Comments:
Do not use Clorox on plug trays: it will absorb chlorine and slowly release it into the soil, which will kill the plant.
Plug and Transplant Production is a good book.
Water
(continued)
Management for high salts
1. Provide good drainage
2. Use an appropriate media
3. Never allow medium to dry out (but this tends to cause algae buildup)
4. Monitor salt levels
5. Leach periodically
TDS = total dissolved (salts/solids)
Sum of all types of salts present (parts per million)
|
Excellent |
<175 ppm |
|
Good |
175-525 |
|
Ok |
525-1400 |
|
Doubtful |
1400-2100 |
|
Unsuitable |
>2100 ppm |
Dissolved salts are measured in parts per million, which is the same as milligrams per liter
Common salts: Ca, K, CO3, Fe, Mg, SO4, fluoride, Na, NO3, HCO3, chloride
Sodium (Na)
· >100 ppm is toxic
· USDA rating for Na:
o Excellent < 20% of total salts
o Good 20-40 %
o Ok 40-60%
o Doubtful 60-80%
o Unsuitable > 80% of total salts
Iron
· Ferrous (Fe2+) form in water
· When mixed with oxygen
o Forms a precipitate
· Fe3+ = ferric
· This is a red/brown color
· Insoluble in water, and forms a rusty precipitate
· Avoid over watering
· Use de-ionizer
· Oxidize and filter water
· Modify watering techniques so rust will not stain leaves
o Iron staining will not damage plant (as long as it doesn't interfere with photosynthesis), but will make the plants look odd (ugly)
Boron
Tested only when soils in the area are high to begin with
· USDA rating
o Excellent <0.33 ppm
o Good 0.33-0.67
o Ok 0.67-1.00
o Doubtful 1.00-1.25
o Unsuitable >1.25
· Actually it is more likely to be too little
· Affects seed formation
· Low in Delta, Alaska: need to fertilize with 1 pound per acre
· Low in the western have of Washington state
o Need to put on orchards
Levels of mineral nutrients
· Water minerals can reduce your fertilizer needs
o If you need 100 ppm of potassium:
· Water has 10 ppm
· Add only 90 ppm
· Saves money on potassium fertilizer
o But make sure it is in a form plants can use!
o See handout #1
Water Hardness--Ca + Mg in water
|
Hardness (parts per million - ppm) |
Degree of hardness |
|
0-50 |
Very soft |
|
50-100 |
Soft |
|
100-200 |
Moderately soft |
|
200-300 |
Hard |
|
300+ |
Very hard |
· Hard water is not harmful
· Ca + Mg are fertilizers
· Gradual increase in medium pH
Water Softeners
· Ca and Mg are replaced with Na ions
· Na can rapidly build up in soils yielding
o Increase in pH
o Increase in TSS (total soluble salts)
o Increased EC (electrical conductivity)
Chlorine (Chlorinated water)
· Not normally a problem
· 0.4 ppm can cause problems in hydroponics
· Up to 0.7 ppm in some treated water
o Most of the chlorine escapes as gas
Fluorine (natural or injected)
· Usually 0.5 to 1.0 ppm
· Some plants have problems with it
o Family Liliaceae
§ spider plant
§ dracena
§ spathyphyllum
§ yucca
o Family Marantaceae
§ Prayer plant
§ Parlor palm
Types of watering
systems
1. Overheat watering systems
· Not common with floriculture crops because it wets the foliage
· Examples
o Propagation benches
o Large ground beds of nursery stock outdoors
o Tree nurseries
· Four types
o Stationary or fixed nozzles
§ No moving parts
§ Propagation mist nozzles
o Whirling head nozzles
§ Whole head whirls around
§ Hard to control
§ Large drop size
o Rotating impact nozzle
§ Commonly used for watering of nursery stock outside
o Boom-type sprayers
§ Two types:
· Stationary tank
· Small tractor-like moveable wagon
· Overhead irrigation
o Applies a lot of water--sometimes wasteful
o May have problems with uneven spray
§ Calibrate with cans in spray area
§ Turn on system 15-30 minutes
§ Measure output in cans
o Disease problems due to water dripping from pipes and nozzles
o Nozzle spacing needed is 65% of diameter of spray
