on average planet earth is covered in ___” of topsoil
nutrient-rich matter that sustains most of our food and has a critical role in supporting life
we are loosing ___% of topsoil per year
We are losing topsoil mostly because of? and also because?
1. Agriculture 2. Pollution and Development
The U.s. cropland is eroding ___ times faster than soil replacement
This contributes to the increasing numbers of malnourished in Africa
soil loss
soil is more than dirt because?
It includes a functioning ecosystem; living organisms and dependent on energy flow/nutrient cycling
Soil ecosystems promote these three things?
1. breakdown of organic material to humus 2. bioturbation and mixing with organic particles 3. nitrogen fixation
__% of food comes from terrestrial ecosystems
what’s a critical part of healthy soils is?
plant growth reduces this?
size of nutrient pools
a limited nutrient supply will?
slow plant growth
two things that remove nutrients from soil?
1. leaching 2. erosion
3 things that add nutrients to the soil?
1. dead plants decomposed 2. Atmospheric nitrogen fixed by bacteria and lightning 3. Weathering of parent rock/deposition of sediments
the pool of nutrients is in a state of?
dynamic equillibrium
2 effects of harvesting crops?
1. takes nutrients out of system 2. Decreases recycling
Increased erosion can greatly accelerate?
loss of nutriens
With increased losses, agricultural soils over time
loos productivity unless steps are taken to replenish loss of nutrients
Most common remedy to replenish soil
apply fertilizers
2 other disturbances that alter the soil ecosystem?
1. chemical disturbances 2. Mechanical disturbances
chemical disturbances
poisons such as pesticides that harm soil organisms, reduce decomposition, and decrease nutrient recycling
Mechanical disturbances
can disrupt the soil profile and the ecosystem pathways, reduces recycling and increase the rate of losses by erosion
dryland soils are especially subject to
agriculture is a major contributor to
the loss in soil productivity
two fastest growing population regions are seeing
greatest losses
2 ways to restore fertility to degraded cropland
fertilizer (if not too severe) and repair eroded lands (gully reclamation)
How can we prevent further damage to crop land?
protect existing farmland from ubran sprawl
in PA urban sprawl is taking ____acres per day
Soil conservation can be achieved through these three things which reduce wind and water erosion
terracing, contour farming, and installing windbreaks
4 Rules of Sustainable Agriculture
1. cover the soil with cover crops 2. minimal/no tillage 3. Apply mulch to return nutrients 4. maximize biodiversity by rotating crops
if 80% of farmers reduced their tillage then soil erosion would be reduced