Sustainable Agriculture

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We have seen how industrial agriculture methods including advances in heavy equipment, irrigation technologies, chemical fertilizers and pesticides, and genetic modification of crops and livestock have increased economic efficiencies and yield. However, these benefits have come at high environmental and human health costs. In the beginning, these costs were masked by the enormous quantity of soil and people on Earth who were not yet exposed to the methods of industrial agriculture. Now, however, the environmental and human health impacts of industrial agriculture and the industrial food system are felt globally. From the perspective of environmental science, the methods of industrial agriculture and the industrial food system are ecologically unsustainable. These methods are contributing to a loss of planetary biodiversity, change in global climate, and imbalance of the nitrogen cycle--and this is only the short list of hazards the industrial food system presents to Earth's ecosystem.

Closer Look

There are many programs around the world today dedicated to recovering and promoting the wisdom of traditional agriculture for young people. One successful example is the organic agriculture program at the Sekolah Dasar Pangudi Luhur Kalirejo Primary School in the Yogyakarta District of Indonesia. Watch this short video on the school program.

At the beginning of this Science section of the Food chapter, we noted that even though the industrial food system is a major feature of the contemporary world, one third of the world's population still relies upon traditional, small-scale farming practices. Though a declining population on the world stage, many traditional farmers and fishermen possess intimate knowledge of the natural world that is important for the future of human life and the preservation of the Earth. In many ways, sustainable food systems are attempts to join the wisdom of people working inside traditional food systems with new knowledge from environmental science and technology in order to create a food system that is more ecologically sound than the industrial model.

People committed to building a sustainable food system today are experimenting with a vast array of environmentally friendly techniques along every step in the system (growing, transporting, processing, marketing, consuming, disposing). Here, we will only touch upon five growing techniques characteristic of sustainable agriculture today: input minimization, soil maintenance, water management, diversified planting, and pest and pollinator maintenance.

Input Minimization

Practitioners of sustainable agriculture seek ways to reduce the amount of external inputs needed to maintain long-term crop production and food distribution. This is because minimizing the inputs (fertilizers, pesticides, water, energy) decreases many of the negative environmental impacts of industrial agriculture, such as nutrient run-off; toxicity in crops, soils and water run-off; and production of greenhouse gases. Minimizing inputs is a central principle of sustainable agriculture practices with each annual planting and growing plan.

Soil Maintenance

Soil management is a crucial part of sustainable agriculture since the health of soil is the basis for successful and nutritious crop production. Best practices in sustainable agriculture not only maintain soils, but also build soils by increasing the depth of the O horizon, enhancing the health and diversity of soil organisms, and improving water drainage and retention capacities.

There are many methods to sustainably manage soil. An agricultural region’s soil type, topography, and climate dictate which methods will be most effective in that area. Several methods used to both manage and build soils are briefly described below.

Erosion Control

One of the most important components of soil management is erosion control and prevention. Methods commonly used to prevent erosion include: reduced tillage agriculture, cover cropping, contour planting, terracing, and riparian buffers.

Reduced-Tillage Agriculture

Closer Look

Check out this video about using reduced-tillage systems for organic vegetation production.

Tillage is the agricultural preparation of soil by various mechanical or non-mechanical methods, such as digging, stirring, and overturning. Most historical and modern tilling methods use a plow to turn a field’s soil over before planting. This can help control weeds, aerate soil, and break up compacted soil to allow for better water penetration and absorption. In colder climates, plowing the soil kills many pest insects that normally overwinter in plant residues. However, plowing also exposes the soil to the erosive forces of wind and water, and has led to a massive loss of fertile soils around the world.

An alternative to plowing is called reduced-till agriculture. This method of planting leaves the soil structure intact, decreasing compaction and allowing a crop’s roots to persist in the soil after harvest. This both holds the soil in place and allows for greater accumulation of soil organic matter over time as the roots are decomposed. Reduced-tillage is achieved by cutting small slits in the soil’s surface to plant each crop, so that the majority of the soil is left undisturbed. Soil erosion is usually reduced substantially with reduced-tillage agriculture.

