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Chapter 3

Chapter 3: Agricultural Systems

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Sarah Wakefield

CHAPTER 3: AGRICULTURAL SYSTEMS 3.1 INTRODUCTION  Agriculture of farming is the rearing of animals and the production of crop plants through cultivating the soil  It is the interaction of people and the environment, which has evolved over a period of 10,000 years  Sheep, pigs, goats, cattle, barley, and wheat were the first to be domesticated followed by six other independent origins of agriculture  East Asia: Rice, millet, pigs, chicken, and buffalo  Central America & South America: Potato, maize, beans, squash, llama, alpaca, and guinea pigs  North America: Goosefoot and sunflower  Africa: Cattle, pigs, rice millet and sorghum  The domestication of plants and animals spread from the Near-East to the South-Eastern Europe where cultivation improved and trading networks supported the Greek and Roman Empires.  Term agriculture is derived from both Greek and Latin origin which mean “field” and symbolized the integral link between land-based production and modification of the natural environment.  Greek: agros  Latin: agar  The modification of land has produced the agri-ecosystem in which an ecological system is overlain by socio-economic elements and processes. This system comprises of  Domesticated plants/animals and the people who farm them to produce food and other agricultural products  Agricultural geography looks at various aspects such as  Spatial distributions of crops and livestock  The systems of management employed  The nature of linkages (economic, social, cultural, political, ecological systems)  Food production  Food processing  Marketing  Consumption 3.2 THE AGRI-ECOSYSTEM  The physical environment (land) can be a fundamental significance to the nature of farming systems  Capital can enable the purchase of inputs that can substantially modify the physical characteristics of land  Changeable weather/hydrological cycle can present elements of risk to areas of economic activity  The environment affects the nature of farming, but in turn agriculture affects the environment  Agricultural systems are modification of natural ecosystems and is an artificial human creation. Productivity is increased through control of soil fertility, vegetation, fauna, and microclimate  These modifications are intended to increase the production of biomass, which produces more than the natural environment  Environmental consequences may occur such as  Degradation of soil  Runoffs (nitrate pollution, water pollution)  Effects on wildlife  Agriculture is different from other types of economic activity as it deals with living things  Animals and plants strive on certain characteristics of the land and hence exert a strong influence on the nature and location of agricultural production  The farmer is the essential human component that influences/determines the composition, functioning and stability of the system  The agri-ecosystem differs from natural ecosystems due to their simplicity and small amount of diversity  Plant domestication has produced less genetic diversity compared to their wild ancestors  The biomass of herbivores (sheep, cattle, etc..) are much larger than their equal counterparts which are supported by the natural ecosystem  The cultivation of crops through harvesting or consumption by domestic livestock, removes the energy supplied to the soil which is normally given through dead and decaying organic matter and humus.  Agri-ecosystems require large inputs and outputs of energy from  Human and animal labour  Fuel  Seeds  Fertilizers  Herbicides  Pesticides  Machinery  Water  The most dominant natural resource to farming are climate and soils 3.3 CLIMATE AND AGRICULTURE  Climate and temperature are the two physical constraints that can affect agricultural productivity  Other constraints include  Soil type  Nutrient availability  Topography  Aspect and drainage  Climate determines the geographical regions where crops can be cultivated  Modern plant breeding has modified the amount of water plants need and the temperature in which they can sustain, but climate still affects the geographical location in which they can be grown 3.3.1 TEMPERATURE  Both plant and animals growth are affected by climatic variables  Solar variables  Precipitation available for transpiration  Temperature  Optimum growing conditions can be recognized when a plant gives the highest yield (largest weight of edible part of the crop per unit area  Economically it is best to cultivate a crop in a physical region which is optimal for the plants growth  There are economic limits productions which are influenced by production costs and market demand  Increases in production cost and/or falls in price promote a contraction of the margin of cultivation toward the optimum area  For each crop there is a temperature range within which growth and development can take place. The critical temperatures are  The minimum, below which there is insufficient heat for biological activity  The optimum, at which rates of metabolic processes are at their maximum  The maximum, beyond which growth ceases. Higher temperatures may be harmful or lethal.  Some crops have particular temperature requirements  Low night time and higher day-time temperatures  Winter chilling before flowering and seed setting can occur  Other crops are termed photoperiodic, where day-length triggers the necessary to trigger flowering. There are four groups that are recognised  Short-day/Long-night:  Photoperiod of under ten hours  Soybeans, millet, sweet potatoes  Occur in low latitudes where spring and autumn seasons are warm enough to allow their harvest cycle to be completed  Long-day/Short-night  Photoperiod of over 14 hours  Small grains, timothy, sweet clover  Occur in high latitudes  Immediate day  Photoperiod of 12-14 hours  Inhibition of production, above or below these levels  Day-neutral  Unaffected by variations during the day-length  Crop growing habits, especially with the case of temperature has played an important part in the application of scheduling techniques by farmers to plant and harvest crops using the time and space available 3.3.2 WATER  Water in agriculture is supplied in two ways  Precipitation  Management of water by farmer (when problems arise in the natural supply of water  Water transports nutrients to and through plants and play a vital role in weathering, leaching and erosion  Water controls the inputs of nutrients to and losses from the system. These losses are due to  Evapotranspiration  Drainage to groundwater  Lateral flow (runoff)  Throughflow (streams)  In agricultural systems, water deficiencies are a vital limitation on crop yield  The management of water by farmers is affecting the natural hydrological water cycle through tillage, crop cover, land drainage, and irrigation practices – Even the use of pesticides and fertilizers can influence the amount of water stored in the system  Agricultural practices disrupt the annual water balance that is associated with the functioning of any ecosystem  If surplus occurs, the water can accumulate in the soil until maximum storage capacity (field capacity) occurs, which leads to waterlogging or runoff  If evapotranspiration exceeds precipitation, there is a moisture deficit  Irrigated agriculture consumes 2500km on 18% of the worlds cultivated lands (7x the amount used in the 20 century)  The use of irrigation for national food is substantial in areas where padi rice is a significant crop and/or where semi-arid climates occur.  Pakistan (65%)  China (50%)  Indonesia (40%)  Chile and Peru (35%)  India and Mexico (30%)  Capital assistance during the “Green Revolution” (1960’s & 1970’s) was put towards the expenditure, extension, upgrade, and maintenance of irrigation systems.  Irrigation can also lead to problems such as a change in the water-salt balance, which can affect the salinity and alkalinity of the soil.  Salinization occurs when the natural drainage system is unable to accommodate the additional water input. 3.4 AGRICULTURAL SOILS  The primary agricultural management practice is the cultivation of soil which acts as a reservoir for minerals, water, and nutrients required for plant growth.  Tillage of the soil ensure suitable conditions for planting or sowing and feeding the crop  There are different characteristics of soil that are determined on their  Structure  Depth  Texture  Plant nutrient content  Acidity  A vital characteristic of soil is depth  The deeper the soil, the greater the capacity it has to store water and minerals  Shallow soils cannot carry enough water to support plant growth, supply enough nutrients, or support root development  Soil texture refers to the relative importance of particles of different size  Large particles of sandy soils provide light, well drained land that is readily warmed for early sp
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