368 
ivVov.  I,  180.^ 
Supplfimfi}if  to  f/w  “ TrophyU  Af/riculhirifft/' 
145  Baftsia  fnlva.  Wana-ini. 
14G  Mimiisops  olenj^i.  Mimainal. 
147  ,,  hexandra.  Palu. 
SO  Ehenacea*. 
147(«)  Malia  liuxifolia. 
148  Diospyros inontana. 
,,  eniljryopteris 
149 
150 
151 
152 
15:i 
151 
155 
166 
83 
157 
84 
158 
159 
160 
SO 
161 
162 
Kalu-habaraliya. 
fiiiiliiri. 
oval  i folia, 
ebenuin. 
oocavpa. 
liiii'd  lei'i. 
Kalnwara. 
Kalu-kadumlienya. 
Kaluiiiberiya. 
( ioiia,  Porua-malla,  Wal- 
inediiiya. 
,,  tliwaite.^ii.  Uo-mediiiya. 
,,  cnimeiiatii, 
Salvadoracea*. 
Salvadora  persio.i.  Mustard  tree. 
Apocynaceio. 
Ocliio.sla  borbonica.  Mudii  kaduni, 
Alstoiiia  scholaris.  Kuk-attaua. 
Wi'ightia  angustifolia. 
Loganiacaa*. 
Strychnos  nux-vomica.  (!oda-kadiini, 
' ,,  potatonuu.  Iiigini. 
00  Bignoniaceat. 
163  Stereosperiiuim  cbeloniobles.  l.unu-niadalu, 
00  Verbenaeea; 
164  Tectoiia  grandis.  'I'ekka.  Teak- 
165  Premiia  tomentosa.  Bu-seru. 
166  Vitex  tritolia. 
167  ,,  alti.ssiina.  Milila,  Milla,  Sapu-nuhla. 
168  ,,  Beucoxylou.  Nebedda. 
THE  FERTILITY  OP  SOILS. 
(PROFKSaOB  KIXOH.) 
Tne  fertility  of  a soil  i.s  partly  dependent  on  its 
chemical  composition,  but  also  partly  on  its  me- 
chanical and  physical  condition.  Its  productive- 
ness is  influenced  very  largely  by  its  environments 
of  climate  and  weather.  Upon  the  size  ofvthe  pre- 
vailing particles  in  a soil  its  physicl  properties, 
and  therefore  its  fertility,  largely  depends ; the 
actiuil  toUl  number  of  particles  amount  to  many 
millions,  or  even  hundreds  of  millions,  per  grain 
weight  of  soil.  When  the  size  of  the  particles  is 
large,  goo.i  crops  can  only  be  grown  with  the 
copiouo  addition  of  manures,  especially  those  con- 
taining oi’gauic  matter,  or  by  means  of  irrigation. 
Grass  grows  svell  in  soils  with  very  rtne  particles. 
The  coarser  particles  of  the  soil,  including  sand, 
have  little  cohesion,  and  little  power  of  holding 
water.  A gravelly  or  sandy  soil  is  therefore  easy 
to  work  with  a plough,  as  its  tenacity  is  low  ; it  is 
dry,  as  it  holds  little  water,  and  that  is  readily  eva- 
porated; it  is,  under  most  condition.®,  warmer  than 
a clayey  soil  ; it  has  some  advantages  for  market 
gardening.  Soils  containing  very  line  particles  and 
clay  are  tenacious,  and,  as  such,  stiff ; they  retain 
much  more  water  than  sandy  soils,  and  do  not  dry 
so  readily  ; their  capillary  power  is  greater;  they 
are  colder  than  sandy  soils.  Soils  having  very 
much  the  same  ultimate  chemical  composition 
might  be  in  either  of  these  categories,  according 
to  the  fineness  of  their  particles.  Both  sandy  and 
clayey  soils  are  imp>-oved  by  the  addition  of  humus, 
the  decaying  organic  matter  of  the  soil.  In  sandy 
soils  it  holds  together  or  cements  the  .soil  particles  : 
it  increases  their  posverof  holding  w.y.er  and  their 
power  of  absorbing  water  from  the  air,  and  so  ren- 
ders them  less  liable  to  be  burnt  up  in  dry  weather, 
orminic  matter  added  to  clay  diminishes  its 
coherence,  and  makes  it  more  easily  worked  ; the 
ameliorating  effects  of  long  dung  on  heavy  clay 
are  well  known.  Humus  has  a greater  power  even 
than  clay  of  absorbing  water.  Humus  not  only 
exerts  important  effects  of  a iihysical  nature,  but 
it  is  important  from  a chemical  point  of  view  as 
a storehouse  of  the  most  valuable  constituent  of 
plant  food.  The  g-ood  projierties,  and,  therefore, 
the  fertility  of  a soil,  are  increased  by  the  pre- 
sence in  it  of  easily  decomiiosable  compound  sili- 
cates, which  exert  an  influence  on  its  absorptive 
powers  for  some  of  the  important  ingredients  of 
plant  food. 
