divided administrative timing, application methods, and irrigation practices, responsibilities have led agricultural and environmental and through farm management strategies. Examples policies to be developed separately. This was the case in of the latter include the use of buffer zones, rotational the European Union, for example, before efforts to recon- cropping, and aquaculture to absorb excess nutrients. In cile these through Common Agricultural Policy reforms Bangladesh, what is known as fertilizer deep placement started in the mid-1980s. Meanwhile, the diffuse nature has allowed over 2.5 million farmers to abandon the of fertilizer pollution—a form of nonpoint source pollu- traditional broadcasting method of applying fertilizer, tion—has often made it a low priority of environmental resulting in notable reductions in fertilizer use (25–40 policy, hindering attempts to regulate its use. percent) and losses (up to > 50 percent). The method in- While the abundant use of fertilizer sometimes works volves placing fertilizer granules, which stay in place to the advantage of farmers, it is often the case that more more readily, in the root zone, close to where they are judicious use of fertilizer will save them money and en- needed.3 The following are various strategies that can be hance their work’s profitability. In Vietnam’s main coffee used to reduce fertilizer use and losses. growing region, for instance, field studies have estimated Knowledge and information. In general, greater that by lessening and better timing their use of fertilizer, access to agronomic knowledge and data can improve especially with respect to irrigation, farmers could im- farmers’ ability and motivation to apply nutrients more prove yields and revenues by 10 percent and 30 percent precisely and sparingly. Extension and advisory ser- respectively—fertilizer being one of their largest expens- vices, public or private, are one possible conveyor of 2 Farmers may also see it as a way to save time for more lucrative, off-farm work opportunities. In parts of China for instance, the multiplication of such opportunities have led some farmers to apply a full season’s dose of fertilizer to their fields before crop planting as a substitute for monitoring and tending to crop needs continuously over the growing season. 3 A third avenue to mitigate fertilizer pollution involves cleaning up, and while various techniques allow this, it can be far Agricultural Pollution Fertilizer Figure 4: Information-Intensive Farming in Different Contexts Source: © Agribotix. Source: © Iván Ortiz-Monasterio/CIMMYT. Note: Management zone map, created by drone, Note: Handheld N sensor in Yaqui Valley. to measure fertilizer needs. Source: © Feed the Future Kenya Innovation Engine. Source: International Rice Research Institute. Note: On-site soil test (Quest Agriculture). Note: Leaf color chart for rice. these, as are various information and communication service model involving the use of handheld infrared technologies. In Uruguay, for example, the public sector devices to determine the mid-season fertilizer needs of has developed a public agricultural information system crops. In this particular context, the simple diffusion of that combines data from farmers (including soil tests) images showing wide-scale algal blooms in the Gulf of and other sources (for example, weather and satellite-de- California downstream helped to raise awareness and tected farm data) to inform farmer decision-support set the stage for dialogue and change. In West Africa, tools and services. Across a number of countries, farms several nongovernmental organizations are working are increasingly turning to tools such as sensors, global with entrepreneurs to promote the use of mobile soil positioning systems, satellite imagery, and data inter- test kits—while working with fertilizer suppliers—to pretation software to monitor agricultural fields with provide farmers with information about soil properties precision (though resulting gains in fertilizer efficiency and crop aptness even where laboratory testing is inac- can sometimes encourage its use). While this develop- cessible. Another example of a low-cost information tool ment has predominantly occurred in large industrial is the leaf color chart that has been developed to allow farms, precision technologies and service models are farmers in Asia to visually estimate the nitrogen needs also emerging for small- to mid-size commercial farms. of high-yielding rice varieties at different critical growth Illustratively, in Mexico’s intensively cultivated Yaqui stages (see Figure 4). Valley, wheat farmers have experimented with a private Inclusive innovation and technology. Just as tech- less effective and costly than acting preventively, and is not discussed further here. Agricultural Pollution Fertilizer nological innovations can enhance farmers’ access to in- Figure 5: Precision Farming formation as illustrated above, so can they make it easier for farmers to control inputs, thus improving farmers’ ability to act on information. These can involve the de- velopment of fertilizer products (e.g., custom blended formula fertilizer, slow release, enhanced-efficiency nitrogen fertilizers), irrigation systems (e.g., drip), fer- tilizer delivery mechanisms (e.g., variable rate applica- tion technologies), farming techniques (e.g., irrigation management, fertilizer application methods), and plan- ning tools (e.g., management zone mapping site-specific nutrient management). Vietnamese coffee growers who have switched to drip irrigation to save water and asso- ciated labor costs, for example, are finding that they can significantly cut back on the amount of fertilizer they use, often by 50 percent or more. This example being no exception, the diffusion of such technologies often de- pends on government- or donor-supported programs (e.g., access to finance, business development) as well as on the development of private sector service models that enhance access to these. Most critically, the uptake of new technologies depends on how responsive these are to farmers’ existing needs, highlighting the role of inclusive innovation systems that cater to and actively involve a wide variety of actors. Government incentives. One set of strategies in- volves realigning fertilizer prices with their true cost, and generally restructuring policies to encourage farm- Sources: Drone over maize field: © Precision Drone LLC; ers to use fertilizer more sparingly. The removal of most microirrigation: DoneRight Irrigation. agricultural subsidies in New Zealand during the 1980s, for example, led to a stark decline in fertilizer use and aforementioned case of fertilizer deep placement, while environmentally beneficial changes in land use—not the technology’s development and demonstration were to mention fiscal gains. The European Union, in 2003, made possible by donor support, the economic benefits instituted a policy known as cross-compliance under it offers have helped to carry it forward; in Bangladesh, which farm subsidies are contingent on contributions to it has generally improved yields (15–35 percent), mar- ecosystem services and compliance with environmental gins (15–30 percent),4 and soil quality. In various parts law—including that which governs nitrate pollution. In of Latin America, payment for ecosystem service laws the United States, the state of Virginia offers cost shar- have allowed beverage, utility and other companies, ing and tax credits for the adoption of recognized best and environmental nonprofits, to compensate farmers management practices, such as planting trees, shrubs for adopting practices that keep nutrients out of wa- and grasses, and constructing wetlands around fields, ter sources that these payers would otherwise need to especially those that border water bodies, increasing the treat at greater expense. In multiple countries including land’s capacity to absorb runaway nutrients. the United States, Tunisia, China, and India, govern- Market-based incentives. In some cases, the public ment-authored and administered organic standards sector can influence incentives indirectly, by creating have, together with the development of quality assur- context in which market signals take over (for exam- ance infrastructure, enabled markets to reward produc- ple, by supporting private sector capacity or develop- ers for avoiding the use of most synthetic agro-chemi- ing a legal framework for ecosystem payments). In the cals among other practices. 4 These are rough orders or magnitude based on various reports for different crops, including but not limited to rice.