Celebrating National Ag Day: March 18: History of fertilizer dates back more than 8,000 years

Gary Hergert, Rex Nielsen and Jim Margheim

With the fertilizer application season approaching, it is once again time for producers to make decisions as to what their fertility programs will be. Soon many fertilizer-application rigs will be in the fields, spreading great quantities of fertilizer.

Because the use of fertilizer has become such an integral part of modern farming, we rarely give any thought as to where it comes from, how long it has been used and what impact it has had on our food production. With our current ability to test our soils nutrient levels and then convert those soil test results into reliable application recommendations, farmers' biggest concern regarding fertilizer use is cost, how much is needed and then which fertilizer formulation to apply. This has not always been the case.

Current fertilizer practices are relatively recent events that date back to just the last half of the 20th century; however, traditional fertilizer practices are much older.

Although it was previously thought that the concept of fertilizer use may have only dated back 2,000 to 3,000 years, it is now believed that early farmers were using manure to fertilize their crops as long as 8,000 years ago. A team led by Amy Bogaard, an archaeobotanist at the University of Oxford, decided to look for evidence of earlier fertilizer use.

In ancient times, manure would have been the most logical fertilizer to use and, due to the fact that manure has a higher than normal concentration of the rare nitrogen-15 isotope (N-15), the team noted that recent research showed that plants treated with manure have more N-15.  The researchers collected ancient samples of cereals such as wheat and barley, as well as pulses such as peas and lentils, from 13 early farming sites across Europe that dated from 4,400 years to 7,900 years ago.  They analyzed more than 2,500 individual cereal grains and pulse seeds, from which it was concluded that the N-15 levels were higher than normal and consistent with the use of manure for fertilizer.

So how did farmers thousands of years ago realize that manure could increase their yields?

The researchers concluded that early farmers probably first noticed enhanced crop growth in areas of natural dung accumulation where animals gathered.

These areas of high fertility would have been obvious to subsistence farmers who saw differences in productivity between their small plots.

The researchers also surmised that cropping and herding developed at the same time and were integral from the start.

Later the Babylonians, Egyptians, Romans and early Germans all are recorded as having used minerals or manure to increase yields on their farms. However, the predominant source of fertilizer for the next few thousand years was manure.

Putting skulls to work

For thousands of years after agriculture came into existence, manure was the main source of fertilizer.

But sometime in the 18th Century, it became common knowledge that ground-up bones provided crop nutrients. By 1815, England was importing so many bones from the rest of Europe that people on the continent started complaining that England was robbing all other countries of their fertility.

In the United States, the customary source of bones from livestock packing houses was supplanted by thousands of tons of bison bones covering the western prairies, which were left from the slaughter of the great buffalo herds. Many early Nebraska homesteaders were saved from bankruptcy by gathering these bones and selling them for processing into fertilizer. Probably little if any of this fertilizer ever made it back to Nebraska.

Although agriculture science was becoming understood in the 18th century, little was known about actual plant nutrition needs. One of the earliest experimental mineral products for agricultural use was gypsum. Scientists at the time were aware that some benefits could be had from the application of gypsum; however, little was known about its actual mode of action.

It wasn't until the 19th century that ground-breaking research, done by several innovative scientists, finally ushered in the modern era of soil chemistry and plant nutrition. One of the most prominent of these chemists was Justus von Liebig (1803-1873), a German chemist who did pioneering research in organic and biological chemistry.

Liebig's "Theory of Mineral Nutrients" established the foundation of agricultural chemistry.  He determined that the chemical elements of Nitrogen (N), Phosphorus (P), and Potassium (K) are essential to plant growth. To this day N, P and K are considered the fundamental nutrients for crop production. Liebig's "Law of the Minimum" revealed that maximum plant growth is not determined by total available nutrients, but by the least available nutrients.

The findings of Liebig's research also led him to the conclusion that plant nutrients could be depleted by crop removal and that added fertilizer is need for optimum crop production. His ground-breaking discoveries facilitated his development of the first nitrogen-based fertilizer and earned him the title of "Father of the Fertilizer Industry."

