Environmental Factors Affecting Crop Production

- Abiotic

- Biotic

Environmental Factors

Abiotic

Climatic (climate, weather)

Abiotic

Edaphic/Soil factors

Abiotic

Climatic stresses (drought, salinity, acidity, lahar, La Niña

Abiotic

El Niño, greenhouse effect ,global warming

Biotic

Beneficial organisms (pollinators, decomposers, natural

enemies)

Biotic

Pests (arthropods, pathogens, weeds, vertebrate pests and Allelopathy

Weather

The atmospheric conditions in any area at any time, with regards to sun, cloud, temperature,

wind and rain, etc.(deviation from pattern)

Climate

The long-term weather pattern of an

area, including temperature, precipitation, and

wind or weather averaged over long period of

time (seasonal pattern)

Weather

It is the set of all extant phenomena in a

given atmosphere at a given time .

Weather

The term usually

refers to the activity of these phenomena over short periods (hours or days),

Climate

It refers to the

average atmospheric conditions over longer

periods of time

- Sunshine

- Temperature

- Wind movement

- Precipitation

- Relative Humidity

- Mist

- Fog

Climate-interplay of what

1. Solar radiation

2. Temperature

3. Wind movement

4. Precipitation

5. Relative Humidity

6. Mist and Fog

Climatic Factors

Solar radiation

Most important in

agriculture

Solar radiation

Rate at which a surface absorbs radiation (Watt/m2)

- Intensity

- Duration or daylength

- Wavelength

Aspects of Irradiance

Photoenergetic

Direct effect on Photosynthesis

Photocybernetic effect

Effect on development of plants

Photosynthesis

Red and blue

Photoperiodism

Far red and red

Solar constant

Amount of solar radiation that reaches the outer limits of the earth's atmosphere

Photosynthetically active radiation (PAR)

Used by plants to fix CO2 during Photosynthesis

- Heliophytes

- Sciophytes

Classification based on light intensity requirements

Sciophytes

Shade loving

Heliophytes

Sun-loving

Albedo

It reflects radiation/total incident light.

Albedo

Reflects how fast and what degree surface is

heated

Daylength

It varies with latitude, different between day and night and

increases as latitude from equator increases

Flowering and germination

These are affected by daylength

Photoperiodism

Plant response as conditioned by daylength

Photoblastism

Germination response with respect to daylength

1. short day plants

2. long day plants

3. day neutral

Classification of plants based on daylength

Temperature

Important in every chemical, physiological and biochemical processes in plants

- Cool season

- Warm season

- Tropical

- Sub-tropical

Classification of crops based on temperature requirement

Degree Day

Measurement of departure of the

daily mean temperature above the minimum threshold temperature for the plant (base temp)

Growing degree days

Maturity determination

Growing degree days

Predictive tool on suitability of crops to a

particular environment

Growing degree days

Risk prediction associated with crops in specific area

Growing degree days

Determination sowing date and crop growth

and productivity

- High temperature

- Slow growth rate

- Growth ceases with tissue desiccation

Effects of temperature

Temperature and Photosynthesis

Protein denaturation

Temperature and Photosynthesis

Loss of membrane integrity

Temperature and Photosynthesis

Photoinhibition

Temperature and Photosynthesis

Ion imbalance

Relative Humidity

Direct effects on plant growth

Relative Humidity

Disease and pest incidence

- Perishables

- Durables

Postharvest handling

Perishables

Wilting (transpirational loss)

Durables

Difficulty in drying

Durables

Susceptibility to molds and aflatoxin

- Lodging

- Transpiration

- Plant form

- Sterility

- Reduced CO2 levels

- Disease spore dispersal

Effects of wind on plant processes

Precipitation/Rainfall

Water in some form (Rain , drizzle, fog, mist, snow, hail) falling out of the air, and settling on the surface of the earth

Precipiration

It is a condensation in the atmosphere.

Dew

It is condensation at the surface and thus is not a form of precipitation

- Reactant

- Medium of transport

- Temperature regulation

Roles of water in plant growth

- Xerophytes

- Hydrophytes

- Mesophytes

Classification of water based on need for moisture

Xerophytes

Desert plants

Hydrophytes

Aquatic plants

Mesophytes

Land plants

Air circulation

Affects seasonal distribution of precipitation

Topography

Affects amount and distribution of rainfall

Moisture

Influences the phytogeographic distribution of plants

•High RH

•Sufficient low temperature

•Condensation nuclei

•Sufficiently low pressure

Rain formation requires what

Infrared Radiation

The electromagnetic radiation with wavelengths longer

than visible light and shorter than microwaves.

Infrared Radiation

It is felt as heat.

Absorption of Infrared Radiation by carbon dioxide

It happens because the carbon-oxygen bonds can stretch or flex at a frequency that allows them to absorb an infrared photon

Emission of Infrared Radiation by carbon dioxide

It is the oscillating molecule can then re-emit the infrared

energy as a photon travelling in a random direction

Emission of Infrared Radiation by carbon dioxide

This will happen repeatedly over time as the particular molecule absorbs and then re-emits IR photons

Greenhouse Gases

These are efficient in absorbing IR light

- CO2 - Carbon Dioxide

- CH4 - methane

- N2O - nitrous oxide

- Chloroflourocarbons (CFC)

The most important greenhouse gases are:

25

percent

Levels of greenhouse gases have increased by about __ _______ since large-scale industrialization began around 150 years ago

Climate Change

Rising concentrations of greenhouse gases produce an increase in the average surface temperature of the Earth over time

Carbon Cycle

The movement ("flux") of carbon between the atmosphere

and the land and oceans -dominated by natural processes,

eg PS.

Carbon Cycle

It is the natural processes can absorb some of the net 6.2 billion metric tons (7.2 billion metric tons less 1 billion metric tons

of sinks) of anthropogenic carbon dioxide emissions

produced each year (measured in carbon equivalent terms

Carbon Cycle

It is the positive imbalance between greenhouse gas

emissions and absorption resulting in the continuing increase in atmospheric concentrations of greenhouse gases

- Carbon monoxide and carbon dioxide

- Particles

- Sulfur dioxide

- Flourides

- Phytochemical smog

Air Pollutants

Good Ozone

Ozone occurs naturally in the Earth's upper atmosphere - 6 to 30 miles above the Earth's surface

Good Ozone

Where it forms a protective layer that shields us from the sun's harmful

ultraviolet rays

Bad Ozone

Ozone at ground level is a harmful air pollutant.

Bad Ozone

In the Earth's lower atmosphere, near ground level, ozone is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other

sources react chemically in the presence of sunlight

- Koppen's classification

- Thornthwaite's classification

- Modified Corona classification

Climate Classification

Koppen's classification

Based on precipitation and temperature

Koppen's classification

PHL is classified as tropical and rainy

Thornthwaite's classification

Based on the difference between the mean

Modified Corona classification

Based on precipitation

Modified Corona classification

PHL has four basic types of

Type 1

Two pronounced seasons

Type 2

No dry season

Type 1

Dry from Nov to Apr (less than 50mm rain/mo)

Type 2

Very pronounced maximum rains during Nov to Jan

Type 2

No single dry month in regions of this type

Type 3

Seasons not very pronounced

Type 3

Intermediate of Types 1&2, resembles more of type 1

Type 3

Dry season: 1-3 months

Type 4

Intermediate of Types 1&2, resembles more of type 2

Type 4

Rainfall more or less evenly distributed