Sixth Course and International Congress of Hydroponics in Mexico April 17 – 19, 2008, Toluca, Mexico
Dr. Howard M. Resh

Introduction:

This conference is held every two years in Toluca, Mexico.  It is organized by “Asociacion Hidroponica Mexicana A.C.” (Mexican Hydroponic Association).   Gloria Samperio Ruiz is the president who does an excellent job in getting the conference put together with her associates.   They always do an outstanding performance of bringing together speakers and topics from many backgrounds in all parts of the world.  Some of the foreign speakers included; Carlos Arano (Argentina), Dr. Pedro Roberto Furlani (Brazil), Alfredo Rodriguez Delfin (Peru), Rebeca Nelson (U.S.A.), Dr. Tom Papadopoulos (Canada), Dr. Fritz-Gerald Schoder (Germany), Dr. J. Lieth (U.S.A.), Dr. Jorge Fonseca (U.S.A.), Dr. Jeff Broad (New Zealand), Dr. Miguel Urrestarazu Gavilan (Spain), Dr. Ko Welleman (Holland) and myself. 

There were two ongoing sessions, one for the more beginners and the second one for the advanced growers.  The attendance at the conference was over 1200 people.   That makes it the largest hydroponics conference that I am aware of (photo 1).   Attendees had very diversified backgrounds, from traditional farmers with no previous exposure to hydroponics to large commercial growers operating greenhouse facilities in Mexico. 

The conference also included exhibitors of hydroponic systems, greenhouses, greenhouse equipment, hydroponic supplies, such as nutrients, substrates and biological control agents as well as books and videos on hydroponic growing.

In addition, there were a number of cultural events during lunch and the after conference banquet.  These included singers and dancers showing local culture (photos 2, 3).   Some of the performers were from the local university.  At the end of the conference there were several field trips to tourist areas such as the floating gardens, Xochimilco and the cultural town of Tequisquiapan in the state of Queretaro.

In foreground:  Mr. Alfredo Delfin with Ines, right; Gloria Samperio Ruiz

Conference Presentations:

I will only summarize some of the more technical papers.   Papers in the beginners’ session included topics such as, “Substrates”, “Introduction to Hydroponics”, “Basics of Nutrient Solutions”, “Fundamentals of Greenhouse Design and Construction”,  “Floating Systems”, “Green Grass Production”, “Commercial NFT Systems”, and “Pollination.” 

Dr. Ko Welleman discussed nutritional deficiencies and their corrections.  He pointed out how blossom end rot (BER) can be caused by low oxygen, low calcium, high root temperatures and high ammonium, potassium, magnesium and sodium levels.   He described various element deficiencies and their symptoms in plants and their uptake related to pH.

Dr. Jeff Broad of New Zealand made several very interesting presentations on the greenhouse environment and plant growth.   The first one was on the greenhouse environment control, humidity and vapor pressure deficit (VPD).  He pointed out that solar radiation drives transpiration.  He stated that vine plants like tomatoes can transpire about ¼ liter of water per hour during summer conditions.  That is equivalent to 2 liters per day per plant.  Relative humidity control was related to venting.  He suggested that keeping vents open a little later in the early evening will permit the late afternoon transpiration to escape before closing the vents.   This will reduce the humidity in the greenhouse over night.  Also, some heating overlapped with the venting will reduce the humidity as the heated air holds more moisture thus reducing relative humidity.  Dr. Broad explained vapor pressure deficit (VPD) and how in the future more control systems will address temperature and humidity taking into account VPD at the same time.  He explained that VPD measures how much we are below saturation at a given temperature, that is, it represents the shortage or deficit of moisture in the air.   It runs in the opposite way to relative humidity; when RH is high, VPD is low.   The ideal VPD in a greenhouse is 0.85 kPa.  He pointed out that greenhouse vent control must take into consideration wind and rain.  A sophisticated controller will take into account wind direction and strength.

