496 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER.  November  29,  1900. 
Carbonic  Acid  Gas  as  a  Fertiliser. 
On  page  331  Mr.  W.  Mills  treats  this  subject  in  his  usual  able  manner 
from  a  chemical  point  of  view,  and  expresses  his  own  opinion  while 
asking  for  the  Editor’s  on  the  practical  side.  The  latter,  from  the 
excerpt  given  on  the  page  quoted  from  Percival’s  “  Agricultural 
Botany,”  does  not  extend  beyond  the  “  probable ”  value  of  carbonic 
acid  gas  a  fertiliser.  In  Johnson’s  “  How  Crops  Grow,”  page  368, 
appears,  after  stating  “  From  the  atmosphere  the  crop  can  derive  no 
appreciable  quantity  of  those  elements  that  are  found  in  its  ash,”  the 
statement — “  In  the  soil,  however,  from  the  waste  of  both  plants  and 
animals  may  accumulate  large  supplies  of  all  the  elements  of  the 
volatile  part  of  plants.  Carbon,  certainly  in  the  form  of  carbon 
dioxide,  probably  or  possibly  in  the  condition  of  humus  (vegetable 
mould,  swamp  muck),  may  thus  be  put  as  food,  at  the  disposition  of 
the  plant.” 
Passing  to  the  practical,  I  can  hardly  follow  Mr.  Mills  in  “  the  fact  that 
ammonic  carbonate  makes  plants  grow  more  vigorously  than  ammonia 
j)er  se,  tor  by  watering  plants  with  very  dilute  solutions  of  ammonia 
their  luxuriance  is  made  to  surpass  by  far  that  of  similar  plants  which 
grow  in  precisely  the  same  conditions,  save  that  they  are  supplied  with 
pure  water.  What  of  the  carbonate  or  the  value  of  carbonic  acid  as  a 
fertiliser  ?  Hellriegel,  in  1868,  demonstrated  by  experiments  that  an 
artificial  supply,  whether  of  the  gas,  of  its  aqueous  solution,  or  of  a 
carbonate  to  the  soil,  had  no  effect  to  increase  the  crop.  Nevertheless, 
the  value  of  carbonate  of  ammonia  as  a  fertiliser  is  unquestionable,  but 
that  is  not  the  point.  The  average  quantity  of  ammonia  in  the  atmo¬ 
sphere  is  one  part  in  50  millions,  according  to  Ville,  and  are  we  to 
conclude  that  this  ammonia  reaches  the  earth  as  carbonate  ?  In  dry 
weather  the  atmosphere  contains  more  ammonia  than  usual,  since 
ammonia  escapes  from  its  solu'ions  with  the  first  portions  of  aqueous 
vapour;  and  may  we  deduce  from  the  filip  given  to  vegetation  by  the 
first  rain  in  quantity,  after  a  droughty  time,  that  it  is  due  to  the  extra 
amount  of  ammonia  washed  out  of  the  atmosphere  into  the  soil  ?  In 
some  degree  this  may  be,  for  ammonia  and  its  carbonate  are  readily 
soluble  in  water,  and  is  at  the  disposal  of  the  plant  both  in  the 
atmosphere  and  soil.  Ville  has  stated,  1851-2,  that  vegetation  in 
Sandy  subsoil  of  forest . 
Loamy  subsoil  of  forest . 
Surface  soil  of  forest . 
Clayey  soil  of  Artichoke  field . 
Soil  of  Asparagus  bed  not  manured  for  one  year  .  .  . 
Soil  of  Asparagus  bed  newly  manured . 
Sandy  soil  six  days  after  manuring . 
Sandy  soil  ten  days  after  manuring,  three  days  of  rain  . 
Vegetable  mould  compost . 
Cubic  feet  of  air  over 
1  acre  to  height  of  14  inches. 
50,820 
conservatories  may  be  remarkably  promoted  by  impregnating  the  air 
with  gaseous  carbonate  of  ammonia,  and  every  gardener  knows  that  a 
mulching  of  short  manure,  bed  of  fermenting  material,  or  sprinkling 
with  stable  and  cow-house  drainings,  contributes  to  the  health  and  vigour 
of  plants  and  crops.  Truly  foliage  absorbs  ammonia,  as  carbonic  acid 
is  imbibed  by  the  leaves  of  plants.  This  was  conclusively  proved  by 
Peters  and  Sachs  experimenting  on  two  young  Bean  plants  growing  in 
river  sand.  The  absorption  of  ammonia  by  foliage  does  not  appear, 
like  that  of  carbonic  acid,  to  depend  upon  the  action  of  sunlight,  but, 
as  remarked  by  Mulder,  may  go  on  at  all  times,  especially  since  the 
juices  of  plants  are  very  frequently  more  or  less  charged  with  acids 
which  directly  unite  chemically  with  ammonia. 
