Reiziger Hydroponic Nutrient Deficiency Guide

COMMON NUTRIENT DEFICIENCIES Next to carbon dioxide, water and oxygen, plants require nutrients for growth and development. These ‘nutrients’ or ‘minerals’ are chemical elements and are essential for all plants species. There are twelve nutrients, categorised into two groups: macro and microelements. This distinction is made on the basis of the quantity taken up by plants. Macroelements are nitrogen (N), potassium (K), phosphorus (P), calcium (Ca), magnesium (Mg) and sulphur (S).

The micro-elements are iron

species. Sodium (Na) and

The essentiality of a few

(Fe), manganese (Mn), zinc

chloride (Cl) will be found in

micro-elements as cobalt

(Zn), boron (B), copper (Cu)

plants as well, sometimes

(Co) and nickel (Ni) and

and molybdenum (Mo).

in huge quantities, however

some other rare elements

Sometimes silicon (Si) is

these elements do not

is still debated among

also mentioned as nutrient,

have an essential function

scientists. These elements

however this element is

and can be replaced by

may be essential for some

not an essential, but rather

others. These elements

species but not for all and

considered as ‘beneficial’

are taken up by plants

accordingly these elements

and is only taken up by a

due to their presence

are generally neglected.

selective number of plant

in the root environment.

Article written for Reiziger by

University & Research Center. The Netherlands.

Early recognition will help overcome problems.

114

Nutrient Deficiency.

The quantity and the mutual

optimise growth by avoiding these

overcome the problem. In some

ratio of each of these nutrients

shortages by crop management,

cases this is too late and plants

required for optimum growth

in particular fertilisation.

will not recover or the symptoms

differs substantially among plant

In horticulture and specifically

have had already detrimental

species (see graph below). In

in soilless culture systems like

effects on the crop. Deficiency

nature, plants will be provided

hydroponics, an optimal nutrient

may occur due to an absolute

these nutrients by the soil. This

solution is provided to boost plant

lack of the specific nutrient in

natural soil fertility (among other

growth even more. However,

the soil or the substrate or due to

conditions) constrains the growth

if there is an unbalanced

conditions in the root environment

and the development of plants.

fertilisation, depletion of one of the

or the condition of the plant. For

Plant species have evolved

nutrients may occur and plants

instance a too high or too low pH

many strategies to overcome

will start to show symptoms.

will reduce the availability of some

shortages. Some plants have

These deficiency symptoms are

nutrients (Fe, Mn, Zn). Lack of

superior strategies than others

typical for each nutrient and may

oxygen or too low temperature will

and this is one of the pillars of

vary among plant species. Early

reduce the capability of roots to

the biodiversity we can observe

recognition of the symptoms and

take up nutrients as well.

in nature. In agriculture, we

adequate actions will help to Minerals 15%

Dry Matter 13%

TOTAL PLANT

DRY MATTER O

87%

Water

43%

5% H

37% C

Mo Cu 1% 7%

P Mg 5% % S 3 % Cl 2 % 2 % Na 1

Ca 21%

B 25%

MINERALS

Fe 29%

MICRO NUTRIENTS

% N 20

46% Mn

14% Zn

24% Mn

Essential Nutrients.

Nutrients are essential for plant growth as they are part of the ‘building blocks’ of the plant or are indispensable for certain processes.

The lack of nutrients will limit plant growth or influence the life cycle. For example N is the key element in amino-acids, the basic components of proteins. Proteins are one of the

Nutrient Toxicity.

important ‘building blocks’ of plant cells. So it

Plant roots are very selective

to problems with the water

in taking up the required

quality. Toxicity symptoms

quantities of nutrients from

have common features

the root environments. Even

but will have some typical

if the plant has absorbed

aspects for each plant

too much, the plant has

species as well. Toxicity of

mechanisms to reverse the

macro elements is virtually

uptake by excretion of the

unknown, although a too high

surplus of some nutrients.

supply of (one of the) macro-

However, in some cases

elements will cause problems

this selection is overruled

as well. These problems are

if the concentration of a

related to the interferences

certain nutrient is high. For

with other nutrients

some nutrients the plant

(antagonistic effects). In this

cannot control the uptake

case early recognition of the

and toxicity will occur. This

symptoms and adequate

is mainly the case with some

actions are important, but it is

of the micro-elements, like

not always easy to overcome

for B, Mn, Cu and Zn. Under

the problem. In some cases

horticultural and soilless

this may be too late and

culture conditions toxicity

plants will not recover, or the

is usually due to errors

symptoms have already had

made by the preparation

detrimental effects on

of fertiliser solution, an

the crop.

inadequate substrate, or due

is quite obvious that without N, plants are not able to grow at all.

