It is our work with living soil that provides sustainable alternatives to the triple crises of climate, energy, and food. No matter how many songs on your iPod, cars in your garage, or books on your shelf, it is plants’ ability to capture solar energy that is at the root of it all. Without fertile soil, what is life? 

—Vandana Shiva, Indian scholar and environmental activist, 2008

Throughout history, humans have worked the fields, and land degradation has been a common occurrence. Many civilizations have disintegrated from unsustainable land use, including the cultures of the Fertile Crescent in the Middle East, where the agricultural revolution first began about 10,000 years ago. The 2015 Status of the World's Soil Resources report produced by FAO's Intergovernmental Technical Panel on Soils raised global awareness on soil’s fundamental role for life on earth but estimated that 33 percent of land is moderately to highly degraded, and it is getting worse. The report identified 10 main threats to soil’s ability to function: soil erosion, soil organic matter loss, nutrient imbalance, soil acidification, soil contamination, waterlogging, soil compaction, soil sealing, salinization and loss of soil biodiversity. The current trajectories have potentially catastrophic consequences and millions of people are at risk, especially in some of the most vulnerable regions. Moreover, this has become much more relevant as soils are critical environmental buffers in a world that sees its climate rapidly changing.

rocky land in production
Figure I.1. Reaching the limits: Marginal rocky land is put into production in Africa.

In the past, humankind survived because people developed new lands for growing food. But a few decades ago the total amount of agricultural land actually began to decline because new land could no longer compensate for the loss of old land retired from agriculture due to degradation or due to its use for urban, suburban and commercial development. The loss of agricultural land combined with three current trends — increasing populations; greater consumption of animal products produced in large-scale facilities, which creates less-efficient use of crop nutrients; and expanding acreages for biofuel crops—strains our ability to produce sufficient food for the people of the world. We have now reached a point where we are expanding into marginal lands like shallow hillsides and arid areas, which are very fragile and can degrade rapidly (Figure I.1). Another area of agricultural expansion is virgin savannah and tropical rainforest, which are the last remnants of unspoiled and biologically rich land and help moderate climate change. The rate of deforestation at this time is very disconcerting: if continued at this level, there will be little virgin forest left by the middle of the century. We must face the reality that we are running out of land and need to use the agricultural land we have more productively. We have already seen hunger and civil strife over limited land resources and productivity, and global food crises are a regular occurrence. Some countries with limited water or arable land are purchasing or leasing land in other countries to produce food for the “home” market, and investors are obtaining land in Africa, Southeast Asia and Latin America.

Nevertheless, human ingenuity has helped us overcome many agricultural challenges, and one of the truly modern miracles is our agricultural system, which produces abundant food. High yields often come from the use of improved crop varieties, fertilizers, pest control products and irrigation. These yields have resulted in food security for much of the developed world. At the same time, mechanization and the ever-improving capacity of field equipment allow farmers to work an increasing amount of acreage. But we have also spectacularly altered the flows of organic matter and nutrients in an era when agricultural commodities are shipped across continents and oceans. Despite the high productivity per acre and per person, many farmers, agricultural scientists and Extension specialists see severe problems associated with our intensive agricultural production systems. Examples abound:  

