Undercover Farming Magazine September/October 2019

Undercover

farming

ucf

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september/OCTOBER 2019 Volume 16 No 5

I  I R40.00

CROP PRODUCTION

FOOD SECURITY

produce

cannabis

Blueberries Blooming Page 4

Dehumidification Important Page 10

Packaging of Fresh Produce Page 14

Status of Cannabis Page 17

OFFICIAL PROGRAMME: Undercover Farming Western Cape Conference 9-10 0ctober - inside (Pp12-13)

Eco-friendly rain-water harvesting and solar panelling, reducing environmental impact

KwaZulu-Natal’s only commercial plant tissue culture laboratory

Produces 3 million plantlets a year, expanding to 5 million in future

DUBE AGRILAB, BRINGING YOU CUTTING-EDGE FARMING TECH Dube AgriLab supplies high-quality, disease-free, true-to-type young plants through tissue culture.

Located within Dube TradePort Special Economic Zone, adjacent to King Shaka International Airport in Durban, Dube AgriLab is a commercial plant tissue culture laboratory. The facility is specifically geared to servicing the plant propagation needs of local, national and international farmers and professional growers. Utilising an innovative temporary immersion system (TIS) for the more efficient production of tissue cultured plants,

Dube AgriLab can produce 5 million plantlets a year. Through Dube AgriLab’s technical expertise, the laboratory also undertakes research and development, as well as develops protocols for a variety of agricultural and horticultural plants.

This is an eco-friendly facility, utilising rain-water harvesting and solar panelling to reduce its environmental impact, whilst back-up generators maintain the unit’s sterile conditions - preventing contamination and stock loss - in the event of power outages.

FOR MORE INFORMATION, PLEASE CONTACT: MELISSA TIMOTHY E. AGRILAB@DUBETRADEPORT.CO.ZA T. +27 32 814 0000 WWW.DUBETRADEPORT.CO.ZA

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MAIN ARTICLE

PROPRIETOR I ADVERTISING SUZANNE OOSTHUIZEN 012-543 0880 I 082 832 1604 suzanne@axxess.co.za EDITORIAL CONTENT & COMPILATION Johan Swiegers 082 882 7023 editors@axxess.co.za ADDRESS PO Box 759, Montana Park 0159 E-MAIL magazine@axxess.co.za FAX 086 518 3430 ADDRESS PO Box 759, Montana Park 0159 DESIGN Fréda Prinsloo PRINTING Business Print Centre DISCLAIMER Undercover Farming accepts no responsibility for claims made in advertisements or for opinions and recommendations expressed by individuals or any other body or organisation in articles published in Undercover Farming.

COPYRIGHT Copyright is reserved and the content may only be reproduced with the consent of the Editor.

Subscription Online subs: Email to suzanne@axxess.co.za If you subscribe on-line, e-mail your deposit and address details to: magazine@axxess.co.za.

More information from Suzannne Oosthuizen: 012-543 0880.

Subscription form available on inside back page. visit us at I besoek ons by

Scripture for Guidance

Proverbs 16:1-3(KJV) The preparations of the heart in man, and the answer of the tongue, is from the Lord.

All the ways of a man is clean in his own eyes; but the Lord weigheth the spirits. Commit thy works unto the Lord, and thy thoughts shall be established.

Contents 4 8

Blueberry cultivation in South Africa blooming

FRONT PAGE: Blueberry Cultivation in South Africa Blooming. See page 4.

Accuracy of dosing pump controls important for the producer’s ROI

10 Research: Why dehumidification is important to your greenhouse

INSIDE ...

12 OFFICIAL PROGRAMME: Undercover Farming Conference Western Cape ’19

14 Packaging for fresh produce: Important utility, but?

15 Perlite boosts fertiliser efficiency and plant growth 16 Status of Cannabis-containing products (including oils)

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and the cultivation of cannabis for medicinal use

17 First SA license for Cannabis cultivation 18 Nutrient recipe for peppers produced in a hydroponics system

17

20 Growing in Rockwool: A professional’s opinion 22 New Technology: Woven grow bags versus plastic bags?

23 Subscription form 14 18

I

t is one thing to become a farmer because of your tradition, where you grew up and have been exposed to all the disciplines of agriculture, but quite another to decide to purchase a farm and come away from the rushed life in the city. Because the demand for fresh produce rises sharply, influenced by healthy living advice from various walks of life and the bombardment of eatery television shows, many newcomers to agriculture becomes interested in greenhouse and shade net farming. The only way these can make a success is to obtain all the necessary training, background and financial implications as well as the current market demands for fresh produce before even looking for farmland. Yes, there is always money to be made with foodstuffs and yes, there is always space for more farmers to enter the agricultural industry, especially if we can get young people interested in it. These days, although many challenges face producers, more than many systems are in place to accommodate newcomers with zest and an aptitude for management and marketing. A recent comment stated the difference between marketing your own product versus obtaining the services of a fresh produce agency of repute (and we must repeat; repute) who have access to a wide list of foreign markets. It is proved that by using such an agency, the producer in actual fact puts more money in his pocket. As usual, we focus in this issue on a few important issues across the board of the undercover farming industry. On 9-10 October delegates will once more gather at Allée Bleue, Groot Drakenstein in the Boland to listen to speakers presenting subjects of current interest and they will be able to speak to a variety of service providers in the industry. The Undercover Farming Conferences in the Western Cape and Pretoria, over many years are the outstanding events for producers of fresh produce, flowers and fruit under protective cover to rub shoulders and we are looking forward to welcome you all!

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Blueberry farming under the protective cover of shade net structures has tremendously increased in hectares of recent. It is a high value crop and earns a valuable foreign income for the producer.

At the same time, because of the various disciplines in cultivating the berries, the process also offers good employment prospects.

Blueberry cultivation in South Africa blooming

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he blueberry belongs to Vacciniaceae, a subfamily of Ericaceae. All blueberry plants in South Africa originated in USA states. There are 3 commercial types of blueberry, namely the Highbush, the Lowbush and the Rabbiteye blueberry.

The Highbush blueberry has been developed primarily from 2 species, V. corymbosum and V. australe.

The Rabbiteye blueberry (V. ashei Reade) is extremely heterozygous. The plant is generally vigorous, growing to a height of 3 metres or more. Berries vary in colour from glossy black to light blue, small to medium large in size (15mm).

The name Rabbiteye comes from the observation that the blossom ends of wild V. ashei blueberries (large shallow calyx) resemble the conformation of the eye of the common wild rabbit, a pink spot resembling a rabbit’s eye forms on the wild berry when it begins to ripen and takes its dark colour.

In general, the Rabbiteye blueberry plant is classified as erect, spreading and very vigorous. Vigour is generally thought of as stem length or plant density, but should consider plant vitality, too. This species is often considered by plant breeders to offer the greatest possibilities for improvement because of its tolerance to a wide range of soil pH and high temperatures, its inherent drought resistance and its low chilling requirement.

Commercial blueberry cultivation in the southern and western cape of South Africa is primarily concerned with the Rabbiteye blueberry and, more recently, the Southern highbush blueberry. In the north-east of thecountry, the Climax and Tifblue varieties of Rabbiteye blueberries are planted.

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A highbush variety blueberry bush ready to be harvested.

Harvesting blueberries is done manually and therefore creates employment.

Currently, two blueberry types, Highbush and Rabbiteye, are grown commercially worldwide.

Rabbiteye (Tifblue and Climax) are vigorous and grow to about 3m.

This heterozygous variety is suitable for most areas in South Africa. On the other hand, Northern Highbush varieties such as Elliott, Bluecrop, Brigitta, Berkley and Chandler are found suitable for colder areas due to their chilling requirement (more than 700 hours below 7°C) to break dormancy.

Propagation Blueberries are usually propagated from softwood or hardwood cuttings selected from healthy, disease-free mother plants.

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Cuttings are placed in a propagation bed in a growing media that holds moisture well, but allows adequate aeration. A peat / fine pine bark blend or sawdust has proven ideal. Water is delivered by means of an intermittent misting system.

