Cropping Systems

Designed field systems for production of plant species for food and other human needs. This article provides a brief history of agroecosystems, including natural resource use and environmental impact of systems, current developments in management, and promising alternatives for efficient future crop production based on scarce resources. Economic and social implications of different approaches to farming are explored.

Historical Development of Cropping Systems

Organized agriculture, the conscious planting of crops and care of domestic animals, has been a vital part of human culture and society for about 10,000 years. Early agriculturists chose the plants with the largest seeds or fruit and the animals that were most easily domesticated, and often cropping systems were closely integrated with livestock to help use crop residues and cycle nutrients. Current systems of planting crops in rows were introduced as part of the industrial revolution a scant two centuries ago, while the intensive use of chemical fertilizers and pesticides began in the last half of the twentieth century (Plucknett and Smith, 1990). Thus, current chemical agriculture and industrial food systems represent a recent innovation of which the longterm impacts on people, other species, and on the natural environment are difficult to predict.

When global human population and demand for food were low, human activities had relatively minor impacts on the natural environment. Today’s rapidly expanding human population, especially its use of scarce land and non-renewable natural resources, is causing substantial changes in Earth’s ecosystem that may have serious environmental implications for the future. In this historical context, it is not surprising that future cropping systems will be measured for their efficiency of using scarce natural resource and external inputs, and financial rewards will reflect a genuine concern about the security and sustainability of food systems and the survival of humans and other species.

Cropping Systems Designed for Production

Design of cropping systems involves deliberate manipulation of natural environments and landscapes to provide food, feed, fiber, fuel or raw materials for human or domestic animal use. Choice of species and planting systems has focused on maximizing the output of crops and income per unit of land, labor or other scarce resources. Until recently the major emphasis has been on short-term productivity and profits, increasing food for a growing global population, and improving technology for convenient monoculture cropping systems. Agronomic research has focused on improved efficiency of fertilizer and water use. Maximum yields have been achieved by adequate chemical protection against insects and reduced competition from weeds by herbicide application. Most research has been on the favorable lands where best yields are produced. Today there is growing awareness of the finite supply of non-renewable resources, the unintended off-farm effects of farming, and the long-term need for food for an increasing human population, as well as the potential impact of human population on the environment (Shrestha, 2003).

Recognition of these growing constraints has spawned a new generation of systems based on renewable resources. Organic farming is one of the innovations, where chemical inputs are replaced by careful management, crop and animal diversity, and application of principles learned from natural systems (see encyclopedia entry, Agroecology). There is a vital need for research and implementation of more diverse farming systems. Yet there is also preoccupation that any systems that produce less than maximum yields will not sustain a growing population with increasing incomes and demand for animal protein. Increased concern about the future has led to serious attention to developing and extending a sustainable agriculture (Francis et al., 2006).

Cropping Systems Designed for Environmental Preservation Environmental challenges of current cropping systems, especially in the U.S. and Canada, derive in part from our geographic farm patterns organized on a grid system that rarely corresponds to natural features in the landscape (Jackson, 1994). The section lines at each mile do not respect natural land forms; rectangular fields within those sections are designed to accommodate large mechanized equipment. Such political divisions and human-designed boundaries have led to labor- efficient and easily-mechanized cultivation techniques that direct tractors up and down slope, across wetlands and natural waterways, and parallel to field boundaries. The divisions have little respect for natural topography or for the landscape. An environmentally conscious farmer will design systems to include contour cropping to prevent soil erosion, place crops and pastures where they are most appropriate within the landscape, diversify crops within a farm and field to provide habitat for beneficial insects, and rotate crops to enhance soil fertility and reduce use of pesticides. Seeding waterways, planting shrubs and trees as filter strips along streams, and connecting non-cultivated areas from one farm to the next to provide wildlife corridors are some methods used to lessen the negative environmental impact caused by human divisions of the landscape.

Soil management for cropping systems includes preparing land, planting and cultivating crops, and providing sufficient nutrients for crop production. A sophisticated process has evolved over the past century that includes preparing land by plowing and disking, managing weeds with herbicides and cultivation, planting crops in rows with mechanized equipment, and applying chemical fertilizers to provide nutrients for extractive monoculture cereals or short-term rotations. Modern systems have produced impressive yields using this industrial model. Yet environmental impacts of this approach have included massive erosion of topsoil in some sites due to action of wind and rainfall, loss of some pesticides and nutrients with water runoff during heavy rainfall events, and soluble nutrients, pesticides, and breakdown products leaching through the soil profile and vadose zone into the groundwater. These are unintended effects of current cropping systems; they reduce profits by increasing input costs and cause larger scale environmental degradation that eventually will be paid for by society.

No-till or reduced tillage can increase crop residues left on the soil surface, methods that drastically reduce water runoff, thus slowing the loss of soil and nutrients. Band application of herbicides, coupled with timely cultivation, can reduce the economic and environmental costs of weed management. Careful soil testing and analysis can allow reduced nutrient application rates and less potential for contamination of the groundwater, especially by nitrate. No-till systems substantially reduce soil loss, but often require increased use of pesticides, thus negating some environmental benefits. Changes in practices are being implemented by farmers for economic and environmental reasons (Karlen and Sharpley, 1994).

