top of page
Search

NUTRIENTS, pH, TEMPERATURE AND HUMIDITY REQUIREMENTS FOR GENERAL HYDROPONICS

Updated: Jul 31, 2022




CONTEXT

· Essential nutrients

· Nutrient solution composition

· Function and deficiency symptoms of essential nutrients

· pH

· temperature

· humidity

· Cost of basic requirement of nutrients per month


The nutrients are classified into Basic nutrients – Nitrogen, Phosphorous, Potassium And secondary nutrients which is further classified into Macro nutrients and Micro nutrients.


ESSENTIAL NUTRIENTS

These are 17 in number. These nutrients are required by plants for some critical processes to occur. For example: Magnesium- critical component of chlorophyll and chlorophyll is an important pigment to capture light coming from sun that is needed in photosynthesis. Plants are green in color due to presence of chlorophyll in it. Also Magnesium is the centre of chlorophyll molecule.

Essential nutrients are of 2 types:-

1. Macro nutrients (Carbon, Hydrogen, Oxygen ,Sulfur, Calcium, Magnesium).

2. Micro nutrients (Iron, Manganese, Zinc, Boron, Molybdenum, Chlorine, Copper, Nickel).


The only difference between macro nutrients and micro nutrients is that macro nutrients are needed by the plants in higher amount while micro nutrients are needed by plants in smaller amount. Some nutrients like Carbon, Hydrogen, Oxygen are also present in air and water, that is, in our natural environment. Plants takes these nutrients from the environment. Other remaining nutrients are taken by plants from soil or in case of hydroponics from nutrient solution.


NUTRIENT SOLUTION COMPOSITION

“Pre-mixed” nutrient solution needs to be diluted or dissolved in water before use. These “Pre-made” nutrients come in 2,3,4 or even more parts so the ratio can be altered by the growers. Nutrient mix is used for hydroponic system and is regarded as a complete plant food. The nutrients which are required to be in the nutrient solution in general hydroponics are:-

Nitrogen, Potassium, Phosphorous, Calcium, Magnesium, Sulfur, Iron, Manganese, Copper, Zinc, Molybdenum, Boron, Chlorine.

Different brands have different level of these nutrients present in them. Many nutrients also have some “beneficial elements” – Nickel, Cobalt, Silicon, Selenium. These are only beneficial for plants and not essential which means plants will be able to grow without these beneficial elements also. The function of nutrient solution is to provide roots of plants with water, oxygen and essential nutrients in soluble form.


FUNCTIONS AND DEFICIENCY SYMPTOMS OF ESSENTIAL NUTRIENTS

1. Nitrogen:


Function;

· Major part of chlorophyll molecule.

· Component of vitamins.

· Needed in all enzymatic reactions.

· Improves quantity and quality of dry matter in vegetables.


Deficiency symptoms;

· Stunted growth.

· Chlorosis (appears first in older leaves).

· Leaves wither and die.

· Decrease in protein content of leaves.

· Causes early maturity in crops.


2. Phosphorous


Function;

· Have essential role in photosynthesis and respiration.

· Have major role in storage and transfer of energy as ATP and ADP.

· Component of RNA and DNA molecule.

· Helps in development of root, flower initiation.

Deficiency symptoms;

· Delayed maturity.

· Poor development of seed and fruit.

· Purpling of leaves and stems.

· Stunted growth can occur.


3. Potassium:


Function;

· Used in activation of various enzymes promoting metabolism.

· Controls opening and closing of stomata of leaves.

· Maintains balance of electrical charges.

· Involved in protein synthesis.

Deficiency symptoms;

· Chlorosis (since potassium is a mobile elements therefore chlorosis first occurs in older leaves).

· Slow and stunted growth.

· Size and quantity of production may get reduced.


4. Calcium:


Function;

· Have structural role, that is, helps in formation of cell wall and cell membrane.

· Intracellular messenger in cytosol.

· Holds together the cell walls of plants.

· Also involved in activation of various enzymes.

Deficiency symptoms;

· Tips of leaves and roots turn brown and die.

· Weak stem structure due to improper formation of calcium pectate.

· Pre mature fall of buds.

· Deterioration of terminal bud.


5. Magnesium:


Function;

· Centre core of chlorophyll molecule.

· Traps light energy from sun.

· Involved in photosynthesis.

· Activate specific enzyme systems.

Deficiency symptoms;

· Pre mature falling of leaf.

· Interveinal chlorosis.

· Leaf tissue between veins turns yellowish, bronze or reddish.


6. Sulfur:


Function;

· In formation of amino acids, proteins and oils.

· Involved in promoting nodulation in legumes.

· Involved in chlorophyll formation.

Deficiency symptoms;

· Reduction in growth rate.

