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Tuesday, October 28, 2008

Training and Pruning (1)

In general greenhouse crops (tomatoes, peppers and cucumbers) are indeterminant (vining) types to take advantage of the vertical volume of the greenhouse. The plant vines are supported on vine twine by vine clips. The twine is wrapped around some sort of device from which it can be unwound (tomahook, bobbin, etc.).
Plants are trained up the twine to the wires forming a “V” shape. As the plants grow up to the overhead support wire, the twine is unwound, the plants lowered and shifted one space – “LEANED AND LOWERED”.
Tomato vines should not be lowered more than 2 feet at a time OR another good way to tell, DO NOT lower the vine such that an 80 or higher degree bend is created in the vine near the floor. High angles promote stem cracking. Plants are trained to 1-3 stems by removing (pruning) side shoots or “suckers”.
Tomatoes are trained to 1 stem (or 2 stems to replace a topped or broken neighbor
or during a season of high light, i.e., Spring or early Summer).
Peppers are usually trained to 2 or 3 stems. Their stems are much more brittle
than tomatoes and tend to snap if they are leaned and lowered.
Cucumbers have traditionally been trained using such methods as the “V-cordon”
or “umbrella”. However, they can also be trained to 1 stem like tomatoes.
*Side shoots or suckers are so named because they suck nutrients from the main plant.
The process of removing suckers = “sucker pruning” or “suckering”.


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Thursday, August 28, 2008

General Cultural Practices - Plant Spacing & Crop Layout


Plant spacing is determined by two main factors:

1) The availability of light to the canopy - Plants must be far enough apart so that a maximum amount of light reaches the leaves for optimum photosynthesis.
2) The availability of water and nutrients to the roots - Plants must be far enough apart so that all plants have an optimum supply of these items.
*Plant spacing in “vining” greenhouse crops, including tomatoes, is much closer than for field crops.
Example: Field (bush) tomatoes = 4000 – 5000 plants/acre.
Hydroponic greenhouse tomatoes = 10,000 – 11,000 plants/acre.
*Why? A vine has a much smaller diameter than a bush, so they can be closer together and the leaves will still obtain optimum light for photosynthesis. The roots of a plant growing in hydroponics receives all the water and nutrients it requires. They are “spoon-fed” and do not have to grow large systems. The roots of a field grown plant will be more spread out as they search for water and nutrients in the soil matrix. Therefore, field grown plants must be positioned far enough apart to avoid competition of neighboring plants for water or nutrients. NOTE: Drip irrigation allows for closer spacing.
*Typical hydroponic plant spacing:
  • Tomatoes = 2.5 – 3 plants per square meter
  • Peppers = 2.5 – 4 plants per square meter
  • Cucumbers = 1.25 – 3 plants per square meter
  • Melon = 2.5 - 3 plants per square meter
*The typical layout of the greenhouse for vining vegetable crops is in rows tending approximately north and south. This is important because during the day the sun moves from east to west and if the rows were also set up east to west the southern most rows (in the
northern hemisphere) would shade the rows behind them. Typically, tomatoes are also grown in “double rows”. These double rows are usually 5-6 feet apart. With 3 plants per Rockwool slab (1 meter long each) or perlite bag (about 36”), sets of 2 slabs/bags are placed side by side. With 6 plants per slab/bag a single row of slabs/bags is used. Overhead support wires are set at least 2 feet apart.


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GENERAL CULTURAL PRACTICES : Enviromental Conditions Required - 2


2) TEMPERATURE: The optimum growing temperatures (day and night) vary for different
plant species and different varieties within a species. Eg. for most Tomatoes, germination and post-emergence temperatures = 23-25 C (74-77 F). Production optimum temperatures = 22 C (72 F) day/20C (68 F) night.

