Water Management in the Soilless Culture

8/13/2019 Water Management in the Soilless Culture

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SOILESS CULTURE OF HORTICULTURE CROPS

LABORATORY REPORT

Water Management in the Soilless Culture

Arghya Narendra Dianastya

(560000087)

FACULTY OF AGRICULTURE

DEPARTEMENT OF AGRONOMY

KASETSART UNIVERSITY


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I. INTRODUCTION

Hydroponics is a technology for growing plants in nutrient solutions (water

containing fertilizers) with or without the use of an artificial medium to provide mechanical

support. Liquid hydroponic systems have no other supporting medium for the plant roots:

aggregate systems have a solid medium of support. Because of the higher control over

nutrients, hydroponically grown plants generally have a much higher yield than similar plants

grown in soil.

EC and pH measurment of chemical solution is very important. The pH is a parameter

that measures the acidity or alkalinity of a solution. This value indicates the relationship

between the concentration of free ions H+ and OH- present in a solution and ranges between0 and 14. The concentration and pH of nutrient solution must be measured and monitored

during growing period. These method is done using portable EC and pH meter.

An important feature of the nutrient solutions is that they must contain the ions in

solution and in chemical forms that can be absorbed by plants, so in hydroponic systems the

plant productivity is closely related with to nutrient uptake and the pH regulation. Each

nutrient shows differential responses to changes in pH of the nutrient solution.

Nutrient solution has tobe make by using water. Water is very essential for soiless

culture because all nutrients must be solved with water tobe uptaken by plant. Water quality

must be clean, free from diseases, chemical residues, organic and inorganic materials.Making

suitable water for hydroponic can be done by puryfying the water. Water treatments consist

of purification by using water filters, pH adjustment, and sterilization by using oxidative

agents such as chlorine or UV ray.

The impurity in the water can be removed by water filters. The best way to purify

water is using Reverse Osmosis. the RO- water will be cleaned from both ion and cation. The

EC of the water using Reverse Osmosis also become 0.05 mS cm-1. The addition of acids or

alkalis to nutrient solutions also the most common and practical means to adjust pH, and can

be easily automated. There are ways to minimize pH variations and they are worth some

consideration. Most plants are able to absorb either nitrate (NO3-) or ammonium (NH4+) or

both. NH4+ as the sole source of nitrogen or in excess is deleterious to the growth of many

plant species. Some plants yield better when supplied with a mixture of NH4+ (ammonium)

and NO3- (nitrate) compared to NO3- alone. A combination of NH4+ and NO3- can be used

to buffer against changes in pH.


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II. OBJECTIVES

1. To Familiar student with the purification of water to be used in soiless culture

2. To Familiar students with the mantenance of water filter

3. To Familiar students with pH adjustment of water in soilless culture


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III. METHODE

1. For excercise 1, Draws a picture of RO-filter and labels major components and reportsits operation and maintenance

2. For excercise 2, report the pH adjusment by acid solution using the provided tablesand graphs and discuss the following points.

a. Comparison of the efficiency of different acid solutionb. The amount of acid solution to lower pH from 8 to 7 and from 7 to 5 are the

same or not.

c. How does EC of water changing after each pH adjustment3.

For excercise 3, write the report of the result from table 3. Discuss how much theactual total acid solution to be used for adjusting pH of water on the DRFT table and

for how long. Compare the actual amount of acid solution used and the amount from

the calculation.


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Exercise I

1.1 Picture of Reverse Osmosis


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1.2 Basic components common to all Reverse Osmosis Systems:

1. Cold Water Line Valve: Valve that fits onto the cold water supply line. The valve has atube that attaches to the inlet side of the RO pre filter. This is the water source for the RO

system.

2. Pre-Filter (s): Water from the cold water supply line enters the Reverse Osmosis PreFilter first. There may be more than one pre-filter used in a Reverse Osmosis system. The

most commonly used pre-filters are sediment filters. These are used to remove sand silt,

dirt and other sediment. Additionally, carbon filters may be used to remove chlorine,

which can have a negative effect on TFC (thin film composite) & TFM (thin film material)

membranes. Carbon pre filters are not used if the RO system contains a CTA (cellulose tri-

acetate) membrane.