  • With conventional agricultural practices heavily dependent on fossil fuels, unpredictable swings in their prices affect farmers’ net income.
  • Prices farmers receive and food prices in retail stores fluctuate in response to both supply and demand, as well as to speculation in the futures markets.
  • Increasing specialization of agriculture and geographical separation of grain and livestock production areas—even the diversion of food and animal feed crops to ethanol and biodiesel production—have reduced the natural cycling of carbon and nutrients with severe consequences for soil health and water and air quality. 
  • Too much nitrogen fertilizer or animal manure often causes elevated nitrate concentrations in streams and groundwater. These concentrations can become high enough to pose a human health hazard. Many of the biologically rich estuaries and where rivers flow into seas around the world—the Gulf of Mexico, Baltic Sea and increasingly other areas—are hypoxic (have low oxygen levels) during late summer months due to nitrogen enrichment from agricultural sources. 
  • Phosphate and nitrate in runoff and drainage water enter freshwater bodies and degrade their quality by stimulating algae growth. 
  • Antibiotics used to fight diseases in confined, concentrated farm animals, or used just to promote growth, can enter the food chain and may be found in the meat we eat. Perhaps even more important: their overuse on farms where large numbers of animals are crowded together has resulted in outbreaks of human illness from strains of disease-causing bacteria that have become resistant to many antibiotics. 
  • Erosion associated with conventional tillage and lack of good rotations degrades our precious soil and, at the same time, causes reservoirs, ponds and lakes to silt up. 
  • Soil compaction by large equipment reduces water infiltration and increases runoff, thereby increasing flooding while at the same time making soils more drought prone. 
  • Agriculture, as it expanded into desert regions, has become by far the largest consumer of fresh water. In many parts of the world groundwater is being used for agriculture faster than nature can replenish it. This is a global phenomenon, with over half of the largest aquifers and rivers in the world being exploited at rates exceeding recharge. 

The whole modern system of agriculture and food is based on extensive fossil fuel use: to make and power large field equipment, produce fertilizers and pesticides, dry grains, process food products, and transport them over long distances. With the declining production from easily extractable oil and gas, there has been a greater dependence on sources that are more difficult to extract, such as deep wells in the oceans, the tar sands of Canada and a number of shale deposits (accessed by hydraulic fracturing of the rock). All of these sources have significant negative effects on soil, water, air and climate. With the price of crude oil fluctuating but tending to be much greater than in the 20th century, and with the current relatively low price of natural gas dependent on a polluting industry (water pollution and methane emissions with hydraulic fracturing), the economics of the “modern” agricultural system need to be reevaluated. 

The food we eat and our surface and groundwaters are sometimes contaminated with disease-causing organisms and chemicals used in agriculture. Pesticides used to control insects, weeds and plant diseases can be found in foods, animal feeds, groundwater and surface water running off agricultural fields. Farmers and farmworkers are at special risk. Studies have shown higher cancer rates among those who work with or near certain pesticides. Children in areas where pesticides are used extensively are also at risk of having developmental problems. When considered together, the costs from these inadvertent byproducts of agriculture are huge. More than a decade ago, the negative effects on wildlife, natural resources, human health and biodiversity in the United States were estimated to cost between $6 billion and $17 billion per year. The general public is increasingly demanding safe, high-quality food that is produced without excessive damage to the environment—and many are willing to pay a premium to obtain it. 

To add to the problems, farmers are in a perpetual struggle to maintain a decent standard of living. The farmer’s bargaining position has weakened as corporate consolidations and other changes occur with the agricultural input (seeds, fertilizers, pesticides, equipment, etc.), food processing and marketing sectors. For many years the high cost of purchased inputs and the low prices of many agricultural commodities, such as wheat, corn, cotton and milk, caught farmers in a cost-price squeeze that made it hard to run a profitable farm. As some farms go out of business, this dynamic has favored the expansion of production among remaining farmers seeking physical and economic advantages of scale.

We grow more corn, to feed more cows, to make more milk, to buy more land, to grow more corn.

old New England saying

Given these problems, you might wonder if we should continue to farm in the same way. A major effort is under way by farmers, Extension educators and researchers to develop and implement practices that are both more environmentally sound than conventional practices and, at the same time, more economically rewarding for farmers. As farmers use management skills and better knowledge to work more closely with the biological world and with the consumer, they frequently find that there are ways to increase profitability by decreasing the use of inputs purchased off the farm and by selling directly to the end user. 

Governments have played an ambiguous role in promoting sustainability in agriculture. Many promoted certain types of farming and production practices that worsened the problems, for example through fertilizer subsidies, crop insurance schemes and price guarantees. But governments also pour funds into conservation programs (especially in the United States), require good farming practices for receiving subsidies (especially Europe) and establish farming standards (e.g., for organic production and for fertilizer and pesticide use). A new bright spot is that private-sector sustainability initiatives in agriculture are gaining ground. The general public is increasingly aware of the aforementioned issues and is demanding change. Several large consumer-facing retail and food companies (many that are international) therefore see a benefit from projecting an image of corporate sustainability. They are using supply chain management approaches to work with agricultural businesses and farmers to promote environmentally compatible farming. Indeed, the entire agriculture and food sector benefits when it becomes more sustainable, and there are numerous win-win opportunities to reduce waste and inefficiencies while helping farmers become more profitable over the long run.

