Lesson 3.2: Biotic and Abiotic Factors Affecting Crop Production

Biotic factors

Describes living factors in the environment.

- Pathogens

- Insect Pests and Mites

- Vertebrate Pests

- Weeds

- Human factor

The 5 biotic factors that affect crop production

Abiotic factors

Nonliving components of environment.

Pathogens

Organisms, mostly microscopic, that cause diseases or abnormalities in plants

- fungi

- bacteria

- viruses

- mycoplasma

- nematodes

Classifications of pathogens

Weeds

Undesirable plants that often crowd out crop plants or native plant species

- Broadleaves

- Grasses

- Sedges

3 classifications of weeds

- Light

- Water

- Temperature

- Relative Humidity

- Wind

5 abiotic factors

Light Intensity

The level of light received on a plant surface.

Heliophytes

Plants that grow best in full sunlight

Light duration (Photoperiodism)

A plant's response to seasonal changes in length of night and day. This affects flowering and seed dormancy.

Short-day plants

Plants that flower when nights are longer than a critical length (10-14 hrs)

Long-day plants

Plants that bloom only when the period of day is longer than a specific period of darkness (darkness period: 8-10 hrs)

Day-neutral plants

Plants that bear flowers regardless of the length pf dark period.

Blue and Red

Plants mostly use light in the _____ and _____ wavelengths.

Chlorophyll

Green pigment in plants that absorbs light energy used to carry out photosynthesis

420-460, 620-680

Chlorophyll has peak absorptions in the _____-_____ and _____-_____ nanometer wavelengths.

Water

Basic requirement in crop production. 1% is used in photosynthesis and the rest is used for transpiration and cell hydration.

Drought

A long period of low precipitation

Flooding

A heavy flow of water which is greater than the normal flow and goes over the stream's normal channel.

1. Floating

2. Submerged

3. Emergent

Classifications of Hydrophytes (3)

do not have

Submerged hydrophytes (have, do not have) stomata.

Mesophytes

Plants requiring only a moderate amount of water

- Cryophillous

- Non-cryophillous

Classifications of plants based on the temperature requirement for floral induction.

higher

higher RH = _______ shelf life of crops

lower

Wind causes (higher, lower) photosynthetic rate.

Soil

The loose, weathered material on Earth's surface in which plants can grow.

False

(True or False) All fertile soils are productive.

Soil Fertility

Soil's ability to hold nutrients and to supply nutrients to a plant in available and balanced forms.

Soil productivity

A measure of the soil's ability to produce a particular crop or sequence of crops under a specific management system.

Soil Depth

Refers to the distance from the soil surface to the lower layers of a soil through which roots can grow

1. Organic matter content

2. Soil pH

3. Cation exchange capacity

4. Base Saturation

Chemical properties of soil affecting crop production (4)

Organic matter content

The amount and nature of decomposed or partially decomposed organic tissue within soil

Cation Exchange Capacity

The total amount of exchangeable cations that can be held by the soil.

higher

higher cation exchange capacity = _________ fertility

Base saturation (BS)

_______________ represents the percentage of CEC occupied by bases (Ca2+, Mg2+, K+ , and Na+)

Volatilization

Nitrogen vaporizes into the atmosphere in the form of ammonia. Common after fertilizer application.

Insect pests and mites

are invertebrate animals that can be classified into chewing or sucking pests and may attack either on the leaves, stems, roots, flowers and fruits

Vertebrate pests

Include rodents, birds, bats, wild and domestic animals and sometimes even man.

1. Extensive root system

2. Prolific

3. Years of weed seed dormancy

4. Few insect pests

4 "weediness" traits

Human Factor

Capability of the farmer or manager to have the quality traits enhanced by skills in crop production.

1. Passion in farming

2. Innovative

3. Persistent

4. Business-oriented

Important traits that a farm manager must possess (4)

Sciophytes

Plants that grow best in shade

1. Time of day

2. Season

Factors that influence light intensity

Non-photoperiodic plants

Other name for day-neutral plants

Light Quality

The wavelength or color of light absorbed and used by the plant.

