REVIEW AND CONCLUSION. 363 
. 
quantity to weigh 3,500.000 lbs., (p. 158,) are as follows; 
lbs. 
Soluble silica 81.900 
Lime, 143.220 
Potash, 35.910 
Soda, 68,920 
Ammonia, 2.100 
Phosphoric acid, 16.310 
Sulphuric acid, 31.360 
Nitric acid, ? 
Quantity of Available Ash-ingredients necessary for 
a Maximum Crop.—We have already given some of the 
results of Hellriegel’s experiments, made for the purpose 
of determining how much of the various elements of nu- 
trition are required to produce a maximum yield of cereals 
(pp. 215 and 288). This experimenter found that 74 lbs. 
of nitrogen (in form of nitrates) to 1,000.000 of soil was 
sufficient to feed the heaviest growth of wheat. Of his 
experiments on the ash-ingredients of crops, only those 
relating to potash have been published. They are here 
reproduced, 
EFFECTS OF VARIOUS PROPORTIONS OF AVAILABLE POTASH * IN 
THE SOIL ON THE BARLEY CROP. 
Yield 
Potash in | |——-—————— Fo — 
1,000.000 dds. of soél.| of Straw and Chaff. of Grain. Total. 
0 0.798 —-—— ——— 
6 3.869 2.993 6.802 
12 5.740 4.695 10.435 
24 6.859 7.851 14.710 
47 8.195 9.578 17.773 
71 9.327 10.097 19.424 
94 8.693 9.083 17.776 
141 8.764 8.529 17.293 
282 8.916 8.962 17.878 
It is seen that the greatest crop was obtained wher 71 
parts of potash were present in 1,000.000 lbs. of scil, A 
* Other conditions were in all respects as nearly alike as possible. 
