PHOSPHORUS FOR SOILS. 187 
River are nearly all of them deficient in phosphorus, 
if we buy it and use it on alfalfa meadows, then 
feed the alfalfa hay and put back the manure, we 
are steadily adding to our capital of fertility; not 
much is lost, only we sell away in the bones of our 
eattle, pigs and sheep a part of it and in their flesh 
and blood a little more. An alfalfa farm may thus 
become a great laboratory of fertility gathering, 
provided the crops are fed on the farm. When they 
are sold off the story is different. 
How Much Phosphorus?—In England it is the 
custom to apply very large amounts of basic slag to 
their meadows and pastures far in excess of what 
the plants can take up, and they seem to get large 
profit from so doing. There is lack of careful ex- 
periment to show us what amounts of phosphorus 
will pay best sown with or on alfalfa. The require- 
ments of the plant, that is, the amounts actually 
taken away from the soil, are as follows: 1,000 Ibs. 
of alfalfa hay contains 5 Ibs. of phosphoric acid; 4 
tons, or 8,000 Ibs., would then contain 40 lbs. of 
phosphoric acid. Two hundred and fifty pounds of 
16% acid phosphate would contain that amount, 
and should make good what was removed from the 
soil by the 4 tons of hay. That there should be abund- 
ance in supply the writer advises the use of 300 
lbs. annually of 16% acid phosphate, or propor- 
tional amounts of the stuff, if a different percent- 
age is bought. Thus if only 10% of available phos- 
phorie acid is present one would need to use 400 
Ibs. or more. So it is cheaper and better to use only 
