April  11,  1901. 
JOURNAL  OF  HORTICULTURE  ART)  COTTAGE  GARDENER, 
303 
!,i  Tl}e  manuring  of  Fruit  Trees. 
jggJjBfSJl  .  .  [  n. — Phosphates. 
In  the  manuring  of  fruit  trees  phosphorus  holds  a  place  of 
importance  second  to  none.  In  dealing  with  nitrogenous  manuring 
we  saw  that  nitrogen  was  supplied  in  abundance  in  animal  manures, 
and  that  the  soil  also  received  it  through  the  growing  of  leguminous 
plants.  Besides  these  two  ways,  there  is  a  third  source  from  which 
the  soil  is  enriched  to  a  small  extent  with  nitrogen,  and  that  is  the 
rain,  which  brings  down  4  to  5  lbs.  of  nitrogen,  equivalent  to  |  cwt. 
of  nitrate  of  soda  per  acre  per  annum.  On  the  contrary,  the  soil 
derives  no  phosphates  from  either  of  the  two  latter  sources,  and  not 
very  much  ircm  the  first  ;  for,  as  we  saw,  well-rotted  farmyard  manure 
only  contains  about  5  lbs.  of  phosphates  per  ton.  Hence  the  justifi¬ 
cation  for  the  statement  at  the  beginning  of  this  article.  Besides  the 
lack  of  phosphates  from  which  bo  many  fruit  trees  usually  Buffer  uuder 
the  ordinary  system  of  manuring 
(that  is,  with  farmyard  and  stable 
manures,  not  with  poultry  and 
pigeon  manures,  which  contain 
about  20  and  40  lbs.  of  phosphates 
per  ton  respectively),  a  moment’s 
reflection  will  serve  to  show  what 
an  enormous  amount  of  phosphates 
most  fruit  crops,  especially  stone 
fruit  crops,  abstract  from  the  soil. 
In  bearing  a  heavy  crop,  a  tree 
often  uses  all  the  available  phos¬ 
phate  within  reach,  and  then  has 
to  take  a  year’s  ,rest  while  its 
roots  are  opening  up  fresh  feeding 
ground,  and  more  of  the  phosphate 
within  reach  is  becoming  avail¬ 
able.  With  proper  manuring  and 
judicious  thinning,  it  is  doubtful 
whether  any  fruit  tree  need  miss 
a  season’s  blossom.  Of  course 
frost,  caterpillars,  and  blight  are 
matters  we  are  not  concerned  with 
here. 
Having  looked  at  the  necessity 
of  the  phosphatic  manuring  of 
fruit  trees,  we  must  turn  our  atten¬ 
tion  to  the  different  methods  of 
applying  this  indispensable  food, 
and  firstly  as  to  the  various  forms 
in  which  it  can  be  obtained.  A 
phosphate,  of  course,  is  a  salt,  and 
therefore  formed  by  the  chemical 
union  of  an  acid  and  a  base. 
Phosphoric  acid  is,  unlike  most 
acids,  a  solid  substance,  extremely 
sour  or  acid,  and  it  combines  with 
other  substances,  such  as  potash, 
lime,  ammonia,  alumina  (the  metal 
of  clay),  iron,  &c.,  called  bases,  to 
form  salts  of  these  substances — 
phosphate  of  potash,  phosphate  of 
lime,  &c.  Phosphoric  acid  unites 
with  lime  in  four  different  pro¬ 
portions,  either  one,  two,  three,  or 
four  parts  of  the  latter  to  one  of 
the  former.  One  lime,  or  mono- 
calcic  phosphate,  is  called  super¬ 
phosphate  of  lime.  This  is  acid, 
and  quite  soluble  in  pure  water.  The  phosphates  in  dissolved 
bones  and  dissolved  guanos  are  also  of  this  character.  When  these 
manures  are  applied  to  a  soil  in  which  there  is  a  sufficiency  of  lime, 
the  phosphate  speedily  takes  up  another  part  of  lime,  so  that  there  are 
two  parts  of  lime  to  one  of  phosphoric  acid,  and  then  it  is  known  as 
two-lime,  dicalcic,  or  reverted  phosphate.  This  is  very  soluble  in  the 
soil  water,  but  more  slowly  so  in  pure  water.  Phosphate  of  potash 
and  phosphate  of  ammonia  are  also  of  this  second  phosphate  nature, 
only  that  the  bases,  instead  of  lime,  are  potash  and  ammonia 
respectively.  The  third  kind  of  phosphate,  tricalcic,  or  three-lime 
phosphate,  in  which  there  are  three  parts  of  lime  to  one  of  phosphatp, 
is  the  natural  phosphate  of  coprolites  (before  being  treated  with 
sulphuric  acid  to  make  superphosphate),  bones,  bonemeal,  and  the 
insoluble  phosphates  in  some  guanos.  These  are  quite  insoluble  in 
pure  water,  and  only  slowly  dissolved  by  the  acids  of  the  soil  water, 
the  rain,  and  the  root  sap.  The  fourth  kind  of  phosphate,  in 
which  there  are  four  parts  of  lime  to  one  of  phosphoric  acid,  is  basic 
slag,  or  basic  phosphate,  sometimes  called  Thomas’  phosphate 
powder.  This  is  even  more  slowly  soluble  than  the  last  mentioned. 