§ If spray pattern were 20 feet, nozzle spacing would need to be 13 feet
o May have problems with nozzles plugging up
§ Calcium carbonate residues
· Clean with phosphoric acid OR
· Keep running all the time OR
· Use coffee pot cleaner OR
· Vinegar will sometimes work
2. Surface watering
· Tend to go in and out of style
o Water conservation
o Pollution prevention
· Bench surface watering systems
o Perimeter - rigid plastic pipe placed on the perimeter of the bench
§ Flat spray nozzles are spaced along the pipe
§ Water ejected in a fan pattern toward the center of the bench
§ Used with cut flower production, snap dragons, carnations, etc
o A 100 foot bench needs a minimum of 20 gallons per minute water supply
o Modifications
§ Spray tubes
§ Trickle sticks
· Polystyrene tubing surface watering system
o ie Gro-hose, Chapin Twin Wall hose, Ooze Tube systems
o Gro-hose is a 2 inch poly tube with pinholes to let the water out
§ Maximum length 100 feet
§ Pressure tends to drop off at the far end because of loss out the holes
o Twin Wall
§ 3-12 mil poly
§ Up to 2 inch diameter
§ Tube within a tube evens out the pressure
§ Most trickle irrigation systems use this
o Ooze Tube - single tube
§ Water oozes from around a plastic thread
§ Tubing lasts a long time
· Sub-irrigation
o Success depends on
§ Water quality
§ Medium
o Requires specially made benches
o Must be steam pasteurized
o Water evaporates from surface & is drawn up into pots
o Replenished from below
o Capillary mat sub-irrigation system
§ Water delivered on top of capillary system (sand, fiber mat, etc)
§ Uses regular greenhouse benches with sides
· Waterproof
· Or covered with a sheet of poly
· Not limited to length or width
· Need to water plants overhead first to establish capillary link
· Can have problems with salt buildup on the mat
· Algae growth on sand or mat - especially with fertilizers in the water
· Ebb and flow system
o Leak proof tables with sides
o Benches flooded with water or fertilizer
o Wait specified time
o Drain water into holding tank
o Recycle water
o All nitrogen must be used before you dump the water so it doesn't pollute the environment
o Benches must be perfectly flat
o No way to kill algae without killing plants
· Hydroponics
o Gravel beds for support flooded with nutrients
o Rock wool or other inert substance as a support
o Gro-bags (mostly peat)
§ Jiffy 7's to huge blocks
o Root mist chambers
§ Very fast growth this way
o Floating donuts
§ In ponds of nutrient solutions
§ Eg Epcot Center
Measuring systems for watering
· Measure by weight: only 4 pots; establish drying curves for each pot type and potting mix
o Soil dries to wilting point, then water
o Weight one pot to establish watering pattern
· Electrical measurements
o The more water in the pot the more the electrical conductivity
§ Electrodes are embedded in gypsum blocks or plaster of paris
· Saturated salts are in it
§ If salts already saturated, any change in conductivity is due to increased water levels
o Not all that accurate
· Measuring pressure using tensiometer
o Used for large ground beds
o Cannot be moved or seal is broken
o Ceramic tip breaks or cracks easily, and needs to be replaced
o As soils dry
§ water is forced out of ceramic tip
§ Suction pulls on diaphragm in dial
§ High readings (in centibars) means dry soils
o Large one cost about $60
o Use 3-4 per acre
§ If fairly uniform level & wetness
o Aerometer Company probably builds the best.
Handouts
1. Water Quality
2. Perimeter irrigation watering system design
3. Watering systems design
a. Gro-hose
b. Hole spacings
c. Sub-irrigated benches
d. Capillary watering systems
4. Calibrating the drying cycle of a soil mix
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