The second presentation was, “Rootzone environment and the relationship between solar radiation and irrigation.”  He demonstrated through physical principles that for a large leaf area crop such as tomatoes, that intercepts all the sun’s energy, transpiration will be about 12 ml/sq m of greenhouse area/minute or 720 ml/sq meter per hour in the summer.  As a 30% leachate is recommended for crops the irrigation needed during full light will be 720 x 3/2 = 1 liter/sq m/hr.   Therefore, for a one-hectare greenhouse maximum water requirement will reach 10,000 liters/hour.  A shade system will reduce this irrigation water requirement proportionately to the percentage of shade.  Based on this calculation he showed that for every Joule/sq cm of accumulated solar energy we need to apply 3 ml/sq m of irrigation water.   Of this 2 ml/sq m will be transpired and 1 ml/sq m will be run off (leachate).

He discussed crop steering, the need to keep the crop in a “balanced” growth habit such that it is neither too generative nor too vegetative.  He stated that a balanced tomato should have a medium tight growing head, with a distance of about 14 cm from the last truss to growing tip and a stem diameter of 10 to 11 mm.

In regard to steering of the crop he discussed irrigation techniques such as water start time, wetting up, runoff EC control, and maintenance of moisture and EC.   Water start up should be the earliest of: (1) no later than 2 hours after sunrise; (2) solar radiation has reached 200 to 300 W/sq m; (3) once night dryback target has been reached.   Water stop time should be: (1) no more than 2 hours before sunset; (2) at a time such that 200-300 Joule/sq cm solar energy is still expected; (3) at a time when 3% dryback has occurred by sunset.

He went on to discuss sensor instruments such as rootzone monitoring equipment that can assist in making these decisions.  Such equipment as the Autogrow MINDER system that monitors:  media moisture level and temperature, runoff EC, pH and quantity, irrigation EC, pH and quantity, solar radiation, air temperature and humidity.

Dr. Heiner Lieth of the University of California, Davis, spoke about “Production of gerbera and orchids in soilless culture” (photo 4).  He described the growth habits of both potted and cut gerberas.  He emphasized the importance of pH management (5.6 – 6.2) in the nutrient availability for gerberas.  He also discussed biological control methods of pests and diseases.   He then outlined orchid types, their propagation by tissue culture and their various growth stages.  He related environmental conditions and nutrition to successful orchid production.

Alfredo Rodriguez Delfin of the University of La Molina in Lima, Peru presented details on the “Floating System.”  He described the cultural methods for lettuce, basil and onion.  He outlined sowing, transplanting and harvesting techniques.  He continued to explain nutrient solution EC, pH, oxygenation and preparation.  He showed the hydroponic solution formulation developed by La Molina and its preparation.

Dr. Jorge Fonseca of the University of Arizona Yuma Agricultural Center presented two papers on Biosecurity of vegetables and postharvest physiology.  He explained that there are two types of fruit, those that produce ethylene after harvest (climateric), for example, banana, papaya, mangos, tomatoes, that can be picked green and those that do not (non-climateric) such as, pineapple, grapes, citrus, strawberry and pepper which taste the same as when picked.  He pointed out that ethylene production increases as maturity increases and that bruising increases ethylene production in fruit.  In storage and shipping it is important to decrease ethylene production by low temperatures and high carbon dioxide.   Good air circulation with ventilation is key to shelf life.  It is very important to cool product quickly after it is harvested.  A one hour delay between harvest and cooling will cause 8 hours to 1 day loss of shelf life.  Packaging must be specific to the product needs.  Use of modified atmosphere bagging and packaging is specific for various crops so you need to know the best bags with their best mixture of carbon dioxide and oxygen levels.