The misting system should apply water for 10 to 30 second periods each 15 to 30 minutes to ensure that the cuttings remain moist.

Certain commercial nurseries may propagate blueberry plants by means of Tissue culture. The shoot tips are induced to produce multiple shoots in agar media

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Blueberry Cultivation

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supplied with modified standard culturing solutions. After sub-culturing, the shoots are cut off and placed into a peat-perlite rooting mixture under mist, where they root readily.

Establishment and Layout The blueberry is an acid-loving plant – it requires a low pH soil or growing media (4.2 – 5.0 KCl pH) that is relatively low in Calcium and Phosphorous, drains easily and has a high percentage (>2.0 %) of organic material present. Due to the fact that the root system is shallow, fibrous and does not have root hairs present, the plant is a poor competitor for nutrients against weeds. A pine bark mulch on the row or ridge surface of approximately 5 to 10 cm in depth assists in maintaining the moisture for the shallow feeder roots, which are often found only a few millimetres below the soil surface. As the mulch breaks down, the roots will grow into it.

Blueberry plants are usually established as an orchard or field. The plant spacing is commonly 1 to 1.5 metres between plants in the row by 2.5 to 3 metres between rows. This results in a plant density of between 2666 and 3333 plants per hectare. In shallow soils or fields

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that have a relatively shallow water table (around 300mm below the surface), it is preferred to ridge the rows in order to increase the depth of soil for root development above the water table or clay layer that may be present in a lower horizon.

In trials, it has been found that the plant has a preference for pine bark as a mulch or organic material addition in the soil profile. Blueberries can be established in pine bark beds or plant pots. The planting density is increased drastically as compared to the conventional ‘orchard’ layout. A typical spacing for pine bark beds is 900mm between plants within the row by 1.5 metres between the rows. Although production per plant in such a system is lower, the production per hectare is higher than the ‘orchard’ layout.

The harvest period will depend on environmental factors (climate etc.) and cultivar selections. It is preferred to plant at least three cultivars in each field. This is not required for Southern Highbush cultivars but it is vital for Rabbiteye cultivars. The Rabbiteye blueberry is dependent on the presence of compatible companion cultivars for cross-pollination.

Pollination of blueberry flowers by bees.

The companion plants can either be planted within the same row as the primary cultivar or planted in separate rows. For ease of harvesting, separate rows have proven more popular on blueberry farms in South Africa to date.

Pollination When the plants are set into the field, it is important to break up the root-ball or make several vertical slashes with a knife. In transplanting the blueberry plants from the bags into the field, care should be taken to keep the roots from drying out. All flower buds should be removed from new plants. Newly set plants should not be allowed to flower and fruit in the first year unless the plants have sufficient growth and leaf numbers to support fruit development.

Blueberry plants should be planted in either late autumn or in early spring.

Autumn planting allows the plant more time to establish roots before the spring growth begins. The plants should be set at the same depth as they grew in the nursery. The shoulder of the root-ball should not be exposed because this will cause a wicking effect and dry out the root-ball. If the plants are planted too deep, covering the crown, the plants will

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seem to be stunted, not showing any growth for a prolonged period.

Do not apply fertilizer in the planting hole at the time of planting. Another planting system is to dig individual holes of about 50cm by 50cm in size, and fill these holes with a mixture of soil and peat moss, and set the plants in the same way as stated previously.

Irrigation Newly established plants have the most critical water needs, and can be damaged by either over-watering or underwatering. Short periods (1 to 3 weeks) without rain can stress blueberry plants severely. Irrigation during such periods is required for optimum plant performance.

Irrigation of producing blueberry plants during dry periods before harvest results in larger berries and higher yields.

Irrigation in February and March will stimulate growth and fruit bud formation, thus increasing the potential yield for the following blueberry season.

A rapid decrease in soil moisture during dry periods increases the concentration of fertilizer nutrients in the soil solution, which may damage the roots of the blueberry plant. The water requirements of the blueberry plant increases as the plant increases in age and size, but varies according to soil type, organic matter, and natural climatic conditions.

The irrigation system for blueberries should be suited to the requirement of the plant. It should be able to apply relatively small amount of water to a wide surface of the soil on a frequent basis. A micro-sprinkler system proves ideal in spreading the water across the area of the root system. It also aids in ‘watering in’ any fertilizers that may be applied to the soil surface around the plant.

Drip irrigation systems have proven to be problematic in providing sufficient water to the shallow root zone as the soil / organic material blend is generally too loose and ‘airy’ for the water to spread laterally. Most of the water travels down to the lower soil layers. In periods when the plant is in need of larger amounts of water, this may prove fatal to the plant, due to the roots drying out and dying.

Many different irrigation systems are

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For shipment of highly perishable small fruits to fresh markets, consider hand harvesting, grading, and packing into consumer packages, all in one operation, in the field The harvesting of export blueberry fruit is by hand, thus highly labour intensive. The availability of an adequate and dependable supply of hand Plant nutrition pickers at harvest time is a continuous Although blueberry plants do not, problem for blueberry growers. traditionally, require as much fertilizer The fruit is picked directly into 125 as most other crops, it is vital to follow or 150 gram clamshell punnets, in a balanced nutritional program. The which the fruit will be sold to the end blueberry plant is salt sensitive and consumer. The picker is responsible for nitrate sensitive therefor the size and quality grading. This drastically correct placement and reduces the amount of handling which amounts of fertilizer the fruit undergoes, and allows the applied should be waxy bloom to remain on the fruit. The closely monitored. punnets are then transported to the Ensure that no refrigeration facility, and reduced to a fertilizer is applied temperature of 2.0 to 2.2°C, within as directly against short a time period as possible. the crown of Thereafter, the punnets are checked the plant, but and weighed again, as a form of quality rather in a hollow control. This quality control occurs in ‘doughnut’ shape a refrigerated room, which does not around the plant, exceed 8°C, alongside the cold room, avoiding possible therefore, a double-chamber cold room crown damage and is ideal. The fruit does not leave the ensuring coverage of the refrigerated area until it is packed and whole root area. sealed into foam export boxes. From Nitrates and chlorides should be avoided there, it is transported to the nearest in fertilizer blends for blueberry plants. airport, or shipped by road, to an Preferably, Ammonium sulphate, Mono international airport, from which it is Ammonium Phosphate (MAP) or Urea flown to overseas markets. should be used as a nitrogen source.

Mechanical harvesting is, as yet, Potassium sulphate or Mono Potassium not used in South African blueberry Phosphate (MKP) are suitable sources growing. Berries that are mechanically or potassium. harvested have been of a lower quality Granular or dry fertilizer than those that are applications can be applied Mechanical harvesting hand harvested, and in just a few applications to is, as yet, not used traditionally sold only on reach the target amount the processing market. in South African for the season. Fertilizer New developments in blueberry growing. applications of 30 (younger mechanical harvesting plants) to 50 grams have resulted in less damage to fruit and (older plants) are common practice. a ‘softer’ process. The introduction of Fertigation is a ‘spoon-feeding approach, blueberry colour sorter machines has where smaller amounts of fertilizer are proven successful in the USA. applied by means of an injector through Pruning the irrigation system. Fertilizer can A light pruning may be conducted when be injected once or twice a week planting the blueberry plants in the in this way. orchard. The thin, twiggy growth and any Rabbiteye blueberries require sickly or diseased wood are removed, significantly less fertilizer than the leaving only healthy, stronger shoots.

Southern and Northern highbush types.

Pruning in subsequent years is based on A micronutrient blend should be applied principles of ensuring a balance of 8 to 12 as a foliar spray or through fertigation on shoots from young to mature, sufficient a regular basis throughout the growing light penetration and distribution season. Leaf samples taken on a regular throughout the plant, leaving no limbs basis will show if elemental levels are that may hang onto the ground surface optimum or not within the plant. once bearing fruit (skirting the bush) Harvesting and Packing and removal of any old fruiting or dead and diseased wood. Branches that are The blueberries will ripen over a period removed during pruning should be hauled of usually 4 to 6 weeks from the first out of the orchard and destroyed. blue fruit to the last for each cultivar. in place in commercial blueberry plantings around the globe – central pivot, overhead, drip, pulse and microsprinkler. It is advisable to contract a professional irrigation organization to design and install the irrigation system most suitable.

