244 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
manures, &c. The author finds that semi-arid soils frequently fail to nitrify 
dried blood when added in i per cent, amounts, but can nitrify blood if added 
in amounts not greater than is ordinarily applied under field conditions. Green 
manures, especially the legumes, nitrify very rapidly. Fifty per cent, of the 
nitrogen contained in green plant tissues may be converted into nitrates in 
thirty days, while, of course, such manures furnish a valuable source of energy 
for the non-symbiotic nitrogen-fixing organisms. As much nitric nitrogen is 
lost from Citrus soils by leaching, the growing of a winter cover crop is suggested 
as a most effective means of preventing this loss. The prevalent system of 
furrow irrigation causes a very unequal distribution of the soil nitrates, forming 
brown " nitre " spots, which sometimes contain i per cent. N as nitrates. These 
" nitre " spots consist largely of the deliquescent calcium nitrate. The author 
holds that basin or overhead irrigation is more satisfactory in promoting the 
more equal distribution of soil nitrates than furrow irrigation. 
A short bibliography is appended. — A. B. 
Soils Arid and Humid, Comparison of the Nitrifying Powers of. By C. B. 
Lipman, P. S. Burgess, and M. A. Klein (U.S.A. Jour. Agr. Res. vol. vii. No. 2, 
Oct. 1916, pp. 47-82). — A study of the nitrifying powers of some 40 humid and 
150 arid soils obtained from the various State experimental stations showed 
the following results : 
The nitrifying powers of humid soils are greater than those of arid soils with 
regard to soil nitrogen and dried blood nitrogen. Arid soils, however, nitrify 
sulphate of ammonia and cotton-seed meal with much greater vigour than do 
humid soils. — A. B. 
Soils, Availability of Potash in certain Orthoclase-bearing, as affected by 
Lime or Gypsum. By L. J. Briggs and J. F. Breazeale (Jour. Agr. Res. viii. 
Jan. 191 7, pp. 21-28). — It is thought that the application of lime to a soil 
liberates potash from the soil minerals. The point is of importance to the 
Citrus industry of Southern California, where heavy applications of lime and 
gypsum are sometimes made. 
Samples of pegmatite and orthoclase, as representative of the potash-bearing 
rock and mineral from which much of the Citrus soils are derived were finely 
ground and shaken for a number of days with aqueous solution of calcium 
hydroxide and calcium sulphate in various strengths. The calcium hydrate 
solutions did not modify the solubility of potash in either the pegmatite or 
orthoclase, while the gypsum solution depressed the solubility of potassium 
in the orthoclase as the strength of the gypsum increased. 
It was found that similar results followed the addition of gypsum in a Citrus 
soil which was under cultivation as well as in virgin soils. The experiments 
tend to show that the availability of potash to plants in soils of an orthoclase 
nature is not increased by the addition of lime or gypsum, but rather a depression 
in the solubility of potash occurs under such conditions. — A. B. 
Soils, Calcium Compounds in. By E. C. Shorey, W. H. Fry, and W. Hazen 
(Jour. Agr. Res. viii. Jan. 1917, pp. 57-77). — In this paper are given analyses of 
sixty-three samples of soils from nineteen different States. The quantities of cal- 
cium carbonate, calcium sulphate, calcium combined with humus compounds, and 
calcium silicates have in all cases been accurately determined. The figures 
obtained showed a wide variation in the total calcium content and in the 
content of CaC0 3 and the two classes of silicates. Calcium combined with humus 
was present in thirty-four of the samples only. No relation was apparent 
between the total calcium content and the quantity of any of the classes of calcium 
compounds. It was found that it is possible to have two soils with the same 
calcium content but with the kinds of calcium compounds present in quite 
different quantities. A good alfalfa soil is characterized by a high calcium 
content, but low in content of calcium carbonate. — A. B. 
Soils, Fixation of Ammonia in. By J. G. McBeth (Jour. Agr. Res. ix. April 
1917, pp. 141-155). — The author points out that the capacity of a soil to serve 
as a source of plant food depends upon its power to retain water-soluble sub- 
stances, like potash, phosphoric acid, and ammonia, against the leaching action of 
rains. He finds that many semi-arid subsoils have the power of fixing ammonia 
in large quantities, and much of this ammonia cannot be removed by the 
ordinary methods of analysis. If the soil is treated with 10 per cent. HC1 the 
amount of ammonia extracted is the same as when the soil is treated and distilled 
with MgO. Anions have little or no influence on ammonia-fixation in soils. 
The amount of fixation is increased with rise in temperature, the fixation being 
