NOTES AND ABSTRACTS. 
243 
The amount decreases as the water increases. The quantity of nitric nitrogen 
in the surface 6 ft. of potato, oats, corn, and fallow soil decreases as the water 
increases ; but the quantity formed for each is greatest where the largest quantity 
of water was applied. Large quantities of nitric nitrogen disappear from fallow 
soil during the summer months, due to bacteria growth which converts it into 
protein substances, and not to denitrification. The use of irrigation water 
increases the bacterial activities of the soil, which render soluble the nitrogen, 
and where excessive amounts of water are used this soluble nitrogen is lost. 
A fairly complete bibliography is appended. — A.B. 
Soil, Effect of Decomposing Organic Matter on the Solubility of eertain In- 
organic Constituents of the. By Chas. A. Jensen (Jour. Agr. Res. vol. ix. No. 8, 
May 1 91 7, pp. 253-268). — In Southern California many Citrus groves are 
largely mulched by stable manure, hay, clover, and alfalfa. These substances 
soon begin to decompose when exposed to rain, and their decomposition products 
leach into the soil. On certain soils much benefit follows such mulching, espe- 
cially from the clover and alfalfa straws. It was found that the solubility of 
calcium, magnesium, iron, and phosphoric acid in Citrus soils was measurably 
increased by green manure, stable manure, and their extracts, and this was held 
to be due partly to the action of the inorganic salts contained in the organic 
substances and partly to the solvent action of the soluble organic compounds 
formed during decomposition. — A. B. 
Soil, Factors affecting the Evaporation of Moisture from. By F. S. Harris 
and J. S. Robinson (Jour. Agr. Res. vii. pp. 439-461, Dec. 191 6). — The authors 
investigated some of the factors promoting evaporation from soils, and found 
the rate of evaporation from a moist soil to be very rapidly decreased as the 
humidity of the air increased ; air currents up to a certain velocity inciease the 
rate of evaporation ; evaporation is higher from finer than from coarser saturated 
soils ; reduction of intensity of sunshine greatly reduces rate of evaporation 
(but it is not clear whether temperature is taken into account) ; slight changes 
in temperature have a marked effect on evaporation ; a thin dry mulch, especially 
if composed of coarse particles, which are more effective than fine, materialiy 
reduces evaporation ; compacting the surface increases evaporation, and high 
concentrations of dissolved salts reduce it. — F. J. C. 
Soil, Measurement of Inactive Moisture in, by the Dilatometer. By George 
Bouyoucos (Jour. Agr. Res. viii. Feb. 1917, pp. 195-217 ; 1 fig.). — The principle 
of the dilatometer is based upon the fact that water expands when freezing. 
If the amount of expansion that a given quantity of water produces upon freezing 
is known, the total amount of water that freezes in a soil can be calculated. The 
dilatometer consists of a bulb, a thermometer, and a measuring stem . The method 
consists of mixing soil and water in certain definite proportions in the bulb and 
then filling with ligroin. The apparatus is cooled, and the total rise of the ligroin 
in the stem is taken to represent the total quantity of water that freezes in the 
soil.— A. B. 
Soil Nitrates, Effects of Water and Manures on. By F. S. Harris and N. L. 
Butt (Jour. Agri. Res. viii. Feb. 1917, pp. 333-359 18 figs.). — The authors find 
that with a sod soil kept in the laboratory for two and a half years, the total salts 
and nitrates accumulated most rapidly with a moisture content of 23 per cent, to 
28 per cent. Cropped and uncropped soil kept in large tanks under controlled 
moisture conditions showed a decrease in nitrates and total soluble salts as the 
percentage of moisture increased, the nitrates being very low in water-logged 
soil. Under field conditions more nitrates were found in both cropped and 
uncropped (fallow) soils during the summer than just after the corn crop had 
been harvested. Large irrigations decreased the soluble salts in cropped soils 
more rapidly that it did in fallow soils ; and irrigation or manuring affected the 
nitrates relatively more than the total salts. It was also found that in un- 
manned soil the nitrate content was about twice as great with a fallow as with 
a crop, and in manured soil it was about three times as great. The ratio of 
total soluble salts to sodium nitrate in a cropped soil was 24*5 to 1 without 
irrigation ; and 37*5 to 1 with 40 inches of water, while in a fallow soil the ratio 
was 8 - 9 to 1 without irrigation and 16*2 to 1 with 40 inches of water. 
A short bibliography is appended. — A. B. 
Soil Nitrogen and Nutrition of Citrus Plants. By J. G. McBeth (Jour. 
Agr. Res. ix. May 1917, pp. 183-252 ; 18 figs.). — The total nitrogen content 
of Citrus lands is often low and this deficiency must be made good by fertilizers, 