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A fresh range of sweet pepper

About Enza Zaden At Enza Zaden we develop new vegetable varieties that are grown, sold and consumed all over the world. So, it’s very likely that you’ll often find our tomatoes, cucumbers, sweet peppers, lettuce or other vegetables developed by us on your plate. We produce and sell the seeds of those vegetables worldwide.

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Accuracy of dosing pump controls important for the producer’s ROI

The accuracy of dosing pump controls are not just important; they are essential to using your dosing pump efficiently, delivering the output you need for your application and getting the best return on your investment.

C

heaper dosing pumps offer a lower initial purchase price, but they usually don’t come with the precision controls you will see on higher-priced pumps, and a solenoid dosing pump may also introduce unwelcome pulsation into its output. For example, in processes where chemical dosing needs to be highly linear, a cheaper solenoid operated pump may create “peaks and troughs” in chemical levels, due to the inherent pulsation effect of this type of pump.

While this may be fine for some applications, making the cheapest dosing pumps the most economical option overall, for more intensive and niche uses it’s crucial that you put some attention into finding the most suitable dosing pump. higher-end pumps, giving you much more The most basic pump controls will allow flexibility to use the pump for almost any you to adjust the speed or the stroke of the pump, or both, but you can get much application. more consistent output using stepperFinally, there are some additional motor or electronically controlled measures you can take to protect your motor-driven dosing pumps. dosing pump and treatment process; installing a pressure relief valve as an On motor driven pumps you can extra safety device in the event of an also install optional pulsation dampers and/ Buying the cheapest dosing injector blockage, or installing an antior pressure retention pump might seem like a siphon valve to valves for more good way to save money, prevent inadvertent consistent output and but it can quickly prove dosing, for example, in reduced pressure the event of a vacuum more costly than investing head loss, allowing the pump to operate in the correct dosing pump forming in the process circuit during a shutin a wider range of from the outset. down period. operating pressures.

Buying the cheapest dosing pump might Dosing control is most important of all seem like a good when the dose rate may be very small, way to save such as is the case when delivering liquid money, but it can flocculants a stepper motor dosing pump quickly prove suitable for output of just a few ml per more costly than hour. These pumps can combine a very investing in the fast suction stroke with a very slow output stroke free from pulsation, so that correct dosing pump from the the overall dose is extremely consistent outset. and reliable. In the long run this accuracy will also deliver savings on chemicals and While many greatly improve the efficiency of your people make their treatment process. buying decision based primarily Stepper pump dosing controls commonly on pump price, it include pulse length, pulse frequency potentially leaves and volt free contacts, especially on

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Choice of the Correct Dosing Pump

you at risk of facing higher maintenance costs, and with a pump that operates at lower efficiency. For example, while solenoid and peristaltic dosing pumps are suitable for light to medium-duty use, relatively low operating pressures and dosing hoses up to around 20 metres, they might not cope with more intensive tasks.

Motor-driven dosing pumps are an alternative for longer hose lengths and higher output volumes; they also offer the benefit of producing lower pulsation effects than you will see from a solenoid pump. This can be enhanced further by fitting them with pulsation dampers, which reduce hydraulic shock and pressure head loss in the dosing pipeline.

As well as delivering smoother output

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over a long dosing hose, this cuts down on pump wear and tear, and reduces the long-term servicing costs of a motordriven or geared pump accordingly.

Whereas geared pumps support larger bore valves and hoses, ideal for sediment-laden media, dosing liquid flocculants demands high precision and very low flow rates potentially as little as a few ml per hour.

Stepper motor dosing pumps handle this well, often with independent stroke speeds for the pressure and suction phase and a smooth output free from pulsation. In this instance a cheap dosing pump might not be an option due to the specific nature of the task at hand, but choosing the correct dosing pump from those that are suitable can still save you money in the long term.

There are reputable pump suppliers in the country that can help by providing technical assistance and specialist application knowledge to find the right dosing pump for your needs – and unlike discount resellers, they offer on-site service and inspection and for any spare parts or accessories you may need to prolong the economical service life of your dosing pump even further. JS

Blueberry Cultivation

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Blueberry plant pruning is usually conducted directly after harvest for early season Southern highbush cultivars and during winter for Northern highbush and Rabbiteye cultivars. The early season Southern highbush cultivars enter a vegetative growth flush within the weeks directly after harvest is complete.

By pruning the plant directly after harvest, stronger, healthier vegetative growth is encouraged as all weak and old fruiting wood has been removed from the plant.

Cultivar selection Cultivar selections will determine to a large extent the ripening period and, in turn, the ability to reach targeted market windows (timeframes). Not all blueberry cultivars available in South Africa are listed.

Pest Management Crop protection of the commercial blueberry orchard is ideally suited to an I.P.M. (Integrated Pest Management) system in South Africa. Many natural pests and diseases of the blueberry plant and fruit are not yet present in South Africa, thus making crop protection easier and

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possibly even less costly than traditional blueberry growing areas. Certain fruit pests in South Africa have become commercially important in blueberry growing, namely, American Bollworm (Helicoverpa armigera) and certain bird species.

Minor pests on blueberry plants may include, but are not limited to: aphids, australian bugs, beetles, loopers, grasshoppers and locusts. Shade net structures are used on most blueberry farms and kept open during the initial planting, growing and dormancy season.

Also when flowering takes place for pollination by bees. Then the shade nets are closed when fruit begins to form to keep out birds and other preying wildlife that may incur losses.

Due to the ecology and differences between specific orchard sites, it is ideal to implement a program such as the Integrated Pest Management Program, monitoring pest and predator populations, and becoming intimately acquainted with the specific site. After a few years of such monitoring, pest forecasting, scenarios and specific problems can be addressed before they actually occur.

Source: MPG Smallfruit et al.

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Research: Why dehumidification is

important to your greenhouse

With summer on our doorstep and the (hopefully) good rain season ahead in the summer rainfall areas, humidity is once more a factor in the greenhouse system to be managed well.

We have to learn from people that have experience over many years and did proper research on this subject – and then adopt it in our systems to prevent losses in productivity.

T

he best way for greenhouse growers to dehumidify greenhouse air is to let outside air in, according to a researcher. Heating this outside air using the outflowing greenhouse air can lead to considerable energy savings.

By providing the perfect climate, locally available solutions enable growers to operate and produce under optimum conditions. The innovative product range includes ventilation, evaporative cooling, and heating.

Producers are aware of the challenges faced in the greenhouse industry and how climate affects plant growth. For instance in extreme conditions the excessive relative humidity can give rise to water droplets forming on the leaves which can harbour and spread disease or fungi, while the excessive heat will shrivel fruits and stop growth. Some other times the conditions outside a greenhouse impact the natural ventilation process negatively.

The key to sustained quality, quantity and profitability lies in awareness of these conditions and their impact, and

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maintaining control of them.

These and some other challenges faced in a greenhouse can be solved by installing the right combination of climate control equipment to the greenhouse to assure perfect conditions for plant growth.

to just ‘set it and forget it’. However, lost yields, plant stress, disease outbreaks, and wasted energy are still as possible as ever unless we realize the limitations of our equipment and the implications of environmental control decisions.

Understanding Humidity Control Humidity can be the most difficult environmental factor to control in greenhouses. Maintaining set points and correcting for too little or too much humidity can be a challenge for even the most sophisticated monitoring and control equipment. Humidity levels fluctuate with changes in air temperature, and plants are constantly adding water to the air through transpiration.

Although automated controls have added a higher level of precision to the art of sensing and correcting humidity levels, it is still important to have a good understanding of the dynamics of atmospheric water vapour. There is a natural tendency with sophisticated equipment

What is humidity?

