Yet the Dutch are major agricultural exporters. How do they do it?
The Dutch use two strategies to maintain their prominence in the industry. First, the farmers concentrate on producing high-value crops such as flowers and ornamentals. A kilogram of tulip bulbs sells for a lot more than a kilogram of onions. Secondly, the Dutch develop and use cutting-edge technology to modify the growing environment and to minimize the use of costly and hard to obtain labor.
This advanced technology had a stong impact on marijuana growers in Holland. Technology transfer between straight agriculture regarding rockwool, hydroponics, and climate control took place mostly in the larger greenhouse grows which were common through the late 1980?s. These were usually the result of partnerships between marijuana growers, who knew the particulars of growing the plant, and farmers, who hadcommercial greenhouse expertise.
When the government started cracking down on the large grows in 1989, domestic production shifted to boutique gardens, usually with less than 5000 watts of lighting. These gardens use much of the technology common to Dutch commercial technological agriculture, scaled down.
Ironically commercial growers in BC and Switzerland are now importing some of these products for farms which are too large to grow in Holland.
The International Horticultural Trade Show (NTV), is the showcase trade show for the industry. Last year it was held at the convention center at Amsterdam RAI from November 2-5. The event occupies two large convention halls with exhibitions by all kinds of horticultural supply vendors.
The single most interesting item I saw was a cutting shear developed by the agricultural research facility at Ede-Wageningen. The shears, which are not yet available commercially, cut plant tissue using an electrically heated blade. The blade sterilizes the cut and cauterizes it in one step. The researchers say that flowers cut using this process stay fresh several days longer because of the cauterization. They also think that the wound to the mother plant heals faster.
Although most growers don’t realize it, to a great extent clone failure is the result of plant disease, usually a bacteria or fungus. This is especially true of large facilities where temperature, humidity and nutrients are under tight control. The pathogens are often spread during the cutting process ? a single plant can contaminate the shears.
Careful growers usually sterilize cutting tools after each plant. This can be a sterilizing dip such as 5% bleach solution, 3% hydrogen peroxide or 70% isopropyl alcohol. This can be a bother and is also subject to forgetfulness. Thus the sterile cut is an excellent prophylactic.
? For more information write to I Wageningen University and Research Center, P.O.B. 9101, 6700 HB, Wageningen, Holland. Tel. 317-474148.
Mists and evaporation
A number of exhibitors featured micro-mist cooling. These sprayers deliver a very fine mist, usually between 5-15 micrometers. The droplets are so small they instantly evaporate, absorbing heat and cooling the air by as much as 10?C (20?F). These units work best for cooling in areas with low humidity or with good ventilation. A humidistat controls the units when they are used to maintain high humidity in propagation rooms.
Many European exhibitors displayed models. Some were permanent installations while others were connected to moveable fans on sturdy poles. All of the models used pressurized water flowing through tiny nozzles to break the water into tiny droplets.
One manufacturer, Micron Sprayers Ltd., used sonic vibrations to make droplets. He claimed his unit was self-cleaning for this reason.
Micro-misters have been available since the early 90’s and are available through many irrigation equipment manufacturers in North America.
Evaporative coolers use a fan to push air through a moist fibrous material. The water evaporates, cooling the air. Many commercial greenhouses use evaporative coolers and ventilation as the primary means of keeping the air cool. The units are usually matched to very large fans which blow in a steady breeze of cooled air. Evaporative coolers are inexpensive to set up and to operate. There were quite a few manufacturers with systems. These units are also available in North America and are widely used. In many casers they could be adapted to indoor grows, especially in the propagation and vegetative growth rooms, where a relatively high humidity is maintained.
Even in the flowering room, evaporative coolers may be the solution to a heat problem. The moist cool air coming from an evaporative cooler heats up in the grow space and its relative humidity goes down, because warm air has the capacity to hold more water than cool air. Thus the air is not too moist for the flowers and doers not promote mold.
? Micron Sprayers Ltd.: tel 44-1885-482-397; fax 44-1885-483-043; email [email protected]; web www.micron.co.uk
? Cooling Mist: Invernaderos Equipos y Complementos, Cami Faitanar s/n 9, 46210 Picanya, Valencia, Spain; tel 34-96-159-0954; web www.inst.tech#ehome.encis.es
Media and substrates
Although rockwool is the standard media for most hydroponic operations, manufacturers of several other mediums were at the show. A number of suppliers were offering cocopeat, also called “coir.” This is the pithy outer covering of the coconut shell, which is a by-product of coconut processing. It is being used as a substitute for peat in planting mixes. The advantages of coir are that it lasts longer, doesn’t pack down as much, doesn’t experience pH drift and is environmentally friendly as compared with peat or rockwool. It is also conducive to colonization by friendly microbes.
