58 
793 is to be used in the mixture. One thousand pounds of such a 
mixture would contain 30 pounds of nitrogen, 120 pounds of phos- 
phoric acid, and 120 pounds of potash. Table IV shows that guano 
No. 793 contains 24.87 per cent of phosphoric, acid and Table XIX 
shows that the immediate efficiency of the phosphoric acid is 35. 
^ at «^o x! 24.87 per cent X 35 OM - 
Guano No. 793 thus contains inn or ' P er ce 
immediately available phosphoric acid, or 8.7 pounds in 100 pounds 
of material. To furnish 120 pounds of available phosphoric acid, 
120 
^^X 100 = 1,371 pounds of guano No. 793 is required. As guano 
o. 7 
No. 793 also contains 0.99 per cent of nitrogen, the 1,371 pounds will 
1 371 X0.99 
afford — — lnn — = 13.6 pounds of nitrogen. In this guano it is 
only safe to allow for an availability of 50 per cent of the total nitrogen ; 
therefore, this guano probably furnishes only 6.8 pounds of available 
nitrogen. To furnish the rest of the nitrogen (30 pounds — 6.8 pounds = 
23.2 pounds), about 160 pounds of nitrate of soda would be needed. 
This guano will contain practically no water-soluble potash; thus about 
240 pounds of a high-grade potash salt will be necessary to supply 
the 120 pounds of potash required by the formula. The mixture 
now contains 1,371 pounds of guano No. 793, 160 pounds of nitrate 
of soda, and 240 pounds of high-grade potash salt, a total of 1,771 
pounds. The whole mixture of 1,771 pounds is equivalent to 1,000 
pounds of the 3 : 12 : 12 fertilizer. 
Suppose guano No. 881 were to be used in this formula instead of 
No. 793. Table IV shows that No. 881 contains 13.04 per cent of total 
nitrogen, but 3,6 + 4.6 = 8.2 per cent of the nitrogen is present as 
ammonia and nitrate. Table XX shows that the remainder of the 
total nitrogen has practically no immediate availability. Thus only a 
, - .. . . .. 13.04-8.20 . 01 
quarter ot the remaining nitrogen, or j = 1.21 per cent, can 
be counted on. Guano No. 881 is estimated to have only 9.41 per 
cent (8.20+1.21) of effective nitrogen, which is conservative. To 
furnish the 30 pounds of nitrogen required by the formula, about 
320 pounds of guano No. 881 is needed. In the 320 pounds of guano 
No. 881, which contains 4.15 per cent of potash (see Table V), there 
is 13.3 pounds of potash. For the remainder of the potash about 215 
pounds of a high-grade potash salt will be needed. As guano No. 881 
contains 8.94 per cent total phosphoric acid which Table XIX shows 
has an efficiency of 65, it contains 5.81 per cent of immediately avail- 
able phosphoric acid. The 320 pounds of guano thus furnishes 18.6 
pounds of available phosphoric acid. For the rest of the phosphoric 
acid, 101 pounds acid phosphate or a phosphatic guano, as No. 1017, 
