Ch. 13 Flashcards
soil (2)
- mixture of mineral material, organic matter, air, water, and living organisms
- capable of supporting plants growth
formation of soil (2)
- mechanical weathering - physical forces that reduce size of rock particles
- chemical weathering - chemical alteration of rock which makes it easier to fragment
“good soil”
- 45% mineral
- 25% air
- 25% H2O
- 5% organic material
role of minerals
facilitates plant growth (taken up by roots)
role of water
facilitates plant growth (taken up by roots)
air (3)
- facilitates aerobic cellular respiration
- plant roots need oxygen for this process
- CO2 from process + water = carbonic acid
- contributes to chemical weathering
organic matter (2)
- facilitates plant growth (taken up by roots)
- food source
particle size of sand
0.05 - 2.00 mm
particle size of silt
0.002 - 0.05 mm
particle size of clay
<0.002 mm
loam soils
- 40% sand
- 40% silt
- 20% clay
soil structure
way in which soil particles clump together
sandy soil
aeration
water drainage
mineral holding
aeration - high
water drainage - high
mineral holding - low
loam soil
aeration
water drainage
mineral holding
aeration - good
water drainage - good
mineral holding - good
clay soil
aeration
water drainage
mineral holding
aeration - low
water drainage - low
mineral holding - high
role of soil organisms (2)
- bacteria, fungi - decomposition of organic material
- earthworms (and others) - eat and process soil materials; air pockets
- benefit structure by aerating soils
horizontal layers (3)
- differ in chemical composition, physical properties, particle size, and amount of organic material
- a horizon
- c horizon
a horizon (2)
- top soil
- organic and mineral water
c horizon
weathered parent materal
leaching
movement of mineral from top soil layers to bottom soil layers by downward movement of soil water
grassland soil (3)
- amazing with food production
- little rainfall
- large a horizon (supports plant growth)
forest soil (2)
- abundant rainfall
- small a horizon
desert soil (2)
- minimal rainfall
- small a horizon
soil erosion (2)
- wind, water, and ice wears and transports away soil
- occurs where vegetation has been removed
impacts of soil erosion (3)
- water erosion deposits large quantities of soil particles in bodies of water
- wind erosion deposits soil particles on all surfaces
- erosion removes topsoil layer, making land unsuitable for plant growth
suitability of land for agricultural practices
dependent on several soil characteristics, slope, and climate conditions (temp, rainfall)
soil conservation practices (11)
- enhancing organic matter
- avoid excessive tilling
- efficient pest and nutrient management
- preventing soil compaction
- keeping ground covered
- diversifying cropping systems
- contour farming
- strip farming
- terracing
- waterways
- windbreaks
contour farming (2)
- tilling at right angles to the slope of the land
- reduces soil erosion and conserves water
strip farming (2)
- alternating strips of closely sown crops
- reduces soil erosion and conserves water
terracing (3)
- level areas constructed at right angles to the slope
- reduces soil erosion and conserves water
- terracing adapted for large scale agriculture
waterways
maintain depressions on sloping land where water collects and flows off land to minimize erosion
windbreaks (2)
- planting of trees or other plants between fields
- reduces velocity of wind to minimize wind erosion
tilling (3)
- preparation of soil for planting and to control weeds
- large machines are used to turn soil over, break up soil, bury weed seeds, incorporate crop residues from previous crops, and expose dark soils to sun
- process is repeated several times
negative aspects of tilling (3)
- high costs
- time intensive
- soil is prone to erosion
advantages of new tilling practices (2)
- reduced fuel use
2. reduced time involved in preparing soil
reduced tillage
uses less cultivation and leaves 15-30% of soil surface covered with crop residue to reduce erosion
conservation tillage (2)
- uses even less cultivation and leaves >30% of soil surface covered to reduce erosion
- selectively uses herbicides to control weeds