3. Reverse Osmosis Membrane: The Reverse Osmosis Membrane is the heart of thesystem. The most commonly used is a spiral wound of which there are two options: the

CTA (cellulose tri-acetate), which is chlorine tolerant, and the TFC/TFM (thin film

composite/material), which is not chlorine tolerant.

4. Post filter (s): After the water leaves the RO storage tank, but before going to the ROfaucet, the product water goes through the post filter (s). The post filter (s) is generally

carbon (either in granular or carbon block form). Any remaining tastes and odors are

removed from the product water by post filtration.

5. Automatic Shut Off Valve (SOV): To conserve water, the RO system has an automaticshutoff valve. When the storage tank is full (this may vary based upon the incoming water

pressure) this valve stops any further water from entering the membrane, thereby stopping

water production. By shutting off the flow this valve also stops water from flowing to the

drain. Once water is drawn from the RO drinking water faucet, the pressure in the tank

drops and the shut off valves opens, allowing water to flow to the membrane and waste-

water (water containing contaminants) to flow down the drain.

6. Check Valve: A check valve is located in the outlet end of the RO membrane housing.The check valve prevents the backward flow or product water from the RO storage tank. A

backward flow could rupture the RO membrane.

7. Flow Restrictor: Water flow through the RO membrane is regulated by a flow control.There are many different styles of flow controls. This device maintains the flow rate

required to obtain the highest quality drinking water (based on the gallon capacity of the

membrane). It also helps maintain pressure on the inlet side of the membrane. Without the

flow control very little drinking water would be produced because all the incoming tap
http://espwaterproducts.com/replacement-water-filter.htmhttp://espwaterproducts.com/replacement-water-filter.htmhttp://www.espwaterproducts.com/residential-reverse-osmosis-membranes.htmhttp://www.espwaterproducts.com/residential-reverse-osmosis-membranes.htmhttp://espwaterproducts.com/replacement-water-filter.htmhttp://espwaterproducts.com/replacement-water-filter.htm


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water would take the path of least resistance and simply flow down the drain line. The

flow control is located in the RO drain line tubing.

8. Storage Tank: The standard RO storage tank holds up to 2.5 gallons of water. A bladderinside the tank keeps water pressurized in the tank when it is full.

9. Drain line: This line runs from the outlet end of the Reverse Osmosis membrane housingto the drain. This line is used to dispose of the impurities and contaminants found in the

incoming water source (tap water). The flow control is also installed in this line.

1.3 Operation of Reverse Osmosis Machine

Reverse osmosis is a complicated process which uses a membrane under pressure to

separate relatively pure water (or other solvent) from a less pure solution. When two aqueous

solutions of different concentrations are separated by a semi-permeable membrane, water

passes through the membrane in the direction of the more concentrated solution as a result of

osmotic pressure. If enough counter pressure is applied to the concentrated solution to

overcome the osmotic pressure, the flow of water will be reversed.

Water molecules can form hydrogen bonds in the reverse osmosis membrane and fit

into the membrane matrix. The water molecules that enter the membrane by hydrogen

bonding can be pushed through under pressure. Most organic substances with a molecular

weight over 100 are sieved out, i.e., oils, pyrogens and particulates including bacteria and

viruses. Salt ions, on the other hand, are rejected by a mechanism related to the valence of the

ion. Ions are repelled by dielectric interactions; ions with higher charges are repelled to a

greater distance from the membrane surface. The nominal rejection ratio of common ionic

salts is 85 - 98%.

The majority of the commercially manufactured Reverse O smosis (RO) membranes

are usually made from cellulose acetate, polysulfonate, and polyamide. The membrane

consists of a skin about 0.25 microns and a support layer about 100 microns. The skin is the

active barrier and primarily allows water to pass through.

1.4 Maintenance of RO Machine

Reverse osmosis system maintenance consists of nothing more than filter and

membrane replacement on a routine schedule. Beside that, reverse osmosis machine need to

maintain the power of the water pump as well.


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Exercise II

2.1 Comparison of the efficeincy of different acid solution

2.1.1 General Knowledge

pH si very important in hydroponic system. When the pH is not at the proper level

the plant will lose its ability to absorb some of the essential elements required for healthy

growth. For all plants there is a particular pH level that will produce optimum results. This

pH level will vary from plant to plant, but in general most plants prefer a slightly acid

growing environment (between 5.5-6.0), although most plants can still survive in an

environment with a pH of between 5.0 and 7.5.