Humidity is an expression of the amount of water vapour in air. It is an invisible gas that varies between 1 – 4% of our atmosphere by volume. Fogs, mists, and other tiny water droplets are not water vapour.

The maximum amount of water vapour in any given air sample is dependent on the temperature and to a lesser extent the air pressure. The actual amount of water vapour present is also determined by the availability of free water to evaporate.

Water vapour will always move from an area of high concentration (such as inside the leaf cavities) to an area of lower concentration (the greenhouse air).

This is the principle behind evaporative transpiration.

We usually talk of air moisture in terms of relative humidity. Because the absolute amount of water that can be held by air is constantly fluctuating with temperature, relative humidity is a handy way of describing the ratio of water vapour compared to the total amount of water

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to be absorbed for photosynthesis.

Photosynthetic levels can vary by about 5% between VPD’s of 2-10 mb.

Growth and Quality – Most greenhouse plants tend to grow better at higher relative humidity. However, mineral deficiencies, disease outbreaks, smaller root systems, and softer growth are possible consequences of excess humidity.

There is no one level of humidity that is good for all crops.

that could be held in the air at saturation.

Therefore, 50% relative humidity indicates that the air has half the water vapour that it could hold if it were completely saturated. As the air temperature rises, more water vapour can be held in a given amount of air.

And as the air becomes warmer, more moisture must be added to the air to maintain the same relative humidity.

Dehumidification What is vapour pressure deficit?

In greenhouses, we usually try to avoid Relative humidity is still the most humidity levels near commonly used the dew-point since measurement for Humidity is an expression free water condensing greenhouse control, of the amount of water onto plant surfaces even though it is not vapour in air. Fogs, can promote the a perfect indication mists, and other tiny growth of disease of what the plants water droplets are not organisms. Under ‘feel’. Plants respond water vapour. saturated humidity to the difference conditions plants between humidity cannot evaporate water from their leaves levels at the leaf stomata and the humidity so the uptake of nutrients such as calcium levels of the surrounding air. At the same and boron may be limited. It is important relative humidity levels, but at different to remember that when the relative temperatures, the transpiration demand humidity reaches 90%, it takes only a for water from the leaves may be double. slight drop in temperature to reach the Therefore, another kind of measurement, dew-point. called the Vapour Pressure Deficit is The problem is compounded by the fact often used to measure plant/air moisture that not all relationships. Some environmental control surfaces in the companies now offer VPD measurements greenhouse as a part of their humidity management are necessarily programs. at the same Role of humidity temperature The main plant mechanism for coping as the air. Any with humidity is the adjustment of the surfaces that leaf stomata. Stomata opens and close are cooler than in response to vapour pressure deficit; the air at high opening wider as humidity increases. relative humidity When humidity levels drop to about will condense 8 grams / m3 (12 mb VPD), the stomata water vapour. apertures on most plants close to about That is why 50% to help guard against wilting. This dripping can be also reduces the exchange of C02, such a problem thereby affecting photosynthesis. with glazing Transpiration – Plants can control materials during their rate of water loss. Because the the heating leaf stomata have an ability to limit season. transpiration rates, a doubling of the Monitoring moisture deficit may result in only a and controlling 15% increase in the transpiration rate. the relative However, when humidity levels are humidity of the very high, the total uptake of minerals greenhouse air is reduced since plants are unable to is not always evaporate enough water. a guarantee that the dew Photosynthesis – Humidity levels point will be indirectly affect the rate of photosynthesis avoided. Local because C02 is absorbed through condensation the stomata openings. At higher problems can daytime humidity levels, the stomata still occur due to are fully opened allowing more C02

uneven heat distribution and the thermal mass of plant materials, particularly on plants with fruits and other large water filled parts. This causes their surface temperatures to lag behind when sudden changes in air temperature occur.

It’s the same reason a glass of ice water sweats even when the relative humidity of the room air is well below the dew-point. Cold surfaces within the greenhouse cool the air immediately surrounding them. If the cooling reaches the dew-point temperature, water condensation occurs.

Excess humidity is usually more problematic in the spring and fall seasons when the weather is cool and moist.

High humidity is not likely to occur during freezing weather, since the relative humidity of the outside air is very low.

A combination strategy of venting to exchange moist air with drier outside air, and heating to reduce the relative humidity levels, raise the temperature of plant surfaces, and warm the incoming air is usually employed. Glass panes and other cold surfaces in the greenhouse serve as natural dehumidifiers when the outside air is colder, but this, of course, can cause problems with dripping.

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Undercover Farming Conference Wednesday 09 October 2019 09:55

Welcome: Suzanne Oosthuizen - MD: Undercover Farming Expo PTY LTD

10:00 – 10:45

Official Opening / Keynote: Dr Mogale Sebopetsa - Programme: Farmer Support and Development Branch: Agricultural Development and Support Services, Department of Agriculture Western Cape Government “Status Quo of the Department”

10:45 – 11:30

Melissa Timothy - Dube Tradeport Special Economic Zone “The Importance of Biotechnology in the Field of Agriculture in Future Times. Dube TradePort’s role in Enabling Scientific Techniques to be Available to Growers for Supplementation and/or Improvement of Current Agricultural Practices.”

11:30 – 12:00

Tea

12:00 – 12:45

Laura Dewar - GAC Laser International Logistics “Overview of the new Inco 2020 terms and the role of a clearing and forwarding agent for imports & exports”

12:45 – 13:30

Francois Knowles - APAC “Regulation in turbulent times”

13:30 – 14:30

LUNCH

14:30 – 15:15

Mark Hill - Netafim SA “NETBEAT - The first irrigation system with a brain”

15:15 – 16:00

Nico Uys - AgroOrganics “The Microbial Perspective - Not tunnel Vision”

16:00 – 16:30

TEA

16:30 – 17:15

Eldon Kruger - Pratley Marketing “Perlite as growing medium”

17:15 – 18:00

Reinette Champanis - Enza Zaden South Africa “Development of vegetable varieties”

18:00 – 21:00

UNDERCOVER FARMING NETWORK/COCKTAIL EVENT – All REGISTERED DELEGATES INVITED

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Western Cape ’19: Programme Thursday 10 October 2019 08:30 – 09:15

Gail Pedra - Green Meds “Overview of the Cannabis Industry in SA and essential oils - the opportunities in local and export”

09:15 – 10:00

Dudley Pohl - Sunsilicates “Perlite, Vermiculite, Attapulgite - growing mediums”

10:00 – 10:45

Theo Fisher - Escience Associates PTY LTD “Estimating the economic impact of the recent Western Cape drought and the potential for large scale netting as water saving measure”

10:45 – 11:15

TEA

11:15 – 12:00

Deon Snyman - PlusNet/Geotex “An overview of shade netting and shade net cover construction”

12:00 – 12:45

Tom Murray - Woolworths “What is next”

12:45

Official closing of conference

13:00 – 15:00

LUNCH

Allée Bleue Wine Estate Conference Centre Groot Drakenstein Western Cape Undercover farming I

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Packaging for fresh produce: Important utility, but?

The most developed economies are the highest users and producers of packaging. These markets, being fairly mature, are however undergoing significant changes in the packaging value chain due to especially environmental and demographic changes brought about by the so-called new economy.

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t the same time, new opportunities are being created by emerging economies as they strive to satisfy the expectations of their growing populations. Globally, the packaging market is divided into 5 main categories of materials: glass, paper, metal, plastics, board and wood (with textiles being marginal). Historically, this market has seen growth in the use of rigid plastic materials and flexible materials.

Around the world there is a concerted effort to work towards a common goal to, reduce, rework, recycle, recover and renew packaging materials in order to achieve measurable reductions in the total Global Packaging Carbon Footprint.

To achieve this, the choice of material, pack design, manufacturing process, choice of print method and supply chain are essential to consider upfront at the point of packaging design.