Green

The color of wavelengths that most plants reflect.

- Drought

- Flooding or water logging

Causes of moisture stress (2)

1. Hydrophytes

2. Mesophytes

3. Xerophytes

Classifications of plants according to water requirements (3)

Hydrophytes

Plants with adaptations that enable them to survive in very wet habitats or submerged or at the surface of water.

Floating Hydrophytes

Plants that thrive by floating on water(e.g. water lily, azolla, water hyacinth)

Submerged Hydrophytes

Plants with shoots under water and roots anchored at the bottom of a body of water (e.g. sea grass, water ferns)

Emergent hydrophytes

Plants with shoots extended well above the water with roots anchored in soil (e.g. lowland rice, gabi).

Xerophytes

Plants with adaptations that enable them to survive in dry habitats or habitats where water is in short supply

- Tropical

- Temperate

Classifications of crops based on their optimum temperature for growth

Tropical plants

Plants that grow in a hot, humid environment (above 10 degrees C). Examples are corn, soybean, cotton, sugarcane.

Tropical plants

Plants originate at or near the equator and between the Tropics of Capricorn and Cancer (23° north and south of the equator)

Temperate plants

Also called cool-season crops. Examples include alfafa, wheat, barley.

Cryophillous plants

Plants that require low temperature for floral induction.

Non-cryophillous plants

Plants that require warm temperatures for floral induction (e.g. tropical crops).

Relative humidity (%RH)

Amount of water vapor in the atmosphere expressed as percentage.

100%

Percentage of RH (Relative Humidity) in which the atmosphere is saturated with water vapor that it can no longer absorb additional moisture.

higher

higher RH = _______ pollen germination rate

lower

Higher temperature = __________ RH

Wind

An important factor in growth of crops described as the movement of air caused by differences in air pressure

Edaphic

A term which means relating to soil

Soil fertility and productivity

Edaphic factors that affect crop production

- Soil texture

- Soil structure

- Soil depth

Physical properties of soil affecting crop production.

Soil texture

Refers to the size of individual soil particles and is determined by the proportions of particle sizes in the soil

Soil structure

How the particles that make up a soil are organized and clumped together to form compound particles.

Soil pH

measure of the acidity or alkalinity of a soil

acidic

Soils are considered strongly __________ at pH 3.0 - 4.0

4.0 - 5.0

Soils are moderately acidic at pH ____-_____.

slightly

Soils are (slightly, moderately, strongly) acidic at pH 6.0 - 6.9.

7.0

neutral pH level

7.1 - 7.5

Soils are slightly alkaline at pH _____-_____.

alkaline

Soils are (alkaline, acidic) at pH 7.6 - 8.0.

8.0

pH level ______ indicates strong alkalinity.

30

Cation exchange capacity of clay is about ____ m.e. per 100 grams.

9

Cation exchange capacity for 100 g of sand is ____ m.e.

200

Cation exchange capacity for humus soil is about ______ m.e. per 100 g.

Mycorrhiza

Symbiotic association of plant roots and fungi

Rhizobium

A symbiotic bacterium that lives in the nodules on roots of specific legumes and that incorporates nitrogen gas from the air into a form of nitrogen the plant requires

Thiobacillus

Recycles sulfur in the environment into sulfate

1. Crop removal

2. Soil erosion

3. Nutrient fixation

4. Nutrient Leaching

5. Volatilization

6. Denitrification

6 causes of soil degradation

Crop removal

Refers to the continuous mining of nutrients by the plants every cropping season

Soil Erosion

Wearing away of surface soil by water and wind

Nutrient Fixation

The process of breaking down nutrients into other compounds that are less soluble.

Nutrient leaching

The loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Water moves down to water table by water percolation.

Denitrification

Conversion of nitrates into nitrogen gas (nitric oxide, nitrous oxide, dinitrogen gas)