When pH rises above 6.5 some of the nutrients and micro-nutrients begin to

precipitate out of solution and can stick to the walls of the reservoir and growing chambers.

For example: Iron will be about half precipitated at the pH level of 7.3 and at about 8.0 there

is virtually no iron left in solution at all. In order for your plants to use the nutrients they must

be dissolved in the solution. Once the nutrients have precipitated out of solution your plants

can no longer absorb them and will suffer deficiency and death if left uncorrected. Some

nutrients will precipitate out of solution when the pH drops also.

There are some example the optimum pH range for hydroponic crops and nutrient

available range :

(From Hydroponic Food

Production

by Howard M. Resh

Woodbridge Press, 1987)

NOTE:

This chart is for soiless (hydroponic) gardening only

and

does not apply to organic or dirt gardening.

Plant pH Range

Beans

Broccoli

Cabbage

Cantaloupe

CarrotsChives

Cucumbers

Garlic

Lettuce

Onions

Peas

Pineapple

Pumpkin

Radish

Strawberries

Tomatoes

6.0-6.5

6.0-6.5

6.5-7.5

6.5-6.8

5.8-6.46.0-6.5

5.8-6.0

6.0-6.5

6.0-6.5

6.5-7.0

6.0-6.8

5.0-5.5

5.0-6.5

6.0-7.0

5.5-6.5

5.5-6.5


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Usually, Tap water used in hydroponic has pH above 7 or alkaline. The efficiency of

pH lowering depends on the power of the acid solutions and their concentrations. Strong acid

such as H2SO4, HNO3, HCl has more power to lower th pH than waker acid such as H3PO4.

This is the example of strong and weak acid solutions :

2.1.2 Table

The pH changing as the effect of sulfuric acid, HNO3, and phosporic acid solution with

the equal concentration of 1%

Volume

(ml)

H2SO4 (1%) HNO3 (1%) H3PO4 (1%)

pH EC

(mS/cm)

pH EC

(mS/cm)

pH EC

(mS/cm)

0 8 0.36 7.6 0.31 7.6 0.25

0.5 7.3 0.37 7.5 0.31 7.5 0.27

1 7.1 0.37 7.0 0.32 7.0 0.30

1.5 7.0 0.37 7.0 0.32 6.9 0.30

2 6.8 0.37 6.8 0.32 6.7 0.30


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2.5 6.6 0.38 6.7 0.32 6.6 0.30

3 6.6 0.38 6.6 0.32 6.5 0.29

2.1.3 ResultIt can be seen in the table of exercise that H2SO4 and HNO3 give the most dramatical

change in pH of the water. The H2SO4 which is the strongest one of the solution gives the

highest changed of pH of water from 8 to 7.3 with 0.5 ml concentration only. H3PO4 is the

lowest in the term of efficiency with very slow to pH changed.

Sulfuric acid (alternative spelling sulphuric acid) is a highlycorrosivestrongmineral

acid with the molecular formula H2SO4. But, the strong acid as sulfuric acid (H2SO4) is

prohibited since they give extra S or sulphur that can be toxic to plants if the accumulative

concentration is too high.

The main problem with too much phosphorus is eutrophication resulting in excessive

growth of plants and algae in the water. This can seriously limit the use of the water for

drinking, industry, fishing, or recreation. Pollution reduction may not be simply a direct

economic problem for the farmer, but a responsibility that extends beyond the farm fence.

2.2 The amount of acid solution to lower pH from 8 to 7 and from 7 to 5

Volume (ml) pH EC (mS/cm)

0 7.7 0.31

1 7.2 0.32

2 7.0 0.33

3 6.8 0.32

4 6.6 0.33

5 6.5 0.33

6 6.3 0.34

7 6.3 0.34

8 6 0.34
http://en.wikipedia.org/wiki/Sulfur#Spelling_and_etymologyhttp://en.wikipedia.org/wiki/Corrosivehttp://en.wikipedia.org/wiki/Strong_acidhttp://en.wikipedia.org/wiki/Mineral_acidhttp://en.wikipedia.org/wiki/Mineral_acidhttp://en.wikipedia.org/wiki/Molecular_formulahttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Molecular_formulahttp://en.wikipedia.org/wiki/Mineral_acidhttp://en.wikipedia.org/wiki/Mineral_acidhttp://en.wikipedia.org/wiki/Strong_acidhttp://en.wikipedia.org/wiki/Corrosivehttp://en.wikipedia.org/wiki/Sulfur#Spelling_and_etymology


