This foundational treatise on agricultural chemistry traces the development of scientific understanding regarding plant nutrition and soil fertility from the early speculations of Van Helmont and Jethro Tull to the pioneering laboratory work of Boussingault and the epoch-making theories of Justus von Liebig. The author meticulously examines the evolution of ideas concerning the true sources of plant carbon, hydrogen, and oxygen, highlighting the landmark discoveries of Bonnet, Priestley, Ingenhousz, and De Saussure. A central focus of the work is the long-standing controversy surrounding the source of plant nitrogen, detailing the historical debate between the assimilation of free atmospheric nitrogen and the reliance on combined soil nitrogen, while setting the stage for modern bacteriological discoveries.
The text provides a comprehensive analysis of soil fertility divided into physical, chemical, and biological properties. The physical section investigates the absorptive and retentive capacities of soils for water and heat, the influence of soil color and texture, and the critical role of tillage in promoting root development and aeration. The chemical chapters explore the mineral composition of soils, the weathering of silicate rocks such as felspar and mica, and the specific functions of nitrogen, phosphoric acid, and potash as the primary direct plant-food ingredients.
A significant portion of the work is dedicated to the newly discovered biological properties of soils, notably the process of nitrification. The author details the discovery by Schloesing and Müntz that nitrification is mediated by micro-organisms, describing the optimal conditions of temperature, moisture, aeration, and alkalinity required for their activity, as well as the phenomenon of denitrification. The classic field and laboratory experiments conducted at Rothamsted by Sir John Lawes and Sir J. H. Gilbert are frequently cited to illustrate practical outcomes in crop yields and soil composition.
The concluding sections shift from theoretical principles to practical agronomy and the classification of manures. Farmyard manure receives detailed examination, with extensive breakdowns of the chemical composition of solid excreta and urine across different farm animals, influenced by factors such as age, diet, and treatment. The critical functions of straw and alternative litters like peat-moss in absorbing and retaining valuable liquid fractions are analyzed alongside the complex microbiological fermentation processes occurring within the manure heap.
The volume concludes by evaluating the economic and practical implications of nutrient loss through drainage, crop removal, and modern sewage disposal, contrasting natural soil replenishment with the application of artificial fertilizers such as nitrate of soda, superphosphates, and Stassfurt potash salts. Throughout the work, the author emphasizes that rational agricultural practice must be grounded in an exact chemical and biological acquaintance with the means of vegetable nutrition and the action of manures.
