Berry soil and agriculture notes2.pptx

calendargrumpyBiotechnology

Dec 14, 2012 (4 years and 7 months ago)

230 views

Soil & Agriculture

Texture


The percentages (by weight) of different
sized particles of sand, silt and clay that it
contains.


Soil Properties:

Structure


How soil particles are organized
and clumped together. (Sand, silt,
clay)

Friability


How easily the soil can be
crumbled.

Porosity


A measure of the volume of soil and
the average distances between the
spaces.

Permeability


The rate at which water and air
moves from upper to lower soil
layers. It is distances between
those spaces.

Some Soil Properties


Soils vary in the size
of the particles they
contain, the amount
of space between
these particles, and
how rapidly water
flows through them.

Figure 3
-
25

Shrink
-
Swell Potential


Some soils, like clays, swell when H
2
O
gets in them, then they dry and crack.
This is bad for house foundations, etc.

pH


The pH of most soils ranges from 4.0 to
8.0.


But, the soil of the Pygmy Forest in
California is extremely acidic (2.8
-
3.9)
and in Death Valley, California, it is very
basic (10.5).



Plants are affected by pH because of the
solubility of nutrient minerals.

Slope


Steep slopes often have little or no soil
on them because of gravity.



Runoff from precipitation tends to erode
the slope also. Moderate slopes and
valleys may encourage the formation of
deep soils.

Depth


Some soils are very shallow (like in some
places in San Antonio). It can be only
two inches of soil and then you hit rock.
Other areas can have soil 36 inches deep
or more.

Color


Dark soil is rich with lots of organic
matter.



Light soil (like sand) is not so rich
with very little organic matter.

Fig. 3
-
23, p. 68

Fern

Mature soil

Honey

fungus

Root system

Oak tree

Bacteria

Lords and

ladies

Fungus

Actinomycetes

Nematode

Pseudoscorpion

Mite

Regolith

Young soil

Immature soil

Bedrock

Rock

fragments

Moss and

lichen

Organic debris

builds up

Grasses and

small shrubs


Mole

Dog violet

Wood

sorrel

Earthworm

Millipede

O horizon

Leaf litter

A horizon

Topsoil

B horizon

Subsoil

C horizon

Parent

material

Springtail

Red Earth

Mite

Organic Layer (O
-
horizon)


The uppermost layer; it is rich in
organic material.


Plant litter accumulates in the O
-
horizon and gradually decays.



In desert soils the O
-
horizon is
completely absent, but in certain
organically rich soils it may be the
dominant layer.

Topsoil (A
-
horizon)


It is dark and rich in
accumulated organic
matter and humus.


It has a granular texture
and is somewhat
nutrient
-
poor due to
the loss of many
nutrient minerals to
deeper layers and by
leaching.

Subsoil (B
-
horizon)


The light
-
colored
subsoil beneath the A
-
horizon; it is often
where nutrient
minerals have leached
out of the topsoil and
litter accumulate.



It is typically rich in
iron and aluminum
compounds and clay.

Parent Material (C
-
horizon)


This contains
weathered pieces of
rock and borders the
unweathered solid
parent material. Most
roots do not go down
this deep and it is
often saturated with
groundwater.

Layers in Mature Soils


Infiltration: the downward movement of
water through soil.


Leaching: dissolving of minerals and organic
matter in upper layers carrying them to lower
layers.


The soil type determines the degree of
infiltration and leaching.


6.4 billion tons of soils are eroded from
the U.S. each year; this would fill 320
million average
-
sized dump trucks that, if
parked end
-
to
-
end, would extend to the
moon and ¾ of the way back!

Erosion

Definition


Erosion is the movement of soil
components, especially surface litter
and topsoil, from one place to
another.

Importance


In undisturbed ecosystems, the roots of plants
help anchor the soil, and usually soil is not lost
faster then it forms.



Erosion destroys in a few decades what nature
took hundreds to thousands of years to produce.

Global Outlook: Soil Erosion


Soil is eroding faster than it is forming on more
than one
-
third of the world’s cropland.

Figure 13
-
10

SOIL EROSION AND DEGRADATION


Soil erosion is the
movement of soil
components,
especially surface
litter and topsoil,
by wind or water.

Soil erosion increases through activities such as
farming, logging, construction, overgrazing, and
off
-
road vehicles.

Figure 13
-
9

SOIL EROSION AND DEGRADATION


Soil erosion lowers soil fertility and can
overload nearby bodies of water with eroded
sediment.


Sheet erosion
: surface water or wind peel off thin
layers of soil.