Soil Health Integral to Sustainable Agriculture

You might wonder how soil health fits into all this. It turns out that it is a key aspect of agricultural sustainability because soils are foundational to the food production system while also providing other critical services related to water, air and climate. With the new emphasis on sustainable agriculture comes a reawakening of interest in soil health. Early scientists, farmers and gardeners were well aware of the importance of soil quality and organic matter to the productivity of soil after they saw fertile lands become unproductive. The significance of soil organic matter, including living organisms in the soil, was understood by scientists at least as far back as the 17th century. John Evelyn, writing in England during the 1670s, described the importance of topsoil and explained that the productivity of soils tended to be lost with time. He noted that their fertility could be maintained by adding organic residues. Charles Darwin, the great natural scientist of the 19th century who developed the modern theory of evolution, studied and wrote about the importance of earthworms to nutrient cycling and the general fertility of the soil. 

Around the turn of the 20th century, there was again an appreciation of the importance of soil health. Scientists realized that “worn-out” soils, whose productivity had drastically declined, resulted mainly from the depletion of soil organic matter. At the same time, they could see a transformation coming: Although organic matter was “once extolled as the essential soil ingredient, the bright particular star in the firmament of the plant grower, it fell like Lucifer” under the weight of “modern” agricultural ideas (Hills, Jones, and Cutler, 1908). With the availability of inexpensive fertilizers and larger farm equipment after World War II, and with the availability of cheap water for irrigation in dry regions, many people forgot or ignored the importance of organic matter in promoting high-quality soils. In fact, the trading of agricultural commodities in a global economy created a serious imbalance, with some production regions experiencing severe organic matter losses while others had too much. For example, in specialized grain production, most of the organic matter and nutrients—basic ingredients for soil health—are harvested and routinely shipped off the farm to feed livestock or to be industrially processed many miles away, sometimes across continents or oceans. They are never returned to the same production fields, and moreover the carbon and nutrients pose problems at their destinations because the soils became overloaded.

[Organic matter was] once extolled as the essential soil ingredient, the bright particular star in the firmament of the plant grower …

As farmers and scientists were placing less emphasis on soil organic matter during the last half of the 20th century, farm machinery was also getting larger. More horsepower for tractors allowed more land to be worked by fewer people. Large four-wheel-drive tractors allowed farmers to do field work when the soil was wet, creating severe compaction and sometimes leaving the soil in a cloddy condition, requiring more harrowing than otherwise would be needed. The moldboard plow was regarded as a beneficial tool in 19th and early 20th century agriculture that helped break virgin sod and controlled perennial weeds, but with repeated use it became a source of soil degradation by breaking down soil structure and leaving no residues on the surface. Soils were left bare and very susceptible to wind and water erosion. As farm sizes increased, farmers needed heavier manure and fertilizer spreaders as well as more passes through the field to prepare a seedbed, plant, spray pesticides and harvest, both of which created more soil compaction. 
A new logic developed that most soil-related problems could be dealt with by increasing external inputs. This is a reactive way of dealing with soil issues—you respond after seeing a “problem” in the field. If a soil is deficient in some nutrient, you buy fertilizer and spread it on the soil. If a soil doesn’t store enough rainfall, all you need is irrigation. If a soil becomes too compacted and water or roots can’t easily penetrate, you use a big implement to tear it open. If a plant disease or insect infestation occurs, you apply a pesticide. But are these really individual and unrelated problems? Perhaps they are better viewed as symptoms of a deeper, underlying problem. The ability to tell the difference between what is the underlying problem and what is only a symptom of a problem is essential to deciding on the best course of action. For example, if you are hitting your head against a wall and you get a headache, is the problem the headache and is aspirin the best remedy? Clearly, the real problem is your behavior, not the headache, and the best solution is to stop banging your head against the wall!