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2.2.2 Discussion

We can see from the result that the pH adjustment by acid solution to lower pH from

8 to 7 and from 7 to 5 are different. Using HNO3 as a solution, to make pH from 8 to 7 just

take 3 ml of HNO3 but to make pH from 7 to 5 takes 10 ml of HNO3. This is because HNO3

can be used as a buffer for solution. A buffer is an aqueous solution consisting of a mixture of

aweak acid and itsconjugate base or aweak base and itsconjugate acid.ItspH changes very

little when a small amount ofstrong acid orbase is added to it and thus it is used to prevent

changes in the pH of a solution. Buffer solutions are used as a means of keeping pH at a

nearly constant value in a wide variety of chemical applications.

Even HNO3 is a strong acid, but ionized nitric acid will cause a bunch of H+ ions to

exist in solution. The addition of NaHCOO, a weak acid's conjugate base, will cause a bunch

of HCOO- ions to form in solution. The buffer will exist because HCOO- will react with H+

to form HCOOH which is a weak acid and isn't going to fully ionize (source:

http://www.chemicalforums.com/index.php?topic=1428).

2.3 EC and pH

2.3.2 DiscussionIn the report is stated that when the pH is changed into the lower one, the EC also

change into the higher one. This is because there is a relation between the pH and the

electrical current flow [the conductivity] of a solution, but there are other factors that affect

the conductivity. In solutions, the current is carried by ions as cations [+]such as H+ , Na+,

Mg+, etc. and anion as negative charge [-] such as OH-, Cl-, Acetate-, etc. The conductivity

of a solution depends on the concentration of all the ions present, the greater their

concentrations, the greater the conductivity, Of the common ions, the most mobile cation is

the Hydrogen ion [H+] with a value of 350 units, and the most mobile anion is the Hydroxyl

ion [OH-], 199 units. The other common ions have values ranging between 40 and 80 units.

So that strongly acidic or strongly basic solution will have high conductivity, Since the pH is

a measure of the concentration of the Hydrogen and the Hydroxyl ions, for an acidic solutin,

the lower the pH, the greater the conductivity will be. This is because the conductivity is the

sum of the contribution of all the ions present in the solution.
http://en.wikipedia.org/wiki/Aqueous_solutionhttp://en.wikipedia.org/wiki/Weak_acidhttp://en.wikipedia.org/wiki/Conjugate_basehttp://en.wikipedia.org/wiki/Weak_basehttp://en.wikipedia.org/wiki/Conjugate_acidhttp://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/Strong_acidhttp://en.wikipedia.org/wiki/Base_%28chemistry%29#Strong_baseshttp://www.chemicalforums.com/index.php?topic=1428http://www.chemicalforums.com/index.php?topic=1428http://www.chemicalforums.com/index.php?topic=1428http://en.wikipedia.org/wiki/Base_%28chemistry%29#Strong_baseshttp://en.wikipedia.org/wiki/Strong_acidhttp://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/Conjugate_acidhttp://en.wikipedia.org/wiki/Weak_basehttp://en.wikipedia.org/wiki/Conjugate_basehttp://en.wikipedia.org/wiki/Weak_acidhttp://en.wikipedia.org/wiki/Aqueous_solution


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V. CONCLUSION

1. Reverse osmosis is a complicated process which uses a membrane under pressure toseparate relatively pure water (or other solvent) from a less pure solution

2. It can be seen in the table of exercise that H2SO4 and HNO3 give the most dramaticalchange in pH of the water. The H2SO4 which is the strongest one of the solution

gives the highest changed of pH of water from 8 to 7.3 with 0.5 ml concentration

only. H3PO4 is the lowest in the term of efficiency with very slow to pH changed.

3. We can see from the result that the pH adjustment by acid solution to lower pH from8 to 7 and from 7 to 5 are different. This is because HNO3 can be used as a buffer for

solution.

Documents

Water Management in the Soilless Culture