26  The  Production  of  Plant  Food  in  the  Soil. 
in  the  Bordeaux,  Champagne,  and  Bourgogne  districts  where 
high-class  varieties  are  grown,  and  also  in  Sicily.  Rather  more 
than  half  an  ounce  per  square  yard  is  used  to  keep  the  pest  in 
check,1 2  but  six  to  eight  ounces  are  needed  for  the  traitement 
d' extinction  still  practised  in  Algeria  and  Switzerland.'  It 
has  long  been  observed  that  the  treatment  increases  the 
productiveness  of  the  soil,  the  carbon  disulphide,  especially  in 
the  larger  doses,  having  all  the  effect  of  a nitrogenous  manure. 
Two  Italians,  Gavazza  and  Yassallo,  put  this  on  record  in  1884, 
but  the  first  statement  to  attract  much  attention  came  ten  years 
later  from  Oberlin,  an  Alsatian  vine  grower.  At  this  period 
also  Girard  in  France  used  carbon  disulphide  to  clear  a piece 
of  ground  on  which  nematodes  had  ruined  several  crops  of 
sugar  beet,  with  the  result  that,  not  only  were  the  nematodes 
killed,  but  the  productiveness  of  the  soil  increased.  He 
experimented  also  with  other  crops,  and  on  several  farms 
between  1888  and  1892  obtained  crop  increases  varying  from 
5 to  150  per  cent.,  but  usually  about  20  to  30  per  cent.  Similar 
results  are  recorded  elsewhere  with  carbon  disulphide  and  also 
with  other  antiseptics. 
These  observations  are  readily  explained.  The  antiseptic, 
like  heat,  kills  the  injurious  factor,  leaving  a clear  field  for 
the  useful  bacteria.  This  particular  method  of  killing  may 
not  be  practicable  in  agriculture,  but  it  ought  not  to  be  beyond 
the  wit  of  man  to  devise  one  that  is.  Indeed  there  seems  some 
prospect  of  something  of  the  kind  being  done  in  certain  special 
branches  of  horticulture,  &c.,  and  from  the  experience  thus 
gained  a farming  method  may  be  evolved.  This,  however, 
is  not  the  final  problem.  Soil  investigators  are  now  aiming 
at  a fuller  knowledge  of  the  changes  going  on  in  the  soil  and 
the  agents  producing  these  changes,  so  as  to  control  them 
and  get  the  most  out  of  the  soil  and  of  the  organic  matter  and 
other  manures  put  into  it.  For  some  time  to  come  investiga- 
tions on  the  soil  must  be  judged  by  the  extent  to  which 
they  contribute  to  this  end. 
E.  J.  Russell. 
Rothamsted  Experimental  Station, 
Harpenden,  Herts. 
1 200  to  300  kilos  per  hectare. 
2 2,000  to  3,000  kilos  per  hectare. 
