Details about all hydroponic plant nutrients and how their quantity in the nutrient solution affects the growth of a plant and its output. Learn how pH affects the absorption of optimum nutrients in hydroponics.
Plants require 14 types of chemicals for healthy growth besides other elements. These are nitrogen (N), phosphorus (P), potassium (K), Calcium (Ca), Magnesium (Mg), Sulfur (S), Iron (Fe), Manganese (Mn), Copper (Cu), Zinc (Zn), Boron (B), Molybdenum (Mo), Nickel (Ni), Chlorine (Cl). Together these are called plant nutrients. Normally these are available in the soil. In hydroponics these are dissolved in the water.
Besides these nutrients plants also require other elements like oxygen (O), carbon dioxide (CO2), hydrogen (H) and sunlight. Small amounts of oxygen and hydrogen are absorbed from water or from air by the roots. Carbon dioxide is taken in by leaves from the air.
The plant nutrients are further classified into three categories depending on the proportion of requirement. Macro nutrients (N, P, K) are required in the highest proportion.
Secondary nutrients (Ca, Mg, S) are required proportionately in a lesser quantity.
Micro nutrients (Fe, Mn, Cu, Zn, B, Mo, Ni, Cl) are required in a very less or miniscule quantity.
However irrespective of the proportion all are equally essential for the plant health. Certain plant species may require other micro nutrients like Sodium (Na), Selenium (Se), etc. but these are not known in hydroponics.
Plants can uptake only 13 types of nutrients (these are N, P, K, Ca, Mg, S, Fe, Mn, Cu, B, Mo, Ni, Cl) from the nutrient solution.
However plants cannot choose the quantity of each individual nutrient from a hydroponic nutrient solution in exact proportion. Plants just taken in required quantity of water and along with it nutrients in supplied concentration.
However some plants may draw a particular nutrient in more quantity than the others. For example leafy greens may draw more nitrogen (N) compared to other nutrients while fruiting plants my draw more of potassium (K) compared to other nutrients.
The proportion of nutrients required varies from plant to plant. Therefore the nutrient solution mix has to be prepared as per the plant requirement.
One type of plant may require more potassium (K) whereas another type may require more phosphorus (P).
However a master mix with the addition of an individual element at the particular plant life stage will work for most hydroponic home growers.
Leafy greens have only one life stage. Flowering plants have two life stages. Fruiting plants have three life stages.
These are commonly referred to as the vegetative stage, flowering stage, and fruiting stage.
Ideally a separate nutrient mix has to be prepared for each stage. The vegetative stage requires higher proportion of Nitrogen (N). The flowering stage requires higher proportion of Phosphorus (P). The fruiting stage requires higher proportion of Potassium (K).
Preparing a master mix and then increasing the proportion of required nutrient at the particular stage is the best method to follow.
The quantity of nutrients a plant draws is proportional to the amount of water it consumes and also depends on the pH of the nutrient solution.
The plants uplift water depending on the weather. Plants draw more water in hot weather and less water in cold weather.
If the concentration of nutrients in the hydroponic solution is too high then the plants will become toxic. This may be visible in drooping or drowsy leaves or the plant will gradually burn turning leaves slowly to yellow.
If the concentration of nutrient solution is too low then plants will start showing nutrient deficiency symptoms.
Initially burning may appear like a deficiency tempting one to increase nutrient concentration which may be drastic. Therefore it is essential to vary the concentration of plant nutrient in hydroponics depending on the season of the year and also depending on the location of the site.
At a pH of around 6.5 most plants are able to draw all nutrients in required proportion. However for optimum performance a pH that best suits a particular type of plant has to be maintained.
Get more details on the importance of pH and how it affects plant performance in the post on hydroponic nutrient parameters (what is TDS EC CF PPM and pH?) from the hydroponics guide.
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