Journal of the Chemical Society, 64(2): 486-487 (1893)

Soil and Nitrification. By P. P. Dehérain (Compt. rend, 116, 1091-1097).—Drainage from unmanured land, and land which was manured with 60,000 kilos, of farmyard manure per hectare, contained the following amounts of nitric nitrogen (kilos, per hectare):—

  Spring Summer Autumn Winter
Unmanured 28.87 15.21 31.69 15.17
Manured 52.21 24.79 42.89 19.44

In practical agriculture, only a portion of this nitrogen is utilised; wheat and oats take up the nitrates formed in the spring, root crops that formed in the summer; the nitrates formed in the autumn and winter are lost.

In 1891, large vessels were filled with soil from Vanteuil (Seine-et-Marne), and the drainage from the soils collected and examined. The following amounts of nitric nitrogen were obtained per cubic metre of soil.

  No. 1 No. 2
24th March, 1891 584 grams 539 grams
7th April, 1891 664 grams 466 grams

Other soils examined in.1892 gave 884 grams and 440 grams of nitric nitrogen per cubic metre in July, and 250 and 285 grams six weeks later. It was found that soils give much greater amounts of nitrates when fresh than when kept for some time; thus soil from Wardrecques gave 116 grams of nitric nitrogen in 1890, and only 33 grams in 1891; whilst soil from Blaringhem gave 108 (in 1890) and 39 grams (in 1891). The effect of stirring on the production of nitrates was next studied. Whilst 100 grams of soil which was not touched gave only 2 milligrams of nitric nitrogen, similar soil kept stirred for the same time (1st November to l5th December) gave amounts varying from 39 to 71 milligrams. The soils yielded drainage in February and March which contained per cubic metre of drainage water the following amounts of nitric nitrogen:—

Soil not stirred 18 8 grams
Soil stirred 1340.0 grams

Nitrification was thus enormously increased by stirring the soil. In order to ascertain whether the time of the year had any effect on the energy of the nitrification, fresh samples of soil were taken in different months. Soils taken in November nitrified with great energy, whilst samples of the same soil taken in January and March, and kept at a very favourable temperature, gave at the most only half as much nitric acid as the samples taken in November. The energy of the nitrifying organisms thus varies with the season.

A hectare of soil 0.09 metre deep would weigh about 1000 tons or 10,000,000 times 100 grams. Calculating the results obtained with 100 grams to a hectare of soil, the amounts of nitric nitrogen would be 440 and 710 kilos, respectively, or from four to six times as much as is required in practice.

After discussing the usual method of working the soil, the author expresses the opinion that, with more suitable implements for the trituration of the soil, a more vigorous nitrification could be induced, analogous to that obtained in the laboratory. N. H. M.