abiotic factors in agriculture and their control

Question 1

what factors effect the choice of which species and varieties of crop or live stock are selected for cultivation

Answer 1

1) market demand
2) if environmental conditions are within the range of tolerance of the food species
3) if the environmental conditions or the species adaptations can be controlled to improve productivity

Question 2

list the abiotic factors which need to be controlled in agriculture

Answer 2

1) temperature
2) water
3) light
4) soil fertility
5) aerations
6) soil salinity
7) PH
8) topography
9) CO2
10) relief
11) wind velocity

Question 3

outline the importance of temperature

Answer 3

importance

1) length of the thermal growing season- temps must be warm enough for growth
2) frost-free periods- some crops become damaged by frost so cant be grown in areas where late frosts are likely
3) impacts evaporation- increases crop water requirements
4) thermoregulation - mammals and birds use food energy to maintain a constant body temp keeping animals warm reduces heat losses ad increases energy put into growth

Question 4

outline how temperature is controlled

Answer 4

locations of the field

1) low lying areas are likely to have frosts as cold dense air collects
2) south-facing slopes in the northern hemisphere receive more solar insulation so are warmer
3) greenhouses, temp controlled from solar heating or burning of fuel such as paraffin
4) transparent woven cloths over fields to help retain warm air close to found
5) live stock can be kept in sheltered buildings that can be heated

Question 5

outline the importance of light in agriculture

Answer 5

1) increaesed light= increased photosynthesis = increased growth
2) phototropism affects the growth and development of crops eg long day lengths increases milk production compared to poultry which grow best with short days
3) some livestock such as sheep mate when days become shorter in the autumn

Question 6

outline how light can be controlled

Answer 6

1) artificial lighting used to extend the growing season such as salad in greenhouses
2) artificial lighting can be used to induce another mating season

Question 7

outline the importance of water

Answer 7

1) nutrient absorption
2) cell wall turgidity proving support
3) transport of materials such as glucose and oxygen
4) gas exchange- water allows stomata to remain open

Question 8

what are some problems of water logged soils

Answer 8

1) higher risk of fungal diseases

2) soil becomes anaerobic increasing denitrifying bacteria reducing soil fertility

Question 9

what are some methods to reduce soil water levels

Answer 9

1) deep plowing
2) avoidance of soil compaction from heavy machinery and livestock
3) provision of conditions that encourage worms

Question 10

what are some issues with water shortages

Answer 10

1) cell dehydration in plants as stomata of leaves close so gas exchange cant occur
2) increase of trampling damage as livestock have to walk further to reach a water source

Question 11

how can water be increased

Answer 11

1) irrigations
2( adding organic matter to increase water retention
3) avoid the compaction of soil
4) soil mulching to reduce evaporation losses from soil surfaces

Question 12

give some examples of macro and micronutrients

Answer 12

macro
- nitrogen, phosphorus, potassium, calcium, magnesium

micro
- iron , zinc and copper

Question 13

how can nutrients be made available in the soil

Answer 13

1) legumes have symbiotic nitrogen-fixing bacteria
2) free-living soil bacteria also fix nitrogen
3) crop rotation gives time for weathering to release more nutrients and to even out demands for certain ones

Question 14

what are the advantages and disadvantages of organic fertiliser

Answer 14

advantages

• many consists of waste products which are locally available
• increase the soil humus content
• they increase soil biota populations

disadvantages

• nutrient composition cant be controlled
• nutrients are released slowly as it has to be decomposed
• bulky with high water content so transport is expensive

Question 15

what are the advantages and disadvantages of inorganic fertilisers

Answer 15

advantages

• nutirent compsoiton can be controlled
• released rapidly

disadvantages

• a large amount of energy is needed for the manufacture
• don’t add organic matter to soil so soil bota and hums may decline
• some are highly soluble so may leach

Question 16

how can aeration be decreased

Answer 16

1) compaction of soil from livestock or machines
2) farming methods that reduce soil organic matter and therefore worm populations
3) shallow roots of crops

Question 17

how can aeration be controlled

Answer 17

1) plowing of surface layers
2) adding organic matter to provide food
3) removing livestock from fields when soil is wet to reduce compaction

Question 18

outline the importance of co2 and how it is controlled

Answer 18

1) limiting factors of the rate of photosynthesis

2) burning of carbon-based fuels in greenhouses

Question 19

outline how topography affects agriculture

Answer 19

1) aspect- undulations such as valleys produce areas that may be more exposed to the sun so maybe warmer
2) first pockets- cold dense air may collect in low lying areas
3) runoff rate- steeper gradients make soil erosion more likley
4) use of mahcinery- hard to use it on land with steep gradients