Manures and the principles of manuring

APPENDIX TO CHAPTER III.

NOTE I. (p. 119).

Determinations of the Quantity of Nitrogen supplied by Rain, as Ammonia and Nitric Acid, to an Acre of Land, during One Year.

(From Dr Fream's 'Soils and their Properties,' p. 62.)

NOTE II. (p. 122).

Nitrogen in Soils at Various Depths.

(1) Rothamsted Soils.

(2) Manitoba Soils.

NOTE III. (p. 130).

Nitrogen as Nitrates in Cropped Soils receiving no Nitrogenous Manure, in Lb. per Acre (Rothamsted Soils).

NOTE IV. (p. 124 and p. 131).

Nitrogen as Nitrates in Wheat-soils variously manured, October 1881, in Lb. per Acre (Rothamsted Soils).

Nitrogen as Nitrates in Barley-soils variously manured, March 1892, in Lb. per Acre (Rothamsted Soils).

NOTE V. (p. 134).

Examples of Increase of Nitrogen in Rothamsted Soils laid down in Pasture.

NOTE VI. (p. 141).

In connection with the loss by drainage of nitrogen in the form of nitrates, it may be mentioned that the water of many of the famous rivers contains large quantities of nitrates. Thus the water of the Seine has been found to contain fifteen parts of nitrates per million of water, and the Rhine eight parts per million. Some idea of what this amounts to per annum may be obtained by the statement that "the Rhine discharges daily 220 tons of saltpetre into the ocean, the river Seine 270, and the Nile 1100 tons."—(Storer's Agric. Chem., vol. i. p. 318.)

NOTE VII. (p. 142).

Examples of Decrease of Nitrogen in Rothamsted Soils.

Manuring, Produce of Wheat, and Alteration in the Composition of the Soil in Broadbalk Field, Rothamsted, from 1865 to 1881.

NOTE VIII. (p. 141).

Amount of Drainage and Nitrogen as Nitrates in Drainage-water from unmanured Bare Soil, 20 and 60 inches deep—average of Thirteen Years.

CHAPTER IV.

NITRIFICATION.

The most important compound of nitrogen for the plant is nitric acid. It is as nitrates that most plants absorb the nitrogen they require to build up their tissue. In nature the nitrogen, present in the soil as ammonia and different organic forms, is constantly being converted into nitric acid. This conversion of nitrogen into nitrates, known as nitrification, is a process of very great importance, and, as has been already pointed out in the Introductory Chapter, is effected through the agency of micro-organisms (ferments).[97] The process of nitrification, as well as the nature of the other changes taking place in the soil between the various compounds of nitrogen, are as yet but most imperfectly understood, but much light has been thrown on this most interesting department of agricultural research during the last few years; and it cannot be doubted that the increased attention which it is receiving from different investigators, both on the Continent and in this country, will be fraught with most important results for practical agriculture.

Occurrence of Nitrates in the Soil.

The occurrence of nitre,[98] or potassium nitrate, in soils has been long known, although it is only within the last few years that we have obtained any precise knowledge with regard to the mode of its production. While its amount in most soils, especially in this country,[99] is very minute, there are certain parts of the world where nitrates are found in large quantities. The nitrate fields of Chili and Peru are the chief natural sources of nitrates, and they are referred to in the chapter on Nitrate of Soda. We have other parts of the world, however (in China and India), where soils rich in nitre occur, and which in the past have formed a source of the commercial article.[100]