THE GEOSPHERE, SOIL, AND FOOD PRODUCTION: THE SECOND GREEN REVOLUTION

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CHAPTER 10 THE GEOSPHERE, SOIL, AND FOOD
PRODUCTION THE SECOND GREEN REVOLUTION
From Green Chemistry and the Ten Commandments of
Sustainability, Stanley E. Manahan, ChemChar
Research, Inc., 2006 manahans_at_missouri.edu
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10.1. The Solid Earth
Geosphere All the rocks, minerals, soil and
sediments that compose the solid earth. Geosphere
connection to green chemistry
Plants that provide most food for humans and
animals grow on the geosphere. Plants growing
on the geosphere already provide, and have the
potential to provide much more, biomass for use
as renewable materials, such as wood, fiber, raw
materials, and fuel. The geosphere is the
source of nonrenewable minerals, ores, fossil
fuels, and other materials used by modern
industrialized societies. Modifications and
alterations of the geosphere have profound
effects upon the environment. Sources of fresh
water are stored in lakes and rivers on the
surface of the geosphere, move by means of
streams, rivers, and canals on the geosphere, and
occur in aquifers underground. The geosphere is
the ultimate sink for disposal of a variety of
wastes
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Physical Nature of the Geosphere
Solid inner coreltliquid outer coreltmantleltcrustltso
il Crust consists of rocks made of minerals
49.5 O, 25.7 Si Mostly silicon oxides or
silicates, such as quartz, SiO2, and potassium
feldspar, KAlSi3O8. Igneous rock is solidified
molten rock Undergoes weathering to produce
secondary minerals. Clays are common secondary
minerals, such as kaolinite, Al2Si2O5(OH)4.
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Human Influences on the Geosphere
Desertification in which normally productive soil
is converted to unproductive desert. Usually in
areas with marginal rainfall As plant cover is
destroyed, surface soil erodes away, surface
water is lost, groundwater in underground
aquifers diminishes, fresh water sources and soil
accumulate salt, and eventually the land becomes
unable to support agriculture, grazing, or even
significant human populations. Old
problem Desertification is reversible Recharge
of underground water aquifers Maintenance of
plant cover Genetic engineering of plants that
grow under adverse conditions
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10.2. ENVIRONMENTAL HAZARDS OF THE GEOSPHERE
Earthquakes consisting of violent horizontal and
vertical movement of Earths surface resulting
from tectonic plates moving relative to each
other.
Liquefaction of poorly consolidated ground
during earthquakes Tsunamis from
earthquakes The anthrosphere can be constructed
to minimize the effects of earthquakes.
Volcanoes due to the presence of liquid rock
magma near the surface
Can cause great loss of life Can affect
weather and climate, such as occurred with the
astoundingly massive eruption of Indonesias
Tambora volcano in Indonesia in 1815.
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Surface Effects on the Geosphere
Weathering is the physical and chemical breakdown
of rock to fine, unconsolidated
particles. Erosion occurs when weathered
materials are moved by the action of wind, liquid
water, and ice. Landslides occur when
unconsolidated earthen material slides down a
slope. Creep characterized by a slow, gradual
movement of earth Expansive soil Permafrost Sinkho
les
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10.3. WATER IN AND ON THE GEOSPHERE
Water commonly moves on the geosphere in streams
or rivers consisting of channels through which
water flows. Rivers collect water from drainage
basins or watersheds. Floodplains are subjected
to periodic floods. Efforts to control floods may
be helpful, but also may be counterproductive.
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10.4. ANTHROSPHERIC INFLUENCES ON THE GEOSPHERE
Human alteration of Earth surface is often
harmful, but can be beneficial. Harmful effects
include
Aggravated flooding Landslides, such as from
piles of mine tailings Acid pollutants from
bacterial action on exposed pyrite,
FeS2 Filling and destruction of wetlands Direct
effects of humans on the geosphere Construction
of dams and reservoirs Flattening whole
mountain tops to get to underground coal
seams Plowing natural prairies to grow crops
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Anthrospheric Influences on the Geosphere (Cont.)