Dr. Fritz-Gerald Schroeder of the Dresden University of Applied Sciences in Dresden, Germany presented two papers.   His first was “Commercial Hydroponic Production of Strawberry” (photo 5).  He indicated that there are about 300 hectares of hydroponic strawberry production in Huelva, Spain.  Dr. Schroeder reviewed strawberry varieties and their type according to daylength response as short-day, winter varieties, normally planted in late September or early October and the day-neutral spring and fall varieties planted in late August, early September or in February/March.  The day-neutral varieties are the most commonly grown ones.    These develop and initiate flowers irrespective of the day length, provided they have received a cold period of about 6 weeks.  They will grow and flower within a few weeks from planting in a hydroponic system.   Some popular varieties include, “Camarosa”, “Seascape”, “Sweet Charlie”, “Earliglow”, “Atlas”, and “Apollo.”  Strawberry plants are graded in quality according to the diameter of the crown.  Most plants will yield from 300 to 400 grams/plant.  The average yield is between 3.8 and 4 kg/sq m of greenhouse. 

He went on to describe the hydroponic growing system.  The most common system is hanging troughs or raised gutters containing a substrate.   Common substrates include peat mixtures, perlite and rockwool slabs.  A drip irrigation system provides the nutrient solution to the plants.  Drainage is collected with a channel underneath the troughs or gutters supporting the plants.  Nutrient solution management and a formulation were presented.  Growing conditions of temperature and humidity were outlined for optimum growth.  The importance of pollination and the use of bumble bees to do this in the greenhouse were discussed. 

Dr. Schroeder’s second paper was on “New Hydroponic Techniques and Development.”  He stated that there are two trends of new hydroponic systems, low-tech and high-tech.  His paper focused on the Chinese greenhouse industry and the “eco-organic type soilless culture system” as well as new developments.  Energy conservation is becoming a significant issue.

The greenhouse industry in China was discussed.  China is now the leading country for protected horticulture that includes greenhouses, plastic tunnels, lean-to structures.  They now have close to 2 million hectars of protected horticulture. 

Eco-organic soilless culture is a trough system using locally available substrates such as, coal cinder, peat moss, vermiculite, coir, sawdust, perlite, sand, rice husk, sunflower stem, maize stem, and mushroom waste.  Organic fertilization is used in the form of sterilized manure.  Irrigation is gravity based with distribution pipes to drippers or channels to the plants. 

Dr. Shroeder then described some high-tech greenhouses such as the Jinnai Farm 21 Plant Factory in Japan.  He then described new light technology using light-emitting diode (LED) lamps for hydroponic production.  With these lights energy consumption can be reduced by 50%.  A mobile raised trough system was described for growing tomatoes, roses and strawberries.  A “walking plant system” is a cultivation system for potted plants and new for tomatoes.  The potted plants are grown in gutters on a belt.   The tomatoes are moved, hanging on a rail system in the greenhouse.  They are moved from the greenhouse to the headhouse or package room.  The work is done on the plants there before they move back to the greenhouse.   These new development and systems are used in combination with hydroponic systems.

Dr. Tom Papadopolos from the Centre of Agriculture and Agri-Food Canada in Harrow, Ontario, spoke about improving the quality of transplants and on hydroponic cultivation of tomatoes.

Dr. Pedro Furlani of Brazil explained the basics of nutrient solutions and commercial NFT system of production. 

Dr. Carlos Arano of Argentina discussed substrates and phytosanitary aspects of growing.

Dr. Resh did two presentations:  Commercial Hydroponic Cultivation of Peppers and Commercial Hydroponic Culture of Watercress.

The conference was well organized and gave diversified presentations that would meet the needs of all attendees according to their previous or no experience with hydroponics (photo 6).

Mr. Alfredo Delfin, Dr. Howard Resh, Dr. Tom Papadopoulos

Post Conference Tours:

After the conference we took several field trips to popular tourist locations in the area.   The first trip was to the floating gardens of Xochimilco in Mexico City (photo 7).   The second was to the popular tourist town of Teqisquiapan.

Floating Gardens of Xochimilco:

In Aztec Xochimilco means “place of the flowers.”  In pre-Hispanic Mexico, the valley in which Mexico City is located was lake Texcoco.  The Aztecs dug a series of canals on the lake edge.   They formed small mud islands as they heaped it around the canals and secured them with reeds.  These plots of land, appeared like floating islands called chinampas (floating gardens).

