Editor's Choice


Electronics light the road ahead for the agriculture sector

23 June 2021 Editor's Choice Opto-Electronics

We are all aware of how the continual evolution of electronics technologies impacts our society, and the vital role they play in many commercial and industrial markets.

The agriculture/horticulture sector is no exception.

Electronic sensors can be used both on the land and in the air to provide data to help farmers make decisions. These range from multispectral sensors deployed on drones that gather information on how farmers can water their crops for the best possible produce, to sensors that indicate when crops need more nitrogen so they can use fertilisers appropriately, to water measuring sensors that give accurate information on the rates and times when plants need irrigation.

These technologies extend far beyond the hardware level, incorporating all the latest buzzwords like artificial intelligence (AI), machine learning (ML) and the cloud. Per the June 2020 research report ‘Paving the way towards digitalising agriculture in South Africa’ (accessible via www.dataweek.co.za/*jun21-agrireport), produced by Research ICT Africa and commissioned by Microsoft, the application of advanced technologies such as ML, AI computer vision, remote sensing, unmanned aerial vehicles (UAVs) and the Internet of Things (IoT) has the potential to transform the agricultural sector under the right enabling conditions. The application of these technologies is part of a broader digital transformation that is occurring globally and is increasingly manifest in the agriculture sector.

The digitalisation of agriculture is defined by the conversion of measurements of agricultural inputs and outputs into digitally stored data for use in automated systems and applications that provide information and assist decision-making. Hence, this transformation unveils an array of opportunities that may help to address South Africa’s food security challenges, create jobs and address historical inequalities. There are also risks involved in the digitalisation of agriculture. These include the potential for digitalisation to cause job losses, further marginalise African countries in the global supply chain as well as increase or create new inequalities.

To put the current state of the sector into perspective, the Food and Agriculture Organization of the United Nations (FAO) estimates that the world’s population will increase by 2 billion by 2050 and during this time land under cultivation will only increase by 4%. Driving sustainable agricultural practices and the development of rural areas is equally important to eradicate extreme poverty and hunger in South Africa and the rest of the African continent. With an estimated 20% to 50% of the South African population being food insecure, food insecurity will become an increasingly urgent challenge.

As of the second quarter of 2019, the agriculture sector employed 885 000 people in South Africa. Due to droughts, the sector did not perform well over that period, but it has the potential to contribute at least 3% towards gross domestic product (GDP). Despite this relatively small contribution towards GDP, agriculture is of great economic importance in South Africa and is the primary sector in rural areas. Furthermore, close to 8,5 million people are directly or indirectly dependent on the industry for their employment and income.

South Africa’s agriculture sector comprises 35 000 registered commercial farmers, 40% of which are engaged in field crop farming, with 60% focused on livestock farming. There are 4 million smallholder farmers in South Africa that are comprised almost entirely of the native black population, farming mainly in former homeland areas on 13% of agricultural land. In contrast, there are 35 000 white farmers (mainly large-scale) producing approximately 95% of agricultural output on 87% of agricultural land.

The Research ICT Africa report goes on to outline the need for policymakers to view the agriculture sector as part of a wider global value chain ecosystem. It recommends concrete measures such as updating policy frameworks, circumventing the limitations of current physical infrastructure, addressing digital inequalities, coordinating efforts to upskill the sector, creating opportunities for finance and harnessing the potential of PPIs (public-private interplays).

Behind all the policies and frameworks, significant advances have already been made in the underlying technologies that power digital transformation in this sector, none more so than the use of LEDs to grow plants efficiently and effectively.

The use of LEDs in horticulture

One of the first questions asked when talking about the use of LEDs for horticulture is, is it as good as the sun? The short answer, in the words of Willem Schmidt – product support engineer at Altron Arrow – is “nothing is as good as the sun and no matter how energy efficient LEDs are, there is still some carbon footprint associated with their use. In South Africa we are also blessed with more sunny days than Europe and other parts of the world, which makes justifying the expense of electronics as a supplement even more difficult.”

There are, however, major advantages to adding the smart use of electronics in horticulture projects. How do you plan exact crop cycles by relying only on nature when seasonal variations disrupt your plans? What if the sun does not shine for several weeks or you get a cold front when you have to deliver a certain amount of fresh herbs for a restaurant or hotel group? Schmidt points out that with the aid of smart electronic systems, factors like temperature, humidity, fertilisation and lighting can all be controlled, effectively making the growing of plants similar to baking your favourite dish with a recipe. The same would also apply to chicken farms where light spectrum, intensity and duration are used for broilers (a chicken that is bred and raised specifically for meat production) to ensure that the chickens reach a certain target weight within a certain controlled period. By employing electronic sensing and control, the farmer can manage the growth rate and the date he wants to harvest his crop in advance.

Focusing on LED technology specifically, Schmidt says by 2016 the efficacy levels of LEDs reached a point where they became a viable option for use in horticulture, and this was the point where various major brands like Cree, Osram, Samsung and others started to invest heavily in the development of LEDs specifically for the horticulture market.

“There are mainly three types of designs or strategies utilised,” he elaborates. “The first and most popular is top-lighting or greenhouses, where LED lighting is often used as supplementary lighting to ensure minimum light levels are present and to provide the option of extending daylight hours. In this type of design it is easier to cater for larger and taller plants. In some cases the lighting system could also be lowered to maintain a certain fixed height above the plant in order to supply a higher intensity of light throughout its lifecycle.

“The second type of design is called inter-lighting, where the light source is placed between the plants and leaves. Because LEDs run at much lower temperatures than high-pressure sodium vapour (HPS) luminaires, this can be done without damaging plants. This type of farming has not been used as widely in South Africa compared to Europe where sunlight is not as plentiful.

