Agriculture and Soils Industrial Agriculture in the US
Transcript
Slide 1
Industrial Agriculture in the US
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Increase yield at lower cost MAKE A LIVING!
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Best available ways to do this: Fertilizers and pesticides
Petrochemical Chemical derived from petroleum or natural gas
Industrial equipment E.g. combine: Combines tasks of harvesting,
threshing, cleaning grain crops Waterworks Irrigation Drainage
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Initially monumental, then decreased: applying one ton of
fertilizer gave average yield of: 1980: 15-20 tons corn 1997: 5-10
tons corn 1910-1983: US corn yields increased 346%. Energy
consumption for agriculture increased 810%. Costs increased.
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1. Increased erosion 2. Salinization 3. Fertilizer and
pesticide effects 4. Reduction in soil biodiversity
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Peter Warshall (biologist, anthropologist): Many farmers and
soil scientists are rejecting the ag-industrial paradigm and
embracing a more holistic understanding of soil as irreplaceable,
multigenerational natural capital
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Plowing is a necessary evil Have to turn the sod to make it
produce To put in seed To allow roots to penetrate To allow water
to infiltrate To air out pathogens and allow microbes to decompose
To stir up nutrients To reduce weeds Plowing leads to loss of
topsoil inevitable
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You tell me!
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Higher prices for crops have been correlated with more erosion.
Why? Higher prices for soy/wheat/corn Stimulate hope for more
income More farming of marginal land More erosion Also, farmers
receive greater government payments for growing high erosion-making
monocrops.
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1937: government spent $460 million ($5.3 billion by todays
terms) 2000: spending $2.1 billion
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at 40% of US farmland
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Make it worthwhile economically (incentive) for farmers to use
conservation methods such as no-till. Create conservation tillage
methods that are not heavily chemically dependent. Too expensive
for farmer and for soil/water health
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What is it? Soluble salts accumulate in soil, damaging roots
Soluble salts can be removed by leaching NOT by evaporation. WHY?
Irrigation water contains salts. Arid, semi-arid
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Good irrigation water: 0.3 kg salts m -3 Apply 10,000 mm water
per season Adds 3000 kg salts per hectare per year Crops extract
water; leave salt behind. Input must not exceed removal rate.
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Need to apply more water than will evaporate BUT without
raising water table leaching requirement: the fraction of
irrigation water that must be percolated from root zone to prevent
salinity A tricky business!
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Additional problem: Where do the leached salts go? To drains;
to water supply
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Leaching of excess nutrients into water Microbial resistance to
pesticides Loss of organic matter Petroleum dependence
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Haber process of nitrogen production Mining of phosphate and
potash Add necessary nutrients to soil Less dependence natural
fertility Organic matter maintenance loses critical importance
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Green Revolution allowed fewer farmers to manage more cropland
Thanks to fertilizers and pesticides Lost need to manage diverse
crop systems Could purchase fertility
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Diminished role of nitrogen-fixers Amplified role of
nitrogen-feeders Speeds up decomposition Decrease of OM changes
structure : erosion Loss of humus: less water-and air holding
capacity More irrigation required Less O, slows aerobic respiration
Cumulative effect: fewer available nutrients Apply more
fertilizer!!
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Mississippi drains 1.2 mill mi 2 Eroded soils, excess nutrients
from fertilizers Dead zone (size of Connecticut): Only algae only
can live! Nitrogen excess; oxygen depletion (only 18% of N applied
to fields is taken up by plants)
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Agriculture is largest non-point source of pollution in US.
Nitrites in water supply: blue baby syndrome
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Haber process: extremely energy-costly Consumes more energy
than any other aspect of agriculture 2200 pounds coal produce 5.5
pounds usable nitrogen Energy required for machinery, pumps,
fertilizers, factories, transportation, seed varnishes,
transportation
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1970s began using plastic sheeting to increase temps, reduce
evaporation Seeds coated with bacteria, limestone, P powder, Seed
coating water-soluble adhesives Fertilizer granules coated with
plastic to slow release of nutrients
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Food miles Before reaching table, most American food moves
>1300 mi from soils it grew in. Most American farm soils contain
seeds, minerals and petrochemical additives harvested 100s-1000s of
miles from the farm.
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Water from dammed rivers travels 100s of miles by aqueduct to
irrigate arid, semi-arid soils Draining soils 110 million acres
drained Fertilizers carried in drains downstream MN River basin:
40% soils are drained Fertilizer goes to Miss.
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Jason McKenney (owner and grower for Pursimma Greens, organic
farm, CSA) Plants are far from simple machines with simple needs.
To understand them as such is to abuse them and, in turn, to
deprive ourselves of the nutrition and taste that we may derive
from them.
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Complex web of biological activity roots, microorganisms,
macroorganisms Provide services for agroecosystems: nutrient
recycling regulate soil organic matter change structure, water
regimes enhance acquisition of nutrients by plants
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Agricultural practices must: Supply organic matter Variety of
niches of organisms; need variety of OM Diverse crops
(intercropping, multicropping) Protect habitat ( aeration,
temperature, moisture, nutrients) Reduce compaction, chemicals,
minimal tilling
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Pay attention to: Soil ecosystem Productive capacity
Agro-ecosystem health