By Julie Etra
Although I have written several articles about corn (Zea mays), for The Eye, this one focuses on an outstanding new discovery that may truly revolutionize the agriculture “industry”? and associated production of this grain worldwide.
A Short History of Corn
First a little background. I have been fascinated with the history of this plant since my graduate studies at Colorado State University in Soil and Crop Science in the early 1980s. The school has one of the largest seed-storage labs in the world. When I was there, the facility had substantial collections of native germplasm of corn from a variety of sources, commonly called heirloom varieties and known as maiz criollo in Mexico, in order to protect ancient characteristics and associated germplasm.
This was the first time I had heard of teosinte, and the CSU farm actually had a few plants. You can also see this plant at the ethnobotanical gardens behind the church of Santo Domingo in Oaxaca City, which is a stunning garden. Teosinte, unlike modern corn, is a perennial plant, meaning that it lives more than two years, unlike short-lived annuals and biennials. Up until the last decade, scientists were unsure whether or how this perennial grass-like plant evolved into the many manifestations of modern corn we eat and use. But with the DNA genome mapping revolution it was determined that indeed, this plant was the ancestor of our modern corn, which is the result of 8,000 – 9,000 years of plant breeding in the state of Oaxaca
Corn now provides about 21 percent of human nutrition across the globe; one cannot underestimate its economic significance. However, it requires large amounts of nitrogen; on a commercial level of production for animal feed, food additives, biofuel, and of course human consumption, the nitrogen required is substantial.
Currently, most nitrogen fertilizers are inorganic, produced from fossil fuels by energy-intensive processes. These are estimated to use 1% to 2% of the total global energy supply and produce an equivalent share of greenhouse gases. In this process, natural gas (CH4) usually supplies the hydrogen, and the nitrogen (N2) is derived from the air to produce ammonium nitrate. In addition, these forms of nitrogen are highly volatile; in other words, if the plant does not immediately use the ammonium nitrate, it ends up in the air or in surface or groundwater, where it can be a serious contaminant, resulting in algal blooms. Nitrate is one of the most common groundwater contaminants in rural areas. It is regulated in drinking water primarily because excess levels can cause methemoglobinemia, or “blue baby syndrome.” Nitrogen production not only consumes energy, but contributes to climate change and pollution.
Prior to inorganic production, nitrogen had been so essential for agriculture that it comprised a major industry, mined from various sources. We were recently in Chile and learned about salitre (saltpeter), which is a mixture of potassium nitrate (KNO3) and sodium nitrate (NaNO3). It is found naturally in large areas of South America, mainly in the Uyuni region of Bolivia and the Atacama Desert in southern Bolivia and Peru and northern Chile. Also known during its peak production as white gold, the saltpeter boom took place in the mid-nineteenth century. It was shipped across the Atlantic from western South America, before the Panama Canal was built, to serve markets in Europe, primarily Germany and England. For several decades it was so important to the Chilean economy, it was central to what was called the Saltpeter Wars (War of the Pacific, 1879-84) with Peru and Bolivia. As the winner of the Wars, Chile gained new coastal territory with significant and lucrative mineral income.
Before saltpeter became a critical industry, bat and/or bird excrement, commonly known as guano, had been the sine qua non for fertilizers, after large deposits made by huge shore bird populations were discovered on the Chincha Islands (Peru). “The Great Heap,” as it was called, accumulated guano to a depth of 200 feet.
In a rare documents exhibition on the guano trade, the Smithsonian’s National Museum of Natural History website (http://americanhistory.si.edu/norie-atlas/guano-trade) notes that:
In the early 19th century, farmers and chemists worldwide claimed that Chincha Islands guano was the world’s finest fertilizer. Hundreds of British, German, and American ships purchased it from the Peruvian government for their own agriculture, waiting offshore up to eight months to load the precious cargo. These nations’ ships also sought, claimed, and mined other guano islands in the Pacific and Caribbean.
Another interesting tidbit from this site explains that the source of labor for extraction changed over time; after South American prisoners and slaves and Hawaiian workers were no longer available, as many as ninety thousand Chinese men were brought in to work the The Great Heap until the late 1870s when the deposits, as well as the bird habitat and the birds, of course, were gone.
Plants in the pea family (Fabaceae), as well as certain other plant families, produce their own nitrogen from the atmosphere through symbiotic bacteria and a process known as nitrogen fixation. In members of the pea family, the bacteria live in nodules on the roots, and the plant provides sugar in return. This is not true in the grass or grain (corn) family.
Nonetheless, corn’s large need for nitrogen has driven decades of research on the possibility of nitrogen fixation in isolated corn landraces (locally adapted traditional varieties of plants or animals). A recent publication (https://news.wisc.edu/corn-that-acquires-its-own-nitrogen-identified-reducing-need-for-fertilizer/) describes just such a miraculous finding in the Sierra Mixe east of Oaxaca City. “Discovered” in April 2018 (the article was published in August 2018), this particular corn produces aerial roots on the stems of the plant. The aerial roots secrete a mucilaginous “goo,” within which reside bacteria that ‘fix’ nitrogen in this oxygen-free but carbohydrate-rich environment. So, the corn gets nitrogen and the bacteria gets sugar. Moreover, the plants are huge, growing 16-20 feet (about 5-6 meters), with up to 10 sets of nitrogen-fixing roots. Now how cool is that? Corn that acquires its own nitrogen.