The South African scene The total packaging sales in a country can be used as an indicator of the strength of a country’s economy, since almost everything sold must first be packaged.

Notwithstanding; the total value of a country’s packaging as a percentage of the country’s GDP remains relatively small.

In South Africa as far back as in 2012, for example, the total value of the country’s packaging industry was estimated at R43 Billion, contributing about 1.5% to South Africa’s then GDP of R 2.86 trillion.

Driven by commercial and environmental pressures, modern packaging design enables reduced packaging energy and material consumption, translates to reduced warehousing costs as well as reduced supply chain costs, reduced masses to landfill, and therefore, ultimately, a reduction in the overall packaging carbon footprint.

Importance of packaging Packaging is essential for the transportation of goods, to avoid damaging products, to keep food fresh and to protect products against theft and to present the product to the Consumer as intended. Accordingly, packaging is designed with both needs of the product,

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The key factor that separates good packaging from bad packaging is design and innovation.

and the consumer, in mind. Research has found the average household buys on average 3 tons of products per year with an estimated 200kg of packaging. Some products have suitable packaging that is fit for purpose, easy to open and simple to recycle. Others are extravagantly packaged, hard to unpick and not easy to separate out for recycling.

The key factor that separates good packaging from bad packaging is design and innovation. Finding the balance between packaging that meets the needs of both producer and consumer is a given.

What sets really well-designed packaging apart is its relative cost of production and its recyclability. Both of these can be reduced using the right amount of material in packaging, using recycled content where appropriate, designing for re-use or for easy disassembly to improve recyclability and ensuring that, at the end of their useful life, packaging materials are valued as a resource.

ENVIRONMENTAL IMPACT There is no doubt that all packaging materials have some sort of impact on the environment. The question is what types have the greatest impact, and whose responsibility is it to limit environmental costs?

Consumers can minimise the

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environmental impact of products and packaging in mind by: • Not buying products containing unnecessary packaging, such as bubble packs, plastic seals with cardboard backing or bottles inside boxes.

• Choosing products packaged simply and with material that can be recycled.,/ • Not using additional plastic, when purchasing fruit and vegetables, and also to rather opt for fresh produce that is sold without packaging.

• Reusing containers, bags, boxes and paper • Buying products in bulk or in larger containers.

PACKAGING CARBON FOOTPRINTS? A packaging system’s carbon footprint is calculated as the total amount of carbon dioxide (CO2) and other greenhouse gases, emitted over the life-cycle of that product or service, expressed as kilograms of CO2 equivalents.

This calculation includes all greenhouse gases that are generated in the manufacture of raw materials, the production of the packaging system, transport materials and finished systems, the use phase (including refurbishment and reuse) and end-of-life disposal.

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Perlite boosts fertiliser efficiency and plant growth For the greenhouse producer who wants increased productivity, an increase of fertiliser efficiency, together with effective water drainage and optimal soil aeration, are essential processes.

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eing used extensively as a horticultural growing medium, Grolite® from Pratley is a unique, naturally occurring processed mineral. Pratley Perlite Mining, part of the iconic Pratley stable of companies, which first brought its solutions to market in 1948, actively mines a volcanic mineral called Perlite at a unique deposit in South Africa. The ore is processed using proprietary technology to produce major products such as Grolite® for the horticultural and hydroponic industry.

“Grolite® allows for improved fertiliser efficiency, which boosts plant health and growth. It also promotes water drainage, while retaining the required moisture, leading to healthier plants and increased crop yields. In a water-scarce country like South Africa, this is vital to horticulturists,” Pratley Marketing Director Eldon Kruger comments.

Tiny micropores on the surface of the Grolite® particles assist in capturing nutrients and water molecules. The capillary action occurring in the voids

between the particles ensures uniform distribution of water and nutrients, which results in consistent and improved crop yields.

Grolite® also maintains optimal soil aeration, a critical factor in normal plant growth. This is because the supply of oxygen to roots in adequate quantities is essential for healthy plant growth.

Grolite® is processed at temperatures in excess of 950°C, resulting in a sterile product that is completely free of weeds and pathogenic microbes.

Unlike ordinary horticultural Perlites, the unusually strong surface structure of Grolite® means it does not deteriorate during transportation or when being mixed.

“This unique feature means hydroponics farmers, for example, can reuse the product for more than one season, increasing its cost-effectiveness. It’s a feature which is quite specific to Grolite®, as the Perlite raw material is from an older deposit which is unlike perlite

deposits found in other parts of the world,” explains Eldon.

Grolite® is available nationwide in various grade sizes to cater for specific blends.

“Pratley experts are always on hand to discuss specific customer requirements, or to respond to any queries,” Eldon concluded.

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Status of Cannabis-containing products

(including oils) and the cultivation of cannabis for medicinal use On the 18th September 2018 the Constitutional Court handed down a judgment, which declared existing legislation, criminalising the use, possession, and cultivation of cannabis, unconstitutional.

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t would, therefore, now not be an offence for an adult person to: a. use or be in possession of cannabis in private for his or her personal consumption in private; b. to cultivate cannabis in a private place for his or her personal consumption in private.

The Court also found section 22A(9) (a)(i) of the Medicines and Related Substances Act, 1965 (Act 101 of 1965) to be unconstitutional, to the extent that it prohibits the actions listed above, and suggested amended wording to that section, which will be in effect until reviewed by Parliament.

STATUS OF CANNABISCONTAINING PRODUCTS (INCLUDING OILS) The Constitutional Court judgment should not be misconstrued to mean that persons may be allowed to prepare cannabis-containing products, including extract cannabis oils from cannabis cultivated in a private place, and then to sell such products to the public.

Currently, there are a number of outlets and individuals that are selling cannabiscontaining products (including oils) for medicinal use.

In terms of the provisions of section 14(1) of the Medicines and Related Substances Act, 1965 (Act 101 of 1965), “no person shall sell any medicine, medical device or IVD which is subject to registration by virtue of a declaration published in terms of subsection (2) unless it is registered.”

The cannabis-containing products and oils that are currently available in South Africa and which have not been registered or approved by SAHPRA are therefore, illegal. Suppliers and users of such illegal products are exposing themselves and others to legal and health risks as the safety, efficacy and quality of these products cannot be assured.

An applicant wishing to apply for registration of a cannabis-containing product must lodge an application with the SAHPRA. At the same time, an application to licence the manufacturer, importer, distributor of the product has to be submitted (see section 3). The safety, efficacy and quality of the product will be evaluated as well as the compliance with

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GMP requirements.

Status of Cannabis culti­ vation and medicinal use On 1 February 2019 on Page 2 of 3 in an amendment of the Act, if, after review, SAHPRA finds that the product is safe, effective and of good quality, and the manufacturer is GMP compliant, it will be registered, allowing it to be available on the market.

In certain specific instances, however, it is possible to apply for individual patient access to unregistered medicines containing cannabis, or specific cannabinoids (tetrahydrocannabinol and/ or cannabidiol), in terms of section 21 of the Medicines and Related Substances Act, 1965 (Act 101 of 1965). As no quality-assured sources for such products are as yet available in South Africa, approval will need to be sought for the importation thereof from other countries (e.g. Canada and The Netherlands).

To date, 56 such applications have been approved by SAHPRA, based on motivation for use in specific patients by an authorized prescriber.

CULTIVATION OF CANNABIS FOR MEDICINAL USE In order to ensure the availability of standardised, quality-assured, locally grown cannabis for the manufacture of suitable pharmaceutical products, the SAHPRA and the Department of Health may permit the cultivation of cannabis solely for medicinal and research purposes. This framework, developed in consultation with the Department of Agriculture, Forestry and Fisheries (DAFF), is intended to control the cultivation, production and manufacturing of cannabis-containing products intended for medicinal use in South Africa.