Fertility was maintained by farmers by annually scraping mud from the canals and applying decaying aquatic vegetation to the islands to prepare seed beds.  These islands became very fertile land growing flowers, fruits and vegetables.  The chinampas were formed by alternating layers of aquatic plants, muck and earth packed inside rectangular cane frames secured to the lake bottom.   The “floating gardens” are anchored by trees planted along the edges of the fields.

This city was founded between the eighth and tenth centuries.  When the Aztecs arrived they conquered the Xochimilcas, and the Aztecs farmed these islands to grow crops.  By the late 1500’s before the Spanish conquest, there were over 22,000 acres of chinampas on the lakes of Xochimilco and Chalco.   Twenty people could be fed by every 2.47 acres of these gardens, supporting most of Tenochtitlan’s residents.   Five hundred years ago Xochimilco was the agricultural center of Tenochtitlan,s 235,000 inhabitants.  Originally it had been the source of all cereal, fruit, vegetables and flowers for the Aztecs, permitting the expansion of their cities around the lakes of the Basin.  When the Spanish arrived they drained the lake bed. 

Today farmers continue to scrape muck and organic debris from the canals and use it as fertilizer for the agricultural gardens.  They harvest chilicastle, shiny green algae on the water’s surface to help maintain soil fertility.

There are numerous nurseries today located on these chinampas (photo 8).   The growers use light-weight poly covered cold frames to protect their plants from rain.   They sell their plants to tourists.   A visit to Xochimilco taking a boat (gondola) ride through the canals visiting the various chinampas is a very popular event for both locals and foreigners.  The boats are brightly painted with flower designs.  Some boats have Mariachi music and will play songs specifically to your request for a nominal fee (photo 9).  Mexican families flock on the weekends to these “floating gardens” with an outing or picnic, usually staying the whole afternoon.   It is a very happy atmosphere with all the boats passing with singing, eating and drinking.   This is a true Mexican tradition for the locals.

Tequisquiapan, State of Queretaro:

Tequisquiapan is located in the State of Queretaro, 188 km from Mexico City.  It has a population of about 55,000 inhabitants.  It is a tourist town and weekend retreat for hundreds of Mexico City residents seeking the clear air and sparkling thermal waters.  With the large vineyards of the region, Tequisquiapan is a center of a wine and cheese producing region. 

Before the arrival of the Spanish conquistadors, this area was known as “Tequesquiatlapan,” meaning “River with carbonated water.”  In Pre-Hispanic times, the valley of Tequisquiapan was an important place for Nahua and Chichimeca chieftains.  The lords of Jilotepec bathed in the thermal waters of one of its numerous springs.   On these special occasions the lords would discuss affairs of state and settle disputes among themselves.  During Mexico’s colonial period residents planted grapevines and wine making took place.  The Spanish conquistadors also brought cows, sheep and goats.   Today, there is a three-day wine and cheese festival during the first weeks of May.   Several of the town’s main attractions include the Parish of Santa Maria (photo 10), built in the 19th century and the Plaza Civica (the main square).  A covered market with many shops of locally crafted items surrounds several sides of the square (photo 11).

Near Tequisquiapan is the peak of San Bernal (Pena de Bernal), a 350 meter high monolith (photo 12), the third largest in the world after the Rock of Gibraltar and Rio de Janeiro’s Sugarloaf Mountain.  Bernal residents are known for their longevity attributed to this monolith.  Bernal has a very nice church, the Parish of San Sebastian, and plaza at the center of town (photo 13).   It has narrow stone paved streets with shops surrounding the central plaza.  Its current population is under three thousand.  

Dr. Howard Resh, Dr. Miguel Gavilan, Dr. Jeff Broad

 

It is always a great pleasure to attend the conference in Toluca, Mexico and re-establish friendships with the organizers, members of the Mexican Hydroponic Association, fellow speakers and participants of the conference and to tour more areas of Mexico to learn of the local culture (photo 14). 

 

 

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