HORT 260 EXAM 2

module 3 slide 8 -

name 3 reasons to check your mist system regularly

clogged nozzles, power failures, and clock malfunctions

what are the 2 types of pipe installation?

overhead and in bench

what is an overhead mist system like

easy to maintain/install, no risers, efficient use of space, drip often

what is an inbench mist system like

risers usually 12-24’’ above crop, harder to work on

spacing of nozzle depends on

riser height, nozzle type, air movement in the structure/bed

nozzles need what

head to head coverage

what is head to head coverage?

the water from one sprinkler goes all the way to the next sprinkler

line strainer

filters water, “y” shape most often used, clean regularly

deflection mist nozzle

stream of water strikes a flat surface upon leaving nozzle, producing mist.

advantage/disadvantage of deflection nozzle

covers a large area at a lower PSI/ coarse, larger mist droplets

mini sprinkler nozzle

large water droplets, spinning action breaks up water stream

name the 2 types of mist control devices

static control system and dynamic control system

static control system

pre-set system using timers (24 hr clock, cycling clock)

dynamic control systems

environmentally controlled

what are the components of a dynamic control system

screen balance, electronic leaf, thermostat, photoelectric cells

solenoid

electronically controlled valve to control water flow to delivery system

normally open (solenoid)

water passes through when current is off. (protection against failure)

normally closed (solenoid)

open only when current is on. (less expensive)

centrifuge fogger

water ejected from spinning nozzle into cool airstream by fan

high pressure fogger

nozzle has very fine orifice; impact pin atomizes stream into droplets

ultrasonic/pneumatic fogger

as water passes through nozzle it is atomized by high frequency sound waves or compressed air

pros of ultrasonic fogger

droplets remain airborne for evaporation, increases rh without overwatering

optimal relative humidity

93-100%

transpiration increases with what 4 environmental factors

light, temperature, wind, relative humidity

what is the key to a propagules environment

keeping its tissue turgid while propagule becomes self sufficient

what should you consider when picking a greenhouse style/frame?

wind, snow load, cost

rooting for most crops is best at what temperature

70-81 degrees F (21-27 C)

construction styles: lean to

sloping roof, usually placed in S/E exposure

construction styles: gothic arch

two curves meeting at middle point, used in more northern areas (snow)

construction styles: evan span gable

two edges meeting at a middle point with a span in the middle (triangle), usually glass acrylic or polycarbonate

construction styles: quonset/hoop

one large curve, common in warmer climates; inexpensive, double wall poly if heated and/or cooled

all construction styles can be

single span or ridge and furrow (gutter connected)

hotbeds

ground bed with bottom heat (electrical wiring etc)

coldframes

ground bed with no heat

heat or sweat chamber

used in seed germination, needs venting

lathhouse

used in hardening off

what are three materials for framing?

wood, metal, PVC pipe

glass

expensive, high heat loss, heavy, permanent

polyethylene

.5 of greenhouses in US; inexpensive, retains heat well, lightweight, brittle in cold temp, short life span

acrylic

excellent heat retention, weather resistant, can be treated for no drip, brittle in cold, expensive

polycarbonate

good heat retention, strong, lightweight, low condensation

fiberglass

lightweight, long lasting, brittle with age

name four characteristics of a bench system

expensive, built of decay/corrosion resistant material, easier sanitation/less disease, can be fitted with bottom heat

what material is preferred underneath ground beds

concrete

two keys of heating for controlling environment

uniform temp, no harmful materials released into environment

name some ways to control heat in a propagation environment

heater/boiler, heat pump, distribution under benches, or other hot water distribution systems, forced air heaters, air distribution fans, thermal blankets

name some ways to control cooling in a propagation environment

ventilation with a roof or sidewall, exhaust fan, vent panel, evaporative cooling, shading

cooling capacity depends on

ambient or outside humidity

what are the two main functions of current day substrates

reservoir of water, oxygen, and essential mineral elements; anchorage

container substrates need to be what 3 things?

repeatable, stable, and free of contaminants

a substrate being repeatable means

it is made up of component well adapted for plant growth, and manageable

a substrate being stable means

it is not easily broken down

a substrate should be free of

pathogens, pests, contaminants, weed seed

the physical properties of phases dictate what

water and O2 for roots, and consequently for plant growth

bulk density is what phase

solid

bulk density is

the weight of dry substance per unit volume of substrate particles

bulk density depends on what

particle size distribution, particle density, and nesting of the material

air filled porosity is what phase

gas

air filled porosity

exists between (macropore) and within soil particles (micropores)

air pores are important why

O2 for respiration and root health

total porosity

dynamic part of the container substrate system, expressed as a % of total substrate volume at container capacity

what is the recommended % for total porosity by the BMP

50-85%

air filled porosity is expressed

as a % by volume of pore space in a substrate filled with air at container capacity

what is the recommended % for air filled porosity by the BMP

10-30%

volumetric moisture content increases with what

increasing micropores

volumetric moisture content is expressed

as a % by volume of pore space in substrate filled with water at container capacity

what is the recommended % for volumetric water content by the BMP

45-65%

what phase is the volumetric water content

liquid phase

volumetric water content is

the max water held following irrigation and drainage due to gravity

smaller pore size mean what

a larger water table

what is a perched water table and where is it

a perched water table is water that gathers where the drainage area is, even though there is an opening

container production has been around since

Ancient egypt, babylon, and greece 2500 years ago

container systems have limited what

reserves of moisture, air, and nutrients

field production take advantage of what

large soil reserves of moisture, air, and nutrients

limited soil reserves have a large affect on

the moisture dynamic with container substrate

substrate is

the base on which an organism lives; components that are used to fill the container and surround roots

early container substrates were

mineral soil based, 5% or less of OM

when did container production become commonplace

1940s

the height of saturation zone in a container depends on

pore size!!!

substrate solution

solutes dissolved in water and water within substrate

cation exchange capacity

indication of how well substrate will hold POSITIVELY charged ions

higher CeC typically produces

higher buffering capacities for nutrients

ph

controls nutrient availability in soils, but has less impact in organic substrates than mineral soils

what ph is generally best for soils

6\.2-6.5 (5.5-6.5)

soluable salts

all mineral salts dissolved in container substrate solution; includes essential plant nutrients and non essential nutrients

what are the five categories of hormones

auxin, gibberellin, cytokinins, abscisic acid, and ethylene

endongenous pgrs

ones that the plant synthesizes for itself;hormones

what is a pgr

plant growth regulator; group of organic substances that are capable of exerting large effects in plants in terms of gene expression, growth, and development

what auxin is most commonly used to induce rooting?

indole-3-acetic acid (IAA)

cytokinins do what

promote cell division in vitro

gibberellin does what

promotes stem elongation (+ cell division)

what role does ABA play in propagation?

seed and bud dormancy, somatic embryo maturation in tissue culture

what is a chimera

a plant with two genetically dissimilar tissue growing sides by side