Feeding Our Nitrogen Addiction

Farmers, backyard gardeners and scholars of science and environment alike understand that nitrogen is one of the most important plant foods. Although ancient sources (including the Hebrew Scriptures) indicate that humans have known about the importance of maintaining the soil for millennia, it wasn’t until the last two centuries that science and environmental studies determined a need to develop artificial means of reintroducing nitrogen into the soil. 

The 1901 edition of James Bolton McBryde’s classic text, Elements of Agriculture, said of nitrogen, “It is important because no plant can grow without a supply of this element, and, furthermore, because the supply in the soil is easily exhausted through careless cultivation, and, when once exhausted, is with difficulty replaced.” 

As a reaction to an increasing worldwide population and a greater ability to ship foodstuffs longer distances, toward the end of the 19th century farmers began to add nitrogen and other fertilizers to the soil to increase yield and profits. 

Soon those who understood science and environment feared that the known natural sources of nitrogen for commercial fertilizer could soon be depleted. Within a few decades, scientists, notably Fritz Haber and Karl Bosch of Germany, had developed a method of synthesizing ammonia from inactive atmospheric nitrogen. The resulting compound has been used ever since to produce nonorganic fertilizer. Haber was hailed as a hero, put forth as the father of modern fertilizer, and was awarded a Nobel Prize in 1918. 

During the remainder of the 20th century, the earth’s population and food production both increased exponentially, foiling the dire predictions by scientists like Paul Ehrlich in his 1968 book, The Population Bomb, that such growth would deplete essential global resources and cause mass starvation before the end of the century. 

Many feel that synthetic nitrogen fertilizers enabled the increase of food production necessary to sustain the dramatic population growth for now, but as Ehrlich recently told Vision, “We just don’t know whether the ecosystems will handle it. It’s the top of the ninth inning and humanity is hitting nature hard, but we have to remember that nature bats last. . . . We cannot just get rid of technology; it can help us solve a lot of problems (and it already has). But as far as I can see, problems are being generated much more rapidly than they are being solved. We can’t have faith in technology pulling a rabbit out of a hat each time, because the rabbits always turn out to have dirty droppings." 

Some of Ehrlich’s concern about resource depletion stems from the increased reliance of crops on synthetic fertilizers. Although he does not advocate simply going back to the ox and plow, there are advantages to nonsynthetic nitrogen soil improvement methods involving the quality of the food grown in such soil.  

Nitrogen is an important component of protein, and the protein content of plants relies upon available soil nitrogen and atmospheric nitrogen collected in the soil by nitrogen-fixing plants. Although there is some debate as to whether organic produce contains more vitamins than nonorganic produce, current health news suggests that organically grown produce has other health benefits, including more health-protecting antioxidants, polyphenols and flavonoids. A Danish study performed on rats showed that those fed an organic diet slept better, had less adipose tissue, showed better immunity and were generally healthier than those fed nonorganic diets. Similar reports dispense common-sense advice that is not at all surprising: for example, an organic diet lessens exposure to pesticides. 

Avoiding pesticides in our food is a common-sense theme in current health research. Nitrogen fertilizers may have a less obvious but nevertheless important effect on the nutritive value of the plants they fertilize, which in turn can affect the health of those who ingest the plants. According to a 1993 review of international literature on the subject published in the Journal of Plant Nutrition, “Nitrogen fertilizers, especially at high rates, seem to decrease the concentration of vitamin C [ascorbic acid] in many different fruits and vegetables. . . . Nitrogen fertilizers are also shown to increase the concentrations of carotenes and vitamin B in plants. Since excess use of nitrogen fertilizers increases the concentration of NO3 [nitrates] in plant foods and simultaneously decreases that of ascorbic acid, a known inhibitor for the formation of carcinogenic N-nitroso compounds from nitrite, it appears that the use of these fertilizers may have a double negative effect on the quality of food plants.” The resulting decreased antioxidants and increased nitrates may therefore play a major role in the upsurge of cancer and cardiovascular disease of people around the world. 

Results of a similar survey published in the April 2001 Journal of Alternative and Complementary Medicine corroborate the earlier review of international data. “Organic crops contained significantly more vitamin C, iron, magnesium, and phosphorus and significantly less nitrates than conventional crops. There were nonsignificant trends showing less protein but of a better quality and a higher content of nutritionally significant minerals with lower amounts of some heavy metals in organic crops compared to conventional ones.” 

Both the quality and quantity of protein stored in a plant depends on how much nitrogen is found in the soil. If a large amount of nitrogen is available at once, as is often the case with artificially fertilized soil, the plant stores the available protein quickly. However, that protein contains fewer essential amino acids, which are the building blocks of proteins and are necessary for proper metabolism. With natural fertilizers and sustainable or organic farming methods, the nitrogen is released more slowly, enabling the plant to build up a higher quality protein (containing more essential amino acids) over time. 

The quality of food we consume is directly related to health. It is therefore certainly worth the effort and expense to seek out those foods with better nutritional quality. 

As the demand for organically grown foods increases, suppliers are reacting positively and more producers are growing foods to meet consumer demand. But to sustain that positive trend, we need to examine the impact of our current agricultural practices and find more healthful methods, which may include less reliance on synthetic nitrogen and a return to some of the sustainable agricultural practices known by our distant ancestors.