TO: Marianne Cicala
FROM: Eric Koperek =
erickoperek@gmail.com
SUBJECT: Floating Gardens
DATE: PM 7:24 Wednesday 17 August 2016
TEXT:
(1) Floating gardens are a very old technology practiced by cultures around the world.
(2) Not all "floating gardens" are truly floating. For example,
chinampas = raised fields found throughout Mexico, Central America, and South America. These are made by digging parallel canals through swamps and piling up the mud to form narrow raised fields that rise only 1 to 3 feet above water. The fields are fertilized by canal mud, water weeds, mussel shells, manure, fish scraps & bones, and crop wastes. Transplants are grown in mud cubes on nursery rafts made from rushes and water weeds (usually water hyacinth). Chinampas are planted the same day crops are harvested so the soil is never left bare. Typically, 6 crops a year are grown on chinampas (raised fields) in tropical climates. Vast amounts of food can be grown without tractors or petrochemicals but this intensive horticultural system requires LOTS or hand labor.
(3) On Lake Titicaca the
native Indians build artificial islands out of reeds. They build their huts and raise garden crops on these artificial islands. Lake mud, manure, water weeds, bones, and fish scraps are piled on top of the reeds to make raised beds for growing potatoes and other cold tolerant crops. The rotting vegetation (sheet composting) provides sufficient nutrients for bountiful crops. Potatoes thrive in the high organic matter soils; I have personally measured yields reaching 5 to 10 pounds of tubers per plant.
(4) The do-gooders at
Practical Action have a project to transfer floating garden technology to Bangladesh and other countries where competition for
land is intense. They build narrow (3 feet to 4 feet wide) rafts from a light framework of bamboo topped with a thick layer of water hyacinth and a top layer of approximately 1/2 topsoil or mud and 1/2 manure. These horticultural rafts are tethered to poles or tied to anchors to prevent them drifting away. The floating gardens are planted primarily with LEAF CROPS and other edible plants that do NOT grow tall. Rafts are ideally suited to crops with SHALLOW
ROOT SYSTEMS = not tomatoes, peppers, sweet corn, squash, or melons.
(5) The secret to floating gardens is buoyancy = keeping your artificial island from sinking. Plants do not grow well with their roots sitting in water. Most artificial islands in Europe and North America are made from styrofoam formed into rafts. The styrofoam has holes that allow roots to reach the water surface. Note: Roots
should never be allowed to drop below water surface or crop growth will be greatly inhibited. Most horticultural rafts are NOT designed for tall growing plants. Best results are obtained when floating gardens are planted with short crops like bush beans and leaf lettuce as these crops do not require great soil depth in order to thrive. Deeper soil = more weight = less buoyancy = more styrofoam needed to keep island afloat. Keeping artificial islands from sinking even 1/4 inch below optimum level involves serious engineering. Read widely then experiment intensively before attempting large scale projects.
(6) All floating garden systems have very high organic matter soils = at least 50% organic matter. Many horticultural rafts are basically sheet composting beds approximately 1 foot thick floating on the surface of still or very slow moving water. Floating gardens require vast quantities of organic matter to maintain productivity. It is good practice to obtain necessary volumes of compost or similar materials BEFORE constructing horticultural rafts. Mixtures containing shredded, composted hardwood bark are light weight and drain well. Good aeration and drainage are essential for healthy plant growth.
(7) Floating gardens are self-watering (unless soil depth is excessive). Water rises from lake surface by capillary action. Problems occur when soil depth rises much above 2 feet. For example, in Mexico, chinampas 3 feet high are cut down by half and the excess soil used to build new chinampas. When raised fields get too high (soil depth around 3 feet deep) much labor is required to irrigate the crops.
(
Test, test, and test again. Much experimentation is necessary to make floating gardens work well, especially true floating islands that sit on top of the water. There is a great deal of very complex biology involved with these intensive horticultural systems. Modern agronomists are basically clueless when it comes to understanding how these ancient agricultural technologies function. Try growing potatoes on an artificial island and you will quickly discover how much you do not know about agriculture. I have been working with chinampas and similar technologies for many decades now = long before you were born. I am humbled every time I venture into the jungle. The Indians have forgotten more than we have learned.
ERIC KOPEREK =
erickoperek@gmail.com
end comment