To determine the best methods, Lawes and Gilbert planted two fields of wheat and turnips, divided these into twenty-four strips, and then applied different fertilizers and chemicals to each, refining the ingredients over time and adjusting them for different crops until they got optimum growth. They also took notice of the different effects on crop yields from inorganic and organic fertilizers and how they affected the biodiversity of the plants and animals around them.
Inorganic fertilizers came from mining or mechanical processes. Organic fertilizers came from animals and plants. Lawes and Gilbert determined that all plants increased yields with the addition of nitrogen and phosphorus, whether inorganic or organic. Trace minerals increased yields on some plants but not others. They added fish meal and animal manure from a variety of animals, which were fed different diets. In 1889 Lawes established a trust from the sale of his fertilizer business, and so experiments continued after his death in 1900. Rothamsted researchers began to test the pH level of the soil to determine its acidity or alkalinity, and then added chalk to vary those results and test the difference it made.
In general, fertilizers accelerated crop growth, but researchers also noticed that where inorganic fertilizers were added, waist-high crops grew on agricultural lands, but in nearby fields, species numbers declined. Up to fifty species of grasses, legumes, weeds, and herbs grew on fields away from treated lots, but as few as three species grew on lots adjacent to fertilized plots. Inorganic fertilizer improved crop yield, but it dramatically decreased biodiversity. The arrival of agriculture initiated the long decline of plant species numbers and is part of the biodiversity crisis we are now experiencing.
The spread of agriculture compounded the effects of man on nature and its suite of plants and animals. Most farmers went along with the reduction of biodiversity, since a decrease of plant species led to fewer weeds. Still, modern agriculture has brought down the number of plant species on earth much like the volcanic eruptions that triggered the Permian extinction and the asteroid that ended the Cretaceous. Fewer species leads to the spread of disease by reducing the number of hosts that carry disease, some of which are better at spreading it than others.
Lawes had trepidation about the situation he had helped create. Though he had been one of the prime movers of inorganic fertilizers, he advised anyone planting vegetables or garden greens to find a location near a farm with a “large supply of yard manure at a cheap rate.” Organic fertilizers, particularly manures, were a better choice even to the inventor of many of our inorganic choices.
In the late 1800s, Europe was struggling to feed its burgeoning population as farmers desperately sought manures for their grains and vegetables. South Pacific islands were stripped of their guano; stables were ravaged for the smallest of droppings; and human refuse, delicately referred to as “night soil,” was tested as well. According to Liebig, even the horse and human bones (good sources of phosphorus) from the Battle of Waterloo were ground up and applied to crops.
Inorganic fertilizers were thought to be the only logical choice by the dawn of the twentieth century, and Queen Victoria knighted Lawes and Gilbert for their agricultural innovation and the benefits their work with fertilizers had brought to UK farmers. Rothamsted Manor, in the center of the fields, has now become a boardinghouse for visiting scientists from around the world. This research station still studies various fertilizers but also looks at refining crops for energy production along with the long-term effects of pesticides, herbicides, and genetic modification.
The agricultural history of the last 160 years is written in the samples of soils, crops, fertilizers, and manures that the research station keeps in its “sample archive,” where we see indications of increased production after the green revolution as well as evidence of the rise of pollution and fallout from Chernobyl in that same period. This portends poorly for man, because agricultural scientists hope soil will play a big part in doubling food production over the next several decades. We would need to double the amount of crops if we are to have enough grain on the table, feed in the barn, and biofuel in the tank in the future for man to keep going. A polluted and depleted soil report is not a healthy place from which to launch this increase in production, particularly as this may be only the first in a line of requests for more grain. The UN reports that we’ll probably be pushing the limits of agricultural production into the next century.
To discuss the future of man and agriculture, we need to go back and take a closer look at the history of this relationship. At the end of the last ice age, about 12,000 years ago, as we entered the present interglacial period, the planet got warmer, rains fell more frequently, and plants grew bigger and faster than they had in over 100,000 years. Along the way, man realized that tending plants was easier than hunting game. The push in this direction may have come as man encountered lower populations of game or even extinctions of some key animals brought on by the development of human hunting skills.
