: Manures and the principles of manuring by Aikman Charles Morton - Fertilizers; Manures

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the genial heat of the soil, particularly in spring, must be of the highest importance to the rising plant; ... so that the temperature of the surface, when bare and exposed to the rays of the sun, affords at least one indication of the degree of the fertility."

Again he says: "The power of soils to absorb water from air is much connected with fertility.... I have compared the absorbent powers of many soils, with respect to atmospheric moisture, and I have always found it greatest in the most fertile soils; so that it affords one method of judging of the productiveness of land."

Where he erred was in overestimating the functions of the mechanical properties of a soil, and in considering fertility to be due to them alone.

During the next thirty years or so, little progress seems to have been made in the way of fresh experimentation.

In 1834, Boussingault, the most distinguished French agricultural chemist of the century, began that series of brilliant chemico-agricultural experiments on his estate at Bechelbronn, in Alsace, the results of which have added so much to agricultural science. It was the first instance of the combination of "science with practice," of the institution of a laboratory on a farm; a combination peculiarly fitted to promote the interests of agricultural science, and an example which has been since followed with such magnificent results in the case of Sir John Lawes's famous Rothamsted Experiment Station, and other less known research stations.

Boussingault's first paper appeared in 1836, and was entitled, "The amount of nitrogen in different kinds of foods, and on the equal value of foods founded on these data."

In the year following other papers were published on such subjects as the amount of gluten in different kinds of wheat; on the meteorological considerations of how far various agricultural operations--such as extensive clearings of wood, the draining of large swamps, &c.--influence of climate on a country; and on experiments on the culture of the vine.

In 1839 Boussingault was elected a member of the French Institute, an honour paid to him in recognition of his great services to agricultural chemistry.

The foregoing is a brief epitome of the history of the development of agricultural chemistry up to the year 1840, the year which witnessed the publication of one of the most memorable works on the subject, which has appeared during the present century--Liebig's first report to the British Association, a work which may be described as constituting an epoch in the history of the science. Liebig's position as an agricultural chemist was so prominent, and his influence as a teacher so potent, that a few biographical facts may not be out of place before entering upon an estimate of his work.

The report above referred to was made by Liebig at the request of the Chemical Section of the British Association. It was read to a meeting of the Association held in Glasgow in 1840, and was subsequently published in book form, under the title of 'Chemistry in its Application to Agriculture and Physiology,' Liebig's position, past training and experience were such as to peculiarly fit him for the part of pioneer in the new science. As Sir J. H. Gilbert has remarked, "In the treatment of his subject he not only called to his aid the previously existing knowledge directly bearing upon his subject, but he also turned to good account the more recent triumphs of organic chemistry, many of which had been won in his own laboratory."

In his dedication to the British Association at the beginning of the book, Liebig says: "Perfect agriculture is the true foundation of all trade and industry--it is the foundation of the riches of States. But a rational system of agriculture cannot be formed without the application of scientific principles; for such a system must be based on an exact acquaintance with the means of nutrition of vegetables, and with the influence of soils and actions of manure upon them. This knowledge we must seek from chemistry, which teaches the mode of investigating the composition and of studying the characters of the different substances from which plants derive their nourishment."

The first subject which Liebig discusses is the scientific basis of the so-called "humus" theory. The humus theory seems to have been first promulgated by Einhof and Thaer towards the close of last century. Thaer held that humus was the source of plant-food. He stated in his published writings that the fertility of a soil depended really upon its humus; for this substance, with the exception of water, is the only source of plant-food. De Saussure, however, by his experiments--the results of which he had published in 1804--had shown the fallacy of this humus theory; and his statements had been further developed and substantiated by the investigations of the French chemist Braconnot and the German chemist Sprengel. Despite, however, the experiments of Saussure, Braconnot, and Sprengel, the belief that plants derived the carbonaceous portion of their substance from humus still seemed to be commonly held in 1840.

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