Rill erosion
: fast
-
flowing little rivulets of surface
water make small channels.


Gully erosion
: fast
-
flowing water join together to
cut wider and deeper ditches or gullies.

Wind Erosion


Saltation


one particle hitting
another and being blown across
the surface of the soil.

Suspension


airborne soil. Ex. soil
from Lubbock is found in Temple,
Texas.


Desertification: Degrading Drylands


About one
-
third of the world’s land has lost some
of its productivity because of drought and human
activities that reduce or degrade topsoil.

Figure 13
-
12

Salinization and Waterlogging of
Soils: A Downside of Irrigation


Example of high
evaporation,
poor drainage,
and severe
salinization.


White alkaline
salts have
displaced cops.

Figure 13
-
14

Salinization and
Waterlogging


Repeated
irrigation can
reduce crop
yields by
causing salt
buildup in the
soil and
waterlogging of
crop plants.

Figure 13
-
13

Solutions



More efficient irrigation


Better planning of farmlands


Genetic Engineering

Fig. 13
-
15, p. 281

Cleanup

Prevention

Soil Salinization

Solutions

Reduce irrigation

Switch to salt
-
tolerant crops
(such as barley,
cotton,
sugarbeet)

Flush soil
(expensive and
wastes water)

Stop growing crops
for 2

5 years

Install underground
drainage systems
(expensive)

Erosion Control
(see Miller pg. 282)


Shelterbelts



can reduce wind erosion.
Long rows of trees are planted to partially
block the wind. They can also help retain
soil moisture, supply some wood for fuel,
and provide habitats for birds.


Minimum Tillage



(conservation
tillage) to disturb the soil as little as
possible while planting crops.


Special tillers break up and loosen the
subsurface soil without turning over
the topsoil, previous crop residues,
and any cover vegetation.


Traditional Agriculture: Low Input
Polyculture


Many farmers in developing countries use low
-
input agriculture to grow a variety of crops on each
plot of land (interplanting) through:


Polyvarietal cultivation
: planting several genetic
varieties.


Intercropping
: two or more different crops grown at
the same time in a plot.


Agroforestry
: crops and trees are grown together.


Polyculture
: different plants are planted together.


SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION


Modern farm machinery can plant crops
without disturbing soil (no
-
till and minimum
tillage.


Conservation
-
tillage farming:


Increases crop yield.


Raises soil carbon content.


Lowers water use.


Lowers pesticides.


Uses less tractor fuel.


Contour Farming


sloping your growing
crops, etc.



You run terraces parallel to the ground to
stop soil from running down a steep slope.
Plowing and planting crops in rows across,
rather than up and down, the sloped
contour of the land.

Terracing



(what you
use for contour farming.)
Dirt goes up to hold the
dirt in place. Broad,
nearly level terraces that
run across the land
contour. Helps to retain
water for crops at each
level and reduce soil
erosion by controlling
runoff.



Strip Cropping



a row crop such as
corn alternates in strips with another
crop that completely covers the soil,
reducing erosion. It catches and
reduces water runoff and helps
prevent the spread of pests and plant
diseases.

Cover Cropping (alley cropping)



several crops
are planted together in strips or alleys between trees
and shrubs that can provide shade (which reduces
water loss by evaporation) and helps to retain and
slowly release soil moisture.


Irrigation Techniques



Conventional center
-
pivot irrigation
-

allows
80% of the water input to reach crops


Gravity
-
flow irrigation
-

Valves that send
water down irrigation ditches.


Drip irrigation
-

Can raise water efficiency to
90
-
95% and reduce water use by 37
-
70%.


Floodplain irrigation
-

allowing the natural
floods to irrigate the crops. Soils in flood
zones tend to be nutrient rich and fertile.

Definition


Hydroponics are growing plants in
fertilized water.

Hydroponics:

Method of suspending plants in
water and the solutions involved.

Ex. cranberries are grown this way.

Costs of Hydroponics:


It is labor
-
intensive and expensive.

You can control the
environment & grow plants
where there is no soil; NASA is
looking into this.

Benefits:

THE GREEN REVOLUTION


THE GENE REVOLUTION


To increase crop yields, we can mix the genes
of similar types of organisms and mix the
genes of different organisms.


Artificial selection has been used for centuries to
develop genetically improved varieties of crops.


Genetic engineering develops improved strains at
an exponential pace compared to artificial
selection.


Controversy has arisen over the use of
genetically modified food (GMF).

Mixing Genes


Genetic
engineering
involves splicing a
gene from one
species and
transplanting the
DNA into another
species.

Figure 13
-
19