The first evidence of domesticated wheat and barley appeared around 9500 BC, and shortly thereafter legumes such as lentils and peas. Farms were present first in the Fertile Crescent of western Asia. The idea quickly caught on, spreading to Egypt and India by 7000 BC, and gradually moved into Europe. Rice and millet started popping up in China around this time.
Man began to domesticate animals about the same time he domesticated plants. Goats were tamed around 10,000 BC in Iran and sheep around 9000 BC in Iraq. Cattle appeared around 6000 BC in India and in the Middle East. Agriculture spread more slowly over the northern and southern climates. It arrived even later among New World natives. Yet American Indians discovered maize and potatoes, some of the most important domestic plants in the world today.
Farming produced up to a hundred times more calories per acre than foraging, but it came at a cost to the health of new farmers. Hunter-gatherers rarely suffered from vitamin deficiencies, but farmers got scurvy, rickets, and beriberi because their diets were so base and unvaried. Infant mortality rose, also likely from poor diet. It seems that less protein, fewer vitamins, higher carbohydrates, and less movement were not what the doctor ordered. Humans who began to rely on agriculture shrank in height by almost five inches. Polynesians, American Indians, and Australian aborigines developed type 2 diabetes from their new high-carbohydrate diet and suffered a higher incidence of alcoholism. Alcohol consumption followed the growth of agriculture. There is some thought that barley was first domesticated for brewing beer rather than making bread. Tending crops, it appears, aroused a farmer’s thirst.
Eventually, agriculture did result in larger populations, which led to the establishment of governments to protect and distribute grain, resulting in less fighting and longer lives. About nine thousand years ago the Sumerians invented counting tokens inscribed with pictures that could be impressed in clay to document land, grain, or cattle ownership. Scribes began drawing them with styli made of reeds. The result was known as cuneiform, perhaps our first written language.
Around one hundred thousand years ago, the world had approximately half a million people—counting Homo sapiens, Neanderthals, and other hominids. There were about six million Homo sapiens twelve thousand years ago at the end of the Ice Age. But then along came agriculture, and from 10,000 BC to AD 1, populations exploded about a hundredfold.
Agriculture improved life because it decreased competition for hunter-gatherers for a while, but then population growth caught up with the increased food supply. Greater populations, confined living, and proximity to domestic animals increased human contact with disease. Our impact on the environment grew. Wild animal diversity shrunk. While we were nomadic, our effect on the land wasn’t too drastic, but once we settled down all hell broke loose.
THE POLLUTION PERIOD
Back at the Rothamsted Institute, I followed Kevin Coleman, a research scientist, into the institute’s sample archive, a focal point for visiting scientists. Housed in a warehouse on the Rothamsted grounds are rows upon rows of five-liter bottles, all dat
ed and stacked on shelves sixteen feet high that hold harvest grain, stalks, seed, and soil from test plots going back 160 years. On one high shelf is a sample of Rothamsted’s first wheat field, dated 1843. To avoid mold, the bottles are all sealed with corks, paraffin, and lead. During World War II, samples were kept in discarded tins that once held powdered milk, coffee, syrup, and other wartime essentials.
The Rothamsted sample archive is a unique collection, since it comprises some three hundred thousand samples of crops and soils taken from agricultural field experiments for which the history is fully documented. “The samples are used by scientists worldwide to understand how changes in agricultural practices affect crop production, soil fertility, and biodiversity,” says Coleman.
But what these vessels also contain is something researchers are not so proud of: a chronicle of human pollution. Over two centuries of industrial growth, soils have recorded what we’ve put into the atmosphere as well as what we’ve poured onto the ground. The Rothamsted sample archive holds evidence of nuclear atmospheric testing in Nevada and on the Bikini Atoll during the 1950s and 1960s. It also has a record of polychlorinated biphenyls (PCBs) from the manufacture of plastics and polycyclic aromatic hydrocarbons (PAHs) from power plants, fresh asphalt, and the fumes of automobiles. There are dioxins, the primary ingredient in Agent Orange, used to defoliate Vietnam. And plenty of heavy metals like zinc and copper from animal feed, cadmium from artificial fertilizers, chromium from tanning, and lead from pipes, vehicle fuel, industrial exhaust, and coal-fired power plants.
