A UK lawn turns 150

The Lawes and Gilbert collaboration grows on.

COURTESY OF ELSPETH BARTLET

There's a patch of ground roughly twenty meters wide near the town of Harpenden, half an hour's train ride north of London. Many such patches are found nearby, but this lawn, a short walk from the red-bricked gables of Rothamsted Manor, is a sliver of English meadow as it may have been more than 250 years ago. It's also Plot 3 of the famous Park Grass experiment that John Bennet Lawes founded in 1856 and is still going strong.

Lawes and his collaborator John Henry Gilbert began their experiment to test whether fertilizers could be used to boost the production of grass for making hay. To this end, they divided up a meadow that had been in grass for at least a century, and treated each twenty-meter strip with a different array of fertilizers.

Some received old-fashioned manure, while many others received the newfangled inorganic kind with which Lawes had made a fortune in years past. Plot 3, near the narrow end of the field, is one of three strips untouched by fertilizer in the original study design, and has remained unsullied for the duration of what has become the world's longest-running ecological experiment.

"The meadow that Park Grass was established on 150 years ago was typical of what you'd find on any lowland farm in England at the time," says Jonathan Silvertown, an ecologist from the UK's Open University. "There are few of those meadows left now, very few. It's a habitat type that has almost disappeared in southern England."

The untouched plots also stand as a reminder of the impact fertilizers can have on biodiversity, says Silvertown, who currently uses Park Grass for research. While Lawes and Gilbert had confirmation of their hay hypothesis within a couple of years, they also recorded a dramatic reduction in plant species growing on the fertilized plots.

These days, comparing the untreated Plot 3 with those doused regularly with fertilizers is an exercise in comparing the sublime and the ridiculous. As many as 50 or 60 different species flourish in the untouched sections, compared to just two or three in some of the fertilized areas. "For most people who see it for the first time, the reaction is ?wow,'" says Silvertown. "The idea that you can so easily manipulate the species of plants just by adding nutrients to the soil can be quite a surprise."

Lawes' initial interests might have been satisfied quickly, but he kept the experiment running throughout his life, along with several others that he and Gilbert had started at Rothamsted. The year before his death, Lawes ensured its further continuance by endowing a trust.

Exactly why he kept it going is a bit of a mystery, says Silvertown, although it might have something to do with a dispute between Lawes and the great agricultural scientist Justuce von Liebig over whether plants source nitrogen from the air or soil. "Liebig believed plants got it from the atmosphere, and Lawes essentially proved him wrong," he says. "Perhaps he kept it going ? as a living testament that he was right."

Either way, Lawes' money has given ecologists a rare gift of real long-term data. "It is only over time, as people start to look at how the systems behave, and start to think about what mechanisms might be operating, that you get the really big payoffs," says David Kemp, chair of Farming Systems at the University of Sydney.

Kemp believes Park Grass has been one of the most important agricultural experiments undertaken, and he's not alone. "The Park Grass Experiment inspired me to switch from studying aquatic to studying terrestrial ecosystems," says David Tilman of the University of Minnesota.

In the course of 150 years, the meadow has inspired more than 170 research papers. One of the most influential ecological theories derived from Park Grass has been Tilman's resource ratio theory, which states that the relative abundance of plant species in a community at equilibrium is determined by competition for essential resources.

In recent years, Silvertown and his colleagues have noted evidence that plant species on adjacent plots have been undergoing evolution, responding to the characteristics of the particular soil type they're limited to. In ongoing research, they're looking at evidence of genetic bottlenecks on some plots and the impact that's had on genetic diversity in chloroplasts.

Even after 150 years, the utility of Park Grass isn't yet exhausted, says Silvertown. "One thing that long-term experiments teach us ? is that the longer you study something, the more surprises there are." He and others from the British Ecology Society hope to soon set up some long-term experiments of their own through a new foundation, the Ecological Continuity Trust (http://ecologicalcontinuitytrust.org). Silvertown says they need about $20 million to get started.