Agricultural Science

erosion

the movement of soil or rock particles from one place to another, usually caused by wind or flowing water

organic content

includes leaves, animal wastes, and any materials derived from living (or dead) organisms. Soils with high organic content tend too be more fertile because the decay of organic material returns nutrients to the soil

Fertility

a measure of essential nutrients (nitrogen, phosphorous, and potassium) found in a soil sample

organic fertilzers

add decayed organic material like composted plants or animal wastes. decayed organic material increases fertility gradually as the materials decompose. organic fertilizers supply the full range of micro nutrients and aid in the maintenance of good soil texture

inorganic fertilizers

useful because farmers can target specific soil needs and add only the necessary chemicals. release nutrients immediately which can also lead to depletion of micro nutrients and soil compaction.

causes of erosion

soils that contain more organic material and allow water to infiltrate and drain through tend to have less erosion and agricultural practices leading to loss or organic content, compaction, and reduced plant coverage tend to increase problems with erosion

effects of erosion

leads to loss of topsoil and reduced arability

no till

soil is disturbed little or not at all to reduce soil erosion by using a machine to insert the seed into the soil

terracing

used when farming on sloped land. cutting steps or planting on a slope of land reduces the rate of water runoff

soil coverage

when harvesting, cut plant material are left to decay on the field. in seasons when a field is not planted, plant-cover crops, like native grasses or nitrogen fixing legumes are planted to hold soil in place.

special irrigation methods

methods such as drip irrigation reduce pooling or runoff

less intensive land use

crops are rotated from one field to another, and a few unplanted fields are left to allow recovery of nutrients and organic matter.

composition of soil

45% mineral, 25% air, 25% water, 5% organic matter

gravel

coarse particles

sand

water flows through too quickly for most crops. good for crops and plant requiring low amounts of water

loam

about equal mixtures of sand, silt, clay and humus. rich in nutrients. holds water but does not become water logged. particle size can vary.

silt

sedimentary material consisting of very fine particles between the size of sand and clay. easily transported by water.

clay

very fine particles. compacts easily. forms large, dense clumps when wet. low permeability to water; therefore, upper layers become waterlogged

humus

black or dark brown organic material that remains after much decomposition has occured on

contour planting

crops are planted in rows that are perpendicular to hills to form water breaks that prevent soil erosion

strip cropping

a special type of contour plowing which produces alternating strips of different crops

shelterbelts

a row of trees are planted as a windbreak to reduce soil erosion of agricultural lands

nutrient

element necessary for growth and reproduction

deficiency

plant condition where an essential nutrient is not sufficiently available

primary nutrients

nitrogen, phosphorous, potassium

secondary nutrients

calcium, magnesium, sulfur

nitrogen nutrient

gives plants green coloring

phosphorous nutrient

stimulates plant growth

potassium nutrient

stiffens stalks and straws

calcium nutrient

gives plant strength

promotes root and leaf growth

magnesium nutrient

photosynthesis

sulfur nutrient

seed production

micronutrients

iron

manganese

boron

molybdenum

copper

zinc

chlorine

construction erosion

construction causes soil to be overturned, which makes it susceptible to runoff

erosion control fence

used for construction erosion with a silt fence fabric that prevents soil from passing through

riparian habitat

vegetation grows along the river in order to slow down and prevent runoff from entering the river

pest

any organism that has a negative effect on human health or economics

philosophies of pest control

chemical technology, ecological pest management

chemical technology

Use of chemicals to kill large numbers of the pest

Short-term protection

Environmental and health consequences

ecological pest management

Control based on pest life cycle and ecology

Control agent may be an organism or chemical

Specific to pest and/or manipulate a part of the ecosystem

Emphasizes protection from pest

Integrated Pest Management

controlling pest populations using all suitable methods - chemical and ecological for long term management an minimal enviro impact

insecticides

kills insects

herbicides

kills plants

rodenticides

kills rodents

fungicides

kills mildews and rusts

acaracides

kills ticks and mites

bacteriocide

kills bacteria such as antibiotic

first gen pesticides (inorganic)

First attempt at chemical technology

Included heavy metals such as arsenic, copper and lead.

Toxic to humans and agricultural plants.

Pests developed resistance

second gen pesticides

Organic chemical (organochlorines).

Used after WWII (presently in developing countries)

Synthesis begins with petroleum ("oil")

Mechanism of actions often unknown.

Bioaccumulation & Biomagnification.

Toxic to animals (humans) and agricultural plants.

Pests developed resistance.

third gen pesticides

Organophosphates and carbamates

Less persistent in environment (good deal)

Acutely potent nerve toxins

More lethal in low dose than organochlorines

fourth gen pesticides

Endocrine disruptors (hormonal chaos)

Target a critical life cycle stage of insects.

Not direct killers per say.

Reduce reproduction (fertility) of population.

Problems with chemical technology problems

Development of resistance by pests

Resurgences (pest comes back stronger)

Secondary pest outbreaks (different pest)

Adverse human health effects

Adverse environmental health effects

resurgences

after "eliminating" a pest, its population rebounds in even higher numbers than previous levels

secondary outbreaks

outbreaks of species' populations that were not previously at pest levels

biomagnification

the concentration of toxins in an organism as a result of its ingesting other plants or animals in which the toxins are more widely disbursed

natural pest control

Cultural control

Control by natural enemies

Genetic control

Natural chemical control

genetic control

Plants or animals are bred to be resistant to the attack of pests

practices for integrated pest management

inspecting crops and monitoring crops for damage

using mechanical trapping devices

natural predators (e.g., insects that eat other insects)

insect growth regulators

mating disruption substances (pheromones)

if necessary, chemical pesticides

water makes up what percentage of the soil?

25%

air makes up what percentage of the soil?

25%

mineral nutrients make up what percentage of the soil?

45%

organic material makes up what percentage of the soil?

5%

what is a trend seen in agricultural industries today?

increase in the periodic use of legumes, such as soybeans, to supply the soil with natural nitrogen

what is soil made of?

water, air, minerals, organic material

sand particle size

0.05-2mm

silt particle size

0.002-.05mm

clay particle size

less than .002mm

what percentage of each soil particle do you want?

33% of each (sand, silt, clay)

gmo

genetically modified organism

gmo pros

may require less water and fertilizer, higher crop yields, more resistant to disease, drought, frost, and insects

gmo cons

unknown ecological effects, less biodiversity, may pose allergen risk

DDT

insecticide that is extremely effective at killing mosquitoes and was widely used starting in the 1940s

Rachel Carson

wrote Silent Spring, which detailed the harmful effects of DDT on the natural environment, especially birds

conventional agriculture methods

system characterized by mechanization, monocultures, and the use of synthetic inputs such as chemical fertilizers and pesticides, with an emphasis on maximizing productivity and profitabilty

organic agriculture methods

relies on crop rotation, green manure, compost, biological pest control, and mechanical cultivation to maintain soil productivity and control pests

malnutrition

an unbalanced diet that does not contain the right quantity and quality of nutrients necessary for adequate nutrition

under-nutrition

caloric intake is below the minimum dietary energy recquirement

ways to prevent soil erosion

no till, contour planting, terracing, crop rotation

crop rotation

planting a field with different crops from year to year to reduce soil nutrient depletion, as the depletion can cause erosion

ribbon test

soil analysis practice where soil is squeezed to see and then examined to see how it stays together to determine its sand/silt/clay