Licensed domestic cultivation of cannabis for medicinal use is aimed at ensuring sufficient local supply for medical, scientific and clinical research purposes and the implementation of control measures necessary to prevent diversion and misuse, as well as to ensure patient safety. In November 2017, SAHPRA published a guideline on the “Cultivation of Cannabis and Manufacture of Cannabis-related Pharmaceutical Products for Medicinal and Research Purposes” (Doc No: 2.44; accessible at https://www.sahpra.org.za/Publications/

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DownloadDoc/5576).

This guideline provides information relating to the standards and controls required for the cultivation and processing of cannabis as a herbal starting material and identifies the critical production steps that are needed to ensure a product of reliable and reproducible quality. An applicant may apply to SAHPRA for a licence in terms of the provisions of Section 22C(1)(b) of the Medicines and Related Substance Act, 1965 (Act 101 of 1965) for any or all of the following activities: • Cultivate/grow and produce cannabis and cannabis resin; • Extract and test cannabis, cannabis resin and/or cannabinoids; • Manufacture a cannabis-containing or cannabinoid-containing medicine; • Import a cannabis-containing medicine; • Export a cannabis-containing medicine; • Distribute a cannabis-containing medicine.

The cultivation of cannabis for medicinal use and the manufacturing of cannabiscontaining pharmaceutical products shall be subject to strict monitoring to avoid any diversion for unapproved purposes.

SAHPRA inspectors will conduct com­pli­ ance investigations and inspection of sites applying for a licence to conduct regu­ lated activities as well as licensed sites.

Communication to all stakeholders on; Status of Cannabis cultivation and medicinal use (9.122_Status_cannabis_ Jan19_v1 February 2019 Page 3 of 3 4 STATUS OF LICENCE APPLICATIONS FOR THE CULTIVATION OF CANNABIS FOR MEDICINAL USE) To date, SAHPRA has received 21 licence applications for the cultivation of cannabis for medicinal use. Of these, one application has subsequently been withdrawn. Of the remaining applicants, 16 applicants have been inspected and four (4) applicants are scheduled for inspection. No licences have yet been issued, but a developmental approach to the approval of suitable licencees is being pursued.

However, as pointed out above, in the interim, section 21 approval has been given for the importation of unregistered cannabis-containing products, in order to meet local needs.

SAHPRA

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First SA license for Cannabis cultivation According to a news report by James Richardson, the House of Hemp company have become the first to receive a Cannabis Cultivation License from the South African Health Products Regulatory Authority (SAHPRA).

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his represents a milestone in what is hoped will be a lucrative and innovative field, namely the medical cannabis and cannabidiol (CBD) sector.

House of Hemp intends to build on existing medical research and further explore the potential of cannabis as a healing plant. Limited evidence suggests cannabis can reduce nausea and vomiting during chemotherapy, improve appetite in people with HIV/AIDS, and reduce chronic pain and muscle spasms.

Furthermore, there is a growing body of evidence that various forms of cannabis could help in the treatment of epilepsy and seizures, post-traumatic stress disorder (PTSD), glaucoma, dementia, Alzheimers, autism, fibromyalgia and a range of auto-immune diseases.

A big part of the licensing process will be that it will enable cannabis researchers to take their work further and conclusively prove what medical benefits, if any, the plant yields.

House of Hemp hope to provide in depth data on how cannabis should be used to treat various conditions including data on standardisation and proper scientific formulation, dosage requirements and combinations of cannabinoids for medical purposes.

Afriplex, the backer of House of Hemp, has already developed four other Active

Pharmaceutical Ingredients (API’s) that are proudly South African and popular in international markets. The company is responsible for popular weightloss aid Herbex.

“Afriplex and our strategic partner, House of Hemp, are extremely honoured to be associated with the first Cannabis License from SAHPRA,” says Danie Nel, Afriplex CEO. “The teams have worked tirelessly over the last seven years to ensure we meet not only local standards but also the legislative requirements and quality standards of international markets.

Being the first in South Africa to receive this accreditation enables us to actively

Packaging for fresh produce: Important utility, but?

While this carbon footprint calculation is most often used in the analysis of the larger product system it can also be understood as a distinct environmental performance metric that can be calculated and optimised separately.

OPTIMISING CARBON SAVINGS There are 3 main types of recycling; closed loop application, closed loop material and open loop in carbon terms, each delivering different benefits.

• Closed Loop Application is where a waste packaging product is recycled back into the same product.

• Closed Loop Material is where a packaging product is recycled into a different product, but is itself recyclable or replaces the same virgin material.

pursue expansion into the cannabis market locally and internationally.”

The company hopes to be well-placed to use their research to export medical marijuana products and treatments to new markets opened up by the legalisation of cannabis.

Nel says: “As new markets open up abroad, we will be able to export to any country that is legally allowed to buy the products. As demand grows, so will the economic development opportunities and the profit potential. Especially since South Africa offers a safe and stable business environment in sub-Saharan Africa, and as a gateway into the rest of Africa and abroad.”

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• Open Loop is where packaging is recycled into a different product, but does not replace the same virgin material and can also not be recycled after this first use.

Life Cycle Assessments (LCA) have proven that Returnable Transit Packaging (RTP) is both a very viable and costeffective alternative to single-trip disposable packaging, offering a fresh and modern approach to plastic packaging.

A local company has developed a wide range of multi-trip, re-usable containers that constitute the broadest offering of Returnable Transit Packaging (RTP) systems in South Africa.

With the obvious cost advantages of moving away from raw materials, not to mention the degradation problematic

reductions in packaging waste, improved product protection and superior logistical efficiency, it is no wonder that the RTP market has been experiencing such consistent growth.

Combining these benefits with the added advantages of improved safety in transport storage, less maintenance and traceability through RFID tags, companies can no longer afford to overlook the long-term benefits of RTP containers over disposable packaging, with applications in almost every commodity industry, including, but not limited to agriculture, automotive, baking, food processing, manufacturing, logistics, pharmaceutical, poultry, retail, waste collection and containment, as well as the wine industries.

Source: LCA

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Nutrient recipe for peppers produced in a hydroponics system

Bell peppers grown in greenhouse hydroponics systems follow similar environmental requirements as tomatoes and eggplants. It is a common production practice to leave all the leaves on the pepper plants. This creates very tall walls of foliage that slightly affect the plants’ nutritional requirements.

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epper growth follows generally two different phases during greenhouse production. After the seedlings are transplanted, the first six weeks of production is geared toward developing a strong vegetative base. After fruit set, the nutrient recipe is changed slightly to keep the plants in balance. For peppers only potassium is significantly increased after fruit set occurs.

Concentrations in parts per million (ppm) at the dripper. Micronutrients are in shaded boxes. (*) See below for explanation on blossom end rot.

Like all nutrient recipes, the numbers in Table 1 are a starting point that will need to be adjusted depending on the local environment (temperature, humidity, solar radiation and water quality) and the different salt accumulations that occur in normal conditions depending on the absorption by any given strain of pepper.

Note that the ammonium (NH4) levels for young and mature plants are very low compared to nitrates. Ammonium is not necessary depending on the substrate included for pH buffering.

Note also that chloride and sodium have upper ranges. These two are considered contaminants even if they have nutritional value for the plants.

They are generally present in the water

A picture of healthy bell peppers in a well-managed greenhouse.

and their requirements are very low like micronutrients.

How to prevent blossom end rot Bell peppers’ most common physiological problem is blossom end rot, which is generally due to a water stress preventing the internal transport of calcium. It is common to increase the concentration of calcium ions in the solution together with chloride, phosphate and boron while reducing potassium to promote the

Table 1. Nutrient solution for hydroponics pepper cultivation 0-6 weeks Mature crop Reference EC 2.2 mS/cm 2.5mS/cm Nitrate (NO3) 200 ppm 180 ppm Ammonium (NH4) 7 ppm 15 ppm Potassium (K) 240 ppm 270-300 ppm (200 ppm*) Phosphate (PO4) 50 ppm 50 ppm Calcium (Ca) 220 ppm 200 ppm (300 ppm*) Magnesium (Mg) 50 ppm 45 ppm Iron (Fe) 1.5 ppm 1 ppm Manganese (Mn) 0.55 ppm 0.55 ppm Zinc (Zn) 0.33 ppm 0.33 ppm Boron (B) 0.3 ppm 0.3 ppm Copper (Cu) 0.05 ppm 0.05 ppm Molybdenum (Mo) 0.05 ppm 0.05 ppm Sulphates (SO4) 20 ppm 20 ppm Chloride (Cl) <300 ppm <300 ppm Sodium (Na) <100 ppm <100 ppm

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absorption of calcium during potential blossom end rot periods, particularly during hot summers (* in Table 1).

