[ CHAPTER XVII.]
SOLUBLE PHOSPHATES IN FARMYARD MANURE.
There is one thing in these experiments of Dr. Vœlcker’s which deserves special attention, and that is the comparatively large amount of soluble phosphate of lime in the ash of farm-yard manure. I do not think the fact is generally known. In estimating the value of animal manures, as compared with artificial manures, it is usually assumed that the phosphates in the former are insoluble, and, therefore, of less value than the soluble phosphates in superphosphate of lime and other artificial manures.
Dr. Vœlcker found in the ash of fresh farm-yard manure, phosphoric acid equal to 12.23 per cent of phosphate of lime, and of this 5.35 was soluble phosphate of lime.
In the ash of well-rotted manure, he found phosphoric acid equal to 12.11 per cent of phosphate of lime, and of this, 4.75 was soluble phosphate of lime.
“That is, indeed, an important fact,” said the Doctor, “but I thought Professor Vœlcker claimed that ‘during the fermentation of dung, the phosphate of lime which it contains is rendered more soluble than in fresh manure.’”
“He did say so,” I replied, “and it may be true, but the above figures do not seem to prove it. When he wrote the sentence you have quoted, he probably had reference to the fact that he found more soluble phosphate of lime in rotted manure than in fresh manure. Thus, he found in 5 tons of fresh and 5 tons of rotted, manure, the following ingredients:
| SP Soluble Phosphate of Lime. IP Insoluble phosphates. TP Total Phosphates. | TSA Total Soluble Ash. TIA Total Insoluble Ash. TA Total Ash. |
| 5 TONS. (10,000 LBS.) | Potash. | |||||||
|---|---|---|---|---|---|---|---|---|
| SP | IP | TP | Sol. | Insol. | TSA | TIA | TA | |
| Fresh manure | 29.9 | 38.6 | 68.5 | 57.3 | 9.9 | 154 | 405 | 559 |
| Rotted manure | 38.2 | 57.3 | 95.5 | 44.6 | 4.5 | 147 | 658 | 805 |
“It will be seen from the above figures that rotted manure contains more soluble phosphate of lime than fresh manure.