Minerals magnified Various minerals important for growth seen closeup and in detail.

K however is never part of any molecule in the plant; it stays 100% in solution as the K+ ion. K controls a lot of functions inside the cell solutions. Another example of the second category nutrients is Cu, which is not part of any building block. Plants can grow to a certain extent without Cu. However, Cu is part of some enzymes that control metabolic processes in the plant, for instance it is necessary for the viability of pollen in grains, or the induction of flowers.

Individual nutrient deficiencies.

The main functions, deficiency symptoms and prevention measures of the essential nutrients are described in more detail on the next pages. For each nutrient, the common features of deficiency symptoms and under which conditions it will occur as well as which measures can be taken to cure the problem are presented. If toxicity is known, this is described as well.

Deficiency symptoms and prevention measures of essential nutrients.

First aid guide for plants.

N Nitrogen Nitrogen is by far the most important nutrient. It is one of the components of amino acids and therefore an important part of the proteins, DNA, enzymes, vitamins and above all, the chlorophyll, which is the key for plants to function.

Stage 01

Stage 02

Stage 03

The plant is a lighter colour as a whole.

Stalks will turn purple and leaves will yellow.

Further yellowing and whitening occurs in top and middle sections.

Purple stalks

Yellowing

Leaf drop

Function

Deficiency

Prevention and cure

Nitrogen is absorbed in two forms: nitrate (NO3-) and ammonium (NH4+). NO3- absorbed by the root is transferred to NH4+ before it is processed into amino acids. For this process some enzymes are needed and molybdenum (Mo) is crucial.

In the plant, nitrogen is very mobile and a lot of nitrogen from proteins and amino acids in older plant parts is recycled.

Nitrogen deficiency will be shown in the first place as growth reduction and soon the leaf colour becomes dull green or pale. Then the oldest leaves turn yellow and in a later stage will become brown and dye off. In the case of fruit crops, the fruit setting will be poor and fruits become small. Since nitrogen is very mobile in the plant, yellowing always starts in old leaves, whereas young leaves and the top of the plant stay green.

To prevent shortages, an adequate fertilisation by sufficient base dressing of soil and substrate and continuous fertigation is required.

Soil or substrate (drainage) analysis will be excellent methods to indicate impending shortage. Plants will recover rapidly after restoring the nitrogen supply.

Deficiency occurs due to incorrect feeding or food contains insufficient nutrient elements. Substrates that contain a lot of fresh organic material can cause nitrogen deficiency because micro-organisms bind the nitrogen.

Raise EC of the feeding.

Add extra nitrogen.

K Potassium K is the nutrient present in the highest quantities. In the plants it stays soluble as ion (K+) and is never part of the dry matter. The majority of K is present in the vacuole solution of cells, keeping the osmotic potential and controlling the water potential of plant tissue.

Stage 02

Stage 03

Tips of younger leaves show grey edges.

Leaves turn yellow from the edge and rust coloured dead spots.

Leaf tips curl up radically and sections of the leaf begin to rot.

Grey edges

Rust spots

Dead edges

Function

Deficiency

Prevention and cure

Stage 01

Potassium can be rapidly moved inside the plant and plant cells and therefore plays an important role in opening and closing of stomata, i.e. the regulation of the transpiration.

Potassium is absorbed solely as K+.

Potassium deficiency starts with some growth reduction and darkening of the young leaves. Symptoms will become visible as necrosis of the leaf margins of the mature, older leaves of the plant and eventually the whole leaf becomes necrotic. In case of fruit crops, the fruit quality (shelf life, colour, taste) is negatively affected.

To prevent shortages, an adequate fertilisation by sufficient base dressing of soil and substrate and continuous fertigation is required.

Soil or substrate (drainage) analysis will be excellent methods to indicate impending shortage. Plants will recover rapidly after restoring the potassium supply, except for the necrotic tissue.

Potassium is absorbed quickly and easily by the plant. In a hydroponic system results are visible within several days. Potassium supplementation via leaf fertilisation is not recommended.

Rinse substrate with water.

Add extra potassium.

P Phosphorus Phosphorus is part of the amino acids and so a basic building block of proteins. In addition to DNA, ATP and ADP-proteins, which form the energy source for all metabolic processes in plant cells, are a typical destination for phosphorus.