· Delayed maturity.

· Stiff and plant stems.


7. Boron:


Function;

· Involved in cell wall formation.

· Also involved in structural integration.

· Essential for cell division.

· Helps in fruit and seed development.

Deficiency symptom;

· Thick, curled and brittle leaves.

· Stunted growth- symptoms first appear on younger leaves.

· Black hearts in beets.

· Hollow hearts in peanuts.


8. Copper:


Function;

· Involved in many enzymatic activity.

· Required for chlorophyll and seed production.

· Helps in synthesis of lignin.

Deficiency symptom;

· Necrosis of apical meristem.

· Distorted leaves.

· Reduced growth.

· Dieback of twigs.


9. Chlorine:


Function;

· Involved in osmotic and stomatal regulation.

· Evolution of oxygen gas in photosynthesis.

· Increase resistance towards disease.

Deficiency symptom;

· Chlorosis of leaves.

· Wilting of plants.


10. Iron:


Function;

· Involved in synthesis of chlorophyll.

· Involved in various enzymatic and metabolic processes.

· Required for photosynthesis.

Deficiency symptom;

· Interveinal chlorosis.

· Laves may become white in colour.


11. Manganese:


Function;

· Acts as co-factor for oxygen-evolving complex (OEC).

· Catalyse water- splitting reaction.

· Involved in metabolic activity.

Deficiency symptom;

· Chlorosis leads to tiny yellow spots.

· Marsh spots in legumes.

· Mottled pattern of light and dark green on leaves.


12. Molybdenum:


Function;

· It converts nitrate into nitrite and then into ammonia.

· Required in symbiotic nitrogen fixation in legumes.

· Acts as co-factor for nitrogenase enzyme to fix atmospheric nitrogen.

Deficiency symptom;

· Inward rolling of leaf margin.

· Necrotic spots at leaf margin.

· No flower formation occurs.


13. Zinc:


Function;

· Derives many metabolic reactions.

· Essential constituent of carbonic anhydrase.

· Helps plant to produce chlorophyll.

Deficiency symptom;

· Leaves formed are abnormally small, mottled and chlorotic.

· Fruit formation is reduced.

· Interveinal chlorosis in younger leaves.



pH
Very important factor for proper growth of plants. It can be easily affected by the presence of any kind of debris or contaminant in water. pH is a measure of hydrogen ion concentration of solution. pH value of a nutrient solution decides the amount of nutrition present in it. Different plants have different preference of pH value and nutrient concentration. pH is maintained between 5.5 and 6.5- it is the range at which all hydroponically grown plants exhibit normal growth. The range of optimum pH for maximum growth of different crops grown hydroponically differs between species, cultivar, climatic conditions, soil. Nutrient disorders and therefore growth reduction occurs when pH is outside the optimum range. The pH of a hydroponic nutrient solution fluctuates because of unbalanced anion and cation exchange reaction with roots. No buffering capacity exist in hydroponics.

For example: Ammonium nitrate has more acidifying effect then nitrate causing drop in pH whereas calcium salts causes rise in pH therefore forming alkaline solution.


TEMPERATURE
Plant’s needs changes according to the environmental conditions surrounding it such as weather, temperature, etc. if our hydroponics system is outside (since outside temperature fluctuates), then the temperature factor need to be considered. Temperature should be kept steady for a nutrient solution. Ideal temperature range lies between 70-78 degree fahrenhite. In winters, a mini water heater should be purchased for a hydroponics system to keep it warm. In summers, nutrient solution should be kept under shaded area and topping of cold water should be provide to it at regular intervals. The temperature of nutrient solution affects some important variables such as oxygen solubility and metabolic processes of plant. If temperature is increased, the rate of metabolic reactions in plants will increase. Now due to increase in metabolism of plants, the respiration rates will also increase due to which oxygen levels present in water starts to decline.

HUMIDITY
It is the amount of water present in air but we are able to measure only the relative humidity(RH) in hydroponics and RH is not the amount of water present in air instead it is the measure of wheat percentage of available capacity we are using whereas Absolute humidity measures the amount of water we actually have in the air. Since warmer air will have more water and therefore 60% humidity 70F indicates that it has more water then 60% humidity at 50F.

In winters, many crops are grown in warehouses which require humidifiers because plants do not evaporate the sufficient amount of water from their surface to compensate for the lack of of water in dry winter air. To measure the actual experience of plant, we should place RH meters at different places. Do not place these RH meters far away from plants in greenhouses to avoid inaccurate measurement. Higher humidity causes fungal disease while lower humidity causes stress in plants.


COST OF BASIC REQUIREMENT OF NUTRIENTS PER MONTH:-

Rs. 130-150 for basic npk