264 Journal of Agricultural Research voi. xvi. no. 10 



used in farm practice requires a rather long time. This is well illustrated 

 at Rothamsted by the Broadbalk Field, which has been continuously in 

 wheat since 1843. On plot 2b, which receives 14 tons of farm-yard 

 manure every year, the first 9 inches of soil gained only 0.098 per cent 

 of organic carbon in the 12-year period from 1881 to 1893 (9, p. 12^), and 

 in 1893, after having received such an annual application for 50 years, 

 or 700 tons per acre in all, the 9-inch layer of soil contained only 1.342 

 per cent more organic matter than the adjacent plot 3, which during the 

 same period had been continuously cropped without any manure or fer- 

 tilizers. By starting with a virgin prairie soil rich in organic matter and 

 putting it under continuous clean cultivation, an appreciable lowering 

 of the organic matter can be induced much more quickly, but even in 

 this case a long period is necessary (d, p. 136). 



On many fields the great variation in texture from place to place, espe- 

 cially in the portion of the soil mass below the reach of the plow, renders 

 any comparison of the relative amounts of useful moisture a laborious 

 task, the difiFerences shown in moisture retentiveness being more depend- 

 ent upon differences in texture than upon any differences in the content 

 of organic matter that may have been induced by dissimilar methods of 

 manuring, cropping, or tillage. Detailed studies of the uniformity in 

 texture of the plots or fields under comparison have usually been omitted, 

 and, hence, it may easily be that many of the data published in support 

 of the common belief are due simply to the coincidence that soils of a 

 finer texture, while they retain more water, also usually have a higher 

 content of organic matter. Under natural grassland conditions the heav- 

 ier soils are the richer in organic matter and in general it appears that 

 when conditions of surface drainage and climate are similar, the finer the 

 texture of the soil the higher will be the organic-matter content when 

 equilibrium between the processes of decay and those inducing an accu- 

 mulation of orgamc matter have once been attained. Under the condi- 

 tions of ordinary mixed farming, arable soils will approach more nearly 

 to grassland than to forest conditions. 



An unusual opportunity for such a study is offered by some plots at 

 this Experiment Station, laid out by Snyder (//) some 25 years ago. In 

 the summer of 191 5, incidental to a study of the effect of different systems 

 of cropping upon the composition, properties, and productivity of the 

 silt loam soil of these plots, we obtained some data upon the water- 

 holding capacity. It so happened that the season was characterized by 

 weather conditions especially favorable for revealing any differences which 

 might exist in the water-holding capacity of the soils of the various plots. 



DESCRIPTION AND HISTORY OF PLOTS 



The land, originally covered by a heavy growth of deciduous trees, had 

 been cleared about 1856, and during the following quarter of a century 

 formed part of a typical grain farm of that period, oats or wheat being 