Indirect effects Pumping so much water from
underground aquifers that the ground
subsides Exposing minerals by strip mining that
weather to produce polluted acidic water Major
effects of mining and extractive industries
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10.5. THE GEOSPHERE AS A WASTE REPOSITORY
Municipal refuse in sanitary landfills Methane
from landfills 2CH2O ? CO2 CH4
(10.5.1) Leachate from landfills Minimization of
the quantities of materials requiring sanitary
landfill Reduce at source Recycle wastes
Burn for fuel Secure landfills for
hazardous wastes
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10.6. HAVE YOU THANKED A CLOD TODAY?
Good, productive soil combined with a suitable
climate and adequate water is the most valuable
asset that a nation can have. Areas that once had
adequate soil have seen it abused and degraded to
the extent that it is no longer productive. One
of the central challenges faced by the practice
of green chemistry and industrial ecology is to
retain and enhance the productive qualities of
soil. Soil receives pollutants Direct, such as
herbicides used to control weed growth
Indirect, such as acid from acid rain
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Soil Structure and Horizons
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Soil
Soil is a term that actually describes a wide
range of finely divided mineral matter containing
various levels of organic matter and water that
can sustain and nourish the root systems of
plants growing on it. Soil is the product of the
weathering of rock by physical, chemical, and
biochemical processes that produces a medium
amenable to support of plant growth. Healthy
soil Contains water available to plants Has a
somewhat loose structure with air spaces Soil
supports an active population of soil-dwelling
organisms, including fungi and bacteria that
degrade dead plant biomass and animals, such as
earthworms. Generally composed of about 95
inorganic matter, but some soils contain up to
95 organic matter, and some sandy soils may have
only about 1 organic matter.
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Soil Horizons
Soil horizons are formed by weathering of parent
rock, chemical processes, biological processes,
and the action of water including leaching of
colloidal matter to lower horizons.
Most important is topsoil. Plant roots take
water and plant nutrients from topsoil Topsoil
is the layer of maximum biological
activity Rhizosphere where plant roots are
especially active Relationships between plant
roots and microorganisms in the rhizosphere
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Inorganic Solids in Soil
Silicates are the most common mineral
constituents of soil, including finely divided
quartz (SiO2), orthoclase (KAlSi3O8), and albite
(NaAlSi3O8). Other elements that are relatively
abundant in Earths crust are aluminum, iron,
calcium, sodium, potassium, and magnesium
contained in minerals such as geothite (FeO(OH)),
magnetite (Fe3O4), epidote (4CaO3(AlFe)2O36SiO2
H2O), calcium and magnesium carbonates (CaCO3,
CaCO3MgCO3), and oxides of manganese and titanium
in soil. Soil parent rocks undergo weathering
processes to produce finely divided colloidal
particles, particularly clays.
These secondary minerals hold moisture and
mineral nutrients, such as K required for plant
growth Can absorb toxic substances in soil,
thus reducing the toxicity of substances that
would harm plants
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Soil Organic Matter
The few percent of soil mass consisting of
organic matter has a strong influence upon the
physical, chemical, and biological
characteristics of soil
Holds soil moisture Holds and exchanges with
plant roots some of the ions that are required as
plant nutrients Temperature, moisture, and
climatic conditions significantly affect the
kinds and levels of soil organic
matter Accumulates under cold, wet conditions
in which soil stays saturated with
moisture Soil from tropical rain forests loses
organic matter readily when vegetation is removed.
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Soil Humus
The plant biomass residues biodegraded by soil
bacteria and fungi losing cellulose and leaving
modified residues of the lignin material that
binds the cellulose to the plant matter.
