yAT t YYYTTT Published Weekly by The Rural Publishing Co., 
' 333 30 th g t . New York. Price One Dollar a Year. 
NEW YORK, AUGUST 9, 1924 
Entered as Second-Class Matter, June 2. 1870, at tlio Post 
Office at New York, N. Y., under the Act of March 3, 1879. 
NO. 4807 
Discussion of a System of Keeping, up Fertility 
HE HOPKINS PLAN—On page 9(!4 you 
express doubts as to whether the “Hopkins 
method” of using limestone and ground 
phosphate rock, etc., will fit the practice 
of eastern farmis. I would like to know 
about the methods used which seem to 
prove (in the long run) that acid phosphate is more 
profitable than the natural ground rock. My idea 
is that it depends on whether immediate increased 
yields are required as against those of a permanent 
condition and increasing fertility. I was born and 
raised on a farm in Northeastern Illinois and al¬ 
though only about one-third of my 68 years were 
spent in active farm work, I have followed reports 
and observed experiments rather closely, and am 
fully satified that the Hopkins method of restor¬ 
ing and maintaining soil fertility will apply in any 
region where grain or live stock is the principal 
product. The foundation of his plan is to obtain 
and keep up a balanced ratio .of plant foods suffi¬ 
cient for a full crop each season. 
SOIL COMPOSITION.—The native composition 
of about 25 different soils of Illinois shows by aver¬ 
age analysis to vary in the surface soil, 0 to 7 inches, 
as follows: 
Lbs. 
Nitrogen— per acre 
Central Illinois timber. 1,870 
Northeastern prairie. 8,900 
Phosphorus— 
Northeastern timber . 810 
Central prairie . 2,030 
Potassium- 
Deep peat . 2,930 
Northeastern timber . 47,600 
Assuming the average amount of mineral plant 
food that becomes available (during a growing sea¬ 
son under ordinary tillage), to be two per cent of the 
nitrogen, one per cent of the phosphorus and one- 
quarter per cent of the potassium, we find that the 
Central Illinois timber soils would liberate annually 
37 lbs. of nitrogen while the northeastern prairie 
could liberate 178 lbs. Of phosphorus S lbs. annually 
available from northeastern timber soils, and 20 lbs. 
from the central prairie soils. The amount of pot¬ 
assium available yearly would be deep peat 7 lbs. 
and from northeastern timber soils 119 lbs. per 
annum. The amount of these elements removed per 
acre annually under full crop production will ap¬ 
proximate 150 lbs. of nitrogen, 20 lbs. of phosphorus 
and 70 lbs. of potassium. Under such a removal 
corn should yield, in favorable season and climate, 
100 bushels per acre, and the Illinois corn belt fre¬ 
quently does so; if however a full crop is received 
annually for 50 years and one-half of the phos¬ 
phorus removed, then one per cent of the remaining 
1000 lbs. will limit the yield to 50 bushels per acre, 
and some of the best Illinois farmers have reached 
that limit. With the exception of deep peat nearly 
all Illinois soils have sufficient potassium to liberate 
the annual needs for a full crop. 
THE NEED OF PHOSPHORUS.—As nitrogen 
varies widely outside of its availability, it appears 
that phosphorus is the controlling element, and to 
put the soil in full crop condition the quantity should 
be increased to 2000 lbs. of actual phosphorus and 
kept there. As none of the Illinois timber soils have 
naturally scarcely 1,000 lbs. of phosphorus and onlv 
a few prairie soils over 1200 lbs., we find the main 
part of the State has always been deficient in phos¬ 
phorus. However the residues of crops and man¬ 
ures have restored perhaps one-third of the annual 
removals. It would take 10 tons of fresh manure 
per acre yearly to replace 20 lbs. of phosphorus re¬ 
moved in the 100-bushel corn crop. When grain only 
is sold from farms there are nearly equal propor¬ 
tions of phosphorus and potassium carried away, 
This is a picture of the Don Pedro Dam, in California, where water is stored for power and irrigation. In the East streams are permitted to run on to the ocean, turn¬ 
ing a few wheels, but hurrying water away from the thirsty lan'3. In California such water is held in reservoirs, and used to turn the desert into fertile gardens. 