Alternatives to Monoculture Systems

Monoculture systems have contributed to environmental problems. Continuous cropping of favored cereals (e.g., rice in lowland Asia and maize in central North America) has required increasing applications of fertilizers and pesticides to maintain productivity. These monocultures have received most of the attention of agricultural researchers concerned with increased productivity and by companies that provide fertilizers and pesticides. The Green Revolution also promoted monocultures and use of improved technology to substantially increase cereal grain production in more productive lands, thus reducing the cost of food in some countries and helping to alleviate hunger.

However, from an ecological viewpoint, monoculture systems could be considered a short-term solution that allows farmers to dominate the natural environment for immediate production gains with a large investment of fossil fuel-based production inputs (Francis, 1986). Too often this domination leads to ignoring the models of biological cycling and efficiencies of resource use that occur in natural ecosystems. In contrast, crop rotations and multiple cropping systems provide benefits in soil fertility and pest protection. Use of green manure crops and animal manure or compost reduces the need for imported chemical fertilizers (Power, 1990). External resources such as chemical fertilizers have a high energy cost for production, transportation and application to fields. They often become a source of nutrient pollution that reaches surface and ground water systems. Learning from natural ecosystems in each place can provide clues to the design of more complex cropping systems that make more efficient use of production resources (Jackson, 1994).

Control of weeds, insects, plant pathogens (organisms that cause diseases) and nematodes in monoculture systems is complicated by accelerated evolution of pest biotypes or subspecies resistant to known pesticides. Three decades ago, only a few dozen pest species resistant to pesticides had been identified, but today there are reports of close to 1,000 known pests that are resistant to available chemical products. There is no doubt about the efficacy of chemical pesticides applied at the right time if they can target an undesirable pest, yet farmers and industry are caught in a vicious circle that requires continuous search for new products to control an accelerating array of undesirable species that limit production. The alternatives are to scout fields carefully and identify specific problems, and to design an integrated pest management program that combines the potentials of genetic resistance in crops, rotation of crop species, multiple cropping to provide diversity and homes for favorable predators, choice of planting dates and methods, and judicious use of chemical or biological pesticides where absolutely needed. Reducing pesticide use can decrease costs to the producer and lessen the environmental impact of products ending up where they cause problems. Reduced chemical use will also slow the evolution of pest species to biotypes or strains that are resistant to known chemical and biological products (Bird et al., 1990; Liebman and Janke, 1990).

Integration of crop and animal production systems provides another type of biological efficiency that cannot be realized in monoculture cropping. Use of crop residues for livestock grazing during winter months in the higher latitudes, and primary reliance on forages and grazing provide low-cost feed sources and leaner meat compared with feedlot, grain-fed cattle. Livestock can harvest some fields and areas that are not easily farmed, and can take advantage of feedstuffs such as low-quality hay or roughage that has little other value. Manure from grazing animals enhances the organic matter and fertility of the soil. Animal manure has become a difficult-to-handle waste product where animals are confined and concentrated, but this byproduct should be considered a valuable resource. The combination of crops and livestock provides a wider range of products for sale, thus buffering the variations in weather and prices that cause financial difficulties for farmers in most countries. These efficiencies of cropping system design contribute to profitability and to reductions of the negative environmental impacts of many of today’s prevalent cropping and animal raising practices. A well-designed and profitable farming operation reduces the incentive to plant monocultures of the most profitable crops in the short term, and increases the flexibility to practice good stewardship of land and other natural resources for the long term.

Social Interactions and Implications of Farming Systems

Social dimensions of alternative cropping and farm decision strategies also affect the environmental impacts of these cropping systems in the long term. Concurrent with the growth in field size and scale of farming equipment has been an increase in size of properties owned or managed by each farmer, and consequently a reduction in the rural population (Olson and Lyson, 1999). Larger farms and mechanization have resulted in labor production efficiencies in food production and release of people to other growth sectors such as industry and service. Although modern systems have increased the productivity per unit of labor, they have not necessarily improved rural quality of life for all involved in agriculture. They have increased production per unit of land in some cases, but often have reduced productivity per unit of capital, fossil fuel-based inputs, and other scarce natural resources. Increased farm size has resulted in less field- and site-specific management, and greater homogenization of production practices over larger land areas. As a result, there is less spatial diversity in the farmscape, and need for fewer highly skilled managers. Use of uniform practices across wide areas often results in fertilizer or pesticide applications that are less well tuned to specific nutrient or pest control needs in specific sites on the farm. Over-application of these inputs can contribute to nutrient or chemical loss and reduction of water quality on the farm and downstream. These direct results of increased farm size can cause negative environmental consequences, loss of productive potential of the land, and reduced quality of rural life.

