Mar. lo. 1919 Organic Matter and Water-Holding Capacity of Soil 271 



MOISTURE CONTENT OF THE SOIL 



Between May i and September 2, plots 3 and 4 were sampled 15 times 

 (Table VI) to a depth of i foot, the samples being taken in 3-inch sec- 

 tions from three borings in a north and south line across each plot. In 

 the case of each set one boring was in the corn, another in the sorghum, 

 and the third in the mangels, each being close to a crop row. At the 

 time of the first sampling in each month we sampled the second- and 

 third-foot section also, both on these two plots and on the three others 

 (Table VII). 



From Table VI it will be seen that on every occasion the surface foot 

 of plot 3 contained more moisture than that of plot 4, and, except on 

 the very last date, the same holds true for the four 3-inch sections. 

 Throughout the first three months the difference ranged between 3 and 

 5 per cent, being greatest when the sampling occurred soon after the ces- 

 sation of a rain. During the last half month, at a time when the crops 

 were drawing most heavily upon the soil moisture and there was but 

 little rain, the differences were much less, falling on the average to less 

 than I per cent. 



There is no evidence that, in general, more water was retained in the 

 second and third foot on plot 3 than on plot 4 (Table VII), although more 

 was found on May i, which, however, was not long after the frost had 

 disappeared from the subsoil and there had not been time for the down- 

 ward percolation of the water from the melting snow and the Apri[ 

 rains. With the three other plots, the surface foot was intermediate in 

 moisture between plots 3 and 4, the relative moisture content varying 

 roughly with the nitrogen content (Table VII). Only at the time of 

 the first sampling did they, like plot 3, show a higher moisture content 

 in the second and third foot than plot 4. 



The above remarks apply directly to the total water content, which 

 includes both the nonavailable and the available. As the portion of 

 the soil moisture available to plants for growth and for the maintenance 

 of life appears to be approximately that in excess of the hygroscopic 

 coefficient (i, p. 122; 2), and as the latter value is a little lower for the 

 surface of plot 4, being only y.y compared with 8.1 for plot 3 (Table 

 VIII), we regard the differences in useful water as slightly greater 

 than those in the total water reported in Table VI. 



INFLUENCE OF ORGANIC MATTER UPON MOISTURE CONTENT 

 From the above data it would appear that the greater amount of 

 organic matter in the surface foot of plot 3 is responsible for the con- 

 siderably higher content of both total and free water shown by it through- 

 out most of the summer of 191 5. 



Any advantage possessed by one plot over another, due to topography, lies 

 with No. 4. The surface of the field is almost level, but after very heavy 

 rains and at the time of the melting of the snow in the spring the last water 

 to disappear from the field is found upon that plot (Plate 36). 



