352 
Nitrogen  as  Nitric  Acid,  in  the  Soils 
plots  receiving  the  same  amount  of  ammonium-salts,  as  shown  by 
the  estimates  for  two  years,  as  given  in  our  former  Report,  and 
by  the  composition  of  the  drainage  previous  to  the  soil -sampling, 
as  given  in  Table  VI.  of  the  present  Report ; and  it  is  to  be  sup- 
posed that  more  has  also  passed  below  the  drain-pipes,  and  the 
range  of  the  soil-samples. 
Plots  11,  12,  13,  14,  and  7,  all  receive  400  lbs.  of  ammonium- 
salts,  and  all  the  same  amount  of  superphosphate,  with  the 
addition  of  sodium-salt  to  Plot  12,  potassium-salt  to  Plot  13, 
magnesium-salt  to  Plot  14,  and  sodium-  potassium-  and  mag- 
nesium-salt to  Plot  7.  Thus  the  conditions  of  the  several  plots 
as  to  soluble  matters  within  the  soil  are  very  different.  On 
Plot  11,  with  superphosphate,  there  is  more  produce  than  on 
Plot  10  without  it,  and  therefore  more  crop-residue  ; but  still 
there  will  be  an  excess  of  nitrates  directly  derived  from  the 
ammonium-salts,  compared  with  the  amount  on  either  Plots  12, 
13,  14,  or  7,  where  there  is  considerably  more  growth.  The 
quantity  of  nitrogen  as  nitrate  found  in  the  soil  to  the  depth 
of  27  inches  is,  however,  only  30*8  lbs.,  or  about  the  same 
amount  as  on  Plots  10,  12,  and  14.  But  both  the  previous  and 
the  recent  records  show  a greater  loss  in  the  collected  drainage 
of  Plot  11  than  of  the  other  plots  of  the  series  under  considera- 
tion, and  there  will  doubtless  be  on  the  average  more  loss  below 
the  level  of  the  drains,  and  of  the  range  of  the  soil-sampling. 
Plots  7 and  13,  both  receiving  potash,  yield  the  heaviest  crops 
of  the  series.  If  therefore  the  nitrates  found  to  the  depth  of 
27  inches  depended  wholly  upon  the  amount  of  crop-residue,  we 
should  expect  to  find  the  largest  amount  in  the  soil  of  both 
these  plots.  The  fact  is,  however,  that  the  smallest  amount 
within  this  series  (24'6  lbs.)  is  found  in  the  soil  of  Plot  13,  with 
potassium,  but  without  sodium-  and  magnesium-salts,  and  the 
largest  amount  (39-81bs.)  in  that  of  Plot  7,  with  sodium  and 
magnesium,  as  well  as  potassium-salt  applied.  Even  assuming 
there  may  be  some  error  in  the  actual  figures  (and  by  com- 
parison it  would  be  judged  that  those  for  Plot  13  may  be  too 
low),  the  direction  of  the  difference  is  in  accordance  with 
the  estimates  of  average  loss  by  pipe-drainage,  Plot  13  showing 
more  loss  than  Plot  7 ; whilst  on  the  other  hand,  with  the 
much  higher  amount  of  nitrates  found  in  the  soil  of  Plot  7 at 
the  time  of  sampling,  its  immediately  succeeding  drainage  is 
stronger.  The  conclusion  is,  that  there  is  upon  the  whole  a 
greater  tendency  to  passage  downwards  by  drainage,  and  less  to 
retention  within  the  first  27  inches  of  soil  on  Plot  13  than  on 
Plot  7.  Whether  this  be  due  to  more  free  movement  down- 
wards, with  the  different  conditions  within  the  soil  dependent 
on  the  different  supply  of  saline  matters,  we  have  not  the  means 
