403 
It  would  seem  a simple  matter  when  fields  are  properly  prepared 
to  apply  sufficient  quantities  for  the  needs  of  cultivated  plants,  but 
although  we  have  been  practicing  this  art  for  half  a century,  we 
have  not  yet  learned  the  whys  and  the  wherefores.  Perhaps  the 
chief  difficulty  which  has  arisen  to  prevent  the  improvement  of 
methods  consists  in  the  wide  varieties  of  soil  and  crops  and  our 
lack  of  knowledge  of  the  needs  of  the  plants.  If  the  plants  could 
only  talk  and  tell  us  when  they  are  suffering,  we  could  do  much 
better  but  our  methods  are  still  extremely  crude  in  determining 
the  amount  of  moisture  in  soil,  the  amount  required  by  the  plant 
and  the  stages  when  it  is  beginning  to'  suffer  from  drought.  In 
attempting  to  apply  water  we  have  little  knowledge  of  the  quanti- 
ties needed  by  the  crop  at  particular  times  and  of  the  proper  time 
of  application.  There  is  a wide  field  for  investigation  along  this' 
line  and  it  must  be  carefully  studied  before  it  can  be  said  that  we 
have  laid  the  foundation  of  scientific  irrigation. 
The  duty  or  service  which  water  can  perform  in  irrigation  has 
always  been  given  a prominent  place.  It  was  so  in  the  early  days 
when  water  was  both  cheap  and  abundant  and  its  importance  has 
increased  as  water  has  become  scarcer  and  of  greater  value. 
There  is  so  much  more  irrigable  land  in  the  West  than  can  ever 
be  irrigated  that  much  of  our  agricultural  development  in  the 
future  will  hinge  on  the  amount  of  water  required  for  irrigation. 
The  subject,  as  you  know,  is  one  which  reaches  out  into  many 
branches  of  irrigation.  We  may  measure  the  water  as  it  is  diverted 
front  the  natural  streams  and  obtain  what  is  called  the  gross  duty 
of  water.  We  may  measure  it  at  the  head  of  a lateral  and  deter- 
mine the  duty  of  water  under  laterals.  We  may  measure  it  at  the 
margin  of  a field  and  find  out  the  amount  of  moisture  applied  to 
the  soil,  or  we  may  study  the  crop  and  find  out  its  requirements 
as  regards  duty  of  water.  You  will  be  pleased  to  know  that  water 
has  now  a much  higher  duty  throughout  the  West  than  it  had  for- 
merly. Largely  through  the  efforts  of  the  Irrigation  Investiga- 
tions of  the  Office  of  Experimental  Stations,  U.  S.  Department 
of  Agriculture,  excessive  uses  of  water  have  been  measured  and 
pointed  out  and  as  a result  better  crops  are  now  grown  with  much 
less  water.  There  is,  however,  great  , need  of  continuing  these 
investigations,  since  we  find  that  the  average  duty  of  water  over 
two-thirds  of  a million  acres  of  land  was  recently  shown  to  be  4^ 
feet  per  acre.  Assuming  an  average  rainfall  of  15  inches,  this 
would  represent  a total  of  6 feet  of  water  in  depth  over  the  sur- 
face. A considerable  part?  of  this  is,  of  course,  wasted  before  it 
reaches  the  field  but  an  effort  has  been  made,  as  I have  previously 
stated,  to  reduce  transmission  losses  as  much  as  possible. 
The  people  of  Southern  California  have  demonstrated  that  ex- 
cellent crops  of  all  kinds  can  be  obtained  with  the  use  of  3 inches 
of  water  per  month,  including  both  irrigation  and  rainfall.  This 
is  a district  in  which  plants  grow  practically  the  year  through  and 
in  which  evaporation  losses  are  high.  If  such  results  can  be 
obtained  in  Southern  California,  considerably  less  water,  if  applied 
