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Types of automatic fertilizer systems

January 24, 2018

Without doubt the easiest and best way to accurately, uniformly and effectively fertilize your garden, lawn, plants, bonsai or orchids is to fertigate. Your plants will be healthier, more resistant to disease and pests, require less water and to top it off you will have more time to enjoy them and / or other pastimes

Plants take up chemicals or nutrients at a rate they require, so regular small dosing is ideal. Whilst this is difficult to achieve with most forms of fertilizing, it is easy to achieve with fertigation.

There are several common fertigation methods, some easier and more practical than others. This article discusses methods which are suited to residential and small scale commercial requirements.

1. Pre-Mixed Fertilizer and Sump Pump
2. Venturi – Fixed
3. Venturi – Adjustable & Portable
4. Storage Tank with Inbuilt Venturi
5. Low Pressure Electric Pumped System
6. High Pressure Electric Pumped System
7. Hydraulic driven pumped system

1. Pre-Mixed Fertilizer and Sump Pump

Perhaps the simplest and cheapest method involves premixing fertilizer with water in a large drum. A pump suction hose is placed into the drum and the solution is pumped either through a hand watering sprayer or drip irrigation system to fertilize your plants.

Advantages

  • Simple to mix fertilizer into a known volume of water.
  • Easy to install and requires little maintenance.
  • Minimal cost.

Disadvantages

  • Requires a pump
  • Requires constant mixing of fertilizer / water to ensure settling does not occur. This will either require an agitator motor or potentially a second person to constantly mix.
  • Difficult to estimate exact quantity of fertilizer / water mix required to complete the task.
  • Most likely will result in wasted / residual fertilizer.
  • Large drum need to be stored in between fertilizing.
  • High risk of air entering the irrigation system

2. Venturi - Fixed

Whilst this is a cheap alternative, there are significant drawbacks to this methodology. To correctly size and select a venturi you must know several variables including but not limited to:

  • Fertilizer dose rate required.
  • Water flow rate required (maximum and minimum)
  • Maximum upstream pressure
  • Minimum required downstream pressure.
  • Note: Downstream (output) pressure typically must be 25 - 30% lower than the upstream pressure to ensure a pressure drop across the venturi allowing the venturi to function.
  • Fertilizer density
  • Fertilizer viscosity (Note: check viscosity is compatible with the venturi)
  • Location of fertilizer in relation to the venturi (“x” meters above or below the venturi)

The above parameters can then be compared against venturi manufacturers specifications to select the most appropriate unit. It is highly probable that an exact match may not be available and that a compromise will be required in fertilizer rate, concentration, water flow rate or some other parameter.

It should be recognised that a change in any of the parameters mentioned above will immediately cause a change in the venturi performance and may result in it not working.

There are many reputable and reliable venturi injector providers, perhaps Mazzei Injector Company, LLC being one of the best.

Advantages

  • Comparatively cheap
  • Simple design
  • Easy to install
  • Little maintenance.

Disadvantages

  • Can only operate within a strict band
  • Accuracy unknown at any point in time - accuracy is governed by fluctuating physical parameters.
  • Not flexible
  • Cannot use with different flow rates or markedly different fertilisers.

3. Venturi – Adjustable & Portable

A comparatively cheap solution for gardeners seeking to fertilize a small garden.

Typically, the systems consist of an assembly containing:

  • A dial or some other adjustment mechanism so the user can adjust the fertilizer mix or dose rate.
  • Fertilizer concentrate is contained within a small reservoir.
  • The entire unit is held by the gardener and operated by means of a trigger mechanism.
  • A garden hose is connected to the adjustable venturi assembly.

Whilst the adjustable systems overcome some of the issues associated with venturi sizing etc, there are still limits such as:

  • Limited dose rate flexibility.
  • Water flow rate (maximum and minimum)
  • Maximum upstream pressure
  • Most units can only be used with hand watering systems
  • Fertilizer density
  • Fertilizer viscosity

4. Storage tank with inbuilt venturi

Several systems are available which include a storage tank containing fertilizer concentrate and mixing system. Unlike the fixed venturi described above, these unit either utilise a venturi or bladder compression system to deliver fertilizer. A dial is included where the operator can select typically one of three or four concentration ratios.

