Sustainable Fertilizers for Nursery Production

Fertilizer is a necessary component
of nursery production that is typically expensive and also poses
environmental risks if not used properly. By selecting an appropriate fertilizer
and integrating fertilizer management with other aspects of production
for efficient nutrient use, nurseries can become more economically
and environmentally sustainable. Fertilizer must be applied to container-grown
crops because nursery substrates provide few if any, nutrients
and have low nutrient holding capacity. The limited container volume restricts
the quantity of nutrients that can be held, and frequent irrigation leaches nutrients.
These factors make it difficult to provide adequate levels
of nutrients for plant growth without over-fertilizing
or leaching nutrients, losing them in runoff and
potentially polluting surface waters. Environmentally sustainable solutions
to this dilemma are to apply soluble fertilizers as needed
or use slow release sources. Dry soluble sources can be
applied by hand to each container or mixed in solutions
and applied with irrigation. Fertilizing via overhead irrigation
risks wasting fertilizer because of irrigation falling between pots. Other irrigation systems
such as ebb and flow efficiently apply, recapture
and re-use these nutrients. Here at James Greenhouses, we use an
Ebb and Flow irrigation system and this is the heart of it.
Basically our well water is pumped into storage tanks.
From the storage tanks, once a bench is turned on,
the pumps are activated and the water is pulled from the storage tank
into a mixing tank where fertilizer is added
according to a preset EC level. From here, the water and fertilizer
is mixed and it heads out to the bench. The fertigated water is transferred
to each individual bench from the mixing tanks
and each bench runs for approximately 6 minutes and
it’s approximately 120 gallons total and it’s about a 12 minute
soak time per bench So, all the water
contains all the fertilizer and is at the correct pH and EC
at the time that it reaches the bench. Once the benches
are finished watering and the water begins to drain,
we collect it all in a sump pump and it is all returned
back to our storage tank where it is then ready to be used
again for the next irrigation cycle. Other efficient irrigation systems,
such as low volume sprinkler heads or micro-irrigation result
in slower application of irrigation. Proper management of these systems
will reduce the potential for fertilizer leaching
through containers. Slow release fertilizers,
either synthetic or organic, improve nutrient use efficiency
by gradually releasing nutrients over a period of months. Synthetic slow release fertilizers
usually are dry fertilizers coated with urea, sulfur, resins,
polymers or other materials. These coatings
release nutrients at rates primarily dependent
on temperature and moisture. Sophisticated coating technology
allows precise release rates such that the grower
can select a product that matches the nutrient needs
and production cycle of a crop. Hey, Alan, tell me a little bit about your
fertilizer program here at Grandiflora. Well, a long time ago, we went to using
slow-release fertilizer that we incorporate into our soil mix and because we have so
many different products that we put out: trees, shrubs, ground covers,
vines, perennials, annuals, we have different formulations
for each of the different soils, so our shrubs and trees which are
going to stay in the pot a long time, we use a 12 month slow-release
fertilizer in that soil mix. The perennials which usually are
out of here in a few months, we use a 6 month fertilizer,
just enough that it will stay good and keep releasing whether it’s
in a retail nursery or in the ground. And then for our annuals,
we actually incorporate a 3 month fertilizer. While these products greatly
improve nutrient use efficiency, they are expensive due to the energy
required for production of synthetic fertilizers. Well, they are more expensive, but you
save money on labor because you’re not having to go around every 2 months
and put fertilizer on the top of the pot. With liquid fertilizers in the greenhouse,
they’d have to be hand-watering with an injector or something every week.
And that, that takes a lot of energy, I think that there’s money
savings by putting it in the soil. Even in an annual growing operation,
with 4 inch pots, you can use a slow release fertilizer.
Here we have a 3 month fertilizer. These plants will probably be sold
within 2 months, that means even when they’re
on the shelf in a retail nursery, they’ll hold up and
keep feeding for another month. It’s very common
when your sell your plants to a retailer that they don’t continue to fertilize
and if you’ve given them liquid fertilizer all their life
and then they go to a retail nursery, they’re going to start getting yellow
and they’ll start to fail. So here, just dibbling a little hole
in the corner and putting the slow release fertilizer in will get
feeding throughout the life of the plant. Organic fertilizers often are
manufactured from agricultural, marine or animal by-products including plant
wastes, manures, blood and bone meal. These products are bulky and
typically have low nutrient content and decompose to release nutrients
at rates dependent on temperature, moisture, microbial activity and
characteristics of the organic material. The low nutrient content
and bulkiness of these products make them better suited
for field nursery production. If used in containers,
they often must be incorporated into substrates at rates
comparable to substrate components. While doable,
the combination of organic fertilizer and substrate must be matched to
the crop and production conditions and supplemental fertilizer
still may be necessary to produce commercially
acceptable crops. A carefully planned
and properly implemented nutrient management program
can improve container nursery crop production,
produce healthy plants and be both environmentally
and economically sustainable. To find additional information,
please refer to this document and others which
are available on the project website.

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