It’s fortunate, he adds, that New England’s farmers left before nonnative plants flooded America. Before exotic trees could spread across the land, native vegetation again had a roothold on their former farmlands. No chemicals had been spaded into their soils; no weeds, insects, or fungi here had ever been poisoned to help other things grow. It’s the nearest thing to a baseline of how nature might reclaim cultivated land—against which to measure, for example, old England.
2. The Farm
Like most British trunk roads, the Ml motorway that runs north from London was built by Romans. In Hertfordshire, a jog at Hempstead leads to St. Alban’s, once a substantial Roman town, and beyond that, to the village of Harpenden. From Roman times until the 20th century, when they became bedroom commutes to London, 30 miles away, St. Alban’s was a center for rural commerce, and Harpenden was flat farmland, the conformity of its grain fields disrupted only by hedgerows.
Long before the Romans appeared in the first century AD, the dense forests of the British Isles began coming down. Humans first arrived 700,000 years ago, likely following herds of aurochs, the now-extinct wild Eurasian cattle, during glacial epochs when the English Channel was a land bridge, but their settlements were fleeting. According to the great British forest botanist Oliver Rackham, after the last ice age, southeastern England was dominated by vast stands of lindens mixed with oaks, and by abundant hazels that probably reflect the appetites of Stone Age gatherers.
The landscape changed around 4,500 BC, because whoever crossed the water that by then separated England from the Continent brought crops and domestic animals. These immigrants, Rackham laments, “set about converting Britain and Ireland to an imitation of the dry open steppes of the Near East, in which agriculture had begun.”
Today, less than 1/100 of Britain is original forest, and essentially none of Ireland. Most woodlands are clearly defined tracts, bearing evidence of centuries of careful human extraction by coppicing, which allowed stumps to regenerate for building supplies and fuel. They remained that way after Roman rule gave way to Saxon peasantry and serfdom, and into the Middle Ages.
At Harpenden, near a low stone circle and adjacent stem wall that are the remains of a Roman shrine, an estate was founded in the early 13th century. Rothamsted Manor, built of bricks and timbers and surrounded by a moat and 300 acres, changed hands five times over as many centuries, accruing more rooms until an eight-year-old boy named John Bennet Lawes inherited it in 1814.
Lawes went to Eton and then to Oxford, where he studied geology and chemistry, grew luxuriant muttonchops, but never took a degree. Instead, he returned to Rothamsted to make something of the estate his late father had left to seed. What he did with it ended up changing the course of agriculture and much of the surface of the Earth. How long those changes will persist, even after we’re gone, is much debated by agro- industrialists and environmentalists. But with remarkable foresight, John Bennet Lawes himself has kindly left us many clues.
His story began with bones—although first, some would say, came chalk. Centuries of Hertfordshire farmers had dug the chalky remains of ancient sea creatures that underlie local clays to spread on their furrows, because it helped their turnips and grains. From Oxford lectures, Lawes knew that liming their fields didn’t nourish plants so much as soften the soil’s acidic resistance. But might anything actually feed crops?
A German chemist, Justus von Liebig, had recently noted that powdered bonemeal restored vigor to soil. Soaking it first in dilute sulfuric acid, he wrote, made it even more digestible. Lawes tried it on a turnip field. He was impressed.
Justus von Liebig is remembered as the father of the fertilizer industry, but he probably would have traded that honor for John Bennet Lawes’s enormous success. It hadn’t occurred to von Liebig to patent his process. After realizing what a bother it was for busy farmers to buy bones, boil them, grind them, then transport sulfuric acid from London gasworks to treat the crushed granules, and then mill the hardened result yet again, Lawes did so. Patent in hand, he built the world’s first artificial fertilizer factory at Rothamsted in 1841. Soon he was selling “superphosphate” to all his neighbors.
His manure works—possibly at the insistence of his widowed mother, who still lived in the big brick manor —soon moved to larger quarters near Greenwich on the Thames. As the use of chemical soil additives spread, Lawes’s factories multiplied, and his product line lengthened. It included not just pulverized bone and mineral phosphates, but two nitrogen fertilizers: sodium nitrate and ammonium sulfate (both later replaced by the ammonium nitrate commonly used today). Once again, the hapless von Liebig had identified nitrogen as a key component of amino and nucleic acids vital to plants, yet failed to exploit his discovery. While von Liebig published his findings, Lawes was patenting nitrate mixtures.
To learn which were most effective, in 1843 Lawes began a series of test plots still going today, which makes Rothamsted Research both the world’s oldest agricultural station and also the site of the world’s longest continual field experiments. Lawes and John Henry Gilbert, the chemist who became his partner of 60 years, earning the equal loathing of Justus von Liebig, began by planting two fields: one in white turnips, the other in wheat. They divided these into 24 strips, and applied a different treatment to each.
The combinations involved a lot, a little, or no nitrogen fertilizer; raw bonemeal, his patented superphosphates, or no phosphates at all; minerals such as potash, magnesium, potassium, sulfur, sodium; and both raw and cooked farmyard manure. Some strips were dressed with local chalk, some weren’t. In subsequent years, some plots were rotated with barley, beans, oats, red clover, and potatoes. Some strips were periodically fallowed, some continually planted with the same crop. Some served as controls, with nothing added to them whatsoever.
By the 1850s, it was obvious that when both nitrogen and phosphate were applied, yields increased, and that trace minerals helped some crops and slowed others. With his partner, Gilbert, assiduously taking samples and recording results, Lawes was willing to test any theory—scientific, homespun, or wild—of what might help plants grow. According to his biographer, George Vaughn Dyke, these included trying superphosphate made from ivory dust, and slathering crops with honey. One experiment still running today involved no crops at all, only grass. An ancient sheep pasture just below Rothamsted Manor was divided into strips and treated with various inorganic nitrogen compounds and minerals. Later Lawes and Gilbert added fish meal and farm manure from animals fed different diets. In the 20th century, with increasing acid rain, the strips were further divided, with half receiving chalk to test growth under various pH levels.
From this pasture experiment, they noticed that although inorganic nitrogen fertilizer makes hay grow waist-high, biodiversity suffers. While 50 species of grass, weeds, legumes, and herbs might grow on unfertilized strips, adjacent plots dosed with nitrogen hold just two or three species. Since farmers don’t want other seeds competing with the ones they’ve planted, they have no problem with this, but nature might.
Paradoxically, so did Lawes. By the 1870s, now wealthy, he sold his fertilizer businesses but continued his fascinating experiments. Among his concerns was how land could grow exhausted. His biographer quotes him as declaring that any farmer who thought he could “grow as fine crops by the aid of a few pounds of some chemical substances as by the same number of tons of farm-yard dung” was deluded. Lawes advised anyone planting vegetables and garden greens that, if it were him, he would “select a locality where I could obtain a large supply of yard manure at a cheap rate.”
But in a rural landscape rushing to meet the dietary demands of a rapidly growing urban industrial society, farmers no longer had the luxury of raising enough dairy cows and pigs to produce the requisite tons of organic manure. Throughout densely populated late-19th-century Europe, farmers desperately sought food for their grain and vegetables. South Pacific islands were stripped of centuries of accumulated guano; stables were scoured for droppings; and even what was delicately called “night soil” was spread on fields. According to von Liebig, both horse and human bones from the Battle of Waterloo were ground and applied to crops.
As pressures on farmlands escalated in the 20th century, test plots at Rothamsted Research were added for herbicides, pesticides, and municipal sewage sludge. The winding road to the old manor house is now lined with
