Introduction to agricultural systems


Energy in agricultural systems



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3.2 Energy in agricultural systems (Cox, 1984, p. 187).

Agriculture uses energy and material inputs to increase agroecosystem productivity and concentrate it into forms useful to humans. Energy relations differ between agriculture systems and natural systems, the level of dependance on energy differs among agricultural systems.

As a substitute for stability and to increase productivity, producers used concentrated inputs of energy, nutrients and pesticides, such as human and animal labour, machinery, fossil fuels, fertilizers, and pesticides (Vasey, 1992, p. 245).

The high crop yields and animal productivity of the agricultural system are achieved at a high energy expense, and the ratio between energy used and food energy produced is decreasing. It is also achieved with some environmental costs, because vulnerability to disease, loss of soil fertility, problems with waste disposal, such a manure and leached nitrogen, are increasingly associated with environmental damage.


3.3 People in Agricultural Systems

Models of the origins of agriculture (Jolly and White, 1995, Chapter 15). Most early human groups probably had some knowledge of how plants grow, but hunting and gathering required only a few hours of labour per day for good and adequate nutrition. Farming requires cultivation, the clearing of trees, plowing, hoeing, weeding, and watering which are harder work than hunting and gathering. Why, then, did hunters and gatherers in the Near East switch to agriculture? Several models have been developed to explain this evolution.

Environmental Change: The Oasis Model. Agriculture developed in the lowland plains of the Near East at the end of the last glaciation. In the post-glacial period the climate changed, becoming drier, which forced people to oases where plant resources were more abundant. In response to the relatively high population density at the oases, humans began to domesticate and tend their plants and animals to ensure a regular diet and supply of food.


Increasing Specialization: The Nuclear Zone Model. Agriculture developed in the hill lands of the Near East. In those areas, the wild ancestors of our cereal crops were abundant. Settlers manipulated the wild plants and animals into domestic varieties, probably because the large herds of game animals gradually diminished and disappeared. This model assumes that people like to experiment and change things. In reality, most societies are probably resistant to change and only do so if necessary.

Sedentism and Population Increase: The Marginal Zone Model. As populations increased, some people were forced to more marginal areas that were less desirable than the preferred habitat. People living in the marginal areas had difficulty surviving using the old hunting and gathering techniques so they had to experiment with new methods of securing a regular food supply.

One possibility is that in some areas, such as the Levant, people became sedentary because the area was so resource rich they did not have to move around seasonally to find food. However, population growth gradually outstripped the productive capacity of the area and some people were forced to move to the marginal fringes.



Social Pressure to Generate Surpluses Model. This model proposes that human social systems changed, creating a need for more intensive food production. Surplus production was used to fulfill social and political goals, such as paying tribute.

A Composite Model. This model assumes that natural stands of wild grasses expanded during lush climatic periods in the Near East. A subsequent dry period forced people to withdraw to the few areas that contained permanent sources of water. The large concentration of people in these confined areas could not be supported by hunting and gathering, creating the need for development of a high productivity system of agriculture.

Agricultural systems are both influenced by and influences on social structures. Where society is organized around small villages or tribes, agriculture is often relatively communal, with many families working together and sharing produce on land that they clear and use, often only for a few years, but do not own. Tribal people may feel that they belong to a certain territory, and use parts of it for food production, but they do not have a land tenure system that includes ownership. Tribal people were, and in some cases, still are self-sufficient, producing their own food and fibre, and using little cash in a subsistence economy. Cash crops may be produced (i.e., tobacco, sisal, coffee, tea, nuts) for cash sales to subsidize the food production economy. Cash allows farmers to purchase commodities such as farm inputs, education, medical care, machinery, draft animals, etc.


Commercial systems produce only cash crops, and include most farms in developed countries. For example, prairie farmers produce grains and livestock for sale, using the cash to purchase their groceries from food retailers. These farmers are specialized in the large scale production of crops and livestock, largely based on an industrial model, and may eat none of the food grown on their farms.

The Socio-economic determinants of farming systems (Reading 8. Harwood, 1979, Chapter 7, pp. 63-73). Socio-economic factors that influence the agricultural system include labour, management capability, mechanization and power availability, capital, and market availility.

The availability of labour determines the choice of crops and the farming system. In countries where labour is expensive, it is cost effective to substitute machinery for labour. Where labour is plentiful, it is used in the production of crops, such as vegetables or paddy rice, that are unsuited to mechanized production because they require greater planting precision, better weed control and more timely harvest. Plentiful human labour is often used to reduce the costs of more expensive inputs. For example, in vegetable production in Java, a small amount of fertilizer is placed at the base of each plant in a very labour intensive, but inexpensive, process.


