728 
Supplement  to  the  “ Tropical  Agricult nri!^t'‘ 
[April  1,  1890. 
done,  and,  unfortunately  al.^o  by  tlie  arrears  wliieli 
accumiilato. 
Tlm.se  wlio  deny  any  valu,.-  to  soil  analysis  found 
their  objections  upon  the  means  at  present  at  our 
di.s])Osal  in  ihe  laboratory  of  reproducing  the  na- 
tural condition  of  affairs  going  on  witliin  the  soil; 
in  other  words,  tliey  argue  that  ,ve  c.inimt  say 
what  quantity  of  any  given  ingredient  is  in 
a condition  in  wliich  it  can  he  assimilated  by 
the  plant. 
Let  us  lu!ar  wliat  M.  Yille  says  on  the  sulqect  : 
“ Chemistry  is  powe.dess  to  throw  light  upon  the 
agricultural  qualities  of  tliesoil,  its  resources  and 
its  needs,  heca'use  it  confoumls  in  its  indications 
the  active  assimilable  agents  with  tlie  assimilable 
agents  in  reserve,  the  active  with  the  inert  and 
neutral  princii>les.” 
This  is  the  conclusion  he  arrives  at  from  the 
discussion  of  analy.ses  which  give  the  percentage 
composition  of  the  soil  together  with  the  so-called 
mechanical  analyses,  the  proportions  of  .sand,  clay, 
gravel,  &c.  M.  Anile  further  points  out  that  e.x- 
traction  with  water  yields  results  no  less  un- 
satisfactory, since  the  plant  is  able  to  utilise 
soil  material  which  is  insoluble  in  water. 
In  order  to  remedy  this  evil,  the  existence  of 
which  1 suppose  no  one  will  be  hardy  enough  to 
deny,  various  methods  have  been  suggested  and 
tried  with  the  object  of  attacking  tlie  soil  in  a 
manner  representing  as  nearly  as  pos.sible  the  ac- 
tual conditions  which  prevail  in  a field  under 
cultivation.  A few  such  reagents  may  be  men- 
tioned ; they  include  water  saturated  with  carbo- 
nic acid,  oxygenated  water,  acetic  acid,  citric  acid, 
and  different  salts,  such  as  ammonium  citrate. 
In  a recent  series  of  researches  Dr.  Lernard 
Dyer*  has  experimented  with  a 1 percent  solu- 
tion of  citric  acid,  which  appears  to  approach 
closely,  in  its  action  upon  the  soil,  the  solvent 
power  e.xerted  by  the  acid  secreted  by  the  roots  of 
certain  plants.  1 venture  to  think  that,  notwith- 
standiiH'  the  great  scientific  value  of  such  a line 
of  investigation,  and  of  the  light  it  may  be  ex- 
pected to  throw  upon  many  obscure  functions  of 
plant-life,  it  leaves  us  pretty  niuch  where  we 
were  it  we  attempt  to  base  upon  its  use  any  jnac- 
tical  advice  to  the  farmer  as  to  the  nature  of  the 
manures  or  other  treatment  his  soils  requires. 
I am  prepared  to  go  a step  further  than  iM.  Ville, 
and  to  say  not  that  we  are  unable  to  reproduca 
the  agents  at  work  within  the  .soil  in  supplying 
thejilant  with  food,  but  that  we  should  gain  very 
little  from  an  ec.anomic  point  of  view  if  we  were 
possessed  of  them. 
For,  let  ns  assume  that  the  “ universal  .solvent” 
has  been  found,  that  we  are  possessed  of  a reagent 
which  exercises  the  same  solvent  action  on  the  soil 
as  let  us  say,  a wheat  crop  ; in  other  words,  one 
that  dissolves  from  the  soil  the  same  amount  of 
mineral  and  nitrogenous  matter  a.s  the  wheat  crop 
will  extract  during  the  period  of  its  growth.  We 
are  met  with  the  following  difficulties:  — 
Our  wheat  crop,  though  it  contains  le.ss  nitro- 
gen Isay,  one-third  less)  than  a crop  of  turnips, 
will  nevertheless  benefit  very  much  more  than  the 
latter  by  an  application  of  nitrogenous  manure  ; 
that  is  to  say,  the  wheat  crop  cannot  make  the 
.same  n.se  of  the  nitrogen  in  the  soil  as  the  turnip 
■p,i,3_exercises,  in  fact,  a different  .solvent  act. on 
upon  the  nitrogenous  constituent.-^. 
