Propagation/Greenhouse Management
Part 1 – 148 | Unit 1.3
Water Conservation Tips
n Use a soil mix that includes ingredients such as
compost and coco peat, which hold water effectively
so that you don’t have to irrigate as frequently. Just
as with soil, you want a media that holds water but
doesn’t get waterlogged.
n Understand the natural cycling of water in
your soil mixes, and how water use changes under
different environmental conditions. By being aware
of the rates at which your developing plants use
water you can respond with sufficient irrigation but
avoid overwatering.
n Water in advance of your plants’ needs: early
in the day when they can get fully hydrated and not
lose water to evaporation. If plants are on outdoor
benches, avoid watering during hot, windy condi-
tions to minimize evaporation.
n Be conscious of the amount of water you’re ap-
plying, especially to Speedling/plug trays and gallon
pots. You need to wet the plants’ roots but don’t let
excessive water run through the containers and onto
the ground.
n “Block” or organize your trays of plants in the
greenhouse by life stage and irrigation needs. Group
those that can dry down between waterings and
those that need more consistent irrigation.
n Leave a minimum of space between plant trays
to limit watering empty tabletops and bare ground.
n Whatever your water delivery system (fixed
spray, boom irrigation that moves on a track over
the tables, or hose/watering can with a rose), make
sure it is sized to match your tables/benches so that
you’re not spraying the walls and floors.
n Make sure to have shutoffs on all your hoses. In
a greenhouse or outside, e.g., when irrigating potted
up perennials, use “zonal shutoffs” for fixed irrigation
systems so that you only water areas that have plants.
Water Quality Considerations
Using water efficiently and avoiding unnecessary
runoff will also help protect water quality. But
inevitably, there will be runoff from your greenhouse
operation. Consider implementing ways to protect
water quality:
n Just as you do in the field or garden, try and
meet the plants’ nutrient needs without overfertiliz-
ing. Too much fertility can make your starts vulnera-
ble to pests and diseases, as well as lead to nutrients
lost in runoff water. To minimize nutrient loss from
the soil mix of your perennials, use a stable, slow
release nutrient source, e.g., compost.
n Some nurseries use an “ebb and flow” irriga-
tion system; plants are set in a basin and wick water
up from below. Once the plants are irrigated, the
remaining water is drained off to reuse, thus sav-
ing water and “recycling” any leached nutrients.
The potential drawback to this system in an organic
operation is that if diseases are present there’s a risk
of spreading them amongst the plants.
n Water can pick up particulate matter from
potting soil and other growing media and deposit it
into your water supply; this is true of both organic
and conventional mixes. Figure our where the runoff
is going: Can it be directed to crops or non-crop
vegetation that would benefit? For example, can it
irrigate a windbreak or hedgerow that will cycle
nutrients, rather than having nutrients running off
site into surface or groundwater?
n Develop a system that captures all your runoff
(greenhouse roof, benches, and floors, hardening off
tables, outdoor sites where perennials are watered,
etc.) and put it through a biofilter or sand filtration,
store it in a pond or tank, and then reuse that same
water. Although potentially expensive, such a system
could be eligible for funding from the Natural Re-
sources Conservation Service’s Environmental Qual-
ity Incentive Program (EQIP) to encourage water
conservation and protect water quality.
To minimize the risk of introducing pesticides
and herbicides into the water supply, manage envi-
ronmental conditions to reduce pests and diseases.
Emphasize cultural controls and biological controls
before using controls such as soaps, oils, and Neem
(a broad spectrum insecticide and fungicide).Supplement 2: Conserving Water & Protecting Water QualitySUPPLEMENT 2
Conserving Water & Protecting Water Quality
A number of simple, straightforward, and easy-to-implement greenhouse practices will help
conserve water and protect water quality while enhancing the health of your plants.