SOIL PHYSICS, CHEMISTRY AND MICROBIOI,OG'S' 



935 



foliage of a carob tree shows minimum temperatures 3 to 4 degrees Centi- 

 grade above those cf a thermometer in the open air. 



In the same garden, from March to September 1913, observations were 

 taken of the daily variations of temperature b}' means of a registering thermo- 

 meter 20 ins. from the ground, receiving all the heat of the direct solar rays 

 and those reflected by the soil, exactly as in the case of plants. These observ- 

 ations show dail}^ ranges sometimes approximating 40" C. (104° F). This 

 confirms the great capacity possessed by plants for adapting themselves to 

 wide variations of temperature. 



In another series cf observations made in igii, 1912, 1914 and 1915, 

 the amount of terrestrial radiation in the belt of air in closest contact with 

 the soil was determined. A thermograph was placed in the open air 20 in. 

 from the ground, and another a short distance away 55 in. from the ground, 

 facing north, and protected from the sun and terrestrial radiation. Thus 

 the differences in the fall of temperature, due in particular to morning radia- 

 tion, were ascertained. The results are set out in a series of tables, and 

 the following conclusions are based on them. 



(i) Using two registering thermometers, A and B, at the above re- 

 spective distances from the ground, the minimum daily temperature is regis- 

 tered by that nearest to the ground. This fact comes out very clearly, 

 the difference often being most marked and not subject to anj^ exceptions. 



(2) The annual mean of 470 observations calculated from the monthly 

 average minima was 19.2 degrees by thermograph A (4 % ft. from the ground) 

 and 16.6 degrees by thermograph B (i ft. 7 ^ in. from the ground). 



(3) The annual average of the absolute monthly minimum was 15.7° 

 by thermograph A and 130 by B. 



(4) The absolute minimum for the 4 vears was 11. f)'^ by A and 6.40 

 by B. 



(5) The differences between the minimums of the two thermographs 

 in the 470 observations, taking their average and their maximum value, are 

 summed up as follows : 



{a) The monthly :nean difference A — B was 2.3° C. 



(b) The mean of the maximum monthly differences was 3.8" ; 



(c) The absolute maximum difference throughout the period in 

 question reached the high figure of 5.4"^*. 



These results prove beyond question the importance of the study, in 

 connection with vegetation, of the temperature changes due to terrestrial 

 radiation, which are perfectly distinct from the general cooling of the 

 atmosphere and occur in the lower air strata, the medium of plant life. 



724 - Soluble Non-Protein Nitrogen of Soil. — potter r. s. and Snyder r. s. (I(»\vu 



State College lixperiiueut Station), in Journal of Ai^ricuUwal Research, Vol. VI, Xo. 2, 

 pp. 61-64. Washington, D. C, April 10, i<)i6. 



The writers conclude from their researches into the nitrogenous sub- 

 stances of the soil that information may be obtained relative to the degree 

 of decomposition of the organic matter in the soil by determining the propor- 

 tion of nitrogenous compounds left in the alkali extract of the soil after 

 precipitation of the protein by a suitable reagent. With this problem in 



SOIL PHYSICS, 



CHEMISTRY 



AND 



MICROBIOLOGY 



