Vitamin and Nutrient Deficiency Symptoms in Plants

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.

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.

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), magnesium(Mg) and manganese(Mn) which are 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 (N) - Macronutrient
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.

Phosphorus Deficiency (P) - Macronutrient
Phosphorus deficiency causes older leaves to become dark green and have red or purple patches in them. The only plant I have observed a phosphorus deficiency in, in my yard, is a blackberry bush. Fertilizers that add potassium and/or nitrogen almost always add phosphorus so this may be the reason this deficiency is seldom observed here. Either that or because the soil in Phoenix has adequate levels of phosphorus for the majority of plants.

Potassium Deficiency (K) - Macronutrient
Potassium deficiency is indicated by a burning of older leaves. Unlike salt/fertilizer burn it is limited to older leaves. This, of course, can really slow a plant down because all of its older leaves drop prematurely, so the plant has trouble getting the energy benefit out of leaves that it spent a lot of energy growing. Heavy consumers of potassium appear to run short of it quickly 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, Osomocote Slow Release For Acid Loving Plants for the less sensitive plants that I want a slow release for, and Miracle Grow Bloom Booster for the hard to burn plants.

Iron Deficiency (Fe) - Micronutrient
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 soil iron fertilizer is EDDHA. It's a little hard to find but seems to work the best of anything else I have tried. I also have found that foliar iron fertilizers help as well. I have tried Liquinox Iron and Zinc. It is important that a foliar fertilizer does not have any sulfur in it, because sulfur will burn a plant's leaves.

Magnesium Deficiency (Mg) - Micronutrient
Magnesium deficiency causes older leaves to yellow at the tips and then die back. It can look very similar to salt burn but can be distinguished from salt burn by the fact that it concentrates itself on older leaves and affects the leaf tip rather than traveling the margins of the leaves. I use magnesium sulfate to add magnesium to my plants and for some of my plants that lingered with stunted growth for years, giving them a little magnesium really made a big difference. I have found that loquat, and pacay trees benefit greatly from an occasional dose of magnesium. In fact, for my loquat, magnesium halted the dreaded crispy leaf problem everyone sees here and often attributes to fireblight. Palm trees are also large consumers of Magnesium. To apply magnesium sulfate I mix a three fingered pinch of agricultural grade powder into a gallon of water and poor it around the drip line of the plant.

Manganese Deficiency (Mn) - Micronutrient
Manganese deficiency shows itself in the new leaves of a plant. It looks very much like iron deficiency but causes brown dead spots in the leaves. Palm trees seem to need manganese more than other plants, especially queen palms. However, most plants can probably benefit from an occasional application. I give my plants manganese in the form of manganese sulfate. To apply it I mix a three fingered pinch of agricultural grade powder into a gallon of water and poor it around the drip line of the plant.

Sulfur (S) - Micronutrient
Sulfur comes along with many other fertilizer products I use including gypsum, magnesium sulfate, and manganese sulfate. Sulfur is beneficial in general because it helps to lower the acidify of our alkaline soil. Sulfur acidifies by being processed by microorganisms and turned into sulphuric acid. This affect is temporary but can help to give plants a temporary boost. Sulfur is also utilized by plants directly.

Boron (B), Copper (Cu), Molybdenum (Mo), Zinc (Zn) - Micronutrients
These are the even more micro of the micronutrients. Still, tropical plants can potentially get short of them in alkaline soil. Boron, Molybdenum, and Zinc can be found in Ironite 1-0-1. Since Arizona is the Copper State, copper can evidently be found in huge supply in the soil here and shouldn't be a problem. Greenlight liquid Iron and Soil Acidifier is a source of copper if you decide you need it. See the links below for information describing the symptoms plants exihibit when they are short in one of these nutrients.

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 and magnesium deficiency, is evenly distributed across all leaves of the plant. Salt burned leaves start burning at their tips and progressively turn crispy along the edges of the leaves toward the base. Severely burned leaves may even drop off. 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 at 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
I have found the following links very useful in diagnosing plant nutrient deficiencies. The first 2 links, the "Generalized Guide" from NZ is very good. I have made a print out of both pages and take it into the garden with me for reference.

Generalised Guide To Nutrient Deficiency Symptoms (New Zealand) - Page 1 , Page 2

Guide to Symptoms of Plant Nutrient Deficiencies, ASU

Symptoms of Deficiency In Essential Minerals - Plant Physiology, 4th Edition

Guide To Nutrient Deficiency Symptoms in Corn (New Zealand)