This article originally appeared in Garden Culture Magazine US 09.
Hydroponics, now commonly defined as the soilless growth of plants, has its root foundations in simple observations by early progressive thinkers and tinkerers. Like many scientific discoveries and their evolution to commercial application, progress came in fits and starts, with major discoveries and realizations followed by extended periods of seeming disinterest.
A Rich History
Many written histories of hydroponic plant cultivation methods mention the ancient Hanging Gardens of Babylon, the first written record of which dates to about 290 BC. Penned by Berossus, a Babylonian writer, priest, and astronomer, we only know of Berossus’ writings through quotes by later authors. Five primary authors, including Berossus, are responsible for what we know of the Hanging Gardens today. Their accountings were all written at a later time, based on now lost, previously written accountings by others.
Modern research questions whether the gardens were in Babylon at all, yet the premise that the gardens would in some way qualify as “hydroponic” is doubtful, based on observations by these early writers. Diodorus Siculus, writing between 60 and 30 BC, referenced the 4th century BC texts, Ctesias of Cnidus, for his description of the gardens. After detailing their construction, he includes the following passage,
“…on all this again earth had been piled to a depth sufficient for the roots of the largest trees; and the ground, when leveled off, was thickly planted with trees of every kind…”
Quintus Curtius Rufus, writing in the 1st century AD, references writings of Cleitarchus, a 4th-century BC historian for Alexander the Great, who also described the “…deep layer of earth placed upon it and water used for irrigating it.” Philo of Byzantium, the author who identifies what we accept today as the Seven Wonders of the Ancient World, writing sometime around the 4th or 5th centuries AD, mentions that “…much deep soil is piled on, and then broad-leaved and especially garden trees of many varieties are planted.”
Based on these accounts alone, it seems doubtful that the Hanging Gardens of Babylon could in any way be considered soilless. In all fairness, the irrigation systems required to bring water to plantings of the reported scale, described in the form of aqueducts and water lifts, are similar in concept to irrigation methods employed today in modern hydroponic systems.
Old World References
Another oft-mentioned comparison to modern hydroponics in the Old World are the “floating gardens” built by the Aztecs in the 14th century AD. Arriving in the Valley of Mexico, the Aztec people found a landlocked swamp with five large lakes surrounded by volcanic mountains. For some reason, they chose to settle in swampland surrounding Lake Texcoco and decided to build their capital city on a small island in the lake. Lacking any extra land for growth, the people started building what were essentially rectangular islands, constructed of soil, compost, and sludge from the lake bed.
Contrary to popular belief, these islands, or “chinampas”, didn’t float at all, but were rather attached to the lakebed using willow tree cuttings and a variety of materials including stones, poles, reeds, vines, and rope. Chinampas were incredibly fertile and irrigation was unnecessary since water wicked up from the lake. As many as 7 crops could be harvested in a single year due to the unique methods of composting and mulching developed by the Aztec farmers of the time. However, based on their method of construction it’s clear that the Aztec chinampas, like the Hanging Gardens of Babylon, cannot be classified as hydroponic either.
Earliest Hydroponic Research
Some of the earliest recorded research into the actual reasoning behind the growth of plants, published posthumously in 1648, was written by a Flemish chemist known as Jan Baptist van Helmont (1579-1644). In fact, authorities detained van Helmont in 1634 during the Spanish Inquisition for the “crime” of studying plants and other sciences and sentenced him to two years in prison. And while van Helmont was primarily known as the first to articulate that there are gaseous substances that differ from ordinary air, as well as introducing the word “gas” into the scientific lexicon, he is also known for a single experiment he conducted using a willow tree to determine from where plants derive their mass. This research is commonly known as “the 5-year tree experiment”…
“But I have learned by this handicraft-operation that all Vegetables do immediately, and materially proceed out of the Element of water onely. For I took an Earthen vessel, in which I put 200 pounds of Earth that had been dried in a Furnace, which I moystened with Rainwater, and I implanted therein the Trunk or Stem of a Willow Tree, weighing five pounds; and at length, five years being finished, the Tree sprung from thence, did weigh 169 pounds, and about three ounces: But I moystened the Earthen Vessel with Rain-water, or distilled water (alwayes when there was need) and it was large, and implanted into the Earth, and least the dust that flew about should be co-mingled with the Earth, I covered the lip or mouth of the Vessel with an Iron-Plate covered with Tin, and easily passable with many holes. I computed not the weight of the leaves that fell off in the four Autumnes. At length, I again dried the Earth of the Vessell, and there were found the same two hundred pounds, wanting about two ounces. Therefore 164 pounds of Wood, Barks, and Roots, arose out of water onely.“
Historians have deduced that the experiment was likely not an original idea, rather one motivated by Nicolaus of Cusa’s 1450 description in De Staticus Experimentis of a similar experiment that was apparently never conducted. Further research puts the concept of the experiment back to a Greek work somewhere between 200 and 400 A.D. And while his research method is completely lacking in scientific validity, it was van Helmont’s line of inquiry and experimentation that would ultimately lead to the understanding of photosynthesis.