Management capability includes making decisions, knowledge, preforming technical operations, and supervision. If the management capability of a farm is low, cropping intensity is usually low, and farming system options are limited. An example from the prairies would be continuous cropping with oil seeds, pulses, cereals and forages versus cereal production in a crop-fallow rotation. The first farming system requires more management input than the second because it is more complex.

Mechanization and power range from human power and hand equipment (hoe) to mechanized equipment powered with fossil fuels. Mechanization determines farm size; as farm size increases, the adequacy of human and animal power decreases. These factors are key determinants of labour productivity. On the Prairies, labour is often scarce, so large equipment is used to maximize labour productivity. Mechanization and power also determine how food processing is done beyond the farm gate. In technologically developed countries, food processing is highly mechanized compared to developing countries.

Capital availability determines the ability of a producer to purchase inputs, labour, and is related to the complexity and extent of the food processing industry. Labour can substitute for capital in some tasks, such as weeding which can be done by hand, with purchased chemicals or with tillage equipment. Farmers will not usually grow crops, such as vegetables or flowers, that require high levels of inputs like fertilizer and pesticides, if they have little cash; they will tend to produce field crops such as grains or legumes that require less commercial inputs. On the prairies, continuous cropping systems with a diversity of crops require more inputs (fertilizer and hebicides) than crop-fallow, so will not be used by farmers with limited access to capital.

Market availability determines whether producers or food processors can sell their produce. Potential earning from crops are determined by their market value minus costs. To be effective, markets must be accessible, stable, and provide signals about changes in demand and prices to help in farm planning.


Subsistence farmers rely little on the cash markets, and they often live in countries with very poorly developed market systems. These farmers often have few production resources, low incomes and large families. They may believe that they are better of producing than own food than producing cash crops. As market conditions fluctuate, they have no guarantee that they will earn enough income to purchase the family=s food needs from retail suppliers. In other words, it is cheaper for them to grow their own food, with a small production of cash crops for inputs or dietary diversity, than to rely on markets for their food supply.
3.2 Systems Characteristics of Agriculture.

Holism. The whole agricultural system is more than either its biophysical environment or the human factors applied to the environment. It is both a human and a biophysical system, and a change to any one part of either system will change the entire system. For example, if as freight rates increase with the removal of the WGTA, farmers costs for shipping grains increase. In response farmers may chose to produce less grain for the export market and produce more livestock, forages and feed grains that can be used within the region. A change in the economics of farming could cause a change in production patterns. This, in turn, will cause changes in the biophysical system. An increase in livestock requires an increase in pasture and forage production at the expense of annual crops. As a result, more land is planted to permanent cover crops, and there is less erosion, less tillage induced soil organic matter decomposition, less fossil fuel use for machines and fertilizer production, all of which could be considered environmentally positive. If, however, the livestock is produced in intensive livestock operations, improper manure disposal could cause surface and ground water pollution, which would be environmentally negative.

The concept of holism is illustrated in this example because it is clear that one change - a change in transportation legislation, could ripple through the whole economic and biophysical system. In any system, a Apush@ in one part causes the other parts to Abulge@.


Transformations. Solar energy and other energy inputs, such as human labour, knowledge, fuels and fertilizers, are transformed into food and fibre in agricultural systems. The success of the agricultural system depends on the efficiency of the transformations.

Control. Control through mechanisms such as feedback function in agriculture much as they do in natural systems, except that the level of control in the biophysical environment is often reduced and a human level of control is added. In agricultural systems, lack of biodiversity and simple food webs limit the potential for feedback. For example, if the crop sown is wheat, but the climate is too wet or too dry for wheat, there is a crop failure and very little biomass produced in the system that year. Poor biomass production provides negative feedback to the soil microbial community which shrinks in response to a food shortage, thereby reducing nutrient cycling, which reduces nutrient availability for crop uptake, which further reduces crop biomass production. In a more species-rich grassland, there are some plants adapted to dry conditions and some adapted to wet conditions, so total biomass production is less effected by yearly climatic conditions, the microbial population rarely starves, and the cycling and availability of nutrients vary less widely.

