Chapter 4: Water Management

Question 1

How much of the absorbed water may be transpired into the air by a tree?

Answer 1

As much as 95% (a large tree can absorb hundreds of gallons of water in a day)

Question 2

available water

Answer 2

water remaining in the soil after gravitational water has drained and before the permanent wilting point has been reached; capillary water while hygroscopic water is unavailable for water

Question 3

What causes wilting?

Answer 3

When the available water in the soil decreases to a point at which a plant cannot take up enough to replace the water lost through transpiration.

Question 4

water-holding capacity

Answer 4

ability of a soil to hold moisture; total amount of water held by a soil after drainage occurs (when it is at field capacity); varies with soil texture (sand, silt, and clay content)

Question 5

What types of soils have a greater water-holding capacity?

Answer 5

Fine-textured soil (clays) have a greater water-holding capacity than coarse-textured soils (sands); that is why sandy soils need to be irrigated for shorter periods, but more frequently than clay soils; water needs to be applied slowly and over extended periods of time if infiltration rate is low

Question 6

infiltration

Answer 6

downward entry of water into the soil; or entry of fine particles into drainage or aeration systems, can lead to system clogging and failure; or downward entry of materials from one soil or fill layer to another, as when a gravel road surface mixes with underlying soil

Question 7

percolation

Answer 7

movement of water through/within the soil

Question 8

infiltration rates

Answer 8

speed at which water penetrates the soil

Question 9

percolation rates

Answer 9

speed at which water moves through the soil

Question 10

What influences percolation and infiltration rates?

Answer 10

type of soil (clay soils usually have much lower infiltration rates and percolation rates than sandy soils), soil structure (soil with poor structure, such as compacted soils, have lower infiltration and percolation rates), and bulk density

Question 11

Adaptations to survive in arid regions?

Answer 11

develop extensive root systems (deep, spreading roots to make use of soil moisture over a large volume and tap into water sources found deep underground), shed leaves, become virtually dormant and dry completely, have small leaves, waxy cuticle, tiny leaf hairs, and sunken stomata

Question 12

turgid

Answer 12

fully hydrated to a normal state of distension

Question 13

When do drought stress symptoms develop?

Answer 13

When water loss from the foliage exceeds the rate at which it can be replaced via uptake by the root system.

Question 14

desiccation

Answer 14

severe drying out; dehydration

Question 15

Generally, what is better? Frequent shallow watering or infrequent deep soakings?

Answer 15

Infrequent deep soakings because it encourages the development of a deeper root system and more drought-tolerant trees; soils high in clay can be improved when allowed to dry out between irrigations because the natural shrinking and swelling of the soil can improve the soil structure and water infiltration rate; frequent shallow watering encourages surface rooting and compacts the soil surface, reducing the infiltration rate; however mulch and soil high in organic matter should not be allowed to completely dry out because they resist rewetting

Question 16

drip irrigation

Answer 16

method of minimizing evaporation and runoff by applying small amounts of water through small emitters; apply water slowly to localized areas of the tree root zone, reducing runoff, erosion, and water loss by evaporation

Question 17

basin irrigation

Answer 17

distributes water uniformly to the limited root zone of newly planted trees

Question 18

high pressure water injection

Answer 18

delivers water deep to the root zone but may bypass absorbing roots at the soil surface

Question 19

minimum irrigation

Answer 19

practice of minimizing irrigation needs through the use of drought-tolerant plants and watering only when necessary; only watering enough needed to maintain tree health, growth, and appearance (canopy density and leaf color) using efficient application methods

Question 20

xeriscaping

Answer 20

drought-tolerant landscaping; use of plant materials (usually native plants) and practices that minimize landscaping water use; term for environmentally friendly form of landscaping in dry climates that lack seasonal rainfall or readily available sources of fresh water; copyrighted by the Denver (CO) Water Department in 1981.

Question 21

hydrozone

Answer 21

group of plants in a landscape with similar water requirements; employs the use of highly efficient irrigation methods and plants with low water requirements

Question 22

water budgets

Answer 22

calculation, based on precipitation and environmental factors, that establishes the minimum irrigation needed to maintain plant health; considers evapotranspiration, water-holding capacity, application rate, infiltration rate, and irrigation system efficiency

Question 23

evapotranspiration

Answer 23

ET; loss of water by evaporation from the soil surface and transpiration by plants; plant and soil water loss

Question 24

How to measure soil wetness or dryness?

Answer 24

soil probes, tensiometers, and electronic moisture sensors

Question 25

tensiometers

Answer 25

instrument used to measure soil moisture

Question 26

What information is needed to develop an appropriate watering schedule?

Answer 26

evapotranspiration, water-holding capacity, irrigation efficiency, infiltration, and application rates

Question 27

salinity

Answer 27

amount or percentage of salt in the soil

Question 28

What kind of soil is more suitable for irrigation with recycled water?

Answer 28

sandy soils, because good drainage is essential

Question 29

Benefits of mulching?

Answer 29

improve soil structure and infiltration, limit weed competition (which further reduces evapotranspiration and soil water loss), and reduce soil compaction and erosion; organic mulches also increase soil organic matter as they decompose, which enhances soil biology, fertility, and structure

Question 30

antitranspirants

Answer 30

substance applied to the foliage of plants to reduce water loss (transpiration); chemical sprayed on plants that form a thin, impermeable coating on the foliage or by triggering stomatal closure

Question 31

phytotoxic

Answer 31

term to describe a compound that is poisonous to plants

Question 32

Short-term consequences for tree species that are not compatible with flooding?

Answer 32

lack of oxygen in the soil suffocates roots, changes the chemical composition of essential elements, fermentation in root cells and build up of toxic compounds; photosynthesis may stop and transpiration decline

Question 33

Long-term consequences for tree species that survive flooding?

Answer 33

predisposition to stress factors, including drought and secondary pests (such as root disease, cankers, and borers), toppling due to soil failure/root loss, higher incidence of root and collar rot, long term stress

Question 34

rain garden

Answer 34

landscape feature specifically designed to collect and hold storm water runoff; capture water from parking lots, downspouts, or sloping lawns; plants incorporated must be tolerant of periodic flooding and dry periods