Figure 25: A farmer in Haryana, India stands
in a no-till field of rice seedlings.1

A successful example of reduced-tillage techniques is one that has been employed in the Indian states of Haryana and Begusarai. In 2003, a comprehensive survey of farmers who ploughed their fields vs. those that minimized tillage showed that reduced-tillage methods helped rice and wheat farmers reduce the cost and labor of preparing fields for planting (Figure 25). Additionally, use of diesel fuel on these farms was reduced by 60 liters/hectare, and because pre-seeding irrigation was not needed, water usage was also decreased by 20%. The method also allowed for earlier planting, and thus a longer total growing season. As a result, wheat yield increased by 8%.

Cover Cropping and Contour Planting

Figure 26: Italian ryegrass being used
as cover crop. 1

Whenever bare soil is exposed to the sun it can overheat and dry out, killing soil organisms and greatly increasing the incidence of erosion. In addition, the absence of plant roots in bare soil decreases the infiltration of water and the exchange of oxygen and other gases between the soil and the atmosphere. This also harms the fungi, bacteria, protozoa, and other organisms that live in the soil, thereby decreasing its fertility.

Planting cover crops on fields that are not actively growing food crops can help prevent soil exposure and improve soil health (Figure 26). Cover crops also help hold nutrients near the soil surface, and keep them from leaching out. When legumes are used as cover crops, they fix atmospheric nitrogen that can greatly enhance the soil’s fertility.

Figure 27: A contoured field in Sikkim state, India.1

Contour planting (Figure 27) is a method used to decrease erosion when crops are planted in hilly areas. By planting horizontal rows that follow the natural contours of the land, soil that might be carried downhill by rain water is intercepted and captured on the shelf of the adjacent downhill row. This practice is more effective when a mixture of crops is planted in strips, preferably with some strips being composed of grasses that act as filters that are very effective at trapping soil run-off.

Terracing and Riparian Buffers

Author Michael Pollen writes about the global increase in meat consumption and its ramifications in his book, The Omnivore’s Dilemma.1

In steeply hilled regions, terraced rows can be dug into hillsides (Figure 28). These look like giant staircases, and they provide flat areas on which to grow crops. Each flat step of a terraced area retains more soil, nutrients, and water than it would if it were sloped.

Planting trees with grasses and other densely-growing vegetation near water edges produces riparian buffers which help capture soil and nutrients in runoff before they enter the stream and and cause eutrophication (Figure 29). These features are also especially relevant to the preservation of biodiversity in agricultural landscapes, because riparian habitats often support many plant species and can act as corridors for animals and insects to move throughout the landscape.

Figure 29: Crop fields surrounding a stream
with riparian. 1

Organic Soil Additives

Many of the techniques used to decrease erosion also help increase soil organic matter, nutrient content, and overall fertility. Conversely, increases in soil organic matter can help soils adsorb more water and reduce erosion.

While it is ideal to minimize the amount of any inputs to a site, if the soil in an area has poor fertility to start with or has been degraded through intensive farming or industrial forming practices, it will need to be improved before it will be productive. In general, soil improvement can be accomplished by adding dead plant or animal material and allowing it to decompose. This will increase the amount of carbon, nitrogen, phosphorus, and other macro and micronutrients at the site.

Closer Look

Read more about organic soil additives.

Water Management

Efficient water usage and the control of water movement following rainfall is key to sustainable agriculture. Because water is also needed for drinking, cooking, sanitary, and industrial purposes, balancing water usage among these competing needs within a watershed is critical to a good water management program.

