Lime debris (marl)

When you read about medieval agriculture,  at some point the word marling will come up.  What exactly is it?  Jules Pretty says “marling was common practice on clay soils and, even though it required a high labour input to transport the chalk and lime from often distant locations, it could certainly enhance productivity.” In Le Dite de Hosbondrie marling plays an important role in the manure-making process. Sir Henley says “cause manure to be gathered in heaps and mixed with earth, and cause your sheepfold to be marled every fortnight with clay land or with good earth, as the cleansing out of ditches, and then strew it over.”

These two quotes, taken individually, would give you a very different idea of what marling is. In the first, it would seem marling is the process of adding chalk and lime to a soil. In the second, it seems that marling is the process of mixing manure and clay or “good earth” together. Indeed, both of these are correct.

Wikipedia Commons, Marl from Marl Bet Meir formation

There is a type of soil called marl. This is essentially a sort of lime, which was mixed with clay soils in order to improve the soil. According to the “Southern Grower“, the application of natural marl deposits are considered bulky, but believed to still be improving the soil more than 50 years after the application. Marl is a naturally occurring layer, so in this context, marling would be the process of digging up said marl, and tilling it into the soil. Winiwarter and Blum retains that marl holds water, contains magnesium, and suggests it was preferred by early farmers because first it easily breaks down with little work, and second it is easier than other types of lime to obtain. I’ll discuss actual marl more in another blog about liming in the medieval period.

The reference of marling by Sir Henley – of adding good earth to your manure, is how I’ll focus the rest of this blog. He repeatedly exchanges “earth” and “marl” in this section of the text, so I suspect that he means just the practice of adding good dirt to your manure.

I’ve never heard of simply growing plants in straight manure. Weeds do sometimes grow in your manure pile, or the occasional vegetable, but it is generally the practice that you mix your manure with dirt prior to planting. Manure is heavy, full of water and full of specific nutrients. Good soil helps to balance the moisture content and nutrients while adding trace minerals and keeping the soil mixture from becoming compacted.

Henley’s reason for mixing is because (he claims) manure runs out when it sends it’s benefits downward while marl runs the other way. If you keep with his practice of switching earth and marl, this makes sense. When you grow plants in soil, they pull all the nutrients out of the dirt. (Thus the earth will run out of “benefits”.) When you add manure the nutrients are replenished (sending them down into the dirt), so that your plants can then pull them back out again. As he says ” And if it is spread at second ploughing at sowing it is all the more under the earth and little mixed with it.” – IE, the earth covers too much of the manure, so it just becomes part of the deeper soil, where it can’t have its benefits ultimately given back to the plants unless you then plant crops with deep taproots to bring the nutrients back up.

Richard Jones (Manure Matters, 2106 pp145-158), who has been doing a good bit of research on crop amendments from the medieval elemental and humoral perspective, agrees that manure was seen as hot and moist – but seems to suggest that the medieval person thought of marl as hot and dry, thus it would help bring the heat back to the surface instead of letting the heat go deeper. I think that looking at the amendmentation process from the medieval perspective makes sense – and indeed, Henley (and other authors) refer to hot, cold and dry so often they must have used that as the basis for their soil amendment choices.

In either case however – Henley’s marling isn’t just the use of a type of lime. He is actively mixing together two types of organic matter for the express purpose of spreading it where plants will be grown. So I’ll submit that there is a second definition of marling – where it is the practice of mixing manure with dirt for the purpose of ensuring gardening soil improvements last twice as long as they would normally.

As an aside, in the Southern US, a practice that seems similar to reverse marling has been recommended – which actually matches the concepts given by Henley – to take your wet, hot base (in his case manure, in the South swampy wetlands) and add something dry to hold the heat in (in the South this was sand) so that your plants will grow well.

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