It  should  be  explained  that  while  some  of  the  phosphates  of  natural 
guanos,  as  distinct  from  dissolved  guanos,  are  as  insoluble  as  three  and 
four-lime  phosphate,  iu  the  best  guanos ;  on  the  other  hand,  such  as 
the  real  old  Peruvian,  now  very  scarce,  and  that  recently  introduced 
into  this  country  from  Damaraland,  the  phosphates  are  to  a  large 
extent  soluble  in  pure  water,  and  almost  entirely  so  in  the  soil  water. 
A  knowledge  of  the  above  elementary  facts  is  absolutely  necessary 
to  the  intelligent  and  economical  application  of  phosphate  to  the  soil. 
The  difference  in  the  effects  of  nitrogen  and  phosphate  on  trees  is  very 
marked.  Whereas  nitrogen  produces  luxuriant  growth,  phosphate 
induces  fruitfulness  and — as  the  fruit  on  trees  well  fed  with  phosphate 
grows  in  a  more  solid  and  properly  nourished  manner — earlier  ripening. 
The  application  of  a  soluble  phosphate,  like  superphosphate,  is  very 
quick  in  its  action,  the  phosphate  becoming  diffused  through  the  soil 
in  a  more  thorough  manner  than  is  the  case  with  any  other  form  of 
the  same  manure.  The  phosphate  is  dissolved  by  the  rain,  and  as  it 
is  washed  down  into  the  soil  the 
acid  phosphate  unites  with  the 
chalk  in  the  soil,  which  effervesces, 
and  having  lost  its  carbonic  acid 
(chalk  =  lime  +  carbonic  acid)  the 
lime  unites  with  the  phosphate, 
torming  two-lime  or  reverted  phos¬ 
phate.  If  there  is  not  a  sufficiency 
of  chalk  in  the  soil  this  soluble 
phosphate  is  not  so  suitable,  as  the 
acid  is  injurious  to  the  roots  of 
many  plants.  In  that  case,  the  form 
of  phosphate  to  use  is  basic  slag. 
As  stated  above,  this  is  only  very 
slowly  soluble  in  the  weak  acids  of 
the  soil,  the  rain  water,  and  the 
root  sap  ;  and  even  to  be  so  far 
soluble  it  is  necessary  that  it  should 
be  as  finely  ground  that  90  per 
cent,  of  it  can  pass  through  a  sieve 
with  10,000  holes  to  the  square 
inch.  Much  worthless  stuff  is  sold 
under  this  name.  Dr.  Voelcker,  the 
analyst  to  the  Royal  Agricultural 
S.clety,  stated  some  time  ago  that 
out  of  twenty-two  samples  sub¬ 
mitted  to  him  for  analysis,  fifteen 
were  below  the  guaranteed  standard, 
either  in  grinding  or  analysis,  or  iu 
both. 
Where  soils  are  deficient  in 
lime  and  rich  in  humus,  as  much 
garden  soil  is,  this  is  the  very 
best  thing  to  apply,  as  the 
carbonic  acid  given  off  by  the 
breaking  down  or  decomposition  of 
the  humus  dissolves  the  phosphate, 
which  thus  supplies  both  phos¬ 
phate  and  lime.  But  whereas 
superphosphate  can  be  applied  in 
the  spring,  and  produces  immediate 
results,  basic  slag  must  be  applied 
in  the  autumn  or  early  winter,  or 
its  effects  will  not  be  seen  till 
after  another  season.  Where  the 
soil  is  not  very  chalky  and  not 
very  rich  in  humus,  just  medium 
soils  in  fact,  fruit  trees  derive  great 
benefit  from  an  application  of  basic 
slag  in  the  autumn  at  the  rate  of  10  or  12  lbs.  per  40  square  yards 
(10  or  12  cwt.  per  acre),  followed  by  a  dressing  of  “  super  ”  in  the  spring 
at  the  rate  of  4  or  5  lbs.  to  the  same  area.  There  is  no  doubt  it  is  of 
the  highest  importance  that  trees  should  have  a  dressing  of  phosphate 
every  year.  Perhaps  the  ideal  system  of  manuring  would  be  a  liberal 
application  of  poultry  or  pigeon  manure,  well  rotted,  every  alternate 
year,  the  basic  slag  and  superphosphate  method  advocated  above  being 
adopted  the  other  year.  The  trees  would  thus  receive  a  dressing  of 
phosphate  every  year,  with  the  addition  of  nitrogen  and  potash 
alternate  years.  If  the  soil  was  very  chalky  of  course  the  basic  slag 
would  be  dispensed  with,  the  dressing  of  superphosphate  in  the  spring 
being  proportionately  increased. 
It  may  be  well  to  mention  here  certain  rules  as  to  the  mixing  of 
artificial  manures,  as  many  people  sustain  serious  loss  through  ignorance 
of  them.  Nitrate  of  soda  must  never  be  mixed  with  superphosphate 
cf  lime,  as  chemical  action  takes  place,  resulting  in  the  formation  of 
phosphate  of  soda  and  nitric  acid,  which,  being  volatile,  goeB  off  into 
the  air.  Sulphate  of  ammonia,  on  the  other  hand,  can  be  mixed  with 
Hidalgoa  Wkrcklei. 