The media is sold in several forms. The slabs, made of pressed coir, are probably the most convenient for hydro growers. These are used in the same way as rockwool slabs.
Open cell foam rubber has been available for several years both as an ingredient for planting mediums and as slabs. The manufacturers claim that foam lasts longer, distributes water more evenly, is neutral pH with no pH drift and is environmentally more friendly than rockwool.
A medium something like expanded clay pellets was also on display. The rectangular pieces are very light and hold large quantities of both water and air. They have an irregular surface and are porous so that plant roots can easily grip them. They can be used alone and will wick up water, although the manufacturer recommends using this medium with a drip system or it can be used as an ingredient in a planting mix.
Many horticulturalists recommend adding clay to planting mixes. They say it is a good source of silicone and other micro-nutrients. Silicon plays a controversial role in plant nutrition. No studies have found that plants need silicone. However, when it is present in the medium, plants readily absorb it and hold it in spaces between the cells. Some researchers think it increases plant vigor and resistance to stress and predators. Several companies selling plant mediums offered clay, either as a powder, chips or as a granulate much like kitty litter.
One company, Tref, was selling various sized bits of cork to be used as an ingredient in planting mixes. It would probably make a good substitute for vermiculite or perlite in mixes.
Two Dutch sources of Coco are:
? Dutch Plantin, POB 13, 5427 ZG Boekel, Netherlands; tel. 31-492-32-42-91, web www.dutchplantin.com
? Intra Sales bv, Maatschapslaan 21, 2404 CL Alphen a/d Rijn, Netherlands, tel 31-172-47-66-69.
? There are a number of suppliers and importers in the US as well.
? The sponge-like planting cube is manufactured by Grow-Tech of California, POB 1035, Hollister, CA 95023; tel (408) 637-7070.
? Tref, 3146 BA Maasluis, Netherlands; tel 31-15-261-8230
One drip irrigation manufacturer, “Queen Gil” makes a tape with a molded drip system. Channels built into the tape regulate pressure and resist clogging. The tapes are made with high, medium, low and very low flow channels spaced at various distances. These tapes make it much easier to install drip irrigation.
? Queen Gil: PO Box 26025, 91260, Jerualeum, Israel; tel 972-2-6411-0313
Root zone heating
Root temperature affects the growth and productivity of a crop. Plants with cool roots grow slower, yield less and are more susceptible to disease. Even in a warm greenhouse or grow room plants roots may be too cool for optimum growth. Hotbox displayed two types of heaters for ebb and flow systems. Both were made to fit into commercial ebb and flow tables. The first uses a Styrofoam frame to hold water tubing in an accordion shape. The water warms the planting media. The second mat consists of low power electric heating cable embedded in a reflective plastic sheet. A thermostat controls the heat.
? Hotbox: Unit 1, Gordleton Ind. Park, Sway Rd. Lymington SO418JD, Hampshire, UK; tel 44-1590-683-788
There were many greenhouse manufacturers at the show. Most displayed models of standard greenhouses. Built with polycarbonate plastic or a strong frame covered with plastic film. However, one manufacturer displayed a model of sophisticated tunnels. These have an arch frame but they are also supported using positive air pressure. This has the advantage of streaming air out of the tunnel, pushing pests away from openings.
The same manufacturer showed another tunnel model. This one used automatic controls to cover or remove a lining from the frame. On days with strong sun, even in the winter, the greenhouse can heat up quite a bit (the greenhouse effect) and the best way to prevent heat stress is to remove the cover. This unit removes the cover automatically. I was told that there is also a model, which will cover the greenhouse with one of two covers. A transparent curtain lets in the light but protects the plants from the environment. A shading curtain is used to force flowering of short day plants, which of course includes our favourite.
The folks at Wageningen are also working on a new structure for greenhouses. The model looked something like a tee-pee. It was six sided with vertical walls about one third of the way up. Then the walls start narrowing leaving a circular hole at the center top. The researchers think that the shape and structure promotes natural ventilation and is very efficient at gathering light.
I saw only one company displaying seed sorters. They ranged from simple sieves with particular hole sizes, belt graders, which use a conveyor to move seeds over various sized holes, to pneumatic sorters capable of sorting hundreds or thousands of pounds a day.
? Seed Processing Holland bv, Zoutketen 12, 1601 EX Enkhuizen, POB 32, 1600 AA Enkhuizen, Netherlands; tel 31-228-35-30-00.
Grow more pot
Unlike standard commercial agricultural operations , which can expand production by increasing land and labor, marijuana growers are limited by both. They cannot usually get too big because of the risk of detection, and the difficulty of hiring (and firing) labor. So any technology which increases plant growth or labor productivity increases garden yield. Wise growers stay abreast of the latest grow-tech to ensure that they are maximizing the quantity and quality of their yields.