Stage 01

Stage 02

Stage 03

Plant becomes a sort of dark blue-green.

Dark necrotic spots appear on old and medium aged leaves.

The purple-black necroses expand to the leaf’s stem.

Blue-green

Necrotic spots

Black stems

Function

Deficiency

Prevention and cure

Phosphorus is quite mobile in the plant and like nitrogen, the phosphorus from old plant tissue is recycled. For young plants, the presence of phosphate is indispensable; about three quarters of the phosphorus consumed during a plant’s life cycle is absorbed in the first quarter of its life. The largest concentrations of phosphorus are found in the developing parts of the plant: the roots, the growth shoots and the vascular tissue.

Typically a phosphorus deficiency is seen as growth reduction and very dark coloured green leaves at the top. This is often accompanied with a blue-green to purplish colouring, mainly on the underside of the leaf.

The mature leaves become smaller and leaflets or tops of leaves will curl downwards. Purple colouring will also occur on the stem and petioles.

Stunted growth and lacking to form a heart (lettuce) may also occur, as well as dying of the older leaves (pepper).

The availability of phosphorus in the root environment is complicated as phosphorus is absorbed to the soil and soil chemical properties (pH) influence the form in which phosphorus is available. For soilless culture and hydroponics, it is therefore absolutely necessary to control the pH and keep the pH between 6.2 and 5.0. If the pH is above 6, a drainage analysis is inadequate as P may be present in forms that are not available for plant uptake.

In case of a phosphorus deficiency, reduce the pH, for instance by 10-20% by adding extra NH4+. After additional phosphorus supply or optimisation of the pH conditions, plants will recover rapidly.

Reduce the pH below 6.2.

Add extra phosphorus.

Ca Calcium Calcium is part of the cell wall and cell membranes and therefore indispensable for the elasticity and rigidity of the plant tissues. Ca is taken up as Ca2+ ion and is transported only by the xylem vessels and therefore very immobile in the plant.

Stage 02

Stage 03

Small, light brown spots that increase in size over time.

Spots now appear at the edge of the leaves.

Older leaves die off slowly and yellowish cloudy spots may appear.

Brown spots

Sharp rust spots

Hindered growth

Function

Deficiency

Prevention and cure

The water flow in the plant due to transpiration is the most important factor to provide the plant with calcium. Root pressure (the process caused by the differences of concentration inside and outside the plant) is another important factor as this will bring calcium into littletranspiring plant parts like fruits and plant tops.

Typically necrosis of young tissue, like young leaves, tops or fruits. The main reason is cell lesion due to weak cell walls in combination with permeable membranes. This young tissue is unable to sustain transpiration when exposed to the environment. Calcium deficiency symptoms are among the most common deficiencies in protected horticulture, even in well fertilised conditions.

Take care of adequate base dressing and fertigation, avoid high NH4, potassium and magnesium concentrations. However, this is not a guarantee for prevention of calcium deficiency. Prevent long periods of high humidity and at least prevent sudden shocks in the humidity conditions. For some crops, a foliar application of CaCl2 (0.1%) will help, but needs to be repeated frequently.

Stage 01

The main reason for deficiency is irregularities in water distribution caused by the climate conditions. In addition, high salinity and also high NH4+ concentrations are factors that may cause calcium deficiency.

Rinse substrate with water.

Apply additional calcium.

Mg Magnesium Magnesium is part of the chlorophyll. Without magnesium, the chlorophyll is unable to be active. Furthermore, it is part of some enzymes. It is quite mobile in the plant when chlorophyll is degraded. Magnesium is recycled in the plant.

Stage 01

Stage 02

Stage 03

Small, rusty brown spots or cloudy yellow flecks appear.

The size and number of rust brown spots increase.

Symptoms spread out over the entire sick looking plant.

Small brown spots

Cloudy yellow spots

Plant looks sick

Function

Deficiency

Prevention and cure

It represents a building block for chlorophyll (leaf green) and it is essential for photosynthesis. At the same time, magnesium plays an important role in the energy transfer. Together with calcium, it is also a component of tap water, influencing water hardness. Inorganic magnesium fertilisers are produced using the same bases that are used to produce potassium fertilisers.

Magnesium deficiency causes yellowing of the leaves due to chlorophyll degradation. Plants will try to keep the youngest leaves green, so mature and middle aged leaves will show the deficiencies first. The yellowing is interveinal. In severe situations, the yellow parts become necrotic and leaves may eventually become completely brown. The fruit colour will be negatively affected.

