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Overview
The symptoms of vitamin and nutrient deficiency in plants can be hard to diagnose.
The soil in Phoenix Arizona is relatively alkaline and salty
which makes properly fertilizing a plant even more difficult. Adding fertilizer here
is always a gamble because, as is detailed on the Amending The Soil page,
it is very easy to burn a plant beyond the point of recovery.
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Keep in mind that
there are many plants that need neither vitamins nor nutrients and can grow at
a healthy rate with nothing more than supplemental water. Some don't even need extra water.
Cactus, for example, need no fertilizer and little to no water. In fact, giving them fertilizer can
kill them.
In contrast some plants will show symptoms of vitamin and nutrient deficiencies
in this climate no matter how they are cared for. Plants such as rhododendrons cannot be grown
in the lower desert soil no matter how many amendments are added.
Between these two extremes are plants that can be helped
when nutrient and vitamin deficiencies show themselves.
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In Phoenix Arizona, most non-native plants will need supplemental nutrients at some point.
The macro-nutrients (needed by a plant in larger amounts)
nitrogen(N), phosphorus(P), and potassium(K) exist in the soil in reasonable quantities but will be
depleted relatively quickly by a fast growing plant.
Most micronutrients (needed in small amounts)
appear to be in ample supply with the exception of iron(Fe), which is often chemically unavailable because
of the high alkalinity of the soil.
Organic amendments such as compost will help the soil to naturally replace these substances, and they should
definitely be used, but some types of plants will outstrip the soils ability to produce vitamins
and nutrients. Futhermore,
a gardner might want their plant to grow more rapidly and be more productive than the natural
rate. Of course, the words natural and organic are a bit vague, and adding fish emulsion, one of my favorite fertilizers,
could be classified as organic, but its not really natural seeing as how fish are not jumping
from the sea, crushing themselves to pulp, and spreading themselves in my garden.
Nitrogen Deficiency
The most dominant symptom of nitrogen deficiency is a yellowing of the leaves, and lack of growth.
However, yellowing can also indicate iron deficiency.
Nitrogen is the number one burner of plants when applied in excess so knowing
the difference between these two is important. The answer to this riddle is that lack of nitrogen shows
first in older leaves, whereas iron deficiency shows first in newer leaves.
The reason the lack of nitrogen shows in older leaves first is that plants can easily move nitrogen
around within themselves and that plants give preference to their newer foliage. My favorite nitrogen fertilizers at the
moment are Alaska Fish Emulsion 5-1-1 for the more sensitive plants, Osomocote Slow Release For
Acid Loving Plants for
the less senstive plants that I want a slow release for, and Miracle Grow for the really hungry
and very difficult to burn plants.
Iron Deficiency
Iron deficiency is indicated by a yellowing that begins in newer leaves. The internal veins in the leaves
are often still green, but this is not always the case and depends on the plant. Iron deficiency can also
be caused by overwatering so make sure that a plant is being properly watered as a first step. Iron needs
to be added to the soil in a chelated form, a fancy chemical term meaning that it will stay available
even in high alkalinity. My favorite iron fertilizers are Ironite, and Greenlight liquid Iron and Soil Acidifier.
Ironite has received some bad press in the last couple of years because of alleged toxic metals being present in it.
It is difficult to tell how valid these accusations are and most data indicates it to be relatively safe. Furthermore,
the rates at which ironite would have to be applied to pose a risk seem to be very excessive.
I always found a very small amount of ironite to be effective, and the bag I have will probably last
a very long time. The Greenlight chelated iron is also effective and appears to be out of the negative
spotlight, so it is an alternative. I have found that it is easier to burn one's plants with it than with
Ironite though, so one has to be more careful with it.
Potassium Deficiency
Potassium deficiency is indicated by a burning of the older leaves. Unlike salt/fertilizer burn
it is limited to older leaves. Only heavy consumers of potassium appear to run short of it
here. Legumes like beans and pacay consume large amounts of potassium but need almost no nitrogen, because
they can pull nitrogen from the atmosphere and actually add it to the soil. They are referred to as
nitrogen fixing plants. My favorite form of potassium is Alaska Fish Emulsion More Bloom 0-10-10 for
my more senstive plants, and Miracle Grow Bloom Booster for the hard to burn plants.
Phosphorus Deficiency
Unfortunately, I still do not now how to tell this is happening from looking at a plant. However, most
fertilizers that add potassium also include phosphorus so it is likely to be adequately supplied. Perhaps
it is available in abundance in lower desert soils.
Salt Burn
Salt burn often occurs when too much of the good stuff discussed above is added to the soil and it becomes
bad stuff. Salt burn, unlike potassium deficiency, is evenly distributed across all leaves of the plant.
Salt burned leaves start burning at their tips and progressively turn crispy and may even drop off
depending upon the severity of the burn.
It can be distinguished from sunburn, because sunburn will not affect shaded leaves.
For an in depth discussion of minimizing the damage caused by excessive salt,
go to the Amending The Soil page. Of course, it is best to
avoid salt burn altogether by being conservative with fertilizer and only applying what a plant needs.
If a salt burned plant is not killed outright it will stop growing for a while defeating the entire
purpose of fertilizing it all.
Plant Root Competition
Young and newly planted plants can often have their rootballs invaded by larger established plants nearby.
In Phoenix Arizona, planting next to a larger shade trees is advantagous because of the shelter it can
give from the afternoon soon, so this kind of intrusion is a common occurrence.
The larger plant will take the nutrients water and anything else it can get from the unestablished
plant. The newer plant will show all kinds of nutrient deficiencies and stunted growth because of this.
To remedy this situation, dig a trench between the two plants at a sufficient distance from each of the
plants so that no serious damage to their central rootballs takes place. Since the topsoil here is
shallow any invading roots can usually be found within the first 2 feet of soil. Use a mattock
pick to hack the larger trees roots in half, giving the smaller plant some room to establish itself.
Links to more vitamin and nutrient deficiency symptoms information
Symptoms of Deficiency In Essential Minerals - Plant Physiology, 4th Edition
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