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Liebig and the Vegetable Mould

PMP

Between 1863-4, and in particular the first few months of 1864, Matthew wrote extensively and almost exclusively on the “Vegetable Mould” – the organic soil needed for crops to grow. Matthew was convinced that increasingly intensive farming practices, coupled with short-term policies encouraged by the British land-tenancy system, would lead to an irreparable “exhaustion” of the soil and a catastrophic collapse of agricultural productivity. He had made these views clear in previous articles dating as far back as 1849, but an anonymous article in the Times on 6 January 1863, titled “Exhaustion of Vegetable Mould” and signed simply “From a correspondent”, aired these views to a wider audience. This letter singled out the “ignorance” of Baron Justus von Liebig, a widely-respected pioneer of organic chemistry, for his championing of the use of artificial fertilisers to remedy depleted soil. To Matthew, in many ways a forward-thinking reformer but in this case wedded to his world-view of a beneficent “Mother Earth” providing plants with a natural “stomach” from which to draw nutrients, Liebig’s ideas were a recipe for disaster.

A year later, in the Gardeners’ Chronicle and Agricultural Gazette, it was revealed that the “Times correspondent” was none other than Matthew. Furthermore, Matthew and Liebig had by now exchanged private letters, which now became public (thanks to Matthew). In response to Liebig’s haughty and belittling attitude, Matthew launched a series of attacks on Liebig over the following months, perhaps the most memorable being his image of “the begrimed spectres of Liebig and his goblin followers” in his letter in the Feb 20 issue of the Gardeners’ Chronicle and Agricultural Gazette. In many ways, Liebig was the perfect foil to Matthew – with a noble title (although in fact he earned this through his scientific work), his background as a college-taught “theoretical” chemist rather than a “practical” agriculturist, and perhaps most importantly his ability to match Matthew for adversarial tone (although wisely Liebig stayed out of responding publically to any of Matthew’s articles).

To modern eyes, perhaps the biggest difference between Matthew and Liebig is that the former deduced his views from a combination of (admittedly keen) observation and preconceived ideas of nature, whereas the latter strove to advance knowledge through experiment. Both expressed wonder at the workings of natural soil. Indeed, Baron Liebig wrote: “There is not to be found in chemistry a more wonderful phenomenon, or one which more confounds all human wisdom, than is presented by the soil of a garden or field”.

In the end, each of the various points of view expressed had merit. The Editorial in the Farmer’s Magazine was right to suppose an Armageddon-via-vegetable-mould was not about to happen. Liebig was right in his view that artificial fertiliser could in principle keep a soil replenished, while Matthew was right to criticise the specific methods advocated by Liebig (these were indeed wrong, although they were perfected by later adherents of Liebig’s methods). Matthew was also right to suppose that natural manures, and the soil, have an important role to play in good farming practice.

It’s important to note that Matthew accepted Liebig’s pioneering experiments which showed that both carbon and (sometimes) nitrogen could be sequestered by plants directly from the atmosphere rather than through the soil (see his original Times article). In this sense, Matthew was not in fact reviving the old “Humus Theory” that held that all plant nutrients came through the soil, but doubtless to Liebig the talk of “root-mouths”, “Mother Earth” and a “vegetable mould” provided by Nature as a “means to an end” must have sounded like an ignorant return that discredited point of view.

All this certainly provided for some pretty splendid oratorical fireworks.

Finally, it’s worth noting that Darwin also had an interest in the vegetable mould – see his paper read to the Geological Society on 1 Nov 1837 (details in Darwin (1838) and Darwin (1840)) and his later book “The Formation of Vegetable Mould: Through the Action of Worms, with Observations on Their Habits” (1881). In both the earlier papers and the later book, he proposes (from an idea given him by his uncle Josiah Wedgwood) that earthworms play a major part in the formation of vegetable mould (he even suggests that “animal mould” might be a more appropriate term!). Matthew mentions his interest in the “vegetable mould” to Darwin in his Letter of 3 Dec 1862, and again refers to his many articles on the subject in the Gardeners’ Chronicle in his Letter of 6 June 1864. It’s unclear whether Matthew was aware of Darwin’s earlier publications on the subject.

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