Build a Hydroponic Culture System

Horticulture and the Science of Plants
Youth Adventure Program
David Wm. Reed, Instructor
Department of Horticultural  Sciences
Texas A&M University

BACKGROUND

What is hydroponics?
Hydroponics means "water culture".  Hydroponics is growing plants with their roots submerged in aerated water, periodically flooded with water, or sprayed with water.  Plant roots need both air and water to survive.   The roots are growing in water, so a lack of water is never a problem.  However, supplying air to the roots takes special care. 

How is air supplied to the roots?
There are several ways to achieve sufficient aeration: 1) submerge the roots in water and bubble air through the water with an air pump; 2) place the roots in a trough and run a very thin layer or film of water over the roots so they are barely submerged; 3) the plant roots grow in a solid substrate, such as sand, gravel, beads, hard clay balls, rock wool, peat, and the nutrient solution is dripped through the substrate or the container is flooded with water then drained, or  4) roots can even be suspend  in air and sprayed or misted them with a nutrient solution.  


Types of Hydroponic Systems

There are many kinds of hydroponic systems.  Some are pictured below.

Aerated Hydroponic System
The plants are suspended from a floating platform, and the roots hang down into an aerated nutrient solution.
  The class will build a system similar to this.

hydroponic - floating system
From: www.simplyhydro.com/free2.htm


Hydroponic Trough System (often called Nutrient Film Technique)
The plants are placed in a trough, and a thin film of water flows over the roots and back into some type of reservoir.  The system pictured  below is a combination of an aquaculture fish tank and a hydroponic trough growing system.  The bioreactor removes toxic levels of ammonia.  Instead of pumping water directly out of the fish tank into the bioreactor, the water in collected in sump tank (a holding tank with a water pump), then pumped into the bioreactor; this facilitates settling and removal of solid fish waste.  The water from the bioreactor can be diverted to drain back into the fish tank or to the hydroponic troughs. In 2004, the class used this system.



Solid Substrate Hydroponic System
In this system the plant roots are growing in a solid substrate, such as sand, gravel, glass beads, rockwool, or even peat moss.  The substrate does not hold nutrients very well, so every time the substrate gets dry a nutrient solution is dripped through the substrate.  This type system is very common in commercial production.

How are nutrients supplied to the roots?
Plants absorb virtually all of the essential elements through their roots.   Essential elements are also called nutrients or fertilizers.  The nutrients or  fertilizers are dissolved in the water to supply the plants with all the nutrients they need.
  Plants need 17 essential elements, which are:
 3 supplied naturally by air and water - comprise the bulk of the plant   
    C, H, 0     
 6 macronutrients - required at 0.1 to 6% of the dry weight of plants   
    N, P, K, S, Ca, Mg    
 8 micronutrients - required at 1 to 300 ppm of the dry weight of plants   
    Fe, Zn, Cu, Mo, B, Mn, Cl, Ni 

Hydroponic Nutrient Solutions
The 14  macronutrients and micronutrients must be added to the hydroponic solution.  There are very complex recipes for making the hydroponic nutrient solution.  One of the most common and widely used recipes is Hoagland's Nutrient Solution.  The following table gives all the chemicals needed to make Hoagland's nutrient solution.  Pretty complicated, isn't it!  If you do not want to make your own nutrient solution, you can Google "hydroponic supplies" and you will find many web sites where you can order hydroponic nutrients that you just dissolve in water.   In class, we will actually conduct an experiment where we will test if one can simply use soluble fertilizers that you can purchase in any garden center.
 
Modified Hoagland's Nutrient Solution #1
Macronutrients
Concentration  
millimolar (mM) Chemical
1 KH2PO4
5 KNO3
5 Ca(NO3)2 * 4H2O
2 MgSO4 * 7H2O
Micronutrients
Concentration  
micromolar (µM) Chemical
11.8 MnSO4 * H2O
0.7 ZnSO4 * 7H2O
0.32 CuSO4 * 5H2O
0.16 (NH4)6Mo7O24 *4H2O
46.3 H3BO3
5 Sequestrene 330 (10% Fe)






































 

TAKE HOME LESSONS
1) To learn how to set up a hydroponic system to grow plants.
3) To learn how to monitor the hydroponic nutrient solution to make sure sufficient  nutrients are present. 
5) To compare how plants grown in different fertilizer solutions.

MATERIALS NEEDED
Hydroponic tanks, air pump, tubing, air stones, chemicals for each fertilizer, seedlings.

PROCEDURES
For pictures of the students setting up the system go to pictures.

Experimental Treatments
We will grow plants in  a control and 3 different hydroponic solutions, plus a control.
1)  Control
2)  Hoagland's Nutrient Solution
3)  Scott's 15-16-17
4)  Peters 20-10-20

Objective
The objective is to determine which fertilizer is the best for growing plants in hydroponics.

Assemble the Hydroponic Trays
The class will assemble an aerated hydroponic system with a tank and floating platform.  See the diagram above.

Preparing the Nutrient Solutions
Go to Prepare Hydroponic Solutions and follow the instructions to prepare the solution for the three trays.

Inserting Plants into Hydroponic Trays
You will be supplied with young seedlings.  Insert a seedling in the holes of the hydroponic lids.  Insert the seedlings so that the roots dangle into the hydroponic solution.  We will use two types of plants, such as bean, Chinese cabbage, or squash.  We will use at least five of each type plant in each hydroponic tank.

Daily Measurement of  Water Quality
On the first day, and then every other day thereafter, the class will use instruments to measure the following properties of the hydroponic nutrient solution:
1) pH with a pH meter
2) salts with an electrical conductivity meter
3) nitrate with a  nitrate meter

We will write down the measurements on a Log of Water Quality data sheet and calculate the averages.  We will compare the measurements over time to make sure the the  nitrate, pH and EC salts do not change.

Daily Measurement of Plant Growth
On the first day, and then every other day thereafter, the class will measure  the following:
1) height of each plant
2) number of new leaves formed that are longer that 0.5 cm (about 1/4 inch)

We will write down the measurements on a Log of Plant Growth data sheet and calculate the averages.
We will compare the growth of the plants grown in the different hydroponic tanks.

 Analyze Data
After the last measurements are made, all the data will be averaged.  The class will observe the plants on the final day, evaluate the data, and determine the best  treatment(s).

RESULTS
At the end of the experiment, the class will write a summary of the results, and supply data for the following links:  Final Data Plant Plant 1  and Final Data Plant 2Final Data Water Quality, and Final Pictures.
 
.
We will post final pictures of the Hydroponic Experiment - Testing Fertilizers
The pictures below are from a previous YAP program.
Control Treatment
Hoagland's Solution
Scott's 15-16-17
Peters 20-10-20
control
Hoagland
15-3-15
20-10-20

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