Chemicals required for mixing the nutrient solution are the following: Ca(NO3)2 (Calcium nitrate) KNO3 (Potassium nitrate) KH2PO4 (Monopotassium phosphate) MgSO4*7 H2O (Magnesium sulphate) H3BO3 (Boric acid) MnCl2*4 H2O (Manganous chloride) CuCl2*2 H2O (Cupric chloride) K2SO4 (Potassium sulphate) MoO3 (Molybdenum trioxide) ZnSO4*7 H2O (Zinc sulphate) Fe 330 – Sequestrene (chelated iron) Commonly in hydroponics production, chemicals are mixed in concentrated solutions to be diluted at the time of irrigation. The drawback of this fertilization method is that some of the chemicals present will precipitate out and be removed from the nutrient solution and need to be kept separate in at least two reservoirs.

As a common rule, calcium needs to be separated from phosphates and sulphates to prevent precipitation.

Information sourced from various greenhouse technologists.

greenhouses I shade net I hydroponics I aquaponics Why dehumidification is important

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Steps to avoid crop condensation problems • Make sure your temperature and humidity sensors are accurate, and located in the crop canopy. Test your temperature sensors regularly against an accurate thermometer. Bring various humidity sensors to one spot to see that they are the same. Relative humidity can be checked with a sling psychrometer.

• Use thermal screens at night to prevent radiated heat loss from plant surfaces.

• Avoid sudden temperature elevations at sun up by programming a gradual pre-dawn temperature rise and dehumidification period. (Sudden temperature drops can cause condensation problems as well, particularly on cold glazing ma • Place radiant heat sources near the crop to keep plant surfaces as close as possible to or slightly warmer than air temperatures.

• Use horizontal air flow fans or poly tubes to maintain even temperatures throughout the crop.

• Use a combination of venting and heating to reduce excessive humidity.

• Start dehumidifying at or about 85% RH. Relative humidity above this level is not easily managed without an increased risk of condensation problems and nutrient uptake interference due to inactive plants (lack of transpiration).

An extractor fan and a heat blower in a greenhouse Humidification Although dehumidification is sometimes expensive, it is usually

easier to reduce humidity levels than to increase them. Raising humidity levels without creating excessive free water requires some sort of evaporative device such as misters, fog units, or roof sprinklers, all of which add water vapour to the air, or screens that help hold in the water that is being evaporated from the plant canopy.

Evaporative devices accomplish 3 things: first, they cool the air, raising humidity and relieve stress on the crop. Second, they add water vapour to the air, further increasing the relative humidity.

Thirdly, they reduce the vapour pressure deficit which is the force that evaporates water from the leaves. Screens may also reduce leaf temperatures and help to trap the large amount of water that the plants are evaporating.

Evaporative cooling and screening are often used together. When humidifying under sunny conditions, some venting is necessary since the greenhouse would soon become a steam bath without the introduction of fresh dry air to evaporate more water, and to cool, humidify, and displace hot greenhouse air.

Source: Several local experts & studies by Wageningen UR

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Growing in Rockwool: A professional’s opinion Rockwool is a mainstay of commercial hydroponic growers - and for good reason. It takes up a minimal footprint and, when used correctly, yields like crazy. We asked Dr Lynette Morgan, a world authority on hydroponic vegetable production, to give us some expert advice on growing tomatoes in rockwool. There’s much to be learned as she takes us through how to develop irrigation strategies for your particular growing environment.

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ockwool, also known as stone wool or mineral wool, is the most widely used substrate for the commercial production of hydroponic tomatoes. It is also a great tool for smaller growers who can benefit just as much from its use in a range of different systems and situations. While rockwool is relatively easy to set up and use, it does require some monitoring and irrigation adjustment to make the best of its ability to hold high levels of moisture and aeration at the same time.

Rockwool originally started as a thermal insulation material in the construction industry: its lightweight but highly aerated nature helps keep heat in buildings, while being easy to handle, cut and install.

Rockwool comes in a range of sizes from propagation cubes to large slabs and even a granulated product. Rockwool is manufactured by melting basaltic rock and spinning this molten mix into thin fibres which are then cooled by a stream of air. Although rockwool is a man-made substrate it is essentially made from rock and considered by many to be a natural product. One company dominates the rockwool market world-wide – the product being used by large and small hydroponic growers alike.

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Rockwool Preparation, Propagation and Transplanting Rockwool is highly advanced and is not a single product - growers can select from a number of different rockwool types all of which have slightly different properties and uses. One for example, maintains a slightly drier root zone and is used by tomato growers to steer crops away from overly vegetative growth. Another is used for multi-year use, while a third product is designed for ultra-quick root growth and development.

Along with these product differences, rockwool of many brands comes in a huge range of sizes from tiny propagation plugs for seeds to larger cubes for cuttings, mega sized cubes for large plants, a wide range of slab sizes, and as a granulated product as well.

Setting up to grow with rockwool Placing rockwool Whether you are using the standard rockwool growing slabs, large cubes, or even pots of granulated rockwool, basic preparation is important. Slabs and cubes in particular need to be on a flat, even surface as any indentations will cause the material to sink and create pockets of unwanted moisture. Next, realizing that nutrient solution will be draining from holes cut in the slab’s plastic wrapper or from the base of cubes, some consideration for drainage of this solution away from the slab is important.

There is no point in having it well placed and made drainage holes if the solution can’t be channelled away from the slab and the material ends up sitting in a pool of stagnant waste nutrient. Many small hydroponic systems on the market these days designed for use with rockwool have trays and channels designed to do just this and these are a good choice for inexperienced growers.

Settle rockwool Rockwool, whether it is slabs, small propagation blocks, or large growing cubes, needs to be prepared correctly by fully wetting the substrate before use. Some growers like to adjust the pH of their water to 5.5 before wetting up

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rockwool, but generally for small systems it’s not necessary with good quality brands (unless you have a very `hard’ water supply in which case acidification of the water before making up any nutrients would be a good idea).

Irrigation programs The most common way of applying nutrient to rockwool slabs or large blocks is with the use of dippers. A simple drip irrigation system should use a dripper with a capacity of 2 litres / hour, with one dripper per plant. Because a standard rockwool slab may hold four tomato plants, four drippers per slab are required, which also means that if any one dripper becomes clogged, the entire slab will still be getting enough irrigation until the problem is fixed.

Irrigation Strategy for Rockwool – Moisture Gradient Rockwool is the most widely used substrate for hydroponic tomato production. The irrigation program for any hydroponic plant is vital for successful growth, development and optimal yields. The most common problem experienced by smaller or new growers is over watering, and usually the grower is totally unaware that it is their irrigation program causing problems with plant growth.

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ROCKWOOL

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Flushing vast amounts of nutrient solution through the root zone in a substrate-based system often equates to plant murder - more is not necessarily better when it comes to nutrient application. This type of mistake is easy to make.

After all, many new growers get enthused about hydroponics after seeing a well-run NFT or other solution culture system and assume that plants are more than happy to grow and thrive in a flooded root zone environment.

However, solution culture and substrate systems are completely different and need to be managed in different ways for the plants to get the optimal root zone conditions they need.

In NFT the roots should never be flooded: they sit in a very thin film of nutrient flow (2-3 mm deep), hence the roots have moisture at the base of the root system, but many of the other roots are sitting up in the moist air, accessing all the oxygen they need without being submerged.