Humification, residue is partly soluble soil
humus Humin does not dissolve and stays in the
solid soil. Soil humus
Strongly influences soil characteristics Stron
g affinity for water Exchanges H ion and acts
to buffer the pH of water in soil (the soil
solution) Binds metal ions and other ionic
plant nutrients Binds and immobilizes organic
materials, such as herbicides applied to soil
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Water in Soil and the Soil Solution
Water is taken up by plant root hairs,
transferred through the plant, and evaporated
from the leaves, a process called transpiration
Most of the water in normal soils is absorbed
to various degrees upon the soil
solids Waterlogging (saturation with water) is
bad for soil. Soil solution transfers nutrients
between roots and the soil solid.
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10.7. PRODUCTION OF FOOD AND FIBER ON
SOILAGRICULTURE
Agriculture is the production of food and fiber
by growing crops and livestock. Agriculture is
very closely tied with the practice of green
chemistry in many ways.
Fertilizers, herbicides, and insecticides are
produced and applied to crops and land in
enormous quantities. Annual production of
millions of kilograms of these chemicals demands
the proper practice of green chemistry and
engineering. Conservation tillage, is in
keeping with the best practice of green chemistry
and industrial ecology. Biomass produced by
plants can be used as a renewable source of
organic matter as a raw material and fuel. Some
plants are now being genetically engineered to
produce specific chemicals.
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Agriculture and Green Technology
In many respects, past agricultural practices
have not been very green.
Greatest incursion of the anthrosphere into the
other environmental spheres Cultivation of soil
by humans has displaced native plants, destroyed
wildlife habitat, contaminated soil with
pesticides, filled rivers and bodies of water
with sediments, and otherwise perturbed and
damaged the environment.
However domestic crops temporarily remove carbon
dioxide from the atmosphere and provide organic
raw materials and biomass fuel without any net
addition of carbon dioxide to the atmosphere.
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Plant Breeding
The basis of agriculture is the development of
domestic plants from their wild ancestors. Humans
selected plants with desired characteristics for
the production of food and fiber and developed
new species that often require the careful
efforts of expert botanists to relate them to
their wild ancestors. Modern plant breeding
techniques
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Modern Plant Breeding Techniques
Around 1900 the scientific principles of heredity
started to be applied to plant breeding.
First green revolution in the 1950s and 1960s
resulted in varieties of rice and wheat,
especially, that had vastly increased
yields Techniques used included selective
breeding, hybridization, cross-pollination, and
back-crossing Combined with chemical
fertilizers and pesticides lead to much higher
crop yields India, for example, increased its
grain output by 50. Plants resistant to cold,
drought, and insects further increased crop
yields. Increased nutritional values such as
high-lysine corn
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Modern Plant Breeding Techniques (Cont.)
Development of hybrids produced by crossing
true-breeding strains of plants Corn is
especially amenable to hybridization. Other
factors in increased productivity include
development of crop varieties that resist heat,
cold, and drought irrigation herbicides better
tillage practices.
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10.8. PLANT NUTRIENTS AND FERTILIZERS
Carbon, hydrogen, and oxygen in plant biomass
from water and atmospheric carbon
dioxide Calcium, magnesium, and sulfur are
usually in sufficient abundance in soil. Calcium
is commonly added to soil as lime (CaCO3), which
neutralizes soil acidity but also adds calcium to
soil. Soil(H)2 CaCO3 ? SoilCa2
CO2 H2 (10.8.1) This process also adds
calcium to soil. Nitrogen, phosphorus, and
potassium, are commonly added to soil as
fertilizers.
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Aspects of the Nitrogen Cycle
Nitrogen cycle Atmosphere is 79 N2, but the N2
molecule is extremely stable and not directly
available to plants. Rhizobium bacteria growing
on the roots of leguminous plants, such as clover
and soybeans, convert atmospheric nitrogen to
nitrogen chemically bound in biomolecules. NH4
is produced when plant residues and animal feces,
urine, and carcasses undergo microbial
decay. Lightning and combustion processes
convert atmospheric nitrogen to nitrogen
oxides Ammonia manufacturing plants produce NH3
from atmospheric elemental nitrogen and elemental
hydrogen produced from natural gas. Soil
microbial processes oxidize ammoniacal nitrogen
(NH4) to nitrate ion, NO3-, the form of nitrogen
most readily used by plants. Microbial
processes release gaseous N2 and NO2.
