Basic Principles

Using the energy provided by the sun, plants fix CO2 from the air into sugars (carbohydrates). Plants subsequently synthesize some of the sugars into proteins, lignin, fats and acids using various nutrients. 

Under natural conditions, soil slowly releases nutrients that are taken up by plants. To increase the growth rate of plants beyond the slow rate that can be obtained through natural processes, fertilizers can be supplied to the plants. Molecules containing the nutrients are available in large quantities on earth – but mostly as inert chemical molecules that cannot be absorbed by plants.Rhiyzobium help legumes fix N2

For example, 80 percent of the atmosphere contains nitrogen (one of three primary plant nutrients) as N2. The molecules of this “noble gas” are tightly bound, and the bond can only be broken using massive amounts of energy (such as found in lightning), converting the inert nitrogen into reactive nitrogen. Some crops can fix their own nitrogen from the air, such as legumes, which convert N2 into reactive nitrogen with the help of bacteria. Unfortunately, the quantities produced are insufficient to feed the world population. After years of research, two German scientists invented the Haber-Bosch process, which allows humans convert inert N2 into reactive nitrogen as urea and ammonium fertilizers.

Phosphorus and potassium (the other two primary plant nutrients) are stored in the soil crust and are “inert” to biology also. After mining ore that contains these nutrients and treating it chemically, we convert these inert nutrients into reactive nutrients for plant uptake. Likewise, three secondary nutrients and eight micronutrients are made available for plant growth. Deficiencies in secondary nutrients and micronutrients have been identified in many soils.

The reactive nutrient molecules from fertilizer ultimately end up in the stratosphere, atmosphere, biosphere, pedosphere and hydrosphere of Earth, causing environmental problems (as seen in the below picture). Though the original intention was for the molecules to be taken up only by the plants cultivated by humans to enhance growth and provide food for a growing population, much of today’s fertilizer technology is only about 20-70 percent efficient, depending on the nutrient.

Many factors may play into this, for example, imperfect composition of the fertilizer, untimely application and insufficient availability of water to help dissolve the nutrients. But also socio-economic attitudes may cause inefficiencies. If fertilizers are sold at too low of a price, they may be overused. Some cultures value the dark-green appearance of an over-fertilized crop. More than these, lack of knowledge (or ecological illiteracy) may cause misuse of fertilizers.

Underuse of fertilizer is equally problematic. Soils are drained of nutrients and degrade. Degraded soils are less capable of holding water, wreck nutrient uptake efficiency and gradually lose their production capacity. Yields of crops start to decline, and poor families that cannot afford to replenish the soils with nutrients from fertilizers often fall into even more misery.

Unfortunately, such situations are ubiquitous in many developing nations, which not only affects that family’s nutrition but the food supply of the earth’s growing population.