3) RELATIVE HUMIDITY (RH): The amount of water in the air compared to the total amount of water that the air can hold at a given temperature. %RH = Amount of water in the air X 100 Amount of water possible at a given temp. As the temperature increases the amount of water that the air can hold increases. When the air is saturated water molecules condense. This causes clouds when at altitude or fog when near the ground. How does this relate to tomato plants growing in a greenhouse? As the RH increases around the leaf (concentration of water molecules outside increases) it makes it more difficult for the water molecules inside the leaf to move out (transpiration) via diffusion (the passive movement of a substance from high to low concentration . Therefore, as the RH increases, transpiration decreases, water and therefore
nutrient movement decrease, and nutrient deficiencies can result. ALSO, as RH increases and transpiration decreases, leaf temperatures often increase, since transpiration is the plant’s way of cooling itself.
Optimum RH range for tomatoes (and most plants) = 55% - 95%. During hot, dry weather, fan and pad cooling adds moisture to the air. On hot, humid days, fan and pad cooling adds moisture but does not cool as well. During cool, damp weather, RH inside the greenhouse can approach 95%.

4) CARBON DIOXIDE: As mentioned earlier, carbon dioxide is critical for photosynthesis and enrichment is most important during the Winter on cold mornings. Outside ambient levels are around 330 ppm, part per million, (higher in cities due to industrial exhaust products). Enrichment = 800 to 1000 ppm.

5) AIR CIRCULATIONS: This avoids pockets of high or low temperature, humidity or carbon dioxide. This also reduces the BOUNDARY LAYER (the physical “still air” layer around
the leaf) so that proper gas exchange and transpiration can occur. When cooling fans are off use HAF (horizontal air flow) fans in the upper part of the greenhouse.

6) OXYGEN: All parts of the plant require oxygen for respiration. There is usually no problem supplying the top part of the plant with enough. But waterlogging and high temps. will inhibit oxygen movement to the roots.


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Sunday, July 6, 2008

GENERAL CULTURAL PRACTICES : Enviromental Conditions Required - 1

These factors includes 1) Light 2) Temperature 3) Relative Humidity (RH) 4) Carbon Dioxide 5) Air Circulation and 6) Oxygen. First we will cover - Light: Two factors are important and can be affected by greenhouse structures and coverings . NOTE: Both of these vary with plant species.
  • Quality: Refers to wavelengths of light. (Remember in physics: light spectrum) Visible light = 390-760 nm: blue at the low end, red at the high end. PAR (photosynthetically active radiation) = between 400 and 700 nm (blue, yellow, orange and red… but not green)NOTE: This varies slightly for each plant species.
  • Quantity: Is affected by both day length and sun angle (changes with season): Day Length & Sun Angle.
**The quantity (amount) of light reaching the Earth’s surface is therefore higher in Summer than it is in Winter.
**For tomatoes in the desert southwest or other high light areas:
  1. During the Winter or times of low light the quantity of light available is enough to support 3 – 4 fruit/cluster.
  2. During Spring/Summer/Fall the quantity of light may be too high and shading may be needed. 4 – 5 fruit/cluster is typical.


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GENERAL CULTURAL PRACTICES : Enviromental Conditions Required - 2

2) TEMPERATURE: The optimum growing temperatures (day and night) vary for different
plant species and different varieties within a species. Eg. for most Tomatoes, germination and post-emergence temperatures = 23-25 C (74-77 F). Production optimum temperatures = 22 C (72 F) day/20C (68 F) night.

3)
RELATIVE HUMIDITY (RH): The amount of water in the air compared to the total amount
of water that the air can hold at a given temperature. %RH = Amount of water in the air X 100
Amount of water possible at a given temp. As the temperature increases the amount of water that the air can hold increases. When the air is saturated water molecules condense. This causes clouds when at altitude or fog when near the ground. How does this relate to tomato plants growing in a greenhouse? As the RH increases around the leaf (concentration of water molecules outside increases) it makes it more difficult for the water molecules inside the leaf to move out (transpiration) via diffusion (the passive movement of a substance from high to low concentration . Therefore, as the RH increases, transpiration decreases, water and therefore
nutrient movement decrease, and nutrient deficiencies can result. ALSO, as RH increases and transpiration decreases, leaf temperatures often increase, since transpiration is the plant’s way of cooling itself.
Optimum RH range for tomatoes (and most plants) = 55% - 95%. During hot, dry weather, fan and pad cooling adds moisture to the air. On hot, humid days, fan and pad cooling adds moisture but does not cool as well. During cool, damp weather, RH inside the greenhouse can approach 95%.

4)
CARBON DIOXIDE: As mentioned earlier, carbon dioxide is critical for photosynthesis and enrichment is most important during the Winter on cold mornings. Outside ambient levels are around 330 ppm, part per million, (higher in cities due to industrial exhaust products). Enrichment = 800 to 1000 ppm.