Many of these pollutants are deathly persistent. PCBs, the fluids that keep on lubricating and causing cancers, as well as DDT, the pesticide that keeps on killing, continue to appear in nature. Though amounts have gone down significantly since the 1970s, when both these chemicals were banned from most nations, PCB residuals continue to show up in the breast milk of Inuit mothers, and DDT continues to appear in freshwater fish and the raptors that eat them. DDT is still used in India to control malaria.
But the toxic residuals in our soils are something we may just have to live with. Right now, we have to get planting or starve.
THE NEXT GREEN REVOLUTION
That afternoon, out in the fields, Paul Poulton, a Rothamsted scientist, led me down rows of wheat stalks that displayed the results of a momentous moment in the evolution of agricultural products, the “green revolution.” The seed heads were so thick that the plants appeared to be mostly seed, with a short, thick stock and little else. A light wind rippled through the rows in front of us, looking like ocean waves of wheat grain. The use of these new grains started shortly after World War II and spread like wildfire over much of the planet. Says Poulton, “Rothamsted switched over to these shorter, thick wheat plants about the same time the rest of the world did.”
Norman Borlaug, an American agronomist, won the Nobel Peace Prize in 1970 for creating the first green revolution. A forester and plant pathologist, he walked away from a job at DuPont, a chemical company, in 1944 to join the Rockefeller Foundation’s Mexican hunger project. His first post was as a genetics expert, but by the time he received his Nobel Prize in 1970, he was the director of the Wheat Improvement Program in Mexico.
Wheat was in poor shape in that country, the victim of a plague of maladies, including rust. Borlaug crossed Mexican wheat with rust-resistant varieties from elsewhere and obtained rust-resistance in wheat that grew well in the Mexican environment. Then he bred this wheat in the Sonoran Desert in winter and the Mexican central highlands in summer and developed breeds capable of growing in different climates.
Farmers in that country adopted the new varieties and wheat output began to climb. By the late 1940s, researchers knew they could induce higher grain yields with extra nitrogen, but the seed heads containing the wheat grains grew so heavy that the plants would topple, ruining the crop. So Borlaug worked at crossing wheat with strains that had shorter, thicker, more compact stocks. These plants could produce enormous heads of grain, yet their stiff, short bodies could support the weight without toppling. This transformation tripled and quadrupled production.
When researchers from India applied this idea to rice, the staple crop for nearly half the world, yields jumped several-fold compared with traditional varieties. Chinese agriculturalists started using semidwarf varieties to feed their people, a decision that aided China’s rise to industrial power.
Now scientists tell us we need another green revolution if we are to meet the food demands of the next several decades. Our friends at Rothamsted are trying to participate in this, but it’s not easy. Their current professed goal is to get twenty metric tons of wheat per hectare in twenty years, the so-called 20:20 Wheat. But Poulton says, “The average wheat grain yield for the UK is currently about 8.0 metric tons per hectare, but on the best soils with good management and favorable weather a farmer could hope to get 12 metric tons per hectare.”
It seems the next jumps in crop production will come not from big discoveries like compact wheat but from a series of smaller changes that agronomists hope will add up to larger production. Rothamsted is currently looking at genetic improvements to increase the amount of grain; advanced pest and disease controls to protect plant yields; improved understanding of soil and root interactions to improve water and nutrient uptake; and a number of plant and environmental interactions to mitigate climate change.
Agricultural scientists at the institute are keeping an eye on what others across the Atlantic are doing as well. Jonathan Lynch, professor of plant nutrition at Penn State University, thinks that developing more aggressive root systems might be the answer to increased fertilizer efficiency and water usage. Crossing US beans with several varieties of ancestral stocks found in the high Andes Mountains, he’s working to obtain belowground plant systems with lateral root reach sufficient to search for phosphorus in the topsoil and deeper taproots to go after receding groundwater and rapidly draining nitrogen.