Now  for  the  soil  to  which  ammonia  salts  are  applied  as  fertilisers, 
and  the  measure  of  their  nutritive  effect  determined  by  the  amount 
of  nitrogen  which  vegetation  assimilates  from  them.  When  rains  fall,  or 
dews  deposit  upon  the  surface  of  the  soil,  or  upon  the  foliage  of  a 
cultivated  field  or  garden,  they  bring  to  the  reach  of  vegetation  in  a 
given  time  a  quantity  of  ammonia  far  greater  than  what  is  diffused 
through  the  limited  volume  of  air  which  contributes  to  the  nourishment 
of  plants.  The  first  portion  of  rain  that  falls  usually  contains  much  more 
ammonia  than  the  latter  portions.  Gardeners  know  this,  hence  nee  the 
freshly  fallen  rain  water  for  watering  borders,  having  noticed  the 
difference  to  vegetation  between  it  and  that  of  a  long-continued  rain. 
Assuming  this  to  be  in  the  form  of  carbonate,  Mr.  Mills’  opinion  receives 
a  measure  of  countenance,  but  is  it  not  the  ammonia  that  has  the 
remarkable  effect  upon  vegetation,  deepening  the  colour  of  the  foliage 
of  plants,  an  indication  of  increased  vegetative  activity  and  health,  as  a 
pale  or  yellow  tint  belongs  to  a  sickly  or  ill-fed  growth  ?  It  is  the 
carbonic  acid  gas  that  gives  force  to  the  ammonia,  states  Mr.  Mills, 
inasmuch  as  “  ammonic  carbonate  makes  plants  grow  more  vigorously 
than  ammonia  pfr  se.” 
Admitting  the  probable  or  possible  absorption  and  utilisation  by 
green  plants  of  organic  carbon  compounds  from  the  humus  or  decaying 
vegetable  and  animal  remains  within  the  soil,  what  use  are  they  in  the 
economy  of  vegetation  ?  Not  a  particle,  according  to  Mr.  Mills,  but 
rather  a  waste  of  force  in  the  absence  of  ammonia.  If  so,  what  is  the 
value  of  ammonic  carbonate  over  other  forms  of  ammonia  ?  Its 
carbonic  acid.  Of  this  element  the  soil  contains  a  considerable  per¬ 
centage,  as  determined  by  Boussingault  and  Sewy,  and  shown  in  the 
accompanying  table. 
Composition  of  the  air  in  the  soil 
in  100  parts  by  volume. 
Carbonic  acid.  Oxygen.  Nitrogen. 
14 
0-24 
— 
— 
28 
0-79 
19-66  . 
79-55 
57 
0-87 
19-61  . 
79-52 
71 
0-66 
19-99  . 
79.35 
86 
0-74 
19-02  . 
80-24 
172 
1-54 
18-80  . 
79-66 
237 
2-21 
— 
— 
1144 
9-74 
10-35  ! 
79.91 
772 
3-64 
16-45  . 
79-91 
Cubic  feet  of  carbonic  acid  in  Composition  of  air  above  the  soil 
air  over  1  acre  to  height  of  14  inches.  in  100  parts. 
Carbonic  acid.  Oxygen.  Nitrogen. 
12  .  .  0-025  .  20-945  ,  79-630 
Cubic  feet  of  air  in  acre  Cubic  feet  of  carbonic  acid  in 
to  depth  of  14  inches.  acre  to  depth  of  14  inches. 
4,416 
3,530 
5,891 
10,310 
11,182 
41,182 
11,783 
11,783 
21,049 
“  The  percentage,  as  well  as  the  absolute  quantity  of  carbonic  acid, 
is  seen  to  stand  in  close  relation  with  the  organic  matters  of  the  soil . 
The  influence  of  the  recent  application  of  manure  rich  in  organic 
substances  is  strikingly  shown  in  the  case  of  the  Asparagus  bed  and 
the  sandy  soil.  The  lowest  percentage  of  carbonic  acid  is  ten  times 
that  of  the  atmosphere  a  few  feet  above  the  surface  of  the  earth,  as 
determined  at  the  same  time,  while  the  highest  percentage  is  390  times 
that  proportion. 
“  Even  in  the  sandy  subsoil  the  quantity  of  free  carbonic  acid  is  as 
great  as  in  an  equal  bulk  of  the  atmosphere,  and  in  the  cultivated  soils 
it  is  present  in  fiom  six  to  ninety-five  times  greater  amount.  In  other 
words,  in  the  cultivated  soils  taken  to  the  depth  of  14  inches  there  was 
found  as  much  carbonic  acid  gas  as  existed  in  the  same  horizontal 
area  of  the  atmosphere  through  a  height  of  7  to  110  feet. 
