132
Subtle Agroecologies
any method to quantify the condition of the plant and the risk for those stressors causing economic
damage? and How can you measure improved resilience after the application of biostimulants?
During one of many feld visits to greenhouse growers, I experienced a kind of life-changing incident. A top-level Dutch gerbera grower I was visiting had been facing serious problems with his
crop from the moment he had installed a combined heat and power (CHP) system in a room next
to his new greenhouse. Yearly production fgures gradually dropped from 300 to 200 fowers/m 2 ,
and in addition to that, chemical pesticides showed sub-optimal performance. This had already
been going on for more than a year, and no one was able to discover the reason for these problems.
While brainstorming during a stroll through the greenhouse, a seemingly simple remark of the
grower drew my attention. He said that the irrigation water pipe from the borehole to the greenhouse was installed very close to the CHP’s power output cable. This did not feel right, although
I could not fnd any hard evidence against it. Despite this, and desperate to solve the problem, the
grower changed the irrigation water supply from borehole to tap water and started using a water
vitaliser (a device that improves the molecular structure of water by exposing it to certain vibrations). The result was beyond all expectations: within a week, the grower observed visible change in
the plants’ appearance, and after some weeks, production returned to the previous high level of 300
fowers/m 2 on a yearly basis. This broadened my perspective, and I started collecting publications
about plants, stressors and electric phenomena and undertook some basic measurements myself in
ongoing experiments and with practical growers to become more familiar with the topic.
This chapter is a compilation of what I have learned from publications, participating in experiments and talking to people who are already more familiar with this topic. It has been an interesting
journey, one which has perhaps only just begun. To begin with, the following section explains the
main electrical terms used.
EXPLANATION OF SOME ELECTRICAL TERMS
For a good understanding of the rest of the chapter, here are some short defnitions of terms related
to electricity. Electricity is the set of physical phenomena associated with the presence and motion
of matter that has a property of an electric charge: electrons, as well as protons (H+) and other ions.
At the beginning of the nineteenth century, electricity was considered as being unrelated to magnetism. Later on, many experimental results and the development of Maxwell’s equations 1 indicated
that both electricity and magnetism are from a single phenomenon: electromagnetism.
The movement of any moving charged particles through a conductor is known as an electric
current, measured in (milli)amperes. A simple voltmeter can be used to measure the voltage (or
potential difference) between two points in a system; often a common reference potential, such as
the ground of the system, is used as one of the points. A voltage may represent either a source of
energy (an electromotive force which can create a current) or lost, used or stored energy (potential
drop). Current can fow through electrical conductors meeting a certain resistance (measured in
ohms). The resistance is a consequence of the motion of charged particles through a conductor. In
metals, for example, resistance is primarily due to collisions between electrons and ions.
Conductivity is expressed in mS/cm and is the inverse parameter of resistance. Liquids show a
lower resistance (or higher conductivity) when more ions/electrolytes are dissolved.
Current can be direct current (DC) or alternating current (AC). DC is a one-directional fow
of charge; AC reverses direction repeatedly at a certain frequency (expressed in Hz, fuctuations per
second). This is often sinus shaped, but other shapes such as blocks also exist.
The electrical properties of inductance and capacitance are only observed under AC.
Inductance describes the tendency of an electrical conductor, such as a coil, to oppose a fuctuation
in the electric current going through it. A capacitor is a device which allows electricity to pile up by
1 Maxwell’s equations describe how electric and magnetic felds are generated by charges, currents and changes in the
felds.
Subtle Agroecologies
any method to quantify the condition of the plant and the risk for those stressors causing economic
damage? and How can you measure improved resilience after the application of biostimulants?
During one of many feld visits to greenhouse growers, I experienced a kind of life-changing incident. A top-level Dutch gerbera grower I was visiting had been facing serious problems with his
crop from the moment he had installed a combined heat and power (CHP) system in a room next
to his new greenhouse. Yearly production fgures gradually dropped from 300 to 200 fowers/m 2 ,
and in addition to that, chemical pesticides showed sub-optimal performance. This had already
been going on for more than a year, and no one was able to discover the reason for these problems.
While brainstorming during a stroll through the greenhouse, a seemingly simple remark of the
grower drew my attention. He said that the irrigation water pipe from the borehole to the greenhouse was installed very close to the CHP’s power output cable. This did not feel right, although
I could not fnd any hard evidence against it. Despite this, and desperate to solve the problem, the
grower changed the irrigation water supply from borehole to tap water and started using a water
vitaliser (a device that improves the molecular structure of water by exposing it to certain vibrations). The result was beyond all expectations: within a week, the grower observed visible change in
the plants’ appearance, and after some weeks, production returned to the previous high level of 300
fowers/m 2 on a yearly basis. This broadened my perspective, and I started collecting publications
about plants, stressors and electric phenomena and undertook some basic measurements myself in
ongoing experiments and with practical growers to become more familiar with the topic.
This chapter is a compilation of what I have learned from publications, participating in experiments and talking to people who are already more familiar with this topic. It has been an interesting
journey, one which has perhaps only just begun. To begin with, the following section explains the
main electrical terms used.
EXPLANATION OF SOME ELECTRICAL TERMS
For a good understanding of the rest of the chapter, here are some short defnitions of terms related
to electricity. Electricity is the set of physical phenomena associated with the presence and motion
of matter that has a property of an electric charge: electrons, as well as protons (H+) and other ions.
At the beginning of the nineteenth century, electricity was considered as being unrelated to magnetism. Later on, many experimental results and the development of Maxwell’s equations 1 indicated
that both electricity and magnetism are from a single phenomenon: electromagnetism.
The movement of any moving charged particles through a conductor is known as an electric
current, measured in (milli)amperes. A simple voltmeter can be used to measure the voltage (or
potential difference) between two points in a system; often a common reference potential, such as
the ground of the system, is used as one of the points. A voltage may represent either a source of
energy (an electromotive force which can create a current) or lost, used or stored energy (potential
drop). Current can fow through electrical conductors meeting a certain resistance (measured in
ohms). The resistance is a consequence of the motion of charged particles through a conductor. In
metals, for example, resistance is primarily due to collisions between electrons and ions.
Conductivity is expressed in mS/cm and is the inverse parameter of resistance. Liquids show a
lower resistance (or higher conductivity) when more ions/electrolytes are dissolved.
Current can be direct current (DC) or alternating current (AC). DC is a one-directional fow
of charge; AC reverses direction repeatedly at a certain frequency (expressed in Hz, fuctuations per
second). This is often sinus shaped, but other shapes such as blocks also exist.
The electrical properties of inductance and capacitance are only observed under AC.
Inductance describes the tendency of an electrical conductor, such as a coil, to oppose a fuctuation
in the electric current going through it. A capacitor is a device which allows electricity to pile up by
1 Maxwell’s equations describe how electric and magnetic felds are generated by charges, currents and changes in the
felds.