258 Missouri Agricultural Report. 



phosphorus in the soil is to put back into the manure, in the form 

 of fine-ground raw rock phosphate, somewhat larger amounts of 

 phosphorus than the animal has retained in his bones. It is well, 

 for a time at least, to put back larger amounts than the animals 

 retain, because the soils are already deficient in phosphorus, and 

 also because there may be some waste of manure. 



These statements are based both upon the chemical analysis of 

 soils and crops and manures, and also upon carefully conducted 

 field experiments covering many years. 



The Maryland Experiment Station furnishes some valuable 

 data from probably the earliest systematic investigations, still be- 

 ing continued, and a large amount of information is rapidly ac- 

 cumulating from our more extensive work in Illinois, but the most 

 complete experiments of long duratfon are reported by the Ohio 

 Experiment Station. Where 40 pounds of fine-ground rock phos- 

 phate, costing about 16 cents, were added to each ton of manure 

 and 8 tons of manure per acre were applied for a three-year rota- 

 tion of corn, wheat and clover, the value of the increase in crop 

 yields was equal to $2.66 for each ton of manure used, in case of 

 yard manure (which was worth only $1.64 per ton without the 

 phosphate) ; and, in case of the stall manure, its value was in- 

 creased from $2.22 a ton to $3.42, by the addition of the 16 cents 

 worth of rock phosphate, these results being the average of nine 

 years' experiments on three different series of plots, based upon 

 increased yields, valued at 35 cents a bushel for corn, 70 cents 

 for wheat and $6.00 a ton for clover hay. 



If we deduct the cost of the phosphate used, we still have what 

 might be termed a net value of $2.50 for the phosphated yard 

 manure and $3.24 a ton for the phosphated stall manure. 



Of course, it would be equally appropriate, and possibly more 

 so, to speak of "manured phosphate" instead of "phosphated ma- 

 nure," because the rock phosphate actually furnishes the needed 

 and deficient element, phosphorus, while the manure helps to make 

 it available. On this basis we may say that the value of 40 pounds 

 of rock phosphate is increased from 16 cents to $1.02 by mixing 

 with a ton of yard manure, and from 16 cents to $1.20 by mixing 

 with a ton of stall manure, after deducting the value of the un- 

 treated manure in each case. 



The most important fact to keep in mind, however, is that 

 both the manure and rock phosphate are much more valuable when 

 used together than when used separately, because manure is de- 

 ficient in phosphorus and rock phosphate does not act except in 



