The free lance. (Fredericksburg, Va.) 1885-1926, 1907-01-15
VALUE OF CROP ROTATION
ON THE FARM

Suppose five year rotation is
practiced on a given farm. Let this
rotation consist OF corn yielding 30
bushels per acre, crimson clover yielding
T. tons per acre, Irish potatoes yielding
POO bushels per acre. wheat yielding .
bushels per acre, timothy hay yielding
Il. tons per acre and running for two
years. The problem is to find out the
amounts of plant food removed by the
various crops The corn with the stOver
would take - pounds OF nitrogen, ID
pounds of phosphorus and 40 pounds
of potassium; the crimson clover 90
pounds of nitrogen. Ii pounds Of
phosphorus and 60pounds ofpotassium;
the Irish potatoes "a pounds ofnitrogen,
20 pounds OF phosphorus and IS pounds
of potassium; the wheat with the straw
% pounds of nitrogen, IL pounds OF
phosphorus and If pounds OF postas-
stun; and timothy hay 76 pounds OF
nitrogen, 30 pounds OF phosphorus and
80 pounds OF potassium. In five years
there would be taken from the soil by
this system of cropping 23S pounds OF
nitrogen, 81 pounds Of phosphorus and
204 pounds OF potassium. Suppose
however, that the crimson clover crop
is plowed under. There would be- 60
pounds OF nitrogen added to the soil
presumably taken from the air az crimson
clover is q leguminous crop and has the
power of assimlating atmospheric
nitrogen through the heterogeneous
which resHle in the nOdules growing on
its roots under favorable conditions.
There will be Ii pounds OF phosphorus
and 66 pounds Of potassium more in the
soil than would have been there II the
crimson clover had been cut for hay and
removed entirely from the land. Under
these favorable conditions there would
still be 11s pounds OF nitrogen, n
pounds of phosphorus and 22S pounds,
of potassium removed from the soil in
five years. Follow this practice up 30
years. and we find that $500 pounds OF
nitrogen, $3.50 pounds OF phosphorus
and II 400 pounds OF potassium will
have been removed from the coil by this
system of crop rotation. Is it any
wonder that the land should become
exhausted under these conditions. aud
yet this is not overdrawing condition
which has prevailed on many farms.
lt will be argued by some that a large
per cent OF the fertilizing material con
tained in these crops has been returned
10 the land. This might be true on a
stock or dairy farm, but on thousands OF
farms where clean culture has been prac
ticed comparatively little has been re-
turned to the soil. Suppose, however,
that half of all the elements removed by
this system of crop rotation has been re-
turned TO the soil. There would still be
,450 pounds OF nitrogen, | ,92j pounds
of phosphorus and ,, 700 pounds OF po-
tassium to account for The needed
nitrogen can be obtained from the cir
through the growth OfleguminOus crops,
but the supply OF phosphorus and po-
tassium removed from the soil would re-
quire an application each year OF 800 to
500 lbs. OF phosphoric acid, and 800 to
900 pounds Of sulphate of potash.
Suppose. however, that the soil through
the stores which nature has provided
can supply & of the needed elements OF
plant food, il is still evident that an
application OF from 100 To 200 pounds
OF acid phosphate. and 30 to l00pounds
of sulphate or muriate OF potash would
be necessary to MAINTAIN the land in
good condition for crop growing.
Andrew NJ. Soule. Director.