HOW DOES THE INFLUENCE OF DIFFERENT PHYSICAL FACTO
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HOW DOES THE INFLUENCE OF DIFFERENT PHYSICAL FACTORS ON AGRICULTURAL VARY WITH SCALE?
The location of agriculture at all scales is the result of the interaction between physical, cultural and economic and behavioural factors.
Farming in Great Britain has been characterized by technological changes in recent decades which has led to massive increases in yields and improved stock rearing. Much of this change is due to the application of scientific research in plant and stock breeding and improved mechanization. But even today agriculture relies heavily on the physical environment. All crops require a specific range of temperature, moisture, soil ands drainage conditions and these factors can be modified by the farmer but only to a limited degree.
If we accept that a farmers choice of land usage is controlled by the physical environment, we must identify the optimum conditions and limits to production of any one crop . This will help to identify the spatial pattern of environmental controls. This was central to the ideas explored by McCarty and Lindberg in the Mid West of the USA and gave rise to the Optima Limits Model in 1966. Away from the optimum physical conditions become hostile and production/ yields decline. The optimum is the area where yields are highest and variability best, where soils are fertile, temperature and rainfall ideal and ground surface level for cultivation.
Farmers will take account of physical conditions at a local scale when considering which crops to grow. For example, the Moray coast in NE Scotland between Elgin and Lossiemouth is a rich agricultural area where winters are relatively mild and summers averaging 17oC, rainfall occurs throughout the year and is typically 600mm. There are a variety of soils but mainly glacial sandy loams on the higher ground and alluvial soils where there were once areas of open marshy conditions.
A variety of crops are grown, both cereal and root crops. However, there are limitations to agriculture in this area. The main problem is that of wind erosion, the sandy loams are light soils which dry out quickly with high infiltration rates. During early spring or late autumn strong winds can pick up the soil and cause localized wind erosion. Despite this being a well-known problem there are few conservation measures; the only evidence being improving the structure of the soil using manure. There have been no attempts to re-establish hedgerows.
Wetness limitations occur such as at Plewlands Farm to the north of Gordonstoun and at Begrow Farm to the west towards Hopeman. At Plewlands, the wetness means that either rough grazing or root crops occur and cereal growing is avoided in the wetter parts. At Begrow Farm the wet areas are given over to horse paddocks.
From this it is clear that farmers should pay special attention to physical limitations before making decisions about landuse.
The sketch map below illustrates further some controlling physical factors:
The next scale at which physical factors impact on farming can be termed the \'meso scale\'. Within the context of the UK this would focus on regional differences, for example, between East Anglia and the West Country. Physical factors for consideration at this scale might include rainfall variations,length of daylight, temperature and relief.
If a line is taken north through the Isle of Wight, to the west at least half of the cultivated area is given over to permanent grass, the further west one goes the greater the proportion of grass. Whilst to the east of this line, cereals are far more important. The predominance of grass in the west and cereals in the east are related to physical differences. Grass provides the cheapest fodder crop for cattle and provides grazing in the summer and hay or silage in the winter. Rainfall is heavier in the west [west Wales 1100mm/year] and gives rise to good grass growth hence prevalence of dairying in places like Devon and west Wales. In eastern England, the sowing of cereal crops is much easier than in the west as the date of return to field moisture capacity is much later in the drier east. Excessive moisture content of soils is less, this helps to make cultivation easier.
Modern grain production requires the use of machinery e.g. combines, which cannot be economically employed on the smaller farms in areas of
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Agronomy, Agricultural soil science, Land management, Soil, Agriculture, Crop rotation
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