5)
AIR CIRCULATIONS: This avoids pockets of high or low temperature, humidity or carbon dioxide. This also reduces the BOUNDARY LAYER (the physical “still air” layer around
the leaf) so that proper gas exchange and transpiration can occur. When cooling fans are off use HAF (horizontal air flow) fans in the upper part of the greenhouse.

6)
OXYGEN: All parts of the plant require oxygen for respiration. There is usually no problem supplying the top part of the plant with enough. But waterlogging and high temps. will inhibit oxygen movement to the roots.


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Friday, May 23, 2008

Guide To Propagate Chilly seedlings


Propagating seedlings means simply germinating seeds and growing the seedlings until they are big enough to be planted into a bigger pot, or directly into the ground.

The first thing you'll need to propagate seedlings is some really good quality seed compost. There's no hope for your seeds if you just go outside and scoop up some earth from your garden as its physical structure just won't be up to scratch and it will also be host to lots of pathogens which will cause problems later on for your new seedlings.
But you don't want potting compost either as it has too many nutrients and put seedlings at risk of fertilizer damage, plus it provides a lovely environment for liverworts and moss, which will then compete with your seedlings for water, space and light.
A good soil-based seed compost is the answer for seedlings that are going to take a few weeks to germinate. For plants that grow rapidly, you can just use a soil-free organic mixture. But in my video above (in Malay language), I insists on Peat Moss which is the best media for seedling.

Then you'll need the all important seeds. You should not try propagating seedlings from old seeds; buying fresh ones every year isn't very expensive and will ensure that you grow the best quality seedlings possible. Also, some plants need to be germinated from fresh seedlings and old seeds will simply not grow. So make sure you do your research to get the best results. Chilly seeds can't resist stress (of heat and too high in humid & nutrient). So, an extra care is needed when doing the seedling for chilly.
Finally what you need is a place to grow your seedlings in. This means some seed trays, and somewhere warm and humid. This could be a greenhouse, a conservatory or even just a propagator (a seed tray with lid a bit like a fish tank), but your seedlings need to stay protected from the cold at all costs otherwise they will not make it.
When everything ready, start with filling the tray with enough (but not too much) peat moss. Spray a misty water onto it using a sprayer and then place the seed on each hole. Then carefully sprinkle a small amount of peat over the seed with your only 2 finger to make sure the seed does not expose directly to the air. Put the tray in black & thin plastic bag (or trash bag) and leave it under shelter for 2 days. After 2 days, take out the plastic cover but still need to be put under shelter (or under 50% sunlight). The bud will start to appear on the 5th - 7 day.
Please refer to the posts How To Make Proper Seedlings & Basic Need For Fertigation-Selected Seed & Seedlings


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GENERAL CULTURAL PRACTICES (Enviromental Conditions Required) – TEMPERATURE

Temperature: The optimum growing temperatures (day and night) vary for different plant species and different varieties within a species. For example, if you decided to grow tomatoes:
  • Germination and post-emergence temperatures = 23-25 C (74-77 F)
  • Production optimum temperatures = 22 C (72 F) day/20C (68 F) night.
One of the major reasons for a greenhouse is to control temperature. Air at 70° F will hold twice as much moisture as air at 50°F. In the range of temperatures encountered in a greenhouse, for every 20° F rise in dry bulb temperature, the water-holding capacity of the air doubles, and the relative humidity is reduced by one-half. This relationship is important in managing humidity in the greenhouse. Most of the crops grown in a greenhouse are of tropical or subtropical origin or are grown at inclement times of the year. The greenhouse is used to maintain an optimum night temperature (above freezing). This is usually accomplished with some kind of heating system. During the day, however, the greenhouse structure can actually interfere with temperature control by trapping heat. Therefore, various cooling methods must then be used. Temperature is a measure of heat energy. The energy balance or movement of energy into, within, and out off a greenhouse occurs by three different methods:
  1. Conduction: diffusion of thermal energy through a continuous medium, the rate of which depends on the properties of the medium. Heat energy movement is always from a region of high temperature to lower temperature.
  2. Convection: diffusion of thermal energy between two dissimilar materials, usually between a gas and liquid, gas and solid, or liquid and solid. Heat energy movement is always from a region of high temperature to lower temperature.
  3. Radiation: radiation heat transfer occurs when electromagnetic energy leaves one object and is intercepted and absorbed by another. This differs markedly from conduction and convection. All objects emit radiation, warmer objects more so than cooler objects. The wavelengths usually considered to be involved in radiation heat transfer are in the infrared band.
Radiation Cooling: On clear, cold nights, plants and other objects within a greenhouse will lose heat to the outside by radiation cooling. Because objects within the greenhouse are much warmer than those outside, they lose heat by emitting infrared radiation through the glazing and into the clear sky. Under such conditions, the foliage temperature may be 5°F cooler than the surrounding air. Radiation cooling occurs very little when skies are cloudy.

