Identifying Plant Nutrient Deficiencies

Discussion in 'Plant Help' started by keymaker, 16 Nov 2008.

  1. keymaker

    keymaker Member

    Budapest, Hungary
    It would be really useful to post here a quick summary of the different plant deficiencies caused by the lack of the corresponding nutrients. I know that not all plants act the same and no two tanks are alike, but it would be useful to have a starting point... Just like Clive's post from the "HC issues" topic:

    The reason I'm writing now is that I wonder what kind of deficiencies can the PO4 shortage cause. Not that I have any, but it would be good to know what to look for. Looks like my tap water contains almost 0ppm of it, and TPN+ is known to be on the short side too. It's around 1ppm in the tank...

    Thanks for taking the time to summarize it! :idea:
  2. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Chicago, USA
    There are plenty of deficiency guides out there. JamesC's Plant Deficiencies sums things up pretty good. As you correctly point out, it's very easy to confuse things between different plants. There are some fairly obvious cases such as with N deficiency, everyone can identify yellowing, so that's fairly easy but other's are not that obvious. Sometimes, depending on ambient conditions one deficiency can look like another especially if the hobbyist ignores the other signs in the tank. I see a lot of posts where people see deformed or crinkled leaves and assume it to be a Calcium or Magnesium deficiency when in fact it's a CO2 deficiency. Another variable that few think about is that there can be a difference in behaviour between a chronic deficiency (long term) versus an acute deficiency (sudden).

    The reason one needs to specify which leaves are affected is due to the relative mobility of nutrients within the plants. Some elements such as NPK are highly mobile and there are many chemical pathways for them to move from leaf to leaf. In these cases the plant can move the elements from mature leaves to feed critical new growth. As a result, the mature leaves suffer as nutrients are withdrawn from them in the same way autumn leaves suffer when a tree withdraws it's nutrients for the coming winter. Other elements have fewer chemical pathways to move about so they are relatively immobile and the plant is not capable of transferring them to the new leaf. If a shortage occurs with that particular element then the new leaves suffer the most. So for example, both an N shortage and an Fe shortage cause yellowing but since N is highly mobile there is a higher probability that mature leaves will suffer as the plant redistributes N to care for the new leaves, whereas since Fe is less mobile it is more likely to stay put in the mature leaf and therefore new leaves will be lacking in Fe and thus will tend to show discolouration. Micronutrients tend to have much lower mobility than macronutrients but some have better mobility than others.

    Another complication is that some species have multiple or redundant reaction pathways. What this means is that if a primary element in a certain chemical reaction is in short supply then the plant can substitute a different element in a similar reaction, so for example there are some chemical reactions that require K but the plant may be able to substitute Mg in that particular reaction. To complicate the situation even more, a shortage of one element can be exacerbated by an over-abundance of another. These are some of the issues when people try to control their dosing by using ratios, or when an attempt is made to micromanage concentration levels. It's a real minefield.

    Phosphorous is a highly reactive element. In fact, it's so reactive that all the P that has been created in the universe has already reacted with something else so in nature you will never find P by itself. A lot of energy is released when P bonds to something else and it takes a lot of energy to break a P bond. All creatures great and small therefore use P. If you conceptualize the balance between energy consumption (feeding) and energy dissipation (working) in living things as an economy, then PO4 is the cash currency of that economy as a direct result of it's chemical energy potential. Within the plant P shortages have system wide consequences which effectively and indirectly can be exhibited as slow growth. This is illustrated by considering the end product of photosynthesis - the food reserves which are created is a Phosphate sugar called "triose phosphate" (AKA Glyceraldehyde 3-phosphate, or 3GP). Chronic low P levels have the inevitable effect of low food production, therefore, following the energy currency analogy, I consider low PO4 levels to be the equivalent of a Third World economy. It always amazes me when people panic regarding perceived high PO4 levels in their tap water, or when they use PO4 removers in their filtration. Three months later these same people are asking questions such as "What can be done to improve plant growth and reduce algae?"....

  3. keymaker

    keymaker Member

    Budapest, Hungary
    Clive, thank you for your detailed answer. Really useful and inspiring, as usual. I feel really ashamed as I regularly visit James' site (have been to the algae and DIY TPN+ section several times) but somehow his deficiency list never caught my attention. :oops:

    Your description is really valuable as now I know how to interpret and question the different symptoms and keep in mind the fact that... But I can only repeat what you said :). Thanks again, I'll do some more reading.
  4. Superman

    Superman Member

    I've just been reading this, makes sense with whats been going on it my tank.

    The tips of my old leaves Cyperus helferi started to go kind of "burnt" look and now from the tip they have become yellow and have died off.
    The only thing I have changed with my dosing regime is reducing the 36gs of KNO3 to 30gs per week. In addition, a few of my crypts have melted since the change. So I'm going back to the 36g per week.
    I reduced the amount of KNO3 after reading my water report as it stated it was was around 28ppm and thought I'd see with a small reduction how it would affect my tank.
  5. plantbrain

    plantbrain Expert

    Please note, that ever single nutrient deficiency example from any other source than aquarium aquatic plants is hardly of use.

    These plants are NOT CO2 limited.

    So assuming that all f our plants and their issues are the same is not a good assumption.
    CO2 must be addressed well before looking at nutrients.

    It's really a reverse issue, it's easier to rule out nutrients than it is CO2.
    So I do that, then go back and look at CO2 and assume my light is good(generally folks have enough).

    Tunnel vision with nutrients and 16 of them at that, can cause many variations etc, too much to figure out with any practical ease, figuring out one thing that has a large impact like CO2...........much easier, practical etc.

    A water change and redosing is all that is needed to address nutrients.

    In general, it is extremely tough to show nutrient specific issues with plants with confirmatin and certainly.
    So be very careful and suspicious.
    Most every suspect I've looked at failed when I did it with good CO2 etc, the few that have not where adding more nutrients helped, not less.

    As I got less, the demand for CO2 also was not so much either.
    So I was dealing with CO2 and nutrient issues, not just a single nutrient.
    When you have a pair or three or more factors controlling an outcome, it gets exponentially more difficult to reason through any of it.

    Tom Barr
  6. beeky

    beeky Member

    Chippenham, Wiltshire
    This reminded me of something that happened at school (apologies for going off topic). My chemistry teacher was showing us how reactive phosphorous is and removed a large lump from a jar of oil. She cut a sliver off the end but it shattered and threw little pieces across the floor. She went to quickly get the little pieces but forgot about the large lump on the desk...until it burst into flames filling the classroom with phosphorous and the science block had to be evacuated. Many of us had sore throats afterwards as the phosphorous gas reacts with the saliva giving a tasty dose of phosphoric acid.

    It was quite a few years ago now. Oh, happy days.

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