SOILS FERTILTZEKS. 923 



The control of moisture in orchard soils, F. T. Shutt (Canada Expt. 

 Fanii.s Rpts. 1906, pp. 150-153). — The experiments of previous years on this 

 subject (E. S. R., 18, p. 117) were continued during 1906. The data obtained 

 were strongly confirmatory of those secured in previous seasons, emphasizing 

 more jiarticularly the value of mulching as a means of conserving soil moisture 

 and bringing out prominently the fact that the uni-estricted growth of weeds 

 dries out the soil practically to llic same extent as sod. 



The work of the chemical laboratory of the Ploti Agricultural Experi- 

 ment Station in 1906, B. M. Welbel (GhodlchnuU Otchet Ploty. Selsk. Khoz. 

 Opiiitn. Stantzil, 12 (1906), pp. lJiS-22S, 248-262). — This report summarizes 

 especially 5 years' work with lysimeters to determine the ratio of percolation 

 to precipitation, the rate and progress of nitrification and denitrification in 

 the soil, and the extent and loss of nitrates in drainage water. 



It was found that on an average about 24 per cent of the precipitation passed 

 through the soil of lysimeters 20 cm. (7.8S in.) deep and S.'j per cent through 

 lysimeters 40 cm. (1.5.7G in.) deep, the percolation, however, varying widely 

 with the conditions of season, temperature, wind, amount and intensity of 

 rainfall, and other conditions. 



The lysimeter studies have also shown that nitrification is very variable 

 during the year. During the first 18 months after the lysimeters were filled 

 nitrification was much more active than in later years when the soil had become 

 more compact. Denitrification at the same time apparently increased. These 

 changes were more marked in the surface soil than in the subsoil. Nitrifica- 

 tion has been found to be most active during the spring and summer. The 

 amounts of nitric acid produced during the 5-year period are shown in the 

 following table : 



Nitric acid (HNOs) produced during 5 years in different lysimeters. 



1 Nitric acid per acre. 



Lysimeter. 20 cm. 



j (7.88 in.) 

 lysimeter. 



No. 1, leguminous plants followed by black fallow. 



No. 2, spring: wheat 



No. 3 « 



Poundx. 

 1,272.79 

 1,335.14 

 1,593.44 



" Manured In case of 20 cm. lysimeters and planted to alfalfa in case of 40 cm. 

 lysimeters. 



The figures indicate that nitrification is almost as active in the subsoil as 

 in the surface soil when, as in this case, the subsoil is well aerated. 



In lysimeters which were built so as to inclose the soil without disturbing it 

 only from 2.5 to 3.5 per cent of the precipitation passed through lysimeters 

 2.5 cm. (9.85 in.) deep, and in case of deeper lysimeters not more than 1 per 

 cent. In the same kind of lysimeters the total loss of nitrates in the drainage 

 was very small, amounting during 4 years to only 7.3 lbs. of nitrogen per acre 

 in lysimeters 25 cm. deep, 1.96 lbs. for lysimeters 75 cm. (29.55 in.) deep, and 

 0.9 lb. for lysimeters 1 meter (39.4 in.) deep. The annual losses from this source 

 per acre amounted to only 0.22 lb. for soil to a depth of 1 meter, 0.44 lb. to a 

 depth of 50 cm., and 1.78 to 3.56 lbs. to a depth of 25 cm. These are losses 

 which are fully restored by the nitrogen of atmospheric precipitation. 



The data obtained in the studies showed a close agreement between the 

 progress, of nitrification in the soils and the nitrate requirements of crops. For 

 43854— No. 10—08 3 