Condensation: When the foliage of plants in the greenhouse are cooler than the surrounding air, moisture in the air may condense on the leaf surfaces. This is most common in the spring and fall when days are bright and warm and nights are cool and clear. The moisture that collects on the leaves serves as an ideal medium for the germination of several disease-causing spores, mainly powdery mildew. Condensation also occurs on the inside pf poly-covered greenhouse when the inside air is warm and humid and the outside air is cold. Under these conditions, condensation can rain-down on the foliage creating an environment for diseases.

Greenhouses heat up during the day for two reasons: 1) the greenhouse effect, 2) because the greenhouse is an enclosed space. How much a greenhouse heat up during the day depends on how much solar radiant energy is coming in through the glazing, what happens to that energy, and how much is retained.


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Thursday, May 22, 2008

GENERAL CULTURAL PRACTICES (Enviromental Conditions Required) - Relative Humidity

Different Types & Brands of Digital RH Meter
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Relative humidity (RH): The amount of water in the air compared to the total amount
of water that the air can hold at a given temperature. (%RH = Amount of water in the air X 100 Amount of water possible at a given temp). As the temperature increases the amount of water that the air can hold increases. When the air is saturated water molecules condense. This causes clouds when at altitude or fog when near the ground. How does this relate to plants growing in a greenhouse?
*As the RH increases around the leaf (concentration of water molecules outside increases) it makes it more difficult for the water molecules inside the leaf to move out (transpiration) via diffusion.
*Therefore, as the RH increases, transpiration decreases, water and therefore nutrient movement decrease, and nutrient deficiencies can result.
*ALSO, as RH increases and transpiration decreases, leaf temperatures often increase, since transpiration is the plant’s way of cooling itself.
Optimum RH range for tomatoes (and most plants) = 55% - 95%
In USA & other other advenced Western countries during hot, dry weather, fan and pad cooling adds moisture to the air.
On hot, humid days, fan and pad cooling adds moisture but does not cool as well.
During cool, damp weather, RH inside the greenhouse can approach 95%.


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GENERAL CULTURAL PRACTICES (Enviromental Conditions Required) – TEMPERATURE

Temperature: The optimum growing temperatures (day and night) vary for different plant species and different varieties within a species. For example, if you decided to grow tomatoes:
  • Germination and post-emergence temperatures = 23-25 C (74-77 F)
  • Production optimum temperatures = 22 C (72 F) day/20C (68 F) night.
One of the major reasons for a greenhouse is to control temperature. Air at 70° F will hold twice as much moisture as air at 50°F. In the range of temperatures encountered in a greenhouse, for every 20° F rise in dry bulb temperature, the water-holding capacity of the air doubles, and the relative humidity is reduced by one-half. This relationship is important in managing humidity in the greenhouse. Most of the crops grown in a greenhouse are of tropical or subtropical origin or are grown at inclement times of the year. The greenhouse is used to maintain an optimum night temperature (above freezing). This is usually accomplished with some kind of heating system. During the day, however, the greenhouse structure can actually interfere with temperature control by trapping heat. Therefore, various cooling methods must then be used. Temperature is a measure of heat energy. The energy balance or movement of energy into, within, and out off a greenhouse occurs by three different methods:
  1. Conduction: diffusion of thermal energy through a continuous medium, the rate of which depends on the properties of the medium. Heat energy movement is always from a region of high temperature to lower temperature.
  2. Convection: diffusion of thermal energy between two dissimilar materials, usually between a gas and liquid, gas and solid, or liquid and solid. Heat energy movement is always from a region of high temperature to lower temperature.
  3. Radiation: radiation heat transfer occurs when electromagnetic energy leaves one object and is intercepted and absorbed by another. This differs markedly from conduction and convection. All objects emit radiation, warmer objects more so than cooler objects. The wavelengths usually considered to be involved in radiation heat transfer are in the infrared band.
Radiation Cooling: On clear, cold nights, plants and other objects within a greenhouse will lose heat to the outside by radiation cooling. Because objects within the greenhouse are much warmer than those outside, they lose heat by emitting infrared radiation through the glazing and into the clear sky. Under such conditions, the foliage temperature may be 5°F cooler than the surrounding air. Radiation cooling occurs very little when skies are cloudy.

