If you are looking for more information on Low Tunnel Berry Production please check out these resources:
The first session
of our mini-series set the stage on some of the issues we are seeing regarding
soil health and long-term resiliency in protected spaces. For those of you who missed the first session, or are
interested in revisiting the teachings before building on it in part 2, you can
find the full recording here (Managing Nitrogen in Protected,
Soil-Based Systems). A summary of some of the
information presented is listed below:
One of the
re-occurring themes in protected soil production is an accumulation of
nutrients, specifically things like Mg, Ca, and K, as a result of large
deposits of compost before a cropping season. While these are necessary
nutrients for healthy crop production and good quality fruit, too much of a
good thing is not always a good thing. Typical supplementation focuses so
heavily on achieving a target N value, that a lot of the micronutrients that
come along with that N slip by unnoticed.
Not only are we
concerned with high levels of certain micronutrients, but also have to be aware
of the soil structure itself. One of the soil health indicators we talk a lot
about is percent organic matter. While we like
to see higher percentages of organic matter, it can come at a cost to other
macro- and micro- nutrient availability to the plant when not executed
properly. Paying attention to the cation exchange capacity value, or CEC, on a
soil test, is important for those who regularly apply compost. While not
mentioned in this webinar with Judson, the higher the CEC value, the tighter
bond exists between the soil particles and the nutrients, which make it harder
to make adjustments to the nutrient composition/balance without significant
intervention.
Combine these two
factors with the lack of overhead precipitation in tunnels, we see astronomical
values of these micronutrients, which are going to contribute to a rising pH,
and a significant hinderance on the plant's ability to take up all of the
nutrients in the required quantities/balances that the crop needs. Here is an
example of the soil test presented in the webinar highlighting this exact trend.
The top image highlights a soil that has been supplemented but not to any
excessive extent, and the second image highlights how that soil has evolved
with continual additions of a compost:
When
it comes to the use of compost in protected settings, conducting a compost
analysis before application is strongly encouraged, as is yearly soil testing
so that we see what is happening in these soils that do not have the same
opportunities for drainage as an exposed soil would. Understanding exactly what
you are putting into the soil, and how often, is crucial to avoiding buildup to
the levels displayed here. Generally when it comes to supplying nutrients to
the crop, scenarios that require supplementation are much easier to navigate
compared to a heavily loaded and complex soil as what is projected above. The
use of fertilizer blends can also contribute to the accumulation of certain
nutrients. Consider this - the go-to fertilizer you use in your system is
20-20-20. While that is a great source of nitrogen, your P and K are already
very high, and is going to add to the already-existing nutrient load. In soils
such as these, single nutrient sources are going to be a much better choice as
we attempt to remediate these soils into something that are resilient and will
support crop production well into the future.
Given all of this
information, what can we do to better balance out our nutrient supplementation
to prevent this from happening? One of the best strategies is going to be split
nutrient, application throughout the season. This is a much more targeted
approach, where we know:
1)
nutritional targets for the crop in question
2)
recent soil tests outlining nutrient composition
3)
BONUS when we consider the long-term nutrient output of supplements such
as
compost or manure
From here, we are able to formulate a plan that sees
regularly scheduled nutrient introduction via fertigation into the tunnels,
specifically targeted for when the plant needs those nutrients the most. In
doing so, we can reduce the loss of nitrogen to the environment, prevent
unnecessary buildup that impede production success, maximize the impact that
each $$ of fertilizer has on crop performance, and generally contributes to
resilient and long-lasting productivity of those greenhouse soils.
Interested in learning how to set yourself up for split applications during the
season? Join Judson Reid and Talia Plaskett at noon
(AST) on April 13th for a ‘Lunch and Learn’ session on how to set
yourself up for split applications of nitrogen throughout the season! This is a
great opportunity to help establish the fertigation plan for 2023 and fine-tune
your calculator skills to make sure that you are getting the maximum impact for
every drop of fertilizer injected into the soil. For more information, or to
register for the session, please
check out our learning portal. 