What many people think are individual problems may just be symptoms of a degraded, poor-quality soil.

What many people think are individual problems may just be symptoms of a degraded, poor-quality soil, which in turn is often related to the general way it is farmed. These symptoms are usually directly related to soil organic matter depletion, lack of a thriving and diverse population of soil organisms, chemical pollution or compaction caused by heavy field equipment. Farmers have been encouraged to react to individual symptoms instead of focusing their attention on general soil health management. A different approach—agroecology—is gaining wider acceptance, implementing farming practices that take advantage of the inherent strengths of natural systems and aiming to create healthy soils. In this way, farmers prevent many symptoms of unhealthy soils from developing, instead of reacting after they develop and trying to overcome them through expensive inputs. If we are to work together with nature rather than attempt to overwhelm and dominate it, then building and maintaining good levels of organic matter in our soils are as critical as managing physical conditions, pH and nutrient levels. Interestingly, the public’s concern about climate change has generated a renewed interest in soil organic matter management through so-called carbon farming. Indeed, putting more carbon into the soil can also help reduce global warming.

The use of inputs such as fertilizers, pesticides and fuels—aided by their relatively low cost—was needed for agricultural development and for feeding a rapidly expanding global population. Let’s not ignore that. But it overlooked the important role of soil health and helped push the food production system towards practices where environmental consequences and long-term impacts are not internalized into the economic equation. It could then be argued that matters will not improve unless these structural problems are recognized and economic incentives are changed. Many farming regions have become economically dependent on a global system of export and import of commodities that are not compatible with long-term soil health management. Also, the sector that sells farm machinery and inputs has become highly consolidated and powerful, and these corporations generally have an interest in maintaining the status quo. Input prices have increased markedly over the last decades while prices for those commodities, with the exception of short-term price spikes, have tended to remain low. It is believed that this drives farming towards greater efficiencies, but not necessarily in a sustainable manner. In this context, we argue that sustainable soil management is profitable, and that such management will cause profitability to increase with greater scarcity of resources and higher prices of crop inputs. Even the interests of corporations in the agricultural and food industries can be served in this paradigm.

This book has four parts. Part 1 provides background information about soil health and organic matter: what it is, why it is so important, why we have problems, the importance of soil organisms, and why some soils are of higher quality than others. Part 2 includes discussions of soil physical properties, soil water storage, and carbon and nutrient cycles and flows. Part 3 deals with the ecological principles behind, and the practices that promote, building healthy soil. It begins with chapters that place a lot of emphasis on promoting organic matter buildup and maintenance. Following practices that build and maintain organic matter may be the key to soil fertility and may help solve many problems. Practices for enhancing soil quality include the use of animal manures and cover crops; good residue management; appropriate selection of rotation crops; use of composts; reduced tillage; minimizing soil compaction and enhancing aeration; better nutrient and amendment management; good irrigation and drainage; and adopting specific conservation practices for erosion control. Part 4 discusses how you can evaluate soil health and combine soil-building management strategies that actually work on the farm, and how to tell whether the health of your soils is improving.


Hills, J.L., C.H. Jones and C. Cutler. 1908. Soil deterioration and soil humus. In Vermont Agricultural Experiment Station Bulletin 135. pp. 142–177. University of Vermont, College of Agriculture: Burlington, VT.  

Magdoff, F. 2013. Twenty-First-Century Land Grabs: Accumulation by Agricultural Dispossession. Monthly Review 65(6):1–18. 

Montgomery, D. 2007. Dirt: The Erosion of Civilizations. University of California Press: Berkeley, CA. 

Montanarella, L., et al. 2016. World’s soils are under threat. Soil (2):79–82. 

Tegtmeier, E.M. and M.D. Duffy. 2004. External costs of agricultural production in the United States. International Journal of Agricultural Sustainability 2: 1–20. 

FAO and ITPS. 2015. Status of the World’s Soil Resources (SWSR)—Main Report. Food and Agriculture Organization of the United Nations and Intergovernmental Technical Panel on Soils, Rome, Italy.