• Journal  of  the  Chemical  Society,  Maach,  1891. 
<Ir,  since  the  nitrogen  in  the  .soil  is  continually 
changing  its  condition,  and  there  are  external 
sources  of  nitrogen  which  may  have  som.^  he.iring 
in  the  above  instance,  we  may  take  a case  which 
is  even  h;ss  ambiguous. 
'J'he  mangel  crop  reniove.s  from  the  soil  nearly 
double  as  much  phosphoric  acid  as  the  turnip  crop 
doe.s;  nevertheless,  manuring  with  siqierphosphate 
is  of  less  henelit  in  the  case  of  mangels  than  with 
turnips,  the  recognised  reason  being  that  mangels 
are  able  to  utilise  the  phosphoric  acid,  as  it  exists 
iti  the  soil,  to  a greater  extent  than  turnips.  So 
that  it  will  be  necessary  for  us  to  devise  one  sol- 
vent for  t urnips  and  .another  for  mangels,  one  for 
phosphoric  acid  and  one  for  potash — a separate  set 
of  solvents  for  every  crop;  and  such  a scheme,  if 
it  wore  feasible,  would  be  far  too  cumbersome  for 
practical  jmrposes. 
A second  objection  lies  in  the  fact  that  the 
agencies  at  work  within  the  soil  are  unceasing,  and, 
as  a consequence,  the  combinations  in  which  the 
nitrogen  and  mineral  matter  exi.sts  are  also  con- 
stantly changing.  What  is  true  of  the  chemical 
constitution  of  the  soil  today  is  no  guide  as  to  its 
constitution  a week  hence. 
The  determination,  especially  of  the  quantities 
of  nitrates,  of  amnnniura  compounds,  and  of  “or- 
ganic” nitrogen,  jirovides  us  with  no  information 
to  the  purpose,  for  these,  of  all  soil  constituents, 
are  most  rapid  in  their  changes. 
Further  (lifficnlties  present  themselves  in  the 
large  quantities  of  soil  wh.ich  it  is  necessary  to 
enqiloj  in  the  determination  of  the  substances  so- 
luble in  w.itiM’and  weak  acids,  and  the  consequent 
length  of  time  r('(|uii'ed  f->r  eaeli  determination,  and 
also  in  the  initial  difficulty  which  presetits  itself  in 
all  soil  analysis  of  ensuring  the  jiroper  selection  of  a 
sample  which  shall  represent  anything  but  itself. 
This  di fficulty,  which  is  felt  in  all  attempts  to 
judge  of  the  character  of  a soil  from  a given  sam- 
ple, ajiplies  more  particularly  to  a chemical  ana- 
lysis, and  increases  in  proportion  as  the  quantities 
of  the  estimated  substances  diminish. 
A chemical  analysis  alone,  th.jrefore,  is  of  little 
value  in  guiding  tlie  farmer  a.s  to  the  reipiirements 
of  his  soil,  and  it  is  not  in  the  refinement  of  chemi- 
cal methods  that  we  m-iy  lo.ok  for  itelp  in  this  di- 
rection. We  shall,  1 believe,  obtain  much  more 
valualile  information  if  we  c:in  ascertain  the  con- 
ditions under  which  the  fertility  of  the  soil  is 
maintained. 
The  fertility  of  a soil  dejiends  in  the  first  place 
upon  the  presence  of  a sufficiency  of  plant  foml, 
and  secondly  upon  certain  jiroperties,  possessed 
more  or  less  by  all  soils,  which  effect  the  splitting 
up  of  the  mineral  ingredients  in  such  a manner  as 
to  render  them  available  to  ])lants,  as  well  as  re- 
gulating thosnpi  ly  of  water,  air,  warmth,  kc. 
We  shall  discuss  the  most  important  of  these 
projierties,  and  shall  find,  I think,  that  they  are 
c-ipable  of  identification  in  the  la'.ioratory. 
large  number  of  those  pr.iperties  conducive  to 
fertility  are  dependent  upon  the  porosilj-  of  the 
soil— in  other  words,  its  fineness  of  texture. 
(To  be  concluded  in  ne.ct  m«c.) 
IIOUSFIIOLD  HINTS. 
Some  of  t he  most  beautiful  grasses  and  ferns 
for  home  decoration  may  be  made  as  follows  : — 
I ’lice  a sin  ill  saucepan  partly  filled  with  water  on 