Condensation: When the foliage of plants in the greenhouse are cooler than the surrounding air, moisture in the air may condense on the leaf surfaces. This is most common in the spring and fall when days are bright and warm and nights are cool and clear. The moisture that collects on the leaves serves as an ideal medium for the germination of several disease-causing spores, mainly powdery mildew. Condensation also occurs on the inside pf poly-covered greenhouse when the inside air is warm and humid and the outside air is cold. Under these conditions, condensation can rain-down on the foliage creating an environment for diseases.

Greenhouses heat up during the day for two reasons: 1) the greenhouse effect, 2) because the greenhouse is an enclosed space. How much a greenhouse heat up during the day depends on how much solar radiant energy is coming in through the glazing, what happens to that energy, and how much is retained.


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GENERAL CULTURAL PRACTICES (Enviromental Conditions Required) – LIGHT

ENVIRONMENTAL CONDITIONS REQUIRED are included 1)Light 2)Temperature 3) Relative Humidity (RH) 4)Carbon Dioxide 5)Air Circulation and of course 6)Oxygen. I will cover one by one and we starts with light.
*Light: Two factors are important and can be affected by greenhouse structures and coverings (see also posts
Greenhouse Control system-Light and Greenhouse Glazing material). NOTE: Both of these vary with plant species.
  • Quality: Refers to wavelengths of light. (Remember in physics: light spectrum) Visible light = 390-760 nm: blue at the low end, red at the high end. PAR (photosynthetically active radiation) = between 400 and 700 nm (blue, yellow, orange and red… but not green)NOTE: This varies slightly for each plant species.
  • Quantity: The quantity of light monitoring is very crucial especially in countries which have four season. The quantity of light is affected by both day length and sun angle (changes with season): 1)Day Length: eg. In North-West area in USA, day length on June 21 is 14 hours 15 min. On December 21 day length, however, is only about 10 hours. 2)Sun Angle: In June the angle is high = 81o from the horizon (almost overhead). In December the angle is low = 34o from the horizon. **The quantity (amount) of light reaching the Earth’s surface is therefore higher in Summer than it is in Winter. **For tomatoes in the desert southwest or other high light areas: During the Winter or times of low light the quantity of light available is enough to support 3 – 4 fruit/cluster.During Spring/Summer/Fall the quantity of light may be too high and shading may be needed. 4 – 5 fruit/cluster is typical. For Tropical countries like Malaysia & Thailand , the amount of light is almost consistent. But sometimes when droughts happens or at locations where sunlight are so intense, shading may also be needed to cut down some damaging effects from high intensity light of the Sun. This is crucial especially for Chillies and Melons grower.


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Wednesday, May 21, 2008

GENERAL CULTURAL PRACTICES - Greenhouse Preparation

Factors To Consider For The Greenhouse Preparation:

*Select a site for the greenhouse that is appropriate for the operation (see posts
12 Things To Consider When Selecting A Greenhouse Site).
*Select a greenhouse structure that is appropriate for the operation (see posts on
Greenhouse Structure).
*Make sure all equipment is cleaned, serviced and working at optimum efficiency.
*For any crop, incl. tomatoes, the following items must be considered prior to planting:

