IG  Some  Secondary  Actio7is  of  Manures  upon  the  Soil. 
in  1805,  1881,  1893,  and  190'1.  Samples  from  the  other  fields 
date  back  to  1867,  1868,  and  1873,  so  that  in  four  cases  we  can 
ascertain  tlie  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 
accui'ate,  process,  and  in  comparing  samples  taken  at  long 
intervals,  a new  error  is  introduced  by  possible  changes  in  the 
consolidation  of  the  ground.  But  the  figures  agree  better  than 
might  have  been  expected,  and  the  results  may  be  regarded  as 
acciu'ate  to  within  20  per  cent,  or  so.  The  following  table 
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 : — 
TAhLB  I. — Loss  of  Carhonate  of  Lime  from  Rothamsted  Soils. 
Carbonate  of  lime  lb.  per  acre 
Field 
Plot 
Manuring 
Earliest 
date 
1904 
Average 
annual 
loss 
Broadbalk 
3 
Unmanured 
110,500 
90,200 
800 
18(55 
2b 
Dunged 
100,400 
85,100 
590 
(1,  7,  8,  10 
Ammonium  Salts 
85,300 
61.800 
1,100 
9 
Nitrate  of  Soda 
106,000 
92,700 
665 
J-Ioos  1881 
10 
Uiimanured 
86,800 
63,900 
1,000’ 
1 and  4 A 
Ammonium  Salts 
54,300 
37,500 
776 
1 and  4 N 
Nitrate  of  Soda 
59,500 
42, .500 
595 
Agilell  18(57 
Uiimanured 
159,400 
117,700 
930 
liittle  Hoos 
Un  manured 
103,000 
70,500 
1,046 
1873 
1 Another  plot  more  fairly  comparable  -with  the  plots  which  follow  lost  at  the  rate 
of  675  11).  per  acre. 
It  will  he  seen  that  the  unmanured  plots  agree  fairly  well 
in  showing  a loss  of  800-1,000  lb.  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  with 
carbonic  acid  exhaled  from  the  roots  or  arising  from  the  decay 
of  organic  matter  in  the  soil.  Of  course  there  are  many  factors 
which  might  modify  this  figure  in  other  soils  ; it  must  to 
some  extent  depend  on  the  actual  amount  of  carbonate  of  lime 
in  the  soil,  on  the  magnitude  of  the  drainage  through  the  soil, 
this  being  lessened  with  larger  crops  on  normally  manured 
land,  and  also  on  the  proportion  of  carbonic  acid  in  the  soil 