Human control is also a factor in agriculture. Grain prices, input prices, and freight rates are all signals to farmers about what to produce. The more complex the human system, in terms of crop choices, farming practices, infrastructure and markets, the less a change in one of those factors will affect the overall system. For example, for farmers in complex systems, a low price indicates an oversupply of that commodity. In reaction, each farmer can chose to produce another crop for which the price is higher because the system is diverse and complex enough that there is infrastructure and markets for many commodities. Farmers in systems with poorly developed infrastructure and markets may suffer serious consequences as a result of poor prices. As an example, in North Vietnam, the infrastructure surrounding agriculture is very poorly developed and markets opportunities are small, especially for farmers who live far from a major city. Access to seed or specialized equipment that may be necessary to switch from one crop to another may not be available. These systems may have only one, or very few, pathways of production. In more complex systems, there are many pathways.


Hierarchy. Agriculture is hierarchical in that the land subsytems interact with human systems to produce various types of crop and livestock production systems (Figure 3-9). The different production systems together are a local farming system. All of the different farming systems for an area combine into the regional scale land use systems which together are national agricultural systems, until at the top there is just one world agricultural system.

Emergent Properties. It would not be possible to predict the type of agriculture that occurs in any area without knowing how all of the parts interact. Information about the biophysical environment, the form of government, the level of education and technology, the amount of energy used, taken alone would not provide an indication of the type of agriculture that has evolved over time. The interaction of the physical environment and the people of the area must be understood in great detail in order to understand how their agriculture works. For example, the climates and land characteristics of Russia and Canada are similar, but the type of agriculture that has emerged in each location is different. It is only by understanding the historical development of each region, and the human system that has been imposed on its environment that an its agricultural system can be understood. Even small differences in the interaction of people with their environment in the process of producing food can result in the emergence of different agricultural systems.
3.3 Agricultural systems and scale

Global. At the global scale we might view the agricultural system in terms of major differences in the physical environment, economic and social structure. For example, agro-economic systems at the global scale would be all of the international trade in crop commodities, in fertilizer and pesticide inputs, in machinery and equipment. At this level, we would not be concerned about individual farmers, or even farm communities, or farming practices as used on farms or regions, but we would probably look at data from provincial or state governments, probably more often at national levels. In terms of biophysical systems, the focus of study would be broad climatic, vegetation and soil zones versus in temperate versus tropical regions, for example. Social systems that would emerge at this level could be subsistence systems versus the commercial systems, or communities with large extended families and lots of labour versus nuclear family and mechanization.


Regional. At the regional scale, we would be interested in relationships of the region to other regions and other countries. Several kinds of farming systems could be represented within one region. Using the Prairie region as an example, the agricultural system consists of mechanized grain and livestock production systems, and not much vegetable, fruit or flower production.

At the regional scale, climate is relatively uniform, and the agricultural system is a function of soil type, markets, government policy, historical development or economics.



Landscape. At the landscape scale, we would be interested in local factors that influence the type of farming system practised, such as topography, distance from market, farmer education, access to credit, etc.

Summary. The characteristics of the physical environment, the amount and kind of energy used in the production system, and the organization of people all interact to produce unique agricultural systems. Agricultural systems consist of concrete things like land, technologies like tractors and varieties, and processes like leadership, planning and decision-making. They vary depending on the qualities of the land, the technologies and the processes (Bawden and Ison, 1992, p 17). Individual farms vary, because even within a community, the characteristics of the land (topography, soils, vegetation), of the people (goals, values, skills, education) and energy (amount and size of equipment, use of N inputs) can vary. No two farms, even farm neighbours, are exactly alike.

At the regional level, differences among farming systems are greater because differences in land (soils, topography, vegetation and climate), energy (photosynthesis, fossil fuel and equipment use) and people (goals, values, skills, market opportunities, relation to industry) are greater. At

the international level, there are very large differences among agricultural systems, which reflect the large differences in land, energy, and people from different countries and regions of the world (i.e., Kalahari desert, Tropical Asia, Canadian Prairies).

3.4 Tropical Agricultural Systems
3.4.1 The tropical resource base

The tropics are that part of the world located between 23 degrees N and S of the equator. They comprise 38% of the earth's land surface, contain 45% of the world population, and include most of the developing countries of the world. The Aimage@ is often of lush jungle with no climatic limitation, but in fact there are both wet and dry agricultural systems in the Tropics. Rainfall varies from 0 to 10,000 mm, and decreases with increasing latitude.

There are six broad zones of vegetation formation, based mainly on climate (Figure 3-10 from Manshard, 1974. Figure 4.3, p. 23).

