1. Environmental Influence on Agriculture Environmental factors are a major influence in determining the type of farming practised on the land in an area. It has been suggested that there is an optimum or ideal location for each specific type of farming based on climate, soils, slopes and altitude. As the distance increases from this optimum conditions become less than ideal. Consequently the profitably of producing the crop or rearing the animal is reduced.

2. TEMPERATURE This is critical for plant growth, as each plant requires a minimum growing temperature. In temperate latitudes the critical temperature is 6 C. below this figure most members of the grass family cannot grow. In Britain, wheat, barley and grass begin to grow only when the average temperature rises above 6 C. The growing season = the no: of days between the last severe frost of spring and the first of autumn. Frost has beneficial effects as it breaks up the soil and kills pests in winter, but it may also damage plants and destroys fruit blossom in spring. Within the tropics there is a continuos growing season provided moisture is available. Temperatures and length of growing season decrease with distance from the equator and height above sea level.

3. PRECIPITATION AND WATER SUPPLY The mean annual rainfall for an area determines whether its farming is likely to be based upon: tree crops, grass or cereals, or irrigation. The effectiveness of this annual total depends on temperatures on the rate of evapotranspiration. However seasonal distribution of rainfall is usually more significant for agriculture.

4. The type of precipitation is also important; Long steady periods of rain allow the water to infiltrate into the soil. Short heavy downfalls can lead to surface run off and soil erosion. Hail, falling during heavy convectional storms in summer in places such as the Canadian Prairies can destroy crops. Snow can be beneficial as it insulates the ground from extreme cold in winter and provides moisture when melting in spring. India depends upon a monsoon. If this fails there is drought and risk of famine. In the Sahel countries should rainfall decrease even by a small amount then the crops fail disastrously whereas in Britain, a short fall of a few mm a year would barley be noticed.

5. WIND Strong winds increase evapotranspiration rates, which allows the soil to dry out and to become vulnerable to erosion. Several localised winds have a harmful effect on farming; Mistral – brings cold air to the south of France Khamsin – a dry, dusty wind found in Egypt. Other winds are beneficial to agriculture, the fohn and Chinook melt snows in the Alps and on the Prairies respectively, so increasing the length of the growing season.

6. ALTITUDE The growth of various crops is controlled by the decrease in temperature in height. In Britain, few grasses can give commercial yields at heights exceeding 300m. Whereas in the Himalayas wheat can ripen at 3000m. As height increases so does exposure to wind and the amounts of cloud, snow and rain while the length of the growing season decreases.

7. GRADIENT Slope affects the depth of soil, its moisture content and its pH and therefore the type of crop which can be grown on it. It influences erosion and is a limitation on the use of machinery. Many steep slopes in S.E Asia have been terraced to overcome some of the problems of a steep gradient and to increase the area of cultivation.

8. SOIL 1 Clay soils tend to be heavy, acidic, poorly drained, cold and ideally should be left under permanent grass 2 sandy soils tend to be lighter, less acidic, perhaps too well drained, warmer and more to suited to vegetables and fruit. 3 lime soils (chalk) are light in texture, alkaline, dry and give high cereal yields. Soils can be improved by e.g.. Applying fertilisers but there is a limit to the increase in their productivity.

9. GLOBAL WARMING Scientists agree that the greenhouse effect will not only lead to an increase in temperature but also to changes in rainfall patterns. The global increase in temperature will allow many parts of the world to grow crops which are at present are too cold for them e.g.. Vines in S. England. Some places will become wetter and more stormy e.g.. Australia. While others are likely to become drier e.g.. American Prairies.

10. CASE STUDY : PHYSICAL CONTROLS ON FARMING IN THE FORMER SOVIET UNION Soviet Union is the largest country in the world but physical controls of climate, relief and soils have restricted farming to small parts of the country. Of the land area of 22.27 million km 2 only 27% was farmed in 1989. This mainly occurred in forest belt where land had been cleared and also on the Steppes. The remaining 73% consisted of, forest, tundra, desert and semi- desert. After WW2, farmers were encouraged to exceed their production targets by being offered incentives. However, this was difficult in states such as Kazakhstan as natural grassland had to be ploughed in order to grow wheat and other cereals.

11. The unreliable rainfalls did not guarantee reliable crop yields therefore to help cereal production irrigation schemes were introduced. Due to these schemes farming has extended in semi-desert areas where cotton is now grown. This is an example of one of the Soviet’s water transfer schemes by which water from rivers in the wetter parts of the country was diverted to areas suffering a deficiency. Future water transfer schemes are more ambitious and may involve diverting water from the north to the south. However, environmentalists fear that this could result in the ocean receiving less cold water and being warmed up causing pack ice to melt and sea levels to rise.