“  The  accumulation  of  such  a  percentage  of  carbonic  acid  gas  in 
the  interstices  of  the  soil  demonstrates  the  rapid  formation  of  this 
substance,  which  must  as  rapidly  diffuse  off  into  the  air.  The  roots, 
and,  what  is  of  more  significance,  the  leaves  of  crops,  are  thus  far 
more  copiously  fed  with  this  substance  than  were  they  simply  bathed 
by  the  free  atmosphere  so  long  as  the  latter  is  unagitated. 
“  When  the  wind  blows,  the  carbonic  acid  of  the  soil  is  of  less 
account  in  feeding  vegetation  compared  with  that  of  the  atmosphere. 
When  the  air  moves  at  the  rate  of  2  feet  per  second,  the  current  is 
just  plainly  perceptible.  A  mass  of  foliage  2  feet  high  and  200  feet 
long  situated  in  such  a  current,  would  be  swept  by  a  volume  of 
atmosphere  amounting  in  one  minute  to  48,000  cubic  feet,  and  con¬ 
taining  12  cubic  feet  of  carbonic  acid.  In  one  hour  it  would  amount 
to  2,280,000  cubic  feet  of  air,  equal  to  720  cubic  feet  of  carbonic 
acid,  and  in  one  day  to  69,120,000  cubic  feet  of  air,  containing  no 
less  than  17,280  cubic  feet  of  carbonic  acid. 
“  In  a  brisk  wind,  ten  times  the  above  quantities  of  air  and  car¬ 
bonic  acid  would  pass  by  or  through  the  foliage.  It  is  plain,  then, 
that  the  atmosphere,  which  is  rarely  at  rest,  can  supply  carbonic  acid 
abundantly  to  foliage  without  the  concourse  of  the  soil.  At  the 
same  time  it  should  not  be  forgotten  that  the  carbonic  acid  of  the 
atmosphere  is  largely  derived  from  the  soil.”  —  (Johnson’s  “  How 
Crops  Peed,”  pages  219,  220.) 
The  carbonic  acid  in  the  water  of  soil  does  not  exceed  2  per  cent, 
of  its  volume  of  the  gas.  Granted  that  carbonic  acid  is  imbibed  by 
roots  with  water  and  other  elements  in  solution,  it  follows  that  soils 
containing  much  decaying  vegetable  matter  will  afford  a  more  regular 
supply  of  carbonic  acid,  and  the  vegetation  in  consequence  will  nrofit 
accordingly.  But  is  not  this  due  to  the  ammonia  evolved  and  the 
fertility  of  soil  dependent  thereon  ?  The  more  carbonic  acid  in  a 
soil  the  more  ammonia !  What  of  the  carbon  compounds  in  the  case 
of  bogs,  moors,  and  over-manured  garden  soils  ?  Are  they  “  always 
fertile  ?”  Truly  these  are  poisoned  by  the  acids  termed  ”  humous,” 
which  are  supplied  by  the  decaying  organic  matter  of  the  soil,  and  the 
corrective  is  an  application  of  lime.  Thus  bases  are  needed  to  form 
carbonates,  and  is  it  not  the  base  rather  than  the  carbonic  acid  that 
renders  land  containing  much  decaying  vegetable  matter  fertile  ?  An 
application  of  lime  practically  eats  up  the  carbon  and  generates  both 
ammonia  and  carbonic  acid,  so  that  a  soil  containing  sufficient  decaying 
vegetable  or  animal  remains  to  evolve  a  steady  and  ample  supply  of 
both  ammonia  and  carbonic  acid  is  always  fertile,  other  essential  food 
materials  being  present  and  available  in  adequate  and  corresponding 
measure. 
But  the  value  of  carbonic  acid  gas  as  a  fertiliser  pales  into  insig¬ 
nificance  beside  the  fact  of  o’otaining  gaseous  ammonia  in  the  form 
of  sulphate  at  30s.  instead  of  £40  per  ton.  Really  such  a  fact  is 
almost  too  good  to  be  true,  and  it  is  all  brought  about  by  bringing 
ammonia  in  contact  with  carbonic  acid  gas.  Where  the  ammonia  is 
to  come  from  Mr.  Mills  does  not  explain,  but  the  carbonic  acid  gas  is 
to  be  “  bottled”  from  chimneys,  and  once  it  has  got  into  the  soil  it  will 
spring  therefrom  as  the  pure  article  and  the  sun  will  do  the  rest  in  the 
plant,  but  only  on  the  parts  in  the  atmosphere  or  light. — G.  Abbey. 