Wet evergreen forests - Rainy Climates. This zone covers 25% of the tropical area and occurs near the equator in areas such as the upper Amazon, Congo, Indonesia, and the Philippines. The natural vegetation is evergreen tropical forest, but it is now largely replaced by cropland. Most of the soils are old and highly weathered (Oxisols, lateritic), and most of the nutrients are held in the vegetation. Decomposition of plant material is rapid in the humid, warm climate, and released nutrients are taken up quickly by growing vegetation.

When these soils are cultivated, nutrients are rapidly washed away through leaching or soil erosion. They are not well suited to annual cultivation, and probably are best used in shifting systems with a long fallow period. There are younger and more fertile soils within this zone, especially in river flood plains. They can be very productive and are often used for paddy rice and vegetable production. With the potential to produce three crops per year, the productivity of these systems can be among the highest in the world.

Rice, cassava, and yams are the main food crops produced in the Tropics. Cacao, bananas, rubber and other plantation crops are often produced for export.


Seasonally green, wet forests and humid savannas - Seasonal Climates. This vegetation zone covers 50% of the tropical area, and includes the Cerrado and Mato Grosso in Brazil, the Llanos of Columbia and Venezuela, Yucatan Peninsula, Pacific Coast of Central America, most of the African continent between Sahara and Kalahari desert, and in Asia, covers most of India, inland IndoChina and norther Australia. The climax vegetation is either deciduous or semi-deciduous forest or savanna with well defined dry and wet seasons. Annual precipitation is less than the annual potential evapo-transpiration rate so there is the potential for a net moisture deficit (i.e., water is a major factor limiting plant growth) .

Most tropical crops produced are produced and the soils are similar to rain forest soils, being mainly old and highly weathered and lateritic. There are also some young and productive soils in these regions.


Dry savanna and thorn-bush savanna - Dry Climates. Dry savanna covers about 16% of the tropics, and includes the Sahel between the savanna and Sahara in Africa; the Kalahari Desert, a large proportion of Australia, parts of central India, northeast Brazil, northern Venezuela, and Mexico. Climax vegetation is sparse thorny shrubs and trees, which are climatically adapted to a hot dry climate. There is greater climatic fluctuation than in the moister regions, with a long dry season, and a short wet season. Production typically consists of one crop of corn, sorghum, millet or rice, and nomadic grazing or ranching are also common farming systems. The wet season is unpredictable, so this area is sometimes referred to as the 'famine belt', especially with reference to Africa. The potential evapotranspiration rate is greater than mean annual precipitation.

Tropical Deserts. These regions cover 11% of tropical areas. They have two rainy months or less, and occur in the Sahara, Arabian, Somali and Australian deserts, along coastal strips of Peru, Chile and SW Africa. Vegetation consists of succulent plants. Nomadic grazing is the most common agricultural system, although tropical deserts can be very productive when they are irrigated.

Summary. The Tropical resource base (land: soils, plants and animals) is diverse. Productivity ranges from the highest (i.e., lowland rice production areas of Asia) to the lowest (subsistence and nomadic grazing) in the world. The quality of the land resource base (climate, soil quality) and amount of precipitation determine the potential productivity of each zone.
3.4.2 Major Agricultural Systems of the Tropics

The diverse climate and resource base of the tropics have resulted in the development of many different kinds of tropical agricultural systems, which vary naturally, economically, and socially. The three main types of agricultural systems are pastoral nomadism, shifting cultivation and settled agriculture. The use of inputs, the infrastructure and social characteristics of each type will be discussed in the next section (Figure 3-11 from Spedding, 1979, p. 96).


Pastoral Nomadism (Spedding, 1979, p. 106). Nomads travel, do not live in settlements, and have no individual land ownership or tillage systems. This system is common in the arid and semi-arid tropics where grass yield is low and seasonal, and a large area required to support livestock.

There are only small numbers of people who live in nomadic systems. World wide they include about 15 million people on 10 million sq miles, which is about twice the cultivated area of the world. Population density is very low (.5 to 17 per sq. km.). Nomadic people rely on camels, cattle, sheep, goats and their products, milk, blood, meat, hides, wool, and skins for their livelihood. The system relies on natural grassland for pasture and feeds or forage are not stored. This systems is practised on land that could not sustain other forms of agriculture because of the dry climate.



The major problems associated with this system are overgrazing if the human or animal population is too high, or if drought reduces grass production. Grazing areas have been reduced over time as cultivated agriculture has moved into the semi-arid regions as the human population of the surrounding areas has increased.



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