It  is  evident  that  the  conditions  that  produced
the  humus  w.ill  restore  it.  Seeding  to  grass,  clover
or  alfalfa  has  a  wonderful  effect  in  improving  the
water-holding  power  of  the  soil.  Seeding  down  is.
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SOILS  OF  THE  GREAT  SEMI -ARID  REGION


however,  little  practiced  because  of  the  difficulty
in  getting  the  crop  started  in  much  of  the  semi-arid
region,  and  a  disinclination  on  the  part  of  farmers
to  plow  up  such  a  valuable  crop.
Another  useful  feature  of  the  humus  is  its
property  of  making  plant-food  more  readily  avail-
able to  the  plant.  A  drift  or  loess  soil,  when
new,  will  frequently  contain,  in  combination  with
organic  matter,  800  pounds  of  potash  and  1,200
pounds  of  phosphoric  acid  in  an  acre  of  soil  one
foot  deep.  A  similar  soil  under  continuous  cultiva-
tion for  a  few  years,  will  frequently  contain  only
half  as  much.
The  use  of  barnyard  manure  will  also  serve  to
form  humus,  but  in  the  wheat-raising  sections
relatively  few  cattle  are  kept,  and  in  the  corn-
growing  section  the  cattle  are  usually  fed  in  yards
from  which  the  manure  is  not  easily  collected.
Thus  it  is  that  little  manure  is  applied  to  the  land.
Tillage  in  general, — Tillage  in  the  semi-arid
region  presents  some  phases  that  are  essentially
different  from  those  in  the  humid  section  of  the
country.  The  properties  of  the  soil  which  allow  of
such  abundant  aeration  make  it  desirable  to  pay
fully  as  much  attention  to  compacting  the  soil  as
to  stirring  it.  Otherwise,  the  large  openings  in  the
soil  allow  it  to  dry  out  rapidly.