The vessel is either filled with a proprietary fertiliser produced by the unit manufacturer or in some cases a common standard liquid fertiliser can be used.

The operator must perform some calculations on the basis of:

  • Fertilizer type to be used
  • Vessel size
  • Flow rate anticipated
  • Mix rate setting to the selected on the tank eg Slow medium or fast fertiliser rate.

Advantages

  • Comparatively inexpensive
  • Low maintenance.

Disadvantages

  • Crude dose rate settings
  • May require complex calculations to improve dose accuracy
  • Operator needs to pre-decide flow rates etc to perform calculations for both setting and mixing of fertilizer
  • Typically units are permanently connected and run continually.
  • Variability in fertiliser dose rate from start to end (depletion of vessel)
  • Difficult to know exactly when fertilizer storage has been depleted.

5. Low Pressure Electric Pumped System

Pumped systems are one of the most accurate and flexible of the commonly available fertigation systems.

The better quality pumped systems are fully automatic and negate the need for calculations etc. A water flow sensor determines how much water is flowing through the pipe. This information is used in conjunction with the fertilizer dose setting (selected by the user) to pump fertilizer at a particular rate to ensure the correct concentration is delivered to your plants.

Low pressure electric pumped systems are very flexible and automatically accommodate changes in water flow. You may be surprised at how often the water flow varies when you are watering - even though you are using a residential town supply.

These units can be connected to hand watering hose, drip irrigation or some other irrigation system.

Low pressure pump systems often use a peristaltic type pump which requires the mainline pressure be reduced to circa 180 – 300kPa, resulting in a reduced mainline water flow. However, this flow is more than adequate for hand watering and smaller scale drip systems.

It is very easy and convenient to use a variety of fertilisers and seaweed extracts – all that is required is a simple setting change of the desired concentration on the pump controller dial.

fertigate offers a range of portable and permanent mount units.

Advantages

  • Very easy to use
  • Accurate
  • Flexible
  • Uniform mixture of fertiliser and water
  • Comparatively low cost when considering benefits and ease of use.
  • Relatively easy to install and maintain.

Disadvantages

  • Requires an electric supply (although can run off 12V DC battery)
  • Low pressure system dictates a slightly lower mainline flow rate

6. High Pressure Electric Pumped System

High pressure pumped systems offer all the advantages of the low pressure pumped systems except they can operate at higher mainline pressures and therefore operate at full mainline flow rates.

High pressure pump systems often use a solenoid, diaphragm, piston or some other direct pump.

Advantages

  • Easy to use
  • Very Accurate
  • Flexible
  • Uniform mixture of fertiliser and water
  • Comparatively low cost when considering benefits and ease of use.
  • Relatively easy to install and maintain.

Disadvantages

  • Requires an electric supply
  • More expensive than low pressure electric pumped systems, hydraulic pumped systems or venturi pump systems

7. Hydraulic driven pumped system

These units do not have any electric requirements, the power to drive the hydraulic pump motor comes from the water pressure and flow. Whilst this results in a slight lowering of water pressure, full mainline water flow is essentially available.

These units have a mechanical method of setting the fertiliser dose rate which is very accurate and comparatively simple. The user simply turns a fitting which shows a linear scale of either “% concentration” or “ratio”.

Due to their flexibility and the fact that they do not require electricity, they are a very attractive unit worthy of consideration. They cost more than “Low pressure electric pump systems” but offer a broader range of water flow rate and can pump greater fertilizer volumes.

Advantages

  • Easy to use
  • Very Accurate
  • Flexible
  • Uniform mixture of fertiliser and water
  • Comparatively low cost when considering benefits and ease of use.
  • Relatively easy to install and maintain.
  • No requirement for external power supply

Disadvantages

  • More expensive than low pressure electric pumps or venturi pump systems
  • Replace seals annually.
  • Sensitive to air pockets

fertigate‘s MixRite 2.5 hydraulic powered fertilizer pump is ideally suited for all residential requirements, including flower, vegetable, tree, lawn, bonsai and orchid fertilizing.

 

With an understanding of the types of automatic fertilizing systems available, please refer to our selection guide which will step you through the selection process to assist you selecting the most appropriate automatic fertilizer system for your requirements.



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