Adequate fertilisation with a sufficient base dressing of soil and substrate plus continuous fertigation. Soil or substrate (drainage) analysis will be excellent methods to indicate impending shortage. Plants will recover rapidly after restoring the Mg supply, however the yellowing of the leaves will not disappear. Repetitive spraying with MgSO4 (max 0.5%) is an adequate cure.

When there is a shortage, the leaf green in the medium-aged leaves under the flowering top will be broken up and the magnesium will be transported into the younger leaves of the plant.

Keep root temp at 20-25°C.

Avoid a high EC in the substrate.

Fe Iron Iron is a vital element for plant life. As iron can easily be transferred from Fe2+ to Fe3+, the function of iron ions in plants is to act as an electron donor or acceptor. These reactions occur in many metabolic processes, particularly in the chlorophyll.

Stage 02

Stage 03

Green-yellow chlorosis from inside to the outside.

Continued yellowing of the leaves to almost white.

Leaves show necrosis with growth and flowering inhibited.

Yellow chlorosis

Continued yellowing

Strong yellowing

Function

Deficiency

Prevention and cure

In general, iron is poorly absorbed by the plant. It can only be sufficiently taken up by the roots in certain forms and under proper conditions. Without iron, the assimilation process in chlorophyll cannot function. Iron can be absorbed as Fe2+ or Fe3+, but in normal conditions with abundant oxygen present this will usually be Fe3+. Iron is very immobile in the plant.

Iron deficiency can occur during periods of heavy growth or high plant stress and is easy to recognise as the youngest leaves of plants become yellow, leaving the veins usually green. This phenomenon is called chlorosis. The young leaves can’t draw any iron from the older leaves.

After the initial yellowing, the leaves become necrotic after exposure to high radiation and later die off. In severe situations, plants will die completely.

Adequate fertilisation by sufficient base dressing of soil and substrate and continuous fertigation with the right Fe-chelate type is important.

Fe-chelates are used (in the nutrient solution) to keep Fe in solution otherwise Fe will precipitate rapidly.

The availability of Fe in the root environment is complicated, as the pH plays a major role. In hydroponics, it is absolutely essential to control the pH. Foliar spray of Fe-chelate with max 0.5% may help for prevention.

Stage 01

Keep pH between 6.2-5.0. Poor root development or unformed young root tips (due to soil compaction oxygen deficiency) can be a cause. In case of Fe-deficiency due to pH problems, reduce the pH by 10-20% with NH4+.

Reduce the pH by 10-20%.

Foliar spray of Fe-chelate with max 0.5%.

Mn Manganese The metal manganese is an essential trace nutrient activating different enzyme reactions in the plant and plays an essential role in certain enzymes necessary for photosynthesis.

Manganese is absorbed as Mn2+ but is quite immobile in the plant.

Stage 01

Stage 02

Stage 03

Yellow stripes between the leaf’s side veins on larger leaves.

Yellowing between the side veins spreads further over the leaf.

Yellowing spreads further. Yellowbrown necrotic spots can form.

Yellow stripes

Yellowing spreads

Necrotic spots

Function

Deficiency

Prevention and cure

Manganese acts as an activator for different enzyme reactions in the plant, for example in water-splitting during photosynthesis, the synthesis of amino acids and proteins and the build up of plant cell membranes and chloroplasts. Manganese is generally taken up via the roots. Once inside the plant it is difficult to transport but not as difficult as calcium or iron for example. Silicon and molybdenum improve the transport possibilities for manganese in the plant.

A manganese deficiency causes different physiological changes in the plant due to a decrease in protein production. The symptoms are quite similar to iron, although the youngest leaves may stay green and the symptoms will be visible in the larger top leaves. Compared to iron, the ‘netting’ pattern of the green veins is finer as smaller veins will be kept green, causing a greener touch to the whole leaf compared to an iron deficiency.

The availability of Mn in the root environment is largely dependent on the pH. For soilless culture and hydroponics, it is absolutely necessary to control the pH (keep pH between 6.2 and 5.0). In case of Mndeficiency due to pH problems, reduce the pH, for instance by 10–20% by adding extra NH4+. Foliar spray of MnSO4 or Mn-chelate (max 0.5%) may help for prevention. Cure of affected leaves is sometimes possible.

High concentrations of Mn precipitate into manganese oxide which cause yellow-brown spots on the leaves. Initially, small spots will appear along the main and side veins of the leaf, then the spots will spread out from the veins.

Keep substrate temp at 20-25°C.

Lower substrate pH to 5.0-5.5.