Several other scientists followed in Liebig's footsteps. Their discoveries contributed additional knowledge to the basic understanding of plant nutrition and fertilizer development. Of these scientists, the Nobel prize-winning chemists Carl Bosch and Fritz Haber developed the Haber process, which used molecular nitrogen and methane gas to produce ammonia on an economical and sustainable scale.

Subsequently, the Ostwald process (developed by Wilhelm Ostwald prior to the Haber process) was able to use ammonia from the Haber process to produce nitric acid on a commercial scale. The end result of these discoveries was that most chemical fertilizers could now be produced with nitric acid as the primary, raw material.

By the beginning of the 20th century, scientists had developed the processes to manufacture ammonia and nitric acid, basic components of many chemical fertilizers.

Ammonia production increases

Ammonia and nitric acid, basic components of many chemical fertilizers, could be manufactured by the early 20th Century. But until the middle of the century, use of chemical fertilizer was limited.

Small amounts of bone meal and blood meal were used, but the primary source of fertilizer was manure and plowed-down legumes.

There were several obstacles to chemical fertilizer use:

Chemical (artificial) fertilizers were relatively expensive due, in part, to limited availability;

Mechanized methods of application were yet to be developed;

General knowledge of when and how much to apply on specific crops was not known.

However, this would all change.

With the start of World War II, there was a tremendous increase in nitrogen production, mainly because nitrogen is a principal ingredient in explosives. The government constructed 10 new plants to produce ammonia for munitions when World War II began, all located in the interior of the country.

Most were located near natural gas pipelines so they could use the gas as raw material for nitrogen production. By the end of the war, all plants were producing 730,000 tons of ammonia each year and had the capacity of producing 1.6 million tons

After World War II, the need to manufacture war munitions was replaced with the need to restore food supplies in Europe and the United States.

To accomplish this goal, new advances in crop production were accomplished, including: 1) the development of new and improved hybrids, 2) the development of basic guidelines for crop nutrition and fertilizer requirements, 3) a revolution in equipment design and performance, 4) the large-scale production of phosphates by acidulating rock phosphate and 5) the discovery of massive deposits of potash around the world.

These events, in addition to many other advances in agricultural sciences, set the stage for our modern age of fertilizer.

The modern age of fertilizer is marked by massive funding and research efforts from various federal and state institutions and agencies, a primary goal of which was to develop comprehensive guidelines and information for the most efficient and effective use of fertilizers under differing crop production and environmental conditions.

Foremost among such efforts were those associated with scientists and agronomists from land grant universities (such as the University of Nebraska), the U.S. Department of Agriculture and the Tennessee Valley Authority (TVA) fertilizer branch in muscle Shoals, Ala. The TVA fertilizer branch was created by legislation authored by Sen. Frank Norris of Nebraska.

The "technological age" of the last 20-25 years, in addition to the vision and contributions of farsighted researchers and scientists, has significantly increased knowledge of the complex interactions involving the use of fertilizer and the chemical, physical and biological factors of the soil, as well as the potential effects of fertilizer use on the climate and environment.

The development of high-tech equipment has led to "precision" and "best-management" farming practices, which have resulted in the ability to apply various fertilizer types to a given crop in site-specific amounts.

Technological advances in various fields of study, including crop genetics and breeding, plant and soil testing, and the development of techniques to monitor the movement of nutrients and water within the soil profile have allowed today's farmers to use fertilizers more effectively and efficiently, in addition to being better stewards of the land and environment.

Manure is still an important source of plant nutrients.

However, during the last 75 years, its use has been surpassed by the large-scale production and use of chemical fertilizers. In the mid- to late 1940s, about 2 million tons of chemical fertilizers were used per year; by 1960, over 7 million tons were used per year and over 20 million tons were used in 2014.

There is still much to learn about the complex interactions involving fertilizer use in differing soil and plant ecosystems; however, we have made historical progress since the first use of manure – progress that has been foundational to feeding our nation and providing food and hope to other parts of the world.