The Lois Weedon Plan of Growing Wheat. 605 



Table. For this purpose we take of course the mean results 

 instead of the separate determinations ; which latter, however, 

 although disagreeing with each other sufficiently to show that 

 the figures could not be relied upon to treat of the nice question 

 of the effect of a single even heavy dressing of manure, have 

 still so much of agreement, as to give some confidence at least in 

 the direction^ and in any marked distinctions, which the mean 

 results would indicate as between soil and soil. 



It is seen that the subsoils contain from one-half to one-third 

 only as much nitrogen as the surface soils. From this it is 

 obvious that an inch or two of variation in depth, in sampling a 

 surface soil, might make a comparatively important difference in 

 the percentage of nitrogen obtained. The eflect of the admix- 

 ture of more or less of subsoil, in a sample of professedly sur- 

 face soil, is seen in the difference between tlie mean percentage 

 in the Rothamsted soil which had been cultivated on the Lois 

 Weedon plan, and that of a similar description in the adjoining 

 field, which had grown wheat for several successive years, but 

 without its subsoil being disturbed. Tims the trenched plot at 

 Rothamsted gives a mean percentage of only 0"1417 of nitrogen, 

 whilst the plot in the adjoining field, notwithstanding it has 

 grown wheat for many years successively without manure, gives 

 0-1523 per cent. 



Before proceeding to compare with one another the Rotham- 

 sted and tlie Lois Weedon soils, we may here, in passing, call 

 attention to the fact that, slight as they are, and whether acci- 

 dental or not, the differences which the mean results would 

 show between the plots devoted to the continuous growth of 

 wheat at Rothamsted, under difierent conditions of manuring, 

 are really, at least in direction, such as those manuring condi- 

 tions would lead us to expect. Without laying too much stress 

 on the actual figures, it is seen, then, that whilst the continuously 

 unmanured plot gives 0"1523 per cent, of nitrogen, that which has 

 received for a series of years mineral manure only (which would 

 tend to the extraction of more nitrogen from the soil tlian whore 

 no manure was employed) gives 0'145'J per cent., or rather less 

 than the former, 'ihe j)lot which has received annually anuno- 

 niacal salts (as the results showed somewhat in excess of the 

 available minerals), indicates 01587 jier cent, of nitrogen; or 

 rather more than either the continuously unmanured or the con- 

 tinuously jnincral-manured ])lot. And again, quite conformably 

 with the above, the j)lot wliicii has received continuously both 

 miiicral manure and an excess of ammoniacal salts, shows a 

 slightly lower percentage (0*155G) than where the annnoniacal 

 salts were employed without minerals; though with this excess of 

 ammoniacal salts, a slightly higher one than the unmanured plot. 



VOL. xvir, 2 s 