  • Good light transmission: Choose the proper greenhouse covering and structure. If year-around production is planned, shading must be used in Summer.
  • Adequate cooling: Either passive (vents), active (fan and pad), or both. Heating is necessary in Winter: NATURAL GAS is the most economical way. (Other, more expensive, methods of heating: propane, oil, electric, solar.)
  • Carbon dioxide generation: This is especially important for Winter mornings. The sun rises, but it’s cold. So if fans come on, it’s only for a short time. Plants begin to photosynthesize, using up the ambient carbon dioxide to the point where photosynthesis is effected and even reduced.. If photosynthesis is reduced, fruit set is reduced – and that’s $$!
  • Ground cover: Usually white plastic or a white woven material is put down first. Reflects light back up into the crop increasing photosynthesis. Provides a barrier between the plants and pathogens in the soil. Helps to control weeds.
  • Allows for ease of cleaning: CLEANLINESS IS PARAMOUNT! Trash, leaf litter, etc. is a perfect habitat for bugs/disease.
  • Irrigation system: (see posts on Irrigation System for details and diagram) This inlcudes: 1)Timer/controller to regulate the “fertigation” (water + fertilizer) schedule. This will be hard-wired to solenoid valves that open for watering. 2) Reservoirs to contain the nutrient solution (full strength or concentrate). 3) Injectors (if concentrates are used) to dilute the nutrient solution. 4) Distribution tubing/emitters/drainage and/or recycling system. 5)Possibly integrated pH (acid/base) and EC (electrical conductivity) probes. 6) Overhead support wires: These need to be strong enough to support the crop and high enough (8-14 feet) to make use of the vertical space provided.


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GENERAL CULTURAL PRACTICES: CROP SCHEDULING

Plan ahead… When do you want to market your product for the best monetary return? For hydroponic tomato growers in seasonal countries, get a better price in Winter – no field competition and little from greenhouses in northern latitudes. Alternative: grow year around to maintain stable, consistent market/shelf space. Tomatoes: 2 examples of crop scheduling

  • Example 1: Passively cooled greenhouses (vents): No Summer harvesting. Seed first crop in early July in 1" (or 1.5") Rockwool cubes. Transplant in mid-July into 3" (or 4" with 2 holes) Rockwool blocks. Plant 1-month-old seedlings onto Rockwool slabs in August. Harvest from October until March – Top the plants in February, remove when second crop begins producing in March. Seed a second crop in early December as above. Transplant in mid-December as above. Interplant new 1 month old seedlings onto Rockwool slabs in January. Harvest from this new crop from March until July. Remove plants. Clean.
  • Example 2: Actively cooled greenhouses (fan and pad): Year around harvesting. Seed, transplant and plant first and second crops as above, removing first crop as above in March. Continue second crop, harvesting from March until the next October. Seed, transplant and plant the third crop, as the first, in July/August. When third crop is ready to harvest in October, remove second crop. Continue the process for up to 5 years.

Note: Concentrate on the production end (growing the plants, harvesting, marketing, etc.)
and purchase 1 month old seedlings from a TRANSPLANT GROWER.
NOTE: Why 2 crops/year? Fruit size and quality go down over time.


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GENERAL CULTURAL PRACTICES: CROP AND CULTIVAR SELECTION – Experience

EXPERIENCE: If a grower has experience with a particular crop… stick with it. Example: A family with experience in growing long cucumbers in British Columbia, Canada, moved south of Willcox, AZ and is growing cucumbers… not tomatoes. If a grower does not have experience with a particular crop… Work for someone who is successful with that crop to gain experience.
Hire someone who is experienced… an expert!


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Tuesday, May 20, 2008

GENERAL CULTURAL PRACTICES (Crop & Cultivar Selection) – LOCATION

LOCATION: The selection of a crop will dictate the best location for the operation…
and visa versa.
Example: If a grower chooses tomatoes in Cameron Highlands, Malaysia, the optimum elevation is between 3,000 and 4,000 feet. Any lower and it is usually too hot to grow. Any higher and it is too cold to grow (especially during rainy days)…UNLESS SIGNIFICANT EXPENSE ($$) IS PUT TOWARD COOLING OR HEATING!
Example: If a grower has land at about 2500 feet in elevation in Cameron Highland, a crop
that can tolerate warmer temperatures than tomatoes, such as cucumbers could be selected. The selection of a “cultivar” or “variety” is also important when choosing a location. Seed companies are always coming out with new cultivars (or varieties) to suit different climates and tastes. With the move of many growing operations to higher light regions of the world
… remember photosynthesis… (Most of Asian & Middle East countries, Northern Africa, Northern Australia, Southwest USA, Mexico, Spain) AND the demand for good quality, good tasting tomatoes year around, many seed companies are introducing more HEAT TOLERANT varieties. Example (from one of the greenhouse cultivator company in Southwest USA) TRUST Tomato veriety were selected: a Dutch variety (DeRuiter Seed); optimum day temperature = 72 F. The first 10 acres (and next 30) of greenhouses were passively cooled (no fan and pad/evaporative cooling). They were not able to grow in the Summer and therefore started with transplants (1 month old seedlings started in Canada) in August and removed the crop the following July.


