The History of Plant Fertilizer

Overview

We've all heard the tale of how Squanto taught Pilgrims to set a fish head under each hill of planted corn. This practice, coupled with the ancient Native American custom of pairing beans with certain crops, added crucial nitrogen to the soil. But there are other historical examples of fertilizer use around the world. Implications of what the ancients knew is timely today, as we increasingly reject harmful chemicals and look to the old ways to fertilize our plants.

Asian Ingenuity

The Chinese were among the earliest documented practitioners of using animal and human waste to feed crops. Historians estimate that Chinese farmers began adding manure to their land about 3,000 years ago. They also used the ashes of burned plants to feed the soil, and treated animal bones with ash or lime in order to add potassium.

The Indian "Stinking Water Pot"

Around the same time, farmers in India developed a method called Kunapajala, which used virtually all parts of a hunted animal that wasn't eaten or otherwise utilized. ("Kunapa" means "stinking," in Sanskrit, while "jala" means "water".) The rest of the body, from horns to hooves, was placed in a large pot and cooked with water, plant husks, sesame oil cake, honey, gram and ghee (clarified butter). The resulting liquid was said to be especially good for tree crops during flowering or fruiting times.

Greco-Roman Farmers

Ancient Greeks were early practitioners of fertilization through irrigation, routing the city sewage into their farmlands and olive groves. They also began experimenting with what today are known as cover crops; fallow fields were seeded with nitrogen-producing legumes, especially lupines. Both the Greeks, and later, the Romans, also recognized the value of adding wood ash and river or ocean sediment to the land to adjust the soil's acidity. Greco-Roman agriculture also incorporated the enrichment of farmland through minerals, especially saltpeter and salt brines.

Early Commercial Fertilizers

Starting in the 1500s, identifying and experimenting with specific compounds found in manure, bones, salt, ashes and other natural elements led to a growing sophistication about crop fertility. But commercial fertilizers weren't produced on a broad scale until the1840s, when naturally occurring bat guano from Peru and mined sodium nitrate from Chile began to be exported throughout the world, especially to the United States. Both of these products provided nitrogen to field crops.

Synthetic Fertilizers

From the 1920s through the end of World War II, ammonium sulfate became a popular form of nitrogen fertilizer. A by-product of natural gas, steel and coal mining, ammonium sulfate represented a new source of synthetic commercial fertilizer. In the ensuing years, most ammonia processing plants also produced some form of synthetic fertilizer, including urea. By the 1950s, as understanding of the major three macronutrients (nitrogen, phosphate and potassium, or N-P-K) became clear, manufacturers began to bulk-blend the combinations in granular form. Chemical nitrogen is still largely generated from ammonia plants, while phosphate and potassium are mined, respectively, from phosphate rock and potassium chloride.

Modern Implications

Today, farmers around the world can find both chemical and organic versions of the macronutrients N-P-K, as well as several important trace minerals. While convenient organic blends of N-P-K aren't as readily available at garden centers as are their synthetic counterparts, a blend of soy meal, bone meal and greensand (a powdered sandstone rock) is just one of countless versions of an organic nitrogen, phosphorous and potassium blend which the determined organic farmer or home gardener can blend for herself.