820 EXPERIMENT STATION EECORD. 



"(5) The plants make a larger, more rapid, and earlier growth. These are 

 the results that induce and make it profitable for the tiller of the soil to go to 

 the expense of erecting the tent." 



Studies on tlie movement of soil moisture, E. Buckinoham and F. K. 

 Cameron (U. *S'. Dci)t. Agr.. Bur. *S'o//.s' Bill. 38, pp. 61, fifjs. 23). — The studies 

 reported in this bulletin dealt \Aith the loss of soil moisture by direct evapora- 

 tion from points below the surface, especially as i*elated to the drying of soils 

 under arid and humid conditions, and with a general examination of the theory 

 of capillary action in soils. The measurements of evaporation were made with 

 soils in tumblers or small cylinders under varying conditions of moisture con- 

 tent, compactness, or surface tilth. The examination of the theory of capillary 

 action in the soil was based upon curves representing the distribution by capil- 

 larity of moisture in soil in tubes under different conditions of tilth, etc. 



The results in general show that, contrary to the general belief, " the loss 

 of water by evaporation from points below the surface, while it does take place 

 in measurable (juantities, is nevertheless quite small, and is negligible in com- 

 parison with the losses taking place at or very near the surface. The movement 

 of w?*4:er vapor through the soil is shown to follow the law governing the dif- 

 fusion of other gases through porous media, and is quite slow. Mulching de- 

 creases or inhibits the capillary flow, and diffusion througli the mulch is 

 practically negligil>le. This practice is very effective in conserving soil mois- 

 ture, and is founded on sound scientific principles. An especially interesting 

 illustration is brought out in the comparison of the loss of water from a soil 

 under arid and humid conditions, respectively. As might be expected, the loss 

 at first is much more rapid under the arid conditions, so rai)!d in fact as to 

 overtax the soil's ability to move water from within to the surface by capil- 

 larity, and in consequence a dry layer or mulch is formed which keeps the sub- 

 frequent losses far below those which take place from the soil under humid 

 conditions, where the capillary flow to the surface persists until the moisture 

 content of the whole soil is very low indeed. These laboratory experiments, 

 therefore, clear up in a very satisfactory manner the well-known and apparently 

 contradictory facts observed in the field that the soils o.' arid regions, at depths 

 a little below the surface, are generally wetter and hold their moisture for much 

 longer periods than do the soils of humid areas in dry seasons. 



"An exauainatioii of the curves representing the distribution of moisture in 

 the soil has suggested that, if the subject be regarded from the standpoint of 

 dynamical equilibria phenomena, there appear certain analogies to the theory of 

 electrical and thermal potential. This is a fact of great importance in the 

 theoretical study of the subject, since we are in possession of a well-developed 

 theory of electrical and thermal potential which can be applied to a considerable 

 extent to the phenomena of soil moisture ; it is of probable practical value, 

 because it suggests and gives direction to further experiments and serves as a 

 basis for the correlation of a large number of observations already made, but 

 having hitherto a local rather than a general value. 



" It is clearly recognized that the analogy is imperfect in that the capillary 

 potential and I'esistance to flow are dependent upon the moisture content of 

 the soil, whereas electrical and thermal resistance are practically independent 

 of the amount of current and heat ])assing." 



Quality of commercial cultures for legumes in 1906, M. J. Pruciia and 

 H. A. Harding (New York mate Uta. Bui. 282, pp. 26D-279). — This bulletin 

 i-eviews the results of experiments by 16 experiment stations in the United 

 States during l!)04-5 and reports a continuation of tests of commercial cultures 

 during 190(3 at the New York iState Station. It is stated that the tests made by 



