Insufficiencies

Indications of insufficiencies:

  • Brownish and/or stinking roots
  • Pale looking leaves
  • Different colored spots and/or parts on leaves, flowers or fruits

The different hydroponic techniques explained on this website show different sensitivities to the environmental parameters, especially to the nutrient solution provided. E.g., in aero- and fogponic systems a nutrient solution provision, that is slightly off during a short period of time, might already have significant impact on the plants' state of health [5]. In contrast, a mediabed system allows for more room for failure by ensuring a certain buffer. Hence, leaving the suggested ranges of environmental parameters doesn't immediately lead to dying plants [31, 59]. Additionally, it is not even in our hands providing, e.g., the perfect amounts of each nutrient, as the fertilizers are mostly used premixed. Nonetheless, certain signals should be correctly understood in order to reduce the plants' stress to harmful environmental conditions [1].

You may observe limited growth [31, 59], different colored (spots on) leaves, flowers, fruits or roots [1, 46], or even parts dying off [1]. It is important to spot these changes as soon as possible, in order to take the right counteractions in time and to prevent larger damage. Not all characteristics mentioned are due to insufficiencies, as also diseases might cause different colored parts or spots [1].  Therefore, you will get to know only some main characteristics of how to determine insufficiencies.

But first, please take a look at the provided checklist to make sure you don't make avoidable mistakes.


Checklist hinting towards deficiencies []

It is important to go through the provided checklist, in order to correctly identify what you are dealing with and hence to prevent the attempt to correct what is actually in order, causing more harm than good [1]. Therefore, to eliminate other causes and to identify symptoms correctly, you should make sure to check the following points [5]:

  • The pH is in the target range
  • The EC is in the target range
  • The air Temperature is in the target range
  • The light levels are in the target range
  • The nutrient solution Temperature is in the target range (between 17 and 25 ° C [55])
  • The plants receive sufficient fresh air, so that the leaves are at least sometime during the day visibly moving
  • At least same varieties of plants show similar symptoms
  • The crop is free of pests and diseases
  • The fertilizers used are designed for hydroponic gardens and it are not older than the following rule of thumb: you should renew the nutrient solution (perfect fertilizer for soil grown plants) and readjust the target pH and EC ranges with your hydroponic fertilizers.

If you can ensure all except one of the first 6 points, it is likely you face some sort of deficiency. Because all of theses points are interconnected in a way that regulates the plants' metabolism, some nutrients will ultimately not get where they were supposed to [59]. It should get better, as soon as you corrected the points above. 

In case you are not able to find anything to give reason for a certain deficiency, you might face a not well balanced fertilizer solution, which leads to inadequate (too high or too low) levels of specific nutrient [1, 31]. Check out the following list of nutrient deficiency characteristics.

Nutrient Deficiency characteristics

Nutrient  Deficiency Toxicity 
 Carbon Plants absorb carbon in form of CO2 through the leaves to produce very energetic sugar molecules, which power their whole metabolism [59]. Although a real carbon deficiency doesn't exist, low CO2 levels will slow down growth [31, 46]. Placing a hydroponic system at home should nevertheless provide good levels, wherefore you normally don't have to worry about. - 
Oxygen Plants' roots would be the human's lunges, which is why you want to make sure to have sufficient oxygen levels in your nutrient solution [59]. If the oxygen levels fall to low, your plants' will suffocate within less than an hour. You provide high levels through gushing water pumps or by dedicated aeration for systems like DWC or some mediabed systems [5, 9, 27, 46]. With aeroponic and NFT systems you do not need to further do anything for improved oxygen levels, as they enable air to surround (parts of) the roots. -
Nitrogen The plants' growth stagnates and older leaves get a light green - yellowish color [27]. This is due to the fact that nitrogen is required for the development of chlorophyll [59]. The plants' leaves will turn dark green, but the root system is very restricted and the flowering stage gets delayed [27].
Phosphorous The plants' growth stagnates and first older leaves, then the whole plant starts to turn dark green - blueish to dark [27]. No direct effects are known, but it might lead to zinc and copper deficiencies [27].
Potassium The plants' growth stagnates, the leaves show a papery appearance and dead spots start to spread starting from their edges [27]. No direct effects are known, but it might lead to magnesium deficiency [27].
Sulfur The plants' younger leaves turn yellowish, followed by the older ones [27]. The plant's leaves decrease in size and are mostly deformed [27].
Magnesium The plants' older leaves get a light green - yellowish color (similarly to nitrogen deficiency), but starting at their edges spreading inwards around the veins [27]. No direct effects are known [27].
Calcium The plants' new tips (stems, buds, leaves and roots) will die off. [] No direct effects are known [27].
Chlorine The plants' leaves wilt and the roots' growth stagnates [27]. The plants' leaves decrease in size and show tip burn along with the abscission getting yellowish [27].
Iron The plants' older leaves get a light green - yellowish color (similarly to nitrogen deficiency), but starting at their edges spreading inwards around the veins, similar to the magnesium deficiency. [] No direct effects are known [27].
Manganese Small symptoms are younger leaves turning yellowish around the veins, followed by the older ones. Stronger deficiency is accompanied by died off spots [27]. The plants might show a decreased growth and light green - yellowish colored leaves [27].
Boron The plants' stems and roots die off or get discolored and swollen. Leaves might also become brittle, curled and (partly) discolored [27]. The plants' leaves turn yellow till they die off, starting from the edges [27].
Zinc The plants' leaves turn yellowish around the veins similar to the small symptoms of manganese deficiency [27]. The plants' leaves turn yellowish due to causing an iron deficiency [27].
Copper The plants' younger leaves turn darker and show spots dying off [27]. The plants' leaves turn yellowish due to causing an iron deficiency.  Additionally, the roots become extremely dark and the plants' overall growth is reduced [27].
Molybdenum The plants' younger stems and roots turn light green - yellowish, followed by the older ones [27]. Some plant varieties show leaves turning golden-yellowish [27].

Link to References