“…the rain and the snow come down from heaven, and do not return there without watering the earth and making it bear and sprout, and furnishing seed to the sower and bread to the eater…” —Isaiah 55: 10
Nutrients are dissolved in water H2O
Properties of Water
1. Hydraulic (does not compress so pressure is possible, turgor support)
2. Wonderful Solvent (widest range of possible solutes, transpiration, translocation)
3. Reactant or Product of Reactions (photosynthesis & respiration)
4. High Specific Heat (much heat gives little change in temperature, heat buffer)
5. High Heat of Fusion (evaporating liquid water takes energy away, evaporative cooling)
Where do plants get their water?
1. Precipitation = Rain, snow, sleet, hail
2. Run-off = Streams, rivers
3. Water table = Ponds, lakes
4. Soil water = most important on this list from a plant point of view!
5. Aquifers and springs
Horizon A = leached topsoil
Horizon B = accumulated subsoil
Erosion fits in here somewhere!
|Mud||-------->||Field Capacity||-------->||Wilting Point||-------->||Dry!|
(used by plants)
Clay = high water capacity, high hygroscopic
Sand = low water capacity, low hygroscopic
Irrigation = keeping soil friable!
1. Natural-hope for 4" of rain each month...weather reportHOW MUCH, HOW FREQUENTLY?
2. Sprinkler-washes off mites, insects, dust+kills "eggs" of many "bugs"3. Surface-reduces fungi but raises salts to upper soil
+may apply fertilizer/insecticide at same time
-WATER DROPS ON LEAVES = DEAD SPOTS
-HUMIDITY + = FUNGI +
Moveable vs StationaryFurrow irrigation = between rows in crops4. Trickle Irrigation-as in our greenhouse
Flood irrigation = perimeter furrows, ground level, no runoff-laser guided earth graders-less water/fertilizer/pesticide used5. Wick Irrigation -pots on wet mats (overload) or wicks
-no pulse of these
To keep it friable (between field cap. and wilting point)When in day?
Not like people: 3-squares with 8 glasses
Green Thumb? Dirty Finger!
House Plants:Soak to Field Capacity
let dry to wilting point
soak again, etc.
Early AM so it evaporates before sun hot
NEVER evening, warm but cooling leads to FUNGI
*Too dry? Hydrophobic, water runs off = flash floods
*Too wet? Air excluded from space in soil = anaerobic so plants die!
What to do?
Pots with holes
Perlite in mix
Less Frequent but DEEPER irrigation beneficial
Preserve Water by:
Mulch = plastic, stone, paper, leaves, straw (-evap)
Weeding = controlled spacing (-competition)
Terrarium for plant storage for vacations (Plastic bag)
Symptoms of watering trouble:
Excess moisture:Root Death because of no air in soilDeficient moisture:
Fungi Thive (Damping Off of seedlings)
Cracking (Cabbage, Fruits, Roots)
If roots die, plants WILT!Growth inhibition - Abscisic Acid Produced
Abscission of Leaves -Ethylene Produced
BROWN FINGERS not GREEN THUMB!
Most people kill by overwatering!
Osmosis explains this:
Movement of Water from purer water toward saltier water
Isotonic = No net change (no growth possible)
Hypertonic = Water leaves, Turgor lost, Wilts
Celery wilted in refrigerator...what to do?
Hydroponics = water culture without soil
nutrients, aeration, support are major problems!
1/10 strength + Perlite
1. Photosynthesis (CO2 + H2O --- light ---> CH2O + O2)
2. Prevent Wilting (permit growth)
3. Disolve Minerals in Soil
4. Transpiration - soil>root>stem>leaf>atmosphere in XYLEM
5. Translocation - leaf>stem>flower>fruit>apical bud
6. Evaporative Cooling - leaf>atmosphere
Factors Affecting How Much Water is Needed
1. Stage of GrowthSeedling = low but EVEN2. Environment
Reproduction = high
Dormant = lowTemperature: High = more3. Soil
Light: High = more
Humidity: High = less
Wind: High = moreClay = less4. Plant Characteristics
Sand = moreSucculent = less
Waxy = less
Hairy = less
Fine/thin leaves = more
Deep rooted = less
This page © Ross E. Koning 1994.
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