NEW  YORK,  OCTOBER  28,  1916, 
Vol.  T.XXV 
Soil  Fermentation  and  Feeding  of  Crops 
The  Use  of  Sulphur  and  Raw  Phosphate 
1 
Part  I. 
DYNAMIC  SOIL. — Soil  investigators  are  agreed 
that  soil  suitable  for  the  growing  of  plants 
is  in  what  they  call  a  “dynamic”  condition.  They 
mean  to  express  by  this  term  the  thought  that  the 
soil  is  always  in  a  state  of  change.  It  is  never  quite 
dormant,  even  when  frozen.  Invisible  forces  con¬ 
tinue  to  bring  about  more  or  less  extensive  altera¬ 
tions  which  are  of  importance  in  the  growing  of 
crops.  Among  the  forces  which  are  prominent  in 
lending  to  soils  their  dynamic  quality  we  must  in¬ 
clude  the  many  kiuds  of  invisible  plants  and  ani¬ 
mals  commonly  designated  as  micro-organisms. 
ELEMENTS  AFFECTED  BY  MICRO-ORGAN¬ 
ISMS. — Among  the  chemical  elements  directly  affeet- 
In  the  medium  and  heavy  soils  of  Northern  and 
Central  New  Jersey,  analyses  show  the  presence  of 
organic  carbon  up  to  90.000  pounds  per  acre  to  a 
depth  of  eight  inches.  It  may  be  stated,  further, 
that  water-free  vegetable  material  from  any  source 
contains,  roughly,  50%  of  carbon.  Thus,  a  ton  of 
thoroughly  dried  Timothy  liay  contains  about  1000 
pounds  of  pure  carbon. 
CARBON  COMPOUNDS.— The  compounds  con¬ 
taining  carbon  serve  as  food  for  the  soil  micro-or¬ 
ganisms.  In  feeding  on  the  vegetable  residues  in 
the  soil  the  micro-organisms  cause  the  breaking 
down  of  the  carbon  compounds  and  the  formation  of 
an  invisible  gas  known  as  carbon  dioxide  or  car¬ 
bonic  acid  gas.  The  same  gas  is  produced  when 
coal,  charcoal,  wood  or  any  vegetable  or  animal 
substance  is  burned.  The  carbon  dioxide,  when 
dissolved  in  soil  moisture,  forms  a  weak  acid  which 
ta.tion  of  carbon  compounds  in  the  soil  is  utilized  by 
farmers  for  improving  the  texture  and  increasing  the 
supply  of  available  plant  food.  Green  manures,  an¬ 
imal  manures  and  thorough  cultivation  are  effective 
largely  because  they  either  furnish  material  for  soil 
fermentation,  or  stimulate  this  process.  In  a  word, 
then,  tiie  production  of  carbonic  acid  by  micro-or¬ 
ganisms  is  one  of  the  most  important  factors  in  soil 
fertility. 
CHANGES  OF  NITROGEN.— Vegetable  and  ani¬ 
mal  substances  contain  also  nitrogen,  which  may  be¬ 
come  the  source  of  nitrogen  acids.  As  these  vegeta¬ 
ble  and  animal  substances  decay,  they  part  with  a 
portion  of  their  nitrogen,  which  appears  as  am¬ 
monia.  The  ammonia  is  seized  by  certain  soil  bac¬ 
teria  and  is  ultimately  changed  by  them  into  nitric 
acid,  the  same  acid  which  is  found  in  combination 
in  nitrate  of  soda,  nitrate  of  potash  and  other  ni- 
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The  King  Split  Log  Road  Drag  at  Work.  Fig.  554.  See  page  1364 
ed  by  the  activities  of  soil  micro-organisms,  particu¬ 
lar  mention  must  be  made  of  carbon,  nitrogen  and 
sulphur.  In  its  crude  form,  carbon  is  best  known 
to  us  as  anthracite  or  bituminous  coal  or  wood 
charcoal.  In  its  purest  form,  carbon  is  best  known 
to  us  in  the  diamond.  The  element  carbon  exists 
in  cultivated  soils  as  such  only  in  small  proportions. 
On  the  other  hand,  it  is  present  in  very  large  quan¬ 
tities  in  all  good  soils,  and  exists  there,  in  combin¬ 
ation  with  other  chemical  elements,  in  the  so-called 
soil  humus.  The  hitter  represents  the  partly  decayed 
remains  of  plants  and  other  organisms.  In  rich 
bottom  soils  there  may  be  as  many  as  200.000 
pounds  or  more  of  carbon  per  acre,  occurring  in  the 
form  of  humus  and  of  other  vegetable  remains.  For 
instance,  the  black  prairie  soils  of  Illinois  have 
been  found  to  contain  up  to  100.000  pounds  of  or¬ 
ganic*  carbon  per  acre  to  a  depth  of  6  2-3  inches. 
helps  to  attack  the  mineral  compounds  of  the  soil, 
and  to  make  available  for  the  use  of  the  crops  com¬ 
pounds  of  potash,  lime,  sulphur  and  phosphoric  acid. 
It  is  evident,  therefore,  that  the  fermentation  or  de¬ 
cay  of  vegetable  and  animal  substances  in  the  soil 
leads  to  the  formation  of  carbonic  acid  and  of  other 
acids  containing  carbon,  and  that  these  in  turn  at¬ 
tack  soil  compounds  and  help  to  make  them  avail¬ 
able  for  the  production  of  crops. 
PHYSICAL  CHANGES.— Aside  from  the  chemi¬ 
cal  changes  produced  by  carbonic  acid,  there  is  also 
an  important  physical  change  produced  by  it,  since 
the  bubbles  of  carbonic  acid  gas,  as  they  permeate 
the  soil,  lead  to  the  increase  of  the  pore  space  of 
the  soil,  and  make  the  latter  more  open  aiwl  friable 
in  texture.  The  housewife  or  baker  in  making  bread 
utilizes  carbonic  acid  gas  in  the  same  way  for  pro¬ 
ducing  air  spates  in  tlie  dough.  Hence,  the  fermen- 
tiates.  The  nitric  acid  made  by  bacteria  readily 
combines  with  lime  and  other  mineral  substances  in 
:he  soil,  and  helps  to  make  available  thereby  com¬ 
pounds  of  potash,  lime  and  phosphoric  acid. 
SULPHUR  AND  SOIL  ORGANISMS.— Still  an¬ 
other  constituent  of  plant  and  animal  substances  is 
sulphur.  Also  this  constituent  is  changed  by  micro¬ 
organisms  into  acid,  and  is  made  to  render  service 
similar  to  that  rendered  by  carbon  and  nitrogen 
acids  in  making  mineral  and  other  plant  food  avail¬ 
able  to  vegetation.  To  summarize  it  then,  three  im¬ 
portant  constituent  elements  of  vegetable  and  animal 
materials,  viz :  carbon,  nitrogen  and  sulphur,  may 
be  manufactured  into  acids  by  soil  organisms. 
These  acids  then  attack  various  soil  compounds  and 
increase  their  availability  for  plant  growth. 
EFFECTS  OF  SULPHUR.— Soil  bacteriologists 
have  already  contributed  much  interesting  and  help- 
