Download Building Healthy Soils Fred Magdoff

Building Healthy Soils
Fred Magdoff
[email protected]
The Great Hunger of 2008
Rioting in response to soaring food prices recently has broken out in
Egypt, Cameroon, Ivory Coast, Senegal and Ethiopia. In Pakistan and
Thailand, army troops have been deployed to deter food theft from
fields and warehouses.
Soil Degradation
Intensive tillage, soil
erosion, and insufficient
added residues
Aggregates break down
Soil organic matter decreases
Increased erosion by wind and water
Surface becomes compacted, crust forms
More soil organic matter is lost
Crop yields are reduced
Hunger and malnutrition result
Less soil water storage,
less diversity of soil
organism, fewer
nutrients for plants
… it is our work with living soil
that provides sustainable
alternatives to the triple crises of
climate, energy, and food. No
matter how many songs on your
iPod, cars in your garage, or
books on your shelf, it is plants’
ability to capture solar energy
that is at the root of it all.
Without fertile soil, what is life?
—VANDANA SHIVA, 2008
Aggregates after stability test
% of aggregates
stable to 1.25cm
rain/5mins:
2mm sieves
Organic
management
~70% - high
Conventional
management
~20% - low
Add
organic
matter
Increased biological activity
(& diversity)
Reduced
soil-borne diseases,
parasitic nematodes
Aggregation
increased
Decomposition
Humus and other
Pore structure growth promoting Nutrients
improved
released
substances
Harmful
substances
Improved tilth
detoxified
and water storage
HEALTHY PLANTS
carbon dioxide (CO2)
(0.04% in the atmosphere)
photosynthesis
crop and
animal
residues
respiratio
n
in stems
and
leaves
carbon in
soil
organic matter
root
respiration
and soil
organic
matter
decomposition
crop harvest
erosion
Overall strategies of
ecologically-based agriculture
a) create soil & above
ground conditions for
healthy plants with
enhanced defenses
b) stress pests
c) enhance beneficials
Build internal strengths Prevention (of symptoms and
consequences of weak
into agricultural
ecosystem)
ecosystem
Routine ecologically
sound practices during
season to keep plants
healthy
Reactive
management
Preventive management
pre-season through planting time
(building internal strengths into the system)
1. Crop/plant selection
& planting management;
habitat conservation
& enhancement of field
and surroundings
 create soil & above
ground conditions for
healthy plants with
enhanced defenses
 stress pests
2. Build healthy soil
(below ground
habitat conservation
& enhancement)
 enhance beneficials
Building Healthy Soil
1. Add plentiful amounts of organic
materials from crop residues
(including cover crops) well as offfield organic materials such as
animal manures and composts.
vs.
Building Healthy Soils
2. Keep the soil covered with living
vegetation and/or crop residue.
 Use cover crops or perennial sod
cover routinely.
 Reduce tillage intensity.
•
Supplies food and habitat for maintaining
biodiversity (helps beneficials at expense of pests)
•
Suppresses weeds, insect, and disease cycles
•
Helps grow healthier plants because:
a) development of better soil tilth
b) supplies nutrients and soil holds water better
c) lessens compaction
d) etc.
Building Healthy Soils
3. Use better crop rotations.
Building Healthy Soils
4. Reduce tillage intensity.
 Many different reduced till systems —
conservation till, ridge till, zone-till,
no-till.
 Better planters help.
 Cover crops can help.
Building Healthy Soils
5. Use other practices that reduce
runoff and erosion.
Building Healthy Soils
6. Reduce severity of compaction.
 Don’t travel on wet soils.
A lasting injury is done by ploughing
land too wet.
S.L. Dana, 1842
 Use controlled traffic lanes
(“permanent” beds).
 Better load distribution.
 Increase organic matter.
 Etc.
Building Healthy Soils
7. Use best management techniques to
supply nutrients to plants without
degrading the environment.
Farm boundary
farm-grown crops
fertilizers,
lime, organic
amendment
s
crops
crop
residues
soil
Nutrient Cycles vs. Nutrient Flows
leaching,
runoff, and
volatilizatio
n
Use
Multiple Tactics
Reduce
tillage
Reduce
compaction
Better nutrient
timing, placement,
and amounts
Cover crops
Healthier Crops
Better
rotations
Add various sources of
organic materials (crop residues,
manures, composts, etc.)
Control
erosion