By allowing the rockwool material to drain freely, over-watering becomes more difficult, although vast amounts of nutrient drainage from the base of rockwool slabs or cubes are not an ideal situation either.

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program can be increased or decreased to keep this at the 10-15% level. By doing this, the amount of solution to be given at each irrigation can be worked through and adjusted as the plants grow.

capacityâ&#x20AC;&#x2122;. Field capacity is a term that means the substrate has drained fully but is still holding a good level of moisture for the plant roots to access until the next irrigation.

Having around 10-15% of the nutrient solution fed to the plants, drain from the slab after every irrigation cycle is considered to be optimal. This amount of drainage of solution flushes fresh nutrient solution right through the slab without too much wastage and usually Irrigation Program keeps the EC in the slab fairly stable.

Obviously the When rockwool is amount of nutrient Obviously the amount of irrigated and allowed required is going to to drain naturally, nutrient required is going depend on factors it will then contain to depend on factors such such as the size of the 80% nutrient as the size of the plant, plant, the growing solution, 15% air the growing conditions, conditions, light, pore space and 5% temperature and, in light, temperature and, in rockwool fibre. particular, humidity, particular, humidity, which A typical rockwool which drives plant tomato growing slab drives plant transpiration transpiration and actually holds around and water uptake. water uptake. So the 15 liters of nutrient irrigation program is solution immediately going to change as the plants develop. after irrigation, despite the drainage Commercial hydroponics rockwool holes allowing free drainage of excess growers have some good tools for finesolution. Four gallons is a good reserve tuning their irrigation. A water content of moisture for four plants, so drying meter allows growers to measure the down to wilting point could take a long water content, EC and temperature in period of time for small plants. the rockwool slab root zone using handHow much solution held meters or a continuous monitoring should be given at each system hooked up to the computerized irrigation? Having a irrigation program. drainage collection tray Moisture Gradient Important or channel under each slab allows growers to Rockwool propagation cubes and slabs see how much drainage are designed to be used together to they are getting after minimize root disturbance. For this each irrigation (even if reason, rockwool is best irrigated with this has to be poured short, frequent applications of nutrient, off and measured in a with just enough during each irrigation jug) and the irrigation cycle for the rockwool to reach â&#x20AC;&#x2DC;field

Nutrient application cycle Keep cutting back the irrigation amount until only 10-15% of the solution volume applied drains from the slab, and then the amount of irrigation has been fully adjusted for. How often should nutrient be applied? Rockwool needs small frequent irrigations, particularly under hot or low humidity conditions when the plants are taking up a lot of water.

However, the frequency of irrigation can be as low as once per day (or every other day) for small plants under cool conditions, to over 10 times a day for large plants in a hot or dry environment.

It can be hard to judge just how much moisture the rockwool material may be holding at any one time to determine when to irrigate.

Gauging moisture Like all growing media, moisture in rockwool can be gauged manually. Lightly touching or pressing the rockwool at the base of the slab will soon determine if there is still a good level of nutrient held in the base of the slab or whether it has become too dry. The top and middle layers of the slab should always appear drier than the base where the reservoir of moisture is naturally held, so only the base of the slab should be checked.

Generally, good brands of rockwool are quite forgiving compared to other substrates - the material is naturally well aerated and doesnâ&#x20AC;&#x2122;t suffer the compaction issues that some substrates do during the life of the crop. It does hold high levels of moisture, so the chance of drying out is not as severe as it might be with other substrates and being sterile gives young plants, seedlings and cuttings an advantage as well.

The irrigation program and water holding capacity of the substrate depends on the fibre density and arrangement, which can differ from brand to brand.

By: Dr Lynette Morgan

Undercover farming I

September/October 2019

I Volume 16 No 5 21

greenhouses I shade net I hydroponics I aquaponics

New Technology:

Woven grow bags versus plastic bags?

In the greenhouse and shade net industry there are regularly new technologies coming to the fore. Mostly these were well-researched and carry with them advantageous options for the under cover fresh producer.

J

ohan (Stoffies) Stoffberg and wife Mariaan together with a friend, Carel Breytenbach of AgriLibrium, an agricultural advisory service, took a hard look at the plastic bags being used by tree nurseries.

After much deliberation they concluded that a woven bag may produce better results as it lets air through its sides to the root zone in a grow medium, has a longer lifespan and may be used more times than its plastic contender.

Mariaan jumped in and made a few bags for a well-known tree nursery to be trialled at the nursery. Soon enough they realised the same can be done in various sizes for other applications in the horticultural industry.

Bags were made and offered for trials with tomatoes, peppers, cucumbers, beans, blue berries and even pumpkin.

Trough bags with sweet peppers in a multispan.

Stoffies and Carel, with his 45 years’ experience in agricultural research, received excellent results from a grower who has taken the time and effort to evaluate the crops planted into woven bags with the same variety of each crop in plastic bags, in the same greenhouse, similar grow medium, fertilizing, climate and irrigation.

The woven bags offered oxygen to reach the roots through the side of the bag, not touching the sides so as not to burn or dry, therefore a better root formation was formed than in the plastic bags. It is a general fact that a good root system offers better fruit set and stronger growth of the plant.

Temperature measurements during midSummer varied between six to seven degrees inside a 10 l black bag compared to one degree C inside the woven bag.

The plants in the plastic bags’ stem diameter were 30% to 50% thinner than those in the woven bags.

The plastic bags’ plants tend to grow slenderer a nd lankier.

The woven bags offered oxygen to reach the roots through the side of the bag, not touching the sides so as not to burn or dry, therefore a better root formation was formed than in the plastic bags.

At the date mentioned, it had up to five side-shoots as against the plants in the woven bags which had a single stem each. The lanky stems of the plastic bag plant – because of longer distance between internodes – had the plants grew 200mm taller than those in woven bags.

23

From the producer involved, the following feedback was received.

The second feedback was on tomato plants on 4 April 2018.

Result Woven bag Plastic bag

Root formation of bean plants. The plant on the left’s roots indicate the excellent result being grown in a woven bag against the one on the right, having been grown in a plastic bag under the same conditions throughout.

22 Undercover farming I

September/October 2019

I Volume 16 No 5

Fruit set

Flowering Marble-sized fruit Stem diameter at 5th truss

5 3 3 2 55 26 19mm 9mm

greenhouses I shade net I hydroponics I aquaponics WOVEN BAGS

22

Woven bags offer a longer lifespan as it can be re-used several times with careful handling; thus a good return on investment.

In the first trial project, the researchers were amazed to notice the generous growth of bean plants in the woven bags. He took a plant out of a woven bag and adjacent to that, a plant from a plastic bag and observed the difference in root growth. The woven bag plant’s root system seemed more than four times than that of the plastic bag plant. Its plant and foliage were much denser with 16 flower trusses against the four flower trusses of the bean plant in the plastic bag.

These results after seven weeks were obtained from the same bean variety, Star 2000, same volume grow medium, climate, greenhouse, irrigation and supervisor.

Result

Plastic bag

Woven bag

Top growth 11 gm Root system weight 22 gm Root development Developed in media

and against bag sides

Trusses 4

405 gm 450gm 5-10mm of media around inner side of bag was dry and dense root formation formed in centre.

Flower buds started flourishing.

16 of which 6 developed faster than those in the plastic bag.

Having experienced these positive outcomes, the bags since then were made to customers’ requirements from 10 l up to 800 l and sold to several Cycad , Indigenous tree and fruit tree as well as berry growers.

The tree bags are fitted with strong handles and can therefore be easily moved during dispatch.

Woven bags offer a longer lifespan as it can be re-used several times with careful handling; thus a good return on investment.

Stoffies Stoffberg of TREE BAGS may be contacted at stoffies@treebags.co.za

Undercover

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september/OCtOber 2019 VOlUme 16 NO 5

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New Cucumber Varieties page 4

reducing risks page 6

silicon the solution? page 10

Fertilization of tomatoes page 14

Woven bags with sweet peppers in a multispan.

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Undercover farming I

September/October 2019

I Volume 16 No 5 23