This is Part Two of a series I originally entitled ‘Excerpts on Mineral Manuring, Before the Advent of Commercial Fertilizer,’ and in such, I will be covering the application of lime shells (sea shells found in calcareous strata) to farmland for the purposes of regulating an acidic soil’s pH, improvement of its general texture (especially if it is a light, sandy soil) and thusly its ability to retain nutrients from plant and animal manures later applied, and perhaps adding calcium supplementation. The full post will be in four parts, according to my reference’s author, Sir John Sinclair, who has divided it so in his General Report of the Agricultural State, Volume II. from 1814. Such was profitable when devising my character, Mr. Winter’s suggested improvements to the land around Woodbridge and Hedgely; though if I recall correctly, I (rather, he) cut down the prescribed doses in a few situations to accommodate the large volumes of marl that too would eventually see the fields. But before we get to my reproduction of his instructions on liming, I will add a few vocabulary terms:
Calcination (as it applies to limestone and lime shells) – this is the process of heating the substance to a high enough temperature, that an endothermic reaction occurs, in which the calcium carbonate degases carbon dioxide, leaving behind the more reactive calcium oxide (quicklime).
CaCO3 + heat —> CaO + CO2
Slacking (or slaking) – this is the process of adding water to quicklime, causing it to degrade to a powdery slurry of particulates (for the purpose of integrating such into the soil). The result is also called ‘limewater’.
CaO + H2O —> Ca(OH)2
Lime Shells
Limestone, after undergoing the process of calcination, has long been applied, by Scotch husbandmen, as a manure of stimulus to the soil; and, in consequence of such, an application luxuriant crops have been produced, even upon soils apparently of inferior quality, and which would have yielded crops of only trifling value had this auxiliary been withheld. In fact the majority of soils, unless naturally possessed of calcareous matter, cannot be cultivated with advantage till they are dressed with lime, and hence it is justly considered to be the basis of good husbandry.
In treating of lime, it is proper to explain, 1. How it is prepared for use, 2. How it is applied to the soil, 3. How the land is managed after the lime is applied, 4. What are its effects upon the soil, and 5. What are the rules for its application.
I. How Lime is Prepared for Use
The preparation of lime for laying on the soil consists in the operations of 1. Calcining or burning, and 2. Of slacking it:
The burning of limestone is conducted generally by the proprietors of land whose estates contain limestone rock, or by persons who rent lime quarries from them. They erect kilns, either standing or drawing ones, according to the expected demand, and sell it in shells or calcined limestone at certain rates per measure, varying according to circumstances.
The operation of slacking is extremely simple: It is only throwing water upon the shells until they crack and swell, and finally dissolve into a fine powder. But instead of watering it in great heaps, the practice which at present most commonly prevails is to lay it down in the state of shells upon land under summer fallow, in portions of one firlot, barley measure (1 bushel and 1/2) upon a fall of ground, or thirty six square yards. These heaps will be six yards asunder from centre to centre, upon an eighteen feet ridge and the quantity applied will, under these circumstances, be forty bolls (240 Winchester bushels) per Scotch acre. But if sixty bolls, or 360 bushels per acre, are required, the heaps of the above size must occupy only twenty four square yards, and be at the distance of four yards four inches from each other, and so on, when other quantities of lime are applied. Some farmers however prefer laying up slaked lime in heaps of a size to serve two or three English acres each, instead of those of smaller dimensions, though in this way an additional expense is incurred.
When lime can with any tolerable degree of convenience be watered, that operation ought never to be neglected. When watered soon the whole shells easily dissolve and leave not a particle unpowdered if properly burnt, which is a great acquisition. But when the shells are not completely reduced before they are ploughed in, they afterwards turn into clotted half reduced lumps which lie in the soil for years, and till broken or dissolved by water, are of no use whatever.
In place of watering, which is often inconvenient, sometimes impracticable, the heaps are covered with earth thrown up around the circumference of the base of each heap, in which way the shells are gradually brought into a powdered state. This is an excellent device; and in spreading out the lime thus slightly compounded, it is in a state fit to be divided with the utmost regularity. After spreading lime on fallow, it is of great advantage to harrow the fallow and wait till it gets a shower before ploughing. In this way the first shower becomes a shower of lime water which unites with a large proportion of the soil.
Mr Mitchell, late surgeon in Ayr, strongly recommends a new mode of slacking lime by means of sea water converted into brine. He calculates that 3000 gallons of sea water boiled down to about 600 gallons will slack 64 bushels of lime shells – a quantity sufficient to manure two acres, the expense of which he estimates at only 30s. per acre. Slacking lime with urine, he also considers as an excellent practice.
II. How to Apply Lime
So great is the variety of soils, and other circumstances, that no general rule can be devised for fixing the quantity of pure lime that is required for an acre of land. Thirty two barley bolls, or 192 Winchester bushels of shells per Scotch, or 153 bushels per English acre have been applied with success to light, soft land: a beautiful verdure has been the consequence, and this verdure always indicates a certain degree of melioration, which will appear in future crops. From wanting even this small powdering, some parts of the same field left unlimed had, in comparison, the appearance of barren land. But from forty to sixty bolls, barley measure, (i.e. from 240 to 360 bushels), are generally esteemed proper for different degrees of clay. Indeed from sixty to one hundred bolls have been applied successfully, for both corn and grass, on strong land. The application is generally made when land is under the process of summer fallow, though it is not unusual to apply lime to grass land when the surface is tolerably level.
On the whole it seems agreed, that from 50 to 80 bolls of lime shells per Scotch acre (i.e. from 300 to 480 bushels per Scotch, or from 240 to 384 bushels per English acre), are quite sufficient for the greater part of the most fertile districts in Scotland, and that light soils, which require less in the first instance, are greatly benefited by a frequent repetition.
Lime operates powerfully with earth, particularly when mixed with half rotted vegetable substances requiring farther decomposition. It makes an excellent compost also, with the scourings of ditches, sea ooze, or mud and moss, or wherever there is inert vegetable matter. But it should be rendered mild to answer these purposes without waste, and the rubbish of old walls or old plaster is accordingly preferable.‡
‡ Note: The chemist, Sir Humphry Davy, recommended lime not be applied to nutriment that was already decomposed, as it would render it less active with regard to plant adsorption, but instead would recommend caustic lime (quicklime) for use with inert organic matter (old roots, branches, &c. yet to have broken down) to encourage it into a state of putrefaction.
[Parts three and four, underway]