Some  Secondary  Actions  of  ACannres  upon  the  Soil.  17 
gases,  which  proportion  would  be  increased  with  manured  soil 
and  larger  crops.  Still  these  are  the  best,  indeed  the  only 
figures  available  to  show  the  loss  of  carbonate  of  lime  that 
arable  land  is  likely  to  suffer,  and  we  may  now  proceed  to 
consider  how  far  the  loss  is  affected  by  the  use  of  ammonium 
salts  as  manures.  At  Rothamsted  a mixture  of  sulphate  and 
muriate  of  ammonia  has  always  been  employed,  and  though 
certain  minor  differences  may  be  traced  in  the  action  of  the 
two  fertilisers,  in  the  main  the  two  together  will  behave 
towards  the  soil  of  the  plant  just  like  sulphate  of  ammonia 
alone,  though  in  a slightly  more  concentrated  form.  The  table 
only  gives  a selection  of  the  plots  from  which  results  are 
available  (for  details  see  Hall  and  Miller,  Proc.  Roy.  Soc.  1907, 
B.  77,  1),  but  it  is  clear  that  the  use  of  ammonium  salts  causes 
increased  washing  out  of  the  carbonate  of  lime,  in  fact  from 
the  original  figures  we  may  calculate  an  average  figure  of 
117  lb.  of  carbonate  of  lime  removed  from  each  200  lb.  of 
ammonium  salt  applied.  This  figure  would  indicate  that  the 
carbonate  of  lime  removed  is  the  chemical  equivalent  of  the 
ammonium  salts  supplied  as  manure,  which  suggests  that  when 
they  reach  the  soil  they  begin  by  reacting  with  the  carbonate  of 
lime  and  not  with  the  zeolites  as  originally  suggested  by  Way. 
However,  direct  experiments  made  to  test  this  point  (Hall  and 
Gimingham,  Trans.  Chem.  Soc.  1907,  91,  677)  showed  that 
though  some  interaction  will  take  place  between  the  am- 
monium salts  in  solution  and  carbonate  of  lime,  the  zeolites 
bring  about  by  far  the  greater  part  of  the  change,  even  when 
the  carbonate  of  lime  constitutes  as  much  as  20  per  cent, 
of  the  soil.  Probably  the  carbonate  of  lime  is  brought  into 
the  action  later,  when  the  ammonia  is  liberated  from  its 
zeolitic  compound  in  order  to  be  converted  into  nitrate  or 
taken  up  directly  by  the  plant ; the  question  is  in  any  case 
only  of  technical  interest  since  there  .is  no  doubt  about  the 
final  result  that  the  ammonium  sulphate  behaves  like  an  acid 
and  removes  from  the  soil  whatever  amount  of  carbonate  of 
lime  is  required  to  combine  with  the  sulphuric  acid  it  contains. 
So  far  the  matter  of  the  wastage  of  carbonate  of  lime  is 
clear  enough,  but  another  problem  was  set  up  when  Dr.  J.  A. 
Voelcker  observed  that  the  soil  of  the  permanent  wheat  and 
barley  plots  at  Woburn  which  had  been  receiving  ammonium 
salts  for  about  twenty  years  had  become  actually  acid  to 
litmus  paper  (see  this  Journal,  1899,  60,  515,  and  1901,  62, 
286).  The  acidity  thus  developed  rendered  the  land  unable 
to  carry  barley,  though  its  capacity  to  do  so  was  restored  by  a 
comparatively  small  dressing  of  two  tons  of  lime  to  the  acre. 
Naturally  acid  soils  had  been  known  before,  chiefly  in  peaty 
waterlogged  areas,  but  this  was  the  fii’st  example  recorded  of 
VOL.  70.  C 