iSoraetime.s  it  is  necessary  to  distinguish  between 
what  may  be  called  the  inherent  and,  to  some  ex 
tent,  permanent  fertility  of  the  .soil,  and  its  tem- 
porary fei'tiliy  oi  high  agricultural  “ condition" — 
which  latter  has  been  brought  about  by  the  care, 
skill,  and  capital  of  the  cultivator,  and  which  he 
can  to  a large  extent  remove  in  hi.®  crops.  The 
inherent  fertility  is  much  more  difficult  to  remove, 
and  only  very  slowly  disappears  under  adverse 
circumstances;  upon  it  the  amount  of  the  rent  of 
land  depends  to  a considerable  extent. 
CHE.MICAl.  CO.XIUTIOXS  OF  FKllTILITY. 
I’lants  obtain  from  the  soil  all  the  ash  consti- 
tuents they  contain,  and  most  plants  obtain 
thence,  also,  the  nitrogen  they  require  for  their 
growth.  It  follows  that  if  the  most  important 
chemical  constituents  of  a soil  are  nitrogen,  phos- 
phoric acid,  potash,  and  lime,  the  soil  to  be  fer- 
tile must  not  only  contain  these  constituents, 
amongst  others,  in  a good  proportion,  but  they 
must  be  in  a form  in  which  they  are  available  to 
the  plant  as  food.  If  they  are  locked  up  in  a 
totally  insoluble  form,  they  might  be  jireisent  in 
the  soil  in  large  amounts  and  yet  the  soil  be  abso- 
lutely sterile.  A soil  to  be  fertile  must  also  bo 
free  from  poisonous  and  injurious  matter — such 
as  decomposable  sulphides,  excess  of  ferrous  salts, 
excess  of  saline  matter,  especially  of  common  .salt, 
and  even  from  too  large  a quantity  of  acid  organic 
matter.  But  the  actual  fertility  of  a soil,  as  far 
as  it  can  be  mea.®ured  by  chemical  means,  is  de- 
pendent mainly  on  the  amount  and  the  conditions 
of  the  four  ingredients — nitrogen,  phosphoric  acid, 
])otash,  and  lime. 
It  has  been  .seen  tor  many  years  that  ol  anj’  one 
factor  making  up  the  fertility  of  a .soil  the  ni- 
trogen is  the  most  important.  The  nitrogen  of  a 
soil  is  almost  entirely  contained  in  the  organic 
matter  or  humus,  which  consists  of  the  residues 
of  previous  races  of  plants  which  have  grown  in 
the  soil  and  decayed  there.  Sir  John  Lawes  has 
pointed  out  more  than  once  that  “ fertility  is  due 
to  the  organic  residue  of  previous  generations  of 
plants,  mixed  with  certain  mineral  substances,  the 
most  important  of  which  are  phosphoric  acid  and 
pota.sh.”  Lawes  mid  Gilbert,  in  a paper  read  to 
the  Chemical  Seciety  in  188-5,  also  state  that  “ not 
only  the  facts  adduced  in  this  and  former  papers, 
but  the  history  of  agriculture  throughout  the  world, 
so  far  as  it  is  known,  clearly  shows  that,  pre- 
eminently so  far  as  the  nitrogen  is  concerned,  a 
fertile  soil  is  one  which  1ms  accumulated  within 
it  the  residue,  of  ages  of  natural  vegetation,  and 
that  it  becomes  infertile  as  this  residue  is  e.x- 
hausted.’’  A soil  rich  in  humus  is  rich  in  nitrogen, 
tlvmgh  the  one  is  not  an  exiet  measure  of  the 
other,  as  the  percentage  of  ni  rogen  in  humus  is 
somewhat  variable.  Also,  this  nitrogen  is  not  all 
equally  valuable  to  the  pl.int.  Some  of  it.  may 
be  in  a form  in  which  it  soon  becomes  assimilable, 
