November 3, 1916] 



SCIENCE 



651 



from seven to nine times the necessary sol- 

 vent power. 



PHOSPHORUS, CALCIUM AND NITROGEN REQUIRED BY 



CROPS, COMPARED WITH THAT POSSIBLE OF 



SOLUTION WHEN NITRITE BACTERIA ACT 



UPON TRICALCIUM PHOSPHATE 



(Expressed in pounds) 



The authors desire to point out that the 

 figures in the table were based upon the 

 solvent action which only the nitrogen would 

 exert when it is oxidized. The associated 

 acid radicle as stated on page 402 of the bul- 

 letin may make equal amounts of phosphorus 

 and calcium soluble, thus doubling that re- 

 ported above. Thus, corn, wheat and oats 

 only require one fourteenth of the phosphorus 

 possible of solution when the acid formed by 

 the nitrite bacteria and that which was com- 

 bined with the oxidizable ammonia both act 

 upon the raw rock phosphate. It may be that 

 the phosphorus would be made available even 

 if only converted to the dicalcium form, 

 which would require only half as much acid. 



The recent results of the New Jersey Sta- 

 tion on the oxidation of sulfur and its solvent 

 action on raw rock phosphate in soils support 

 the statement that phosphorus is made soluble 

 by biochemical oxidation in large amounts 

 even in the near presence of other bases. 3 



Limited space is taken to include some field 

 data from the large mass available, showing 

 the advantage of rational systems of perma- 

 nent soil enrichment in crop rotation, in which 



3 Soil Science, p. 533, June, 1916. 



raw rock phosphate, limestone and " home- 

 grown " organic matter are the only materials 

 used. 



WHEAT YIELDS PER ACRE: POUR-YEAR AVERAGE 

 UNIVERSITY OP ILLINOIS FARM 

 Soil Treatment Bushels 



Crop residues 27.6 



Manure 28.8 



Crop residues, phosphorus 42.0 



Manure, phosphorus 45.6 



Crop residues, phosphorus, limestone 46.8 



Manure, phosphorus, limestone 48.9 



These figures demonstrate sufficiently the ad- 

 vantage of mixing organic materials and raw 

 rock phosphate as judged by increased crop 

 yields, and they show that limestone, even 

 when used with raw rock phosphate under field 

 conditions, gives a further increase over that 

 produced by the combination of organic mate- 

 rials and raw rock phosphate. 



In his letter, Dr. Wheeler quotes from Di- 

 rector Thorne of the Ohio Agricultural Ex- 

 periment Station as follows: 



Where we have used floats (raw rock phosphate) 

 as a reenforcement of manure on this farm along- 

 side of aeid phosphate, the acid phosphate has 

 given us a slightly larger net gain in the average 

 of the 18 years' work, and a decidedly large gain 

 during the last half of the period. 



But Wheeler fails to point out that this 

 statement is based upon only one of the two 

 methods used by Director Thorne in comput- 

 ing the increase produced by the phosphates. 

 He might have quoted from Director Thome's 

 writing as follows: 4 



On Section C, Plots 1 and 11, which, it will be 

 observed, are continuous, have regularly given 

 yields so much larger than those of the other un- 

 manured plots of this section as to suggest the 

 possibility that the land covered by these plots 

 may have been at one time occupied by a fence- 

 row, the tract lying near a barn, and for this rea- 

 son it has been deemed best to calculate the in- 

 crease on the general average of all the unfertilized 

 plots. By this method of calculation the average 

 increase on Plots 2 and 3 combined (with raw 

 phosphate) is found to be practically the same as 

 on Plots 5 and 6 combined (with acid phosphate) 

 but when the larger cost of the acid phosphate is 

 deducted the net gain is a little greater on Plot 

 2 and 3. 



* P. 18, Ohio Experiment Station Circular 104. 