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Synthetic Nitrogen Fertilizer
Production of fertilizer nitrogen starting with
the catalytic Haber process at about 1000 times
atmospheric pressure and 500C. The reaction is
N2 3H2 ???2NH3 (10.8.2) Anhydrous
ammonia can be applied directly below the soil
surface or applied as a 30 solution of NH3 in
water.
Held in soil as ammonium ion, NH4 Slowly
oxidized by the action of soil bacteria using
atmospheric O2 to nitrate ion, NO3-, which is
used directly by plants.
Other forms of nitrogen include solid NH4NO3 and
urea,
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Phosphorus Fertilizers
Phosphorus is an essential plant nutrient
required for cellular DNA and other
biomolecules. Phosphorus is utilized by plants as
H2PO4- and HPO42- ions. Phosphate minerals that
serve as fertilizer phosphorus occur as
fluorapatite, Ca5(PO4)3F, and, Ca5(PO4)3OH. Phosph
ate minerals are treated to make them more water
soluble 2Ca5(PO4)3F (s) 14H3PO4 10H2O
? 2HF(g)
10Ca(H2PO4)2H2O (10.8.4) 2Ca5(PO4)3F(s)
7H2SO4 3H2O ?
2HF(g) 3Ca(H2PO4)2H2O 7CaSO4 (10.8.5) ?
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Potassium and Micronutrients
Potassium required by plants Potassium as the
potassium ion, K, is required by plants to
regulate water balance, activate some enzymes,
and enable some transformations of
carbohydrates. Potassium for fertilizer is
simply mined from the ground as salts,
particularly, KCl, or pumped from beneath the
ground as potassium-rich brines.
Plants require several micronutrients including
boron, chlorine, copper, iron, manganese,
molybdenum (for N-fixation), and zinc. Soil
normally provides sufficient micronutrients.
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10.9. PESTICIDES AND AGRICULTURAL PRODUCTION
Most common agricultural pesticides are
insecticides and herbicides Recombinant DNA
technology is having some significant effects
upon pesticide use.
For example, splicing of genetic material into
cotton, corn, and other crops that cause them to
produce an insecticide that is generated by some
kinds of bacteria. Breeding of genetically
modified plants that are not affected by
herbicides, for example Roundup-ready soybeans
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10.10. SOIL AND PLANTS RELATED TO WASTES AND
POLLUTANTS
Soil is a repository of large quantities of
wastes and pollutants, and plants act as filters
to remove significant quantities of pollutants
from the atmosphere.
Sulfates and nitrates from the atmosphere,
including acid-rain-causing H2SO4 and
HNO3 Gaseous atmospheric SO2, NO and NO2 are
absorbed by soil and oxidized to sulfates and
nitrates. Soil bacteria and fungi are known to
convert atmospheric CO to CO2. Lead from leaded
gasoline Organic materials, such as those
involved in photochemical smog formation, are
removed by contact with plants and are especially
attracted by the waxy organic-like surfaces of
the needles of pine trees.
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Potential Pollutants Added Deliberately to Soil
Insecticides and herbicides added to soil for
pest and weed control Chemicals from hazardous
waste disposal sites can get onto soil or below
the soil surface by leaching from landfill or
drainage from waste lagoons Petroleum
hydrocarbons, are disposed on soil where
adsorption and microbial processes immobilize and
degrade the wastes. Soil can be used to treat
sewage. Leakage from underground storage tanks
of organic liquids, such as gasoline and diesel
fuel PCBs contaminating soil in New York State
from the manufacture of industrial
capacitors Analyses of PCBs in United Kingdom
soils archived for several decades have shown
levels of these pollutants that parallel their
production. PCBs and similar pollutants in
Arctic and sub-Arctic regions believed to be due
to the condensation of these compounds from the
atmosphere onto soil in very cold regions (next
slide).
