Chapter 7 Horticulture (UNIT 3)

Methods of Reducing Transpiration

Antitranspirant, Misting House plants

irrigation

hand watering, or computer automated controlled

surface irrigation

furrow and flood, or flood the entire soil surface. Not super efficient , salt can build up in the soil

Sprinkler irrigation

most common, wets foliage (could cause bacteria) , but high install cost

problems with sprinkler irrigation

large evaporative loss, high labor cost, expensive installation, power costs, salt buildup, maintenance costs, pollution

low volume irrigation

trickle or drip irrigation, water delivered right to root zone

disadvantages of low volume irrigation

clogging of emitters, damage from rodents, possibly high installation cost, salt buildup still can occur

Properties of water

High specific heat, substrate for chemical processes, universal solvent, turgor, polar molecule, transpiration

turgor

stomates require water to open, cells must have water to enlarge, without water, plants cannot grow

Polar molecule

hydrogen bonding creates cohesion, surface tension helps water move through the plant (adhesion, cohesion, capillary action)

Transpiration

how plants pull up water through themselves: water evaporates from stomates, evaporation creates “pull”, water moves from soil to stem and leaves and out through stomates

Evapotranspiration

total water loss from plant and soil surface

Less humidity with transpiration and evapotranspiration

more T and ET

more humidity with transpiration and evapotranspiration

less T and ET

Permanent wilting point (PWP)

plant wilts so much it can’t recover

incipient wilting

temporary loss of turgor, usually happens when water absorption cannot keep up with transpiration

root tips

most water uptake, high surface area, little to no resistance to movement, the water is filtered by the plant later

membranes

“filter” water can feely pass, many other things cannot, active transport can move nutrients

Temperature control types

misting or syringing, fan and pad cooling, frost protection, heat capacity of water

Misting or Syringing 

cools plants by direct contact and evaporation, reduces plant stress, often done on high value turf

fan and pad cooling

evaporative cooling for greenhouses, must be planned/sized correctly 

frost protection

irrigation can prevent damage from a radiation frost, ice freezing gives heat to plant tissues, irrigation must continue until all ice melts

heat capacity of water (site selection)

large bodies of water moderate temperatures

antitranspirant

compounds applied to reduce water loss, not widely used, may reduce transplant 😮 and winter burn

types of irrigation

surface irrigation, sprinkler irrigation, low volume irrigation

Water Deficiency

when stomates close, photosynthesis stops

signs of severe water deficiency/over watering

• Wilting

• Drying of leaf tips

• Yellowing of older leaves

• Death of leavers

• Leaf, flower and fruit abscission

• DEATH

gravimetric

weigh moist soil, dry it, weigh it again

gypsum blocks/Electrical conductivity (EC)

porous block with wire embedded, more water allows more elctrical current

Neutron Probes

Works, but very expensive and radioactive

Tensiometers

Porous cup filled up with water, tube connected to vacuum gauge, comonly used and fairly accurate

Time-domain reflectometry (TDR)

More accurate than gypsum blocks, but more expensive, Requires a datalogger, Becoming most common

Et and radiation measurements

Calculate how much water has left the soil based on weather data

xeriscaping

Plan to reduce landscape water consumption, Often necessary in arid/semi-arid locations

Principles of xeriscaping

• Design for efficient water use

• Select drought-tolerant plants or plants with low water requirement

• Use efficient irrigation equipment

• Relatively small lawn

• Use mulches

• Harvest water (bioswales)

• Use appropriate maintenance practices

ZONE I

the oasis zone, Near house, Has potted plants, flower beds, gardens and turf, May have water feature

ZONE II

Transitional zone, Once established, these plants only need occasional watering (often drip irrigation), Berms and swales direct water to oasis zone

ZONE III

Arid zone, Once established, little or no irrigation, Often native plants