Susan McCouch, professor of plant breeding and genetics at Cornell University, focuses on acid soils, a problem on 30 percent of the earth’s surface. Acid releases aluminum into the ground, which inhibits root growth in plants, so the plants stop taking up water and nutrients, and they die. But McCouch is creating hybrid species of grains from ancestral lines, some in the wild, to achieve aluminum tolerance.
Researchers at Rothamsted are also working with the problem of acid soils by the use of biochar, what Brazilians refer to as terra preta, or black earth. Ancient Indian societies along the Amazon thrived using terra preta—charcoal from slow, smoldering fires—to enrich the relatively sterile tropical rain forest soils. Researchers are hoping that modern-day societies can do the same.
BLACK EARTH IN THE AMAZON
To get a picture of the potential of terra preta, one must visit the central Amazon near Manaus. I flew into Venezuela in early August and took a two-day ride aboard a bus, which climbed up and over the Sierra de Pacaraima down into the Amazon Basin. The road wound through the forested mountains in the dark night, and the way looked clear until around the bend ahead came another bus. At the last second, both buses veered toward the outer shoulders, and as we whisked by each other dangerously, a hanging limb from the jungle struck our right front window and turned it into a giant spiderweb of glass, which the driver chose to ignore. His side of the double window was still clear.
We traveled all day, first through savanna, then dense tropical forest, and arrived by evening in the city of Manaus perched at the junction of the Rio Negro and the Amazon River. The city was alive with vendors, farmers, and tourists in the afternoon sun. Manaus is the largest city in the central Amazon. A group of archaeologists greeted me at the station, and soon I was headed by ferry across the Rio Negro to their field site on the Amazon.
By morning we rolled out of hammocks, ate a hearty breakfast of eggs, fruit, bread, and coffee, then headed out to the field. University of São Paulo archaeologist Eduardo Góes Neves and some fifty volunteer archaeologists from Latin Americ
a, the US, and the UK were excavating an archeological site on a papaya farm that overlooked the Amazon River. This location harbored community graves and other ancient relics going back more than two thousand years. The lush orange color of the fruit and the robust green leaves on the trees were due to the soils left by ancient Indians who once occupied these lands.
The banks of the river were plentiful with terra preta, a gift of civilizations past. While most Amazonian soils were notoriously nutrient-poor, yellowish, and sterile, terra preta was dark, fragrant, and rich—a farmer’s delight. Neves and others believe that by devising a way to enrich the soil, early inhabitants created a foundation for agriculture-based communities that harbored far greater populations than was previously imagined.
Amazonian soils have very little rock in them, which means that early civilizations made their homes and worship sites from wood. These structures, no matter how elaborate, degraded over time, leaving little evidence of past human glory. The principle evidence of ancient civilizations was in the ceramics they formed and fired, pieces of which have survived in the soil.
Early Amazonian life wasn’t easy. Indians used stone axes to fell trees along the banks of the rivers. The task was long and tedious, taking days to weeks to cut down large trees. The process created small openings in the forests, letting in some light, but not enough to thoroughly dry out the vegetation. Farmers started fires to clear the forest for crops, and the fires would smolder for days, creating charcoal that was the basis of terra preta.
Most Amazonians today use “slash-and-burn” methods to create space for their crops. Natives use chain saws to clear much larger spaces than the ancient Indians did. This creates large spaces with lots of light, plentiful kindling, and huge, hot fires that produce quantities of ash but little charcoal. Ash has sufficient nutrients to last a few seasons, after which the land goes fallow, whereas terra preta, or biochar, can last far longer. One farmer near Neves’s study site cultivated crops on terra preta soil for forty years without ever adding fertilizer. William Woods, a soil scientist and professor of geography at the University of Kansas, claimed this was amazing and told me: “We don’t even get that in Kansas,” a US state famous for its soil.
The Next Species: The Future of Evolution in the Aftermath of Man Page 8