In 1699, John Woodward (1665-1728), an English naturalist, antiquarian, and geologist challenged Helmont’s theoretical deductions by publishing the results of “water culture” experiments he conducted using spearmint grown in differing sources of water. His experiments showed that the spearmint grew better in water to which he added very small amounts of soil, versus “plain” water, and distilled water. His research also led him to the differing conclusion that more than water was necessary for plant growth, and that soil was at least partly responsible for the increase in the mass and weight of plants, indicating that he too failed to clearly grasp the fundamental concepts of plant nutrition.
Unfortunately, progress in these areas of research remained stagnant until the first proper water culture experiments undertaken by a French agricultural scientist and chemist, Jean-Baptiste Boussingault (1801-1887), around 1840. Boussingault had established the very first agricultural experiment station near Alsace, France four years earlier, and was responsible for a plethora of discoveries related to soil chemistry and plant nutrition. Many of his experiments involved raising plants in various soil substitutes, including sand, ground quartz, and charcoal, which he irrigated with solutions of mineral nutrients.
Also in 1840, Boussingault’s fan and contemporary, German chemist Justus Freiherr von Liebig (1803-1873), published Die organische Chemie in ihrer Anwendung auf Agricultur und Physiologie (Organic Chemistry in its Application to Agriculture and Physiology), which proffered the then ridiculous proposition that chemistry could drastically increase yields, and cut the costs associated with growing food. As a boy, Liebig had lived through “the year without a summer”, a volcanic winter event that occurred in the Northern Hemisphere after the massive 1815 eruption of Mount Tambora in what is now known as Indonesia. Near total crop losses that season led to widespread food shortages, causing a global famine, and much of Liebig’s later work towards increasing world food production was reportedly shaped by this unsettling experience.
Liebig made significant scientific contributions to agricultural chemistry and was the first to put forth a theory on mineral nutrients, identifying as essential to plant growth the now-familiar elements including nitrogen (N), phosphorus (P), and potassium (K). Interestingly, Liebig’s major downfall was his lack of experience in the practical applications of his research. One of his best-known achievements was developing nitrogen-based fertilizer, arguing in the 1840’s that it was necessary to grow the best possible crops. However, he later convinced himself that there was plenty of nitrogen supplied to plants through ammonia contained in precipitation, and strongly argued against using nitrogen in fertilizers in his later years.
Despite his wavering, he is commonly known as the “father of the fertilizer industry” – not only for his identification of nitrogen and other elements as being necessary for plant growth but also for his development of the Law of the Minimum, which observed how individual nutrient components affected crop growth.
In 1860, Ferdinand Gustav Julius von Sachs (1832-1897), a German botanist and author of Geschichte der Botanik (History of Botany) (1875), a highly regarded historical chronicle of the various branches of botanical science from the mid-1500’s through 1860, published his nutrient solution formula for “water-culture”, and revived the use of this technique as the standard tool when researching plant nutritional needs. His plant nutrient formula, with only minor changes, was almost universally used for the next 8 decades.
Sachs’ experiments blazed the trail, and in rapid succession, other scientists followed up his work – the most notable of which was Johann August Ludwig Wilhelm Knop (1817-1891), a German agricultural chemist. While Sachs’ interest lies primarily with studying plant processes while establishing botanical knowledge, Knop can rightfully be called the true father of water culture, as his experiments laid the foundation for what we now know today as hydroponics.
In his early experiments, Knop sprouted seeds in sand and fiber netting before transplanting the seedlings into cork stoppers with drilled holes, securing them with cotton wadding, and then suspending them in glass containers filled with solution. By doing so, Knop inadvertently established the technique most widely used for future laboratory experiments.
Using this method, Knop was the first to realize that plants gain a large amount of weight simply from the food stored in their seeds and that seeds provide nourishment to the parts of the plant that form first. By this time it had also been established that soil nutrients must be in a soluble form for plants and that the number of soluble nutrients in soil was minuscule compared to those that were insoluble. These two pieces of information would form the basis for Knop’s future scientific experimentation.
What wasn’t available then were specific ways to measure these properties, such as osmotic pressure, nor did researchers of the day have any idea of what those properties might be. And while Knop deduced that nutrient solutions that were too concentrated might do more harm than good, he had no idea why.
Despite this lack of understanding, in 1860, Knop successfully grew plants, without soil, weighing many times more than their seeds and containing a larger quantity of nutrients. In 1868, other scientists using Knop’s methods, grew buckwheat weighing 4,786 times more than its original seed, and oats weighing 2,359 times more. These experiments firmly established the fact that plants can indeed be grown successfully, and productively without soil.
And Then, All Was Quiet
Over the next few decades, little effort towards developing commercial applications continued to leave the promise of water culture unfulfilled. William F. Gericke, the man who actually coined the term “hydroponics”, in his book The Complete Guide to Soilless Gardening (1940), laments the fact that “… after 1868, the conditions were as auspicious for the birth of hydroponics as they were in 1929,” the year Gericke began in earnest his research to find out if food crop production using water culture could be commercially viable.
In the next installment, we’ll explore events occurring in the 20th century that led to the birth of hydroponics as it is known today, as well the missteps and misinformation that again led to its virtual abandonment as a practical alternative method of food production for many years to follow.