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GENERAL CULTURAL PRACTICES - (Crop & Cultivar Selection) – MARKET

INTRODUCTION
General cultural practices include all information, techniques and skills required to successfully produce a crop and optimize yields – the main goal of any grower! We will concentrate on tomatoes with reference to other crops to illustrate the variability in cultural practices between crops.
CROP AND CULTIVAR SELECTION
This is one of the most important decisions a grower will make and depends on:
MARKET… LOCATION… EXPERIENCE

1)MARKET:
  • Research the region. Know if there are other growers in the area = competition. If there are too many tomato growers… try cucumbers, peppers, basil, melon, chillies/capsicum etc.
  • Know the market. Brokerage houses, grocery vs specialty stores, farmer’s markets, restaurants, etc.
  • Hydroponics/greenhouse culture is expensive. Therefore, a high cash-value crop must be chosen. These include: 1)Tomatoes: Indeterminant (vining) varieties to take advantage of the vertical space in the greenhouse that has been paid for! Beefsteak: large fruit, harvested individually. Cluster, truss or TOV (tomato on the vine): medium to large fruit, harvested as an entire truss. Cherry: small fruit, harvested individually or as an entire truss. 2)Peppers/Capsicums: Colored bells only, primarily yellows – require sun protection. 3)Cucumbers: Long (European, seedless, parthenocarpic, burpless). They are thin-skinned and must be wrapped in plastic after harvest. 4)Lettuce: Head, leaf or cos; specialty or bred for hydroponics/CEA ( Controlled Environment Agriculture). Summer Bibb or “Limestone” lettuce. 5)Melons: Many types of Melons (Musks, Signal, Cupid, Rock, Sweet etc) 6)Specialty Greens, Herbs and Medicinals: Several types and varieties.
NOTE: Consult seed companies for suitable crops/varieties.


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12 Thing To Consider When Selecting Greenhouse Site - Expansion, Labour & Management Residence

10. Capability of Expansion – Purchase more land than you anticipate using in the beginning so that you have the ability to expand your operation. Locate the initial greenhouses such that future expansion will utilize the land area most efficiently.

11. Availability of Labor – The grower needs people who will want to work as laborers and who are “trainable” to become a retainable workforce.
*Such skills included pruning/training the plants and harvesting/packing the fruit.
*SPECIALTY LABOR will include people with additional training in such fields as plant production, plant nutrition, plant protection (insects and diseases) computers, labor management, marketing, etc. These may or may not be part of the regular workers, but could be call on as consultants as needed.

12. Management residence – The grower/manager residences should be close to the
greenhouse so that they can get to the greenhouse quickly in case of emergencies.


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Friday, May 16, 2008

12 Things To Consider When Selecting Greenhouse Site - Utilities, Roads & North-South Orientation

7. Utilities – Availability of utilities should include telephone service, three-phase electricity and fuel for heating and carbon dioxide generation.*Note that, when compared to propane, electricity or fuel oil, natural gas is the most economical heating energy source.

8. Roads – Need access to good roads to transport the “product”. Good roads close to a large population center, or to a brokerage center aids wholesale and retail marketing.

9. North-South Orientation – The greenhouse should be oriented north-south, AND the
plant rows within the greenhouse should be oriented north-south. *If oriented north-south, the greenhouse structure itself will not cast consistent shadows on any one area of the plants throughout the day. *If oriented north-south, the plant rows will receive equal light throughout the day. If oriented east-west the south most rows (in the northern hemisphere) will shade the rows to the north.


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12 Things To Consider When Selecting Greenhouse Site - Pest Pressure & Level and Stable Ground

5. Pest Pressure – Choose a site away from existing agriculture production areas which could harbor insect pests in the fields. Insect pests of concern include white flies, aphids, spider mites and thrips (see here for pests and control methods).

