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Unit 6.1 Plant Nutrition

2. AQUAPONICS
PLANT NUTRITION

3. Plant Nutrition Hydroponics Aquaponics
Uses minerals that are water soluble and ready to be taken up by plant roots
Scientific research has provided information on what minerals in what quantities are needed
Aquaponics
Nutrients available are related to fish
Size
Number
Quantity of food
Precise analysis requires a lab report

4. Plant Nutrition Nitrogen Phosphorous Calcium Potassium Sulfur
MACRO Nutrients
Micro nutrients
Nitrogen
Phosphorous
Calcium
Potassium
Sulfur
Magnesium
Iron
Manganese
Boron
Zinc
Copper
Molybdenum

5. Ph and nutrient availability to plants
pH – concentration of hydrogen ions 0.0 to 14.0
Less than 7.0 acidic
7.0 neutral
Greater than 7.0 basic
Important to plant growth
Very low pH <4.5 or high pH >9.0 can severely damage plant roots
pH level changes directly affects availability of nutrients
Majority of nutrients available at pH range
Extremely low levels cause some micronutrients (manganese) to be released at toxic levels
New, popular grow mediums like perlite, LECA, and rockwool have neutral pH

7. Concentration of elements
Aquaponics – built in fertilizer
No precisely mixed formula
Supports a variety of vegetables but lacks specific nutrients needed for some fruiting plants

8. Concentration of elements
Average Concentration for Healthy Plant Growth (PPM)
Nitrogen (N) (nitrate form)
70-300
Nitrogen (N) (ammonium form)
0-31
Potassium (K)
Phosphorous (P)
30-90
Calcium (Ca)
Sulfur (S)
60-330
Magnesium (Mg)
25-75
Iron (Fe)
Boron (B)
Manganese (Mn)
Zinc (Zn)
Molybdenum (Mo)
Copper (Cu)
Carbon (C)
Oxygen (O)
Hydrogen (H)
Are supplied by
Water (H2O)
And Carbon Dioxide Gas (CO2)

9. Plant uses of Individual elements
Each element has a specific function in plant growth

10. Nitrogen (n) Component of proteins Essential part of protoplasm
Occur as stored foods in plant cells
Part of chlorophyll
Part of amino acids
Part of alkaloids
Part of some plant hormones

11. Sulfur (s) Forms part of protein molecule
% of this element makes up a plant protein
Essential for the action of certain enzymes and coenzymes

12. Phosphorous (P)
Component of some plant proteins (phospholipids, sugar phosphates, nucleic acids, ATP and NADP)
Highest percentages of phosphorous occurs in the parts of plant that are growing rapidly

13. Potassium (K) Accumulates in tissues that are growing rapidly
Migrates from older tissues to growing portions
Ex: during maturing of crop will move from leaves to fruit

14. Calcium (CA) All ordinary green plants need calcium
One of the constituents of the middle lamella of the cell wall in the form of calcium pectate
Affects the permeability of cytoplasmic membranes and the hydration of colloids
Found in combination with organic acids in the plant

15. Magnesium (mg) Constituent of chlorophyll
Occupies central position in the molecule
Only compound of plants that contain magnesium as stable component
Enzyme reactions – mostly those involving transfer of phosphate are activated by magnesium ions

16. IRON (FE) Number of essential compounds in plants contain iron
The site on some electron carriers where electrons are absorbed and then given off during electron transport
Role in energy conversion reactions of photosynthesis and transpiration

17. Boron (b) Exact function in plant metabolism is unclear
Plays a role in carbohydrate breakdown
Boron deficiency – stunted roots and shoot elongation, lack of flowering, darkening of tissues and growth abnormalities

18. Zinc (zn) Essential to normal development of a variety of plants
Large quantities are toxic

19. Manganese (mn) Activator of several enzymes of aerobic respiration
Deficiency sign is chlorosis
Leaf taking on a mottled appearance

20. Copper (cu) Constituent of certain enzyme systems
Ascorbic acid oxidize
Cytochrome oxidase
Found in plastocyanin – part of the electron transport chain in photosynthesis

21. Molybdenum (mo)
Important in enzyme systems involved in nitrogen fixation and nitrate reduction
Plants with deficiency can absorb nitrate ions but are unable to use this form of nitrogen

22. Deficiencies and excesses
Aquaponic crops respond quickly to nutrient deficiencies/toxicities due to no soil buffer
Discoloration of foliage
Deficiencies are more common than toxicities
Potassium
Potassium hydroxide
Calcium
Calcium hydroxide
Iron
Chelated iron
Can add to system in minute quantities with no harm to the fish
Plant growth suffers; fruit set might not occur

23. Nutrient concentration testing
Measuring conductivity
Electrical conductivity (EC) is a measure of the ability of nutrient salts in a solution to conduct electrical current
Helps a hydroponic grower to know the concentration of their fertilizer solution
Varies with the concentration of nutrients in the solution as well as the chemical composition of nutrient solution. Higher EC = higher concentration of nutrient salts
TDS (total dissolved solids) is also a measurement of the concentration of nutrients

24. Nutrient concentration testing
EC readings in aquaponics can provide a guide to changes in nutrient concentration
Reading lower than those in hydroponics
Nutrients in aquaponics are continually generating so a lower concentration is required
Organic nature of nutrients results in lower concentration of salts and lower EC reading
Area needs more study
Generally measured at 77°F – raise in temperature will cause a higher reading of EC even though no nutrients have been added; lower temperature will have a lower reading
Always measure at a consistent 77°F or purchase a temperature compensated meter

25. Advanced nutrient testing
Neither EC or TDS meter indicate precisely what nutrients make up a solution
More complete kits are available for this purpose
Many commercial growers test on a regular basis to ensure proper balance of nutrients for optimum plant production
Regular leaf analysis is an excellent tool for determining health of plants
Dried, crushed, and analyzed
Determine exact nutrient content
Commercial labs offer more precise results
Sometime only way to determine what is wrong with plant since symptoms of deficiencies may be similar

26. Reference
Nelson, R. L. Aquaponic Food Production Raising Fish and Plants for Food and Profit Nelson and Pade, Inc. Montello, WI. Pgs
With contributions from John S. Pade