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Distillation Process of Organohalides and Other
Organic Pollutants that Concentrate in Cold
Regions
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Degradation and Fates of Pesticides Applied to
Soil
Many factors are involved in determining
pesticide fate. Adsorption of pesticides to
soil, strongly influenced by the nature and
organic content of the soil surface as well as
the solubility, volatility, charge, polarity, and
molecular structure and size of the
pesticides. Strongly adsorbed molecules are
less likely to be released and thus harm
organisms, but they are less biodegradable in the
adsorbed form. Leaching of adsorbed pesticides
into water is important in determining their
water pollution potential. Effects and
potential toxicities of pesticides to soil
bacteria, fungi, and other organisms
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10.11. SOIL LOSSDESERTIFICATION AND DEFORESTATION
Soil erosion refers to the loss and relocation of
topsoil by water and wind action. About a third
of U.S. topsoil has been lost to erosion since
cultivation began on the continent and at present
about a third of U.S. cropland is eroding at a
rate sufficient to lower productivity. Erosion
was recognized as a problem in the central United
States within a few years after forests and
prairie grasslands were first plowed to raise
crops, particularly in the latter 1800s leading
to soil conservation measures. Water erosion is
responsible for greater loss of soil than is wind
erosion. See erosion patterns in the continental
U.S. on the next slide.
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Soil Erosion Patterns in the Continental U.S.
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Desertification
The ultimate result of soil erosion and other
unsustainable agricultural practices in
relatively dry areas is a condition known as
desertification. Desertification occurs when
soil Loses permanent plant cover Loses its
capacity to retain moisture Dries out Loses
fertility so that plants no longer grow on
it Interrelated factors involved in
desertification Wind erosion
Water erosion (which occurs during sporadic
cloudbursts even in arid areas) Development of
adverse climate conditions Lack of water for
irrigation Loss of soil organic
matter Deterioration of soil physical and
chemical properties
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Desertification (Cont.)
Desertification is actually a very old problem
Middle East, North Africa, southwestern
U.S. Desertification is one of the most
troublesome results of global warming caused by
greenhouse warming.
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Deforestation
Has occurred extensively in the United States,
but is now being reversed in New
England Particularly severe problem in tropical
regions Once destroyed, tropical forests are
almost impossible to restore because tropical
forest soil has been leached of nutrients by the
high annual rainfalls in tropical regions. When
forest cover is removed, the soil erodes rapidly,
loses the plant roots and other biomass that
tends to hold it together, loses nutrients, and
becomes unable to sustain either useful crops or
the kinds of forests formerly supported.
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Soil Conservation
The key to preventing soil loss from erosion as
well as preventing desertification from taking
place lies in a group of practices that
agriculturists term soil conservation.
Construction of terraces and planting crops on
the contour of the land (next slide) Crop
rotation and occasional planting of fields to
cover crops, such as clover, are also old
practices Relatively new practice of
conservation tillage which involves minimum
cultivation and planting crops through the
residue of crops from the previous year using
minimal quantities of herbicides to deter weed
growth until shading by crops prevents weed growth
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Soil Conservation with Contour Planting and
Terraces
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Perennial Plants
The ultimate in no-till agriculture is the use of
perennial plants that do not have to be planted
each year.
Trees in orchards and grape vines in
vinyards A successful grain-producing plant is
one that dedicates its metabolic processes to the
production of large quantities of seed that can
be used for grain. Perennial plants put their
energy into the development of large, bulbous
root structures that store food for the next
growing season rather than producing
grain. Genetic engineering may eventually
develop successful grain producing perennial
plants
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Trees and Erosion
Among the most successful plants at stopping
erosion are trees, some of which grow back from
their roots after harvesting.