6. Level and Stable Ground – The ground upon which the greenhouse will sit must be
  • Graded for routing surface water to a drainage system or a holding pond. (Typical grade = ½ % or a 6 inch drop over a distance of 100 feet.)
  • Compacted such that there will be no settling of the site after the greenhouse has been constructed.


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12 Thing To Consider When Selecting Greenhouse Site - Elevation & Microclimate

3. Elevation – will effect the summer maximum and the winter minimum temperatures.
Choosing an appropriate elevation will minimize heating costs in the winter and cooling costs in the summer. Example: In Arizona tomato production is most economical between 4000 and
5000 feet (1220m-1520m). Below 4000 feet cooling costs in summer will be more whereas above 5000 feet heating costs in the winter will be more. Lower elevations might be suitable for peppers or cucumbers.

4. Microclimate - Factors which falls in microclimate considerations:
  • Latitude – Unless the global climate changes drastically, sea level at the poles will be colder than sea level in the tropics… latitude makes a difference!
  • Large bodies of water – will tend to moderate the temperature (e.g., coastal areas tend to have smaller day/night temperature differences than inland areas)
  • Trees, mountains or other obstructions – may cast shadows on the greenhouse, especially in the morning or afternoon hours. Mountains can also effect wind and/or storm patterns.
  • Clouds and fog – Note that certain areas (e.g., on the lee side of certain mountain ranges, or near coastal regions) may develop clouds or fog during certain times of the day or year that will reduce potential sunlight.
  • High Wind Areas – High winds can “suck” heat away from the greenhouse structure and therefore increase the heating energy demands.
  • Blowing dust/sand – High winds can “kick up dust or sand”, especially in desert regions, which can damage some greenhouse glazings.
  • Snow – The weight of heavy, wet snow on a greenhouse could crush it. However, high winds in snow areas can also blow snow up against the greenhouse structure (snow drifts) and cause damage to it. This danger can be reduced by using windbreaks (trees, snow fences, etc.).


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Thursday, May 15, 2008

12 THINGS TO CONSIDER WHEN SELECTING A GREENHOUSE SITE: Solar Radiation & Water Supply

Selecting a “good” site for the location of a greenhouse is crucial. But what constitutes a “good” site? There are several things that should and must be considered in order to increase the
chances of a successful operation and business.
12 THINGS TO CONSIDER WHEN SELECTING A GREENHOUSE SITE:
1) Solar Radiation – Plants require sunlight in order to perform photosynthesis. When plants experience cloudy days their photosynthetic rates, and therefore their ability to grow and yield a product, such as tomatoes, cucumbers, peppers, etc., will be reduced. Therefore, a region and location with high light intensity year-round is desired.

2) Water – Water quantity and quality is crucial. Water will be needed for irrigation (maximum of 1 gal/plant/day for tomatoes). Water will be needed for the evaporative cooling system and can equal or exceed the irrigation water amounts (10,000 – 15,000 gal/acre/day). In the past, excess irrigation and bleed-off water from the evaporative cooling system was allowed to “run off” onto the ground adjacent to the greenhouse (with a rec. minimum percolation rate into the soil of 1”/hr.).
*HOWEVER, due to more strict regulations and a desire to avoid ground water contamination with high concentrations of salts, large greenhouses are now recirculating the nutrient solution.
*THEREFORE, excess nutrient solution should be recycled and/or mixed with the cooler bleed-off water and redirected onto designated areas, such as grass, shrubs, trees/windbreaks, etc.
*No matter what the source of the water, a water analysis should be done.
*Note: Sea water = 32,000 ppm (mg/l) VS Tucson water = 200-400 ppm.
Note: 640 ppm TDS (total dissolved solids) = 1 mmhos/cm or 1 mS/cm.

*Desired salt levels in the source water:
SO4 < 240 ppm_____ Cl < 140 ppm___ Non-Fertilizer Salts
Ca < 120 ppm______ Fe < 5 ppm_____ Na <50 ppm
Mg < 24 ppm_______Zn < 5 ppm_____Al < 5 ppm
K < 10 ppm________Mn < 2 ppm_____F < 1 ppm
P < 5 ppm_________B < 0.8 ppm
NO3 < 5 ppm_______Cu < 0.2 ppm
Mo <>


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