Figure 30: Drip irrigation.1

Much cultivated land is currently in areas that do not have predictable annual rainfall, and with a changing climate, rainfall frequency and intensity will be increasingly unpredictable. Therefore, using groundwater for irrigation will probably continue to be necessary in the near term. However, as discussed above, the use of groundwater for irrigation can lead to mineral deposits and salinization. These factors can be mediated by soil-based solutions, appropriate timing of water application, and the use of efficient modern irrigation technologies.

One of the most effective water conservation technologies is drip-line irrigation, which is a method that saves water and fertilizer by allowing water to drip slowly to the roots of crops through a network of valves, pipes, tubing, and emitters that lie at the soil surface (Figure 30). Very little water is lost through evaporation in drip-line systems, as opposed to the larger sprinkler systems discussed earlier in this chapter.

Diversified Planting

As explained earlier, industrial agriculture increases efficiencies of scale by producing mass quantities of a single crop species on a large unit of land. These monocultures, however, create many problems, as discussed above. By maintaining crop diversity, problems created by pest insects can be reduced. With high crop diversity, the impact of a single pest species is greatly reduced. In addition, crop diversity invites a greater variety of insects, some of which are natural enemies to plant pests, and some of which are helpful pollinators.

Leaving un-farmed land such as forest or grassland between fields also promotes plant diversity on the landscape scale. This, in turn, provides additional habitat for the pollinators and other natural enemies to pests.

More diversified plantings can also help maintain soil fertility, because different crop species use different amounts of each micro and macronutrient. Frequent crop rotation prevents the exhaustion of a particular nutrient from the soil, and intercropping can have a similar benefit without needing to rotate crops as frequently. There are also many benefits to using perennial crops, which are crops that are alive year-round and are harvested multiple times before dying. If perennial crops such as fruit, nut-producing shrubs, or trees are grown, they have the added benefit of not removing substantial plant biomass upon harvest, thereby leaving most nutrients intact and promoting healthier soil.

Pest and Pollinator Management

Closer Look

Learn more about integrated pest management in this video.

Insects and other arthropods are critical in agricultural ecosystems. It is important to minimize the presence and effect of pest insects while encouraging the presence and function of pollinating insects. There is some disagreement over whether targeted pesticide use has a place in sustainable agriculture. However, it is possible to operate productive farms without synthetic chemical pesticides.

Before the Green Revolution, all farms were 'organic' by default because there were no mechanical technologies developed or synthetic agricultural chemicals. The resurgence of organic farms has led to more research into organic horticultural science, and new techniques for pest management have been developed and are being used alongside older methods. A key principle to decreasing pest damage to crops is the use of diverse plantings within a farm field.

In addition to using plant species that attract insects that feed on pests, organic farmers also use trap plots to prevent large outbreaks of pests. These consist of mixed plantings of crop species alongside plants that attract predatory insects. Trap plots lure pests into areas with more predators in order to prevent their spread to larger crop plantings.

It would be wise to learn from principles developed in the field of ecology, as well as from traditional agricultural systems that have organically formed in conjunction with natural systems for long periods of time. By combining ecological principles, traditional knowledge, and modern technology, humanity could significantly improve the environmental and human health of human agricultural ecosystems with sustainable methods.

Nicholas Tete SJ, of St. Xavier’s University College in Jharkhand, India is a Healing Earth scholar and specialist in sustainable food systems. He has been kind enough to provide the following more detailed studies of sustainable agriculture techniques. Though written in an Indian context, the basic ideas are transferable to any region of the world. To open the documents, click on the title.

Sustainable Organic Farming

Sustainable Farming and Small Farmers

Agro-Ecosystem

Soil Conservation Measures

As seen throughout this section, the science of food and the activities of food growing, transporting, processing, marketing, consuming, and disposing raise serious ethical questions. We turn now to these moral issues.

Questions to Consider

  • If you were to plant and maintain a garden where you live, what methods of sustainable agriculture from those discussed by Fr. Tete above would you try to use?
  • If someone was admiring your garden, how would you explain the environmental and human health benefits of the sustainable methods you are using? ?