Wood and wood products are probably the most
widely used renewable resources. Hybrid tree
varieties have been developed that are
outstanding producers of biomass. Wood is a
renewable resource used for construction in place
of steel, aluminum, and cement, all produced by
very energy-intensive processes. Wood is about
50 cellulose, a carbohydrate polymer that is
used directly to make paper. Cellulose can be
broken down chemically or biochemically to
glucose sugar which can be used by yeasts to
generate ethanol and protein.
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Water and Soil Conservation
Conservation of soil and conservation of water go
together very closely. The condition of the soil
largely determines the fate of the water and how
much is retained in a usable condition. Soil in a
condition that retains water allows rainwater to
infiltrate into groundwater. Measures taken to
conserve soil usually conserve water as well.
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10.12. AGRICULTURAL APPLICATIONS OF GENETICALLY
MODIFIED ORGANISMS
Recombinant DNA technology involves taking
genetic material from two different organisms and
combining them so that traits of both are
displayed. During the 1970s, the ability to
manipulate DNA through genetic engineering became
a reality, and during the 1980s, it became the
basis of a major industry. Direct manipulation of
DNA can greatly accelerate the process of plant
breeding to give plants that are much more
productive, resistant to disease, and tolerant to
adverse conditions. In the future, entirely new
kinds of plants may even be engineered. Plants
produced by this method are called transgenic
plants. Example corn and cotton have been
genetically engineered to produce their own
insecticide. Could lead to a second green
revolution
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The Major Transgenic Crops and their
Characteristics
Two characteristics of tolerance for herbicides
that kill competing weeds and resistance to
pests, especially insects, but including
microbial pests (viruses) as well The most common
transgenic crop grown in the U. S. is the
soybean, of which about 89 of the crop was
transgenic in 2006. The percentage of U.S. corn
that was transgenic in 2005 has been estimated at
52. In 2006, it was estimated that 83 of the
cotton grown in the U. S. was transgenic. Small
fractions of the potato, squash, and papaya crops
were transgenic.
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Insect-Resistant Transgenic Crops
Insect resistance has been imparted by addition
of a gene from Bacillus thuringiensis (Bt) that
causes the plant to produce a natural insecticide
in the form of a protein that damages the
digestive systems of insects, killing them.
Bt cotton has saved as much as a half million
kilogram of synthetic insecticides in the in the
U. S. each year.
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Herbicide-Resistant Transgenic Crops
The most common herbicide-resistant plants are
those resistant to Monsantos Roundup herbicide
(glyphosate, structural formula below)
Virus resistance in transgenic crops has
concentrated on papaya, a tropical fruit that is
an excellent source of Vitamins A and C and is an
important nutritional plant in tropical
regions. Genetically engineered papaya
resistant to ringspot virus
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Future Transgenic Crops
Increased efficiency of photosynthesis, which is
only a few tenths of a percent in most
plants Development of the ability to support
nitrogen-fixing bacteria on plant roots in plants
that cannot do so now Golden rice which
incorporates ?-carotene in the grain
Two of the genes used to breed golden rice were
taken from daffodil and one from a bacterium!
Tomatoes that ripen slowly and can be left on the
vine longer than conventional tomatoes Higher
levels of lycopene, which is involved with the
production of Vitamin A, in tomatoes Modification
of the distribution of oils in canola to improve
the nutritional value of the oil Increased
Vitamin E content in transgenic canola oil
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Future Transgenic Crops (Cont.)
Decaffeinated coffee and tea
Coffee trees in which all the beans ripen at
once Improved transgenic varieties of grass and
other groundcover crops can be quite useful
Tolerances for adverse conditions of water and
temperature, especially resistance to heat and
drought Disease and insect resistance are
desirable Reduced growth rates for less
mowing, saving energy Transgenic foods that
produce contain vaccines against
disease Cholera, hepatitis B, and various kinds
of diarrhea Banana as a vaccine carrier