288 ACTIONS OF AKTIFICIAL MANURES 



none of this carbonate of lime, it has remained only in the 

 layer stirred by the plough, and has never worked downwards. 

 The old maxim that lime sinks in the soil is only true of lime 

 on pastures, where it is buried by the slow but persistent 

 action of earthworms bringing up mould to the surface; in 

 arable land, as the Rothamsted analyses prove, the lime wastes 

 but does not sink. The very special distribution of carbonate 

 of lime in the Kothamsted soil affords, however, an exceptional 

 opportunity of studying the rate at which this important soil 

 constituent is removed by natural causes, and also of how the 

 natural removal is decreased or accelerated by the constant 

 use of certain artificial manures. Samples of soil from the 

 Rothamsted plots were not taken at the very beginning of 

 the experiments, at least none have been preserved ; the 

 earliest which are available date from 1856, and later samples 

 from the same Broadbalk field were taken in 1865, 1881, 1893, 

 and 1904. Samples from the other fields date back to 1867, 

 1868, and 1873, so that in four cases we can ascertain the 

 effect of thirty years' action of the manures a long enough 

 period to make the change in composition perceptible in the 

 analyses. Of course, there are many sources of error in the 

 analytical figures ; soil sampling is never a very accurate 

 process, and in comparing samples taken at long intervals, a 

 new error is introduced by possible changes in the consolida- 

 tion of the ground. But the figures agree better than might 

 have been expected, and the results may be regarded as 

 accurate to within 20 per cent, or so. Table XCVII. shows 

 the actual amounts of carbonate of lime, calculated as pounds 

 per acre, in the surface soil from certain of the plots in 

 the various Rothamsted fields at the dates given, while the 

 last column of the table gives the average annual loss deduced 

 from these figures. 



It will be seen that the unmanured plots agree fairly well 

 in showing a loss of 800-1000 Ib of carbonate of lime per 

 acre, due to the washing action of the rain alone, or rather to 

 the solvent action of rain-water after it has become charged 



