No. 2, June, 1921] SOIL SCIENCE 219 



1514. Matthews, Donald J. The determination of ammonia in soil. Jour. Agric. Sci. 

 10: 72-85. 2 fig. 1920. — Various methods of determining ammonia in soils have resulted in 

 figures that are too high due to the simultaneous decomposition of nitrogenous compounds. 

 The author describes and figures "aeration apparatus" with which it is possible to recover 

 large quantities of added ammonia with an accuracy of 98-99.5 per cent in 6 hours and with 

 nearly equal accuracy in 3 hours. For most agricultural purposes an aeration of 1| hours is 

 sufficient. Highly manured glass-house soils undergo partial decomposition in the cold with 

 magnesia. In such cases a modification of the method is recommended. The complete 

 recovery of added ammonia from a calcareous soil is difficult unless the soil is finely ground. — 

 V. H. Young. 



1515. Plymen, F. J., AND D. V. Bal. The biological aspects of wheat cultivation on em- 

 banked soils. Agric. Jour. India IS: 289-300. 1920. — Embanked wheat soils were said to be 

 deteriorating giving low yields, and wheat plants grown on them were weak and yellow dur- 

 ing the early stages of growth but recovered later. The soils are heavy and sticky, black in 

 color, get very hard, and form tenacious blocks on drying after rains. They possess good 

 powers for ammonification and nitrogen fixation but nitrification proceeds rather slowly. 

 The retarding effect on young wheat plants may be due to lack of available nitrogen or to 

 the presence of some deleterious substance formed under anaerobic conditions Cultivation 

 and aeration during the monsoon months removes the cause. — F. M. Schertz. 



1516. Prescott, James Arthur. A note on the Sheraqi soils of Egypt. A study in par- 

 tial sterilization. Jour. Agric. Sci. 10: 177-181. Fig. 1. 1920.— During the "sheraqi," or 

 fallow period, in the region of the Nile, the soil becomes extremely dry and greatly cracked. 

 The temperature is maintained at a point near 40°C. for some time. The author shows that 

 this results in partial sterilization of the soil with a great decrease in the number of soil pro- 

 tozoa. Such soils when sampled and moistened up to 20 per cent showed greatly increased 

 bacterial action over soils which were obtained before being subjected to the normal high 

 temperatures and consequent partial sterilization. In partly sterilized soils there was a more 

 rapid accumulation of available nitrogen parallel with that obtained following artificial soil 

 sterilization. — V. H. Young. 



1517. Russell, E. J., and E. H. Richards. The washing out of nitrates by drainage 

 water from uncropped and unmanured land. Jour. Agric. Sci. 10: 22—43. Fig. 1-6. 1920.— 

 The results secured in a series of drain guages at Rothamstead show that uncropped land per- 

 sistently loses nitrogen in the form of nitrates but the rate at which the soil loses its power of 

 producing nitrates from its own stock of nitrogenous compounds is relatively slow. At the 

 beginning the first 9 inches of soil contained about 3500 lbs. of nitrogen per acre and yielded 

 about 40 lbs. of nitrogen per acre to the drainage water. At the end of 50 years the soil still 

 contains 2380 lbs. of nitrogen and is giving it up at the rate of 21 lbs. of nitric nitrogen per 

 acre per annum. If the curve showing the rate of fall continued its present course and with- 

 out further slowing down no less than 150 years would be needed for exhaustion of the 

 nitrogen of the soil. The nitrogen lost from the soil appears in the drainage water wholly as 

 nitrate. The authors find evidence from which they conclude that the subsoil contributes 

 little if anything to the nitrogen content of the soil water. The analyses give no evidence of 

 either the loss of gaseous nitrogen or of nitrogen fixation. The amount of nitric nitrogen 

 in the drainage water is found to be closely related to the amount of rainfall. The months 

 of greatest rainfall, in general October to January inclusive, are the months of greatest nitrate 

 loss. During the last 25 years, 1 inch of water has washed out 1 lb. of nitrogen per acre, and 

 for the 15 years previous to that the rate was 1.1 lb. Soil in situ does not give up its nitrogen 

 as easily as when washed in ordinary laboratory experiments. A close relation between 

 sunshine and soil temperature is revealed and it is found that a period of bright sunshine 

 during the summer months results in an increase in nitrate loss during the succeeding rainy 

 months. The amounts of nitrogen lost and the relation of rainfall, temperature, etc., to 

 nitrate loss are shown in a number of graphs and tables giving the data obtained. — V. H. 

 Young. 



