Fertilizer Selection for Transplant Production
By Ray DeBruhl, Agronomist
The Selection of the proper water-soluble fertilizer is the second most
important step in designing the plant fertility program for growing
hemp transplants. There is not a “one size fits all” fertilizer that
accommodates all the possible water quality scenarios. Water analysis
should be the primary factor that determines the fertilizer analysis that
is applied. In addition, there are other factors that determine the
fertilizer of choice.
A successful fertility program is determined by more than just the rate
of the applied fertilizer. Other factors include the analysis of fertilizer
(NPK), whether it is acidic or basic, the proportion of ammonium (NH4)
vs. nitrate (NO3). And how much is applied to the water.
While some nutrients are supplied by the soilless media and the water,
most of the nutrients are applied after seeding using water soluble
Nutrient availability in the soil media is determined not just by the
presence of nutrient ions but also by the pH of the soil media, and the
media pH is influenced by the alkalinity of the irrigation water. Do not
confuse alkalinity with pH of the water. We are concerned about the pH
of the media not the water pH. In a small cell like the ones we grow
hemp, the cell media pH is not constant, it is constantly changing. Peat
moss has very little buffering capacity, it cannot resist a change in pH.
The media is influenced by the lime in the media, the alkalinity of the
irrigation water, as well as the type of fertilizer used.
Therefore, to a large extent the alkalinity level of the irrigation water
will determine which fertilizer you should use primarily.
Before we begin to select a fertilizer, it is important that we understand
some of the challenges the grower faces.
There are many water-soluble fertilizers available that makes it possible
to develop a fertility program unique to the individual grower. An
example would be that of neutralizing excess bicarbonates which, when
present at low levels can be accomplished by using certain brands of
fertilizers instead of sulfuric acid. Another example is when confronted
with low levels of calcium and magnesium, one could choose to use a
complete fertilizer that is a cal-mag formulation instead of adding
epsom salts and gypsum.
However, accomplishing this would require inventorying several
different fertilizers without knowing growers needs beforehand. This
could be a costly endeavor.
So, the Trilogy Fertility Program relies on a simple 2 part system that
incorporate 2 fertilizers, 20-10-20 or 16-5- 16 as the primary fertilizers
and then epsom salt and either gypsum or calcium thiosulfate as the
Using the water analysis, read the levels given and apply these “If This
Condition, Then That Action”
While these water quality scenarios will not cover everything, it does
give you the most important metrics to examine and what action to
take if a certain condition exists.
Establishing and maintaining proper fertility management programs in
a greenhouse is essential to successful growing of hemp transplants.
Most assume that fertility management begins with the applied water-
soluble fertilizer. Actually, fertility management begins with a correct
analysis of the water quality.
It is necessary to understand the relationship between water quality
and plant nutrition to establish a successful fertility program. When
formulating a fertility program for your crop, water quality should be
given top priority.
The time invested in obtaining a complete water analysis will give you
tremendous returns in plant quality.
The Trilogy Growing Program will determine the fertilizer that you
should be using, based on the analysis of your water. And with the
proper soil media selected, your production goal is better realized
when you start with a scientific approach to your transplant fertilization