Specialization and monoculture cropping systems on individual farms have often been accompanied by concurrent specialization in a larger farming region. As markets and infrastructure develop, new patterns become established; the agricultural industry matures in response to specific economic incentives and government support programs. Some crops begin to dominate the landscape. Examples are maize in the Platte River Valley of Nebraska and wheat in the northern Great Plains. The result is less diversity on each farm, less diversity in the watershed, less habitat for wildlife, and loss of connectivity of those areas that still provide cover. The only corridors left to conceal movement of larger animals are the stream courses, and even their value may be minimized by crop cultivation right up to the banks or heavy grazing by livestock if streams are not protected by fences.

In contrast, smaller farming units provide opportunity for careful placement of crops and design of cropping systems that better fit the topography and natural resources of the farm. Smaller equipment is more easily turned and can fit onto terraces or into smaller fields. The degree of involvement of the farmer with the land may be more intimate when there is greater daily contact with more fields on the farm, as compared to an operator who visits the fields infrequently because of working across a large area. Use of more uniform practices and greater reliance on chemical weed and insect control, in hopes that a single treatment will take care of the crop for an entire season, suggest there may be fewer trips to the field and infrequent scouting for problems as they occur. Wes Jackson has called this a reduction in eyes-to-acres ratio, a result of fewer people on the land and a homogenization of cultural practices across wide areas. The lack of contact or communication between a farmer and the soil may also lead to a sense of psychological distance from the critical natural resources and environment in which the farm operates, and a further move toward farming as a business that is disconnected from natural cycles and processes. With increased farm size may come a separation of ownership from management of the farm; over 50 percent of land currently farmed in the Midwest is cultivated by non-owners. Moreover, with larger farms an increasing amount of the work is done by minimum or low-wage employees, and less by the farm manager. This further removes the people with a vested interest in the long-term quality of the soil and the farm from the work that is conducted there, and may result in less careful management of critical resources such as crop residues and soil.

Specialization in fewer crops and enterprises and the move toward larger farms also has an impact on rural communities. When business operations increase in size, many of the inputs are likely to be purchased farther from home and distant markets are accessed more frequently. Not only are there fewer people to contribute to local business and infrastructure (e.g., schools, churches and civic organizations), but there is more business that leaves the community. Each dollar spent in a rural community circulates three to five times before leaving that community. Although such economic details may appear at first glance to be disconnected to health of the cropping systems and the surrounding natural environment, in reality they are all connected. Consolidation of farmlands into larger tracts under control of fewer owners slowly signals the decline of rural communities. When such towns are no longer viable places to live, people leave for other places. This further removes the farmer and family from community, and reduces even more the contact between people and their food supply.

Choice of crops and animals, design of cropping and crop/animal systems, decisions on input use, and destination of the harvest all impact the local community and the natural environment. The study of individual crops or components of the system in highly specialized, discipline-oriented research and education programs has worked against a needed understanding of the complexities of agroecosystems. Emerging programs that focus courses and student research on integrated systems, on agroforestry and agroecology, and on the viability of rural communities will help to establish the linkages between people and food production. New programs will also help to establish the needed understanding and respect of the realities of human dependence on a healthy natural environment.

— Charles A. Francis

See also

Agrichemical Use; Agriculture, Alternative; Agroecology; Agronomy; Mechanization; Organic Farming; Permaculture; Pest Management; Tillage

References

• Bird, G.W., T. Edens, F. Drummond, and E. Gruden. “Design of Pest Management Systems for Sustainable Agriculture.” Chapter 3 in Sustainable Agriculture in Temperate Zones. Edited by C.A. Francis, et al. New York, NY: John Wiley and Sons, 1990.
• Francis, C.A., ed. Multiple Cropping Systems. New York, NY: Macmillan Publishing Company, 1986.
• Francis, C.A., R. Poincelot, and G. Bird, ed. Developing and Extending Sustainable Agriculture: A New Social Contract. Binghamton, NY: Haworth Press, 2006.
• Jackson, W. Becoming Native to This Place. Lexington, KY: University of Kentucky Press, 1994.
• Karlen, D.L. and A.N. Sharpley. “Management Strategies for Sustainable Soil Fertility.” Chapter 3 in Sustainable Agriculture Systems. Edited by J.L. Hatfield and D.L. Karlen. Chelsea, MI: Lewis Publishing, 1994.
• Liebman, M. and R. Janke. “Sustainable Weed Management Practices.” Chapter 4 in Sustainable Agriculture in Temperate Zones. Edited by C.A. Francis. New York, NY: John Wiley and Sons, 1990.
• Olson, R.K. and T.A. Lyson, eds. Under the Blade: The Conversion of Agricultural Landscapes. Boulder, CO: Westview Press, 1999.
• Plucknett, D. and N.J.H. Smith. “Historical Perspectives on Multiple Cropping.” Chapter 2 in Multiple Cropping Systems. Edited by C.A. Francis. New York, NY: Macmillan Publishing Company, 1986.
• Power, J.F. “Legumes and Crop Rotations.” Chapter 6 in Sustainable Agriculture in Temperate Zones. Edited by C.A. Francis. New York, NY: John Wiley and Sons, 1990.
• Shrestha, A., ed. Cropping Systems: Trends and Advances. Boca Raton, FL: CRC Press, 2004.