“The third strategy is vertical farming, where layers of plants are stacked and the light is placed directly above the crop, in close proximity. The advantage of this type of design is that an area with a comparatively small floor space can be maximised and plants can be grown completely under artificial light without any daylight whatsoever.”

Lighting terminology used in horticulture

Diving deeper into the science, Schmidt explains that the way plants absorb light energy differs radically from how humans see light. The visual spectrum that the human eye responds to spans from around 380 nm to 750 nm in wavelength. Although intensities are very low at the extreme wavelengths, sunlight covers the full spectrum from ultraviolet into the deep infrared range.

For measurement purposes in plants, only the photosynthetically active radiation (PAR) range of 400 nm to 700 nm, where photosynthesis occurs, is used. With general lighting, lumen measurement is used to define the total amount of light available. For plants, micromole (μmol) is specified as the amount of photons available for plants to use in photosynthesis.

The photosynthetic photon flux (PPF) is the total amount of micromoles from the fixture. It is measured in μmol/s and is a similar measure to lumens for general lighting.

Photosynthetic photon flux density (PPFD) is the total amount of micromoles falling on a specified area, measured in μmol/s·m2 and is akin to lux output in general lighting applications.

Chlorophyll a and chlorophyll b refer to the pigment used to absorb radiation for photosynthesis. Chlorophyll a efficiently absorbs red light while chlorophyll b efficiently absorbs blue light (Figure 1). It is for this reason that blue LEDs in 450 nm and red LEDs in 660 nm wavelengths are so popular in horticulture lighting designs as the core components. Although other wavelengths may not fall in the peak absorption areas mentioned, they also play a part in a plant’s development. The PAR region already described only covers 400 to 700 nm, but illuminating a plant with a high ratio of the -730 nm wavelength would result in accelerated stem growth.

“Changing the light spectra could be used in farming to stimulate certain responses in plants and in this manner the body mass and shape could be manipulated and the timing of flowering could be controlled”, continues Schmidt. “The optimal photon flux density required for plants also completely differs between species. Tomatoes are typically grown in full sunlight and can handle a much higher photon flux density than tulips, for example.

“Because plants are so unique in their individual requirements, the electronic control gear in horticulture plays a major role in ensuring that the plant receives the correct light spectra, at the correct intensities, at each specific stage in a plant’s life cycle. Leveraging our broad portfolio of sensors and LEDs, Altron Arrow works closely with local designers to assist them in customising their electronic control gear and lighting systems for their unique requirements.”

Lighting spectral control with Bluetooth Mesh and IoT technologies

Traditional horticultural lighting made use of HID (high-intensity discharge) and fluorescent lamp technologies. In general, metal halide lamps or cool white fluorescent lamps have been used for vegetative growth and sodium or warm white fluorescent lamps for flowering. This has meant that installations would often have to change lamp sources during different growth phases.

With the massive jump in LED efficiency, many horticultural installations are now moving away from traditional sources to LEDs and with the added benefits of extended lamp life, higher operating efficiency and reduced heat generation, LED technology is finally beginning to compete with traditional sources – but there is an additional factor that is often overlooked. LEDs are digital, meaning they are easy to dim electronically and with multi-channel LED sources it is now possible to dynamically change the spectrum of the same luminaire without swapping the lamp source by dynamically dimming each colour channel to simulate different seasons and growth stages.

Plants have evolved under natural sunlight. In order to simulate a particular season, there are three major factors that drive the different metabolic processes: temperature, DLI (daily light integral) and spectral content. This is where the South African company GT Developments comes in. By using Bluetooth technology, its products allow all the luminaires in a facility to be dynamically, wirelessly connected together.

As Bluetooth is a completely open protocol, all the necessary control interfaces, sensors and controllers can be added to the existing Bluetooth network. All the data is captured through a gateway and sent to the cloud. This enables horticulturalists to easily design growth recipes and use standard server-based IoT algorithms, allowing them to monitor, log and control luminaire brightness, spectral content, DLI, air temperature, water temperature, pH, EC, atmospheric CO2, etc. – all through standard IoT interfaces provided by infrastructure providers like Microsoft Azure, Amazon Web Services and Google Cloud, using existing IoT engines and API infrastructure.

The Bluetooth Mesh protocol also has standard defined models for lighting, sensors and generic I/O and level models, allowing any device to be dynamically added to the network to increase the amount of data captured. As lighting infrastructure extends beyond the greenhouse, the same Bluetooth control nodes can be installed into luminaires used for general illumination and the wireless network they create can be used to support other applications like access control, security, HID devices and more.

One product worth noting in GT Developments’ portfolio is the Madea 119 modular LED system. Each module is designed to run in passive mode at up to 3,2 µmol/J, 470 µmol/S at 150 W giving you the one of the most energy efficient units available. When you need the highest possible PPD output you can switch the device into boost mode which pushes the wattage to 250 W, 753 µmol/S and turns on the fan in order to not reduce lamp life.

The fully modular Madea 119 features fully controllable spectrum, is cabled network and Bluetooth-ready, powered by Osram LEDs, locally designed and manufactured and comes with pre-programmed recommended spectra. It is available in a single 150/250 W unit with a single power supply enclosure or a double 150/250 W unit, also with a single power supply enclosure. Every power supply enclosure comes standard with a data interface connector that can either be used to network all the luminaires together or plug in the wireless Bluetooth transceiver to wirelessly control an entire installation.

For more information contact:

• Willem Schmidt, Altron Arrow, +27 11 923 9600, wschmidt@arrow.altech.co.za, www.altronarrow.com

• Michael Nel, GT Developments, +27 81 719 3479, michael@gtdevelopments.co.za, www.gtdevelopments.co.za


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