10 The Bulletin 



of carbonate of lime caused an increase in the (juantity of pliosplioric 

 acid taken up equal to from three to seven bushels an acre per crop. 



"The i)resence of carbonate of lime or vegetable matter may bring 

 about a difference in the quantity of phosphoric acid assimilated by the 

 plants from soils containing equal quantities of active phosphoric acid. 

 The addition of carbonate of lime or of vegetable matter had practi- 

 cally no effect upon the quantity of active phosphoric acid remaining 

 in the soil at the end of the experiment. The phosphoric acid removed 

 in the cropping also had practically no effect upon the quantity of phos- 

 phoric acid remaining in the soil at the end of the experiment. The 

 active phosphoric acid in the soils used varied from fifteen to twenty- 

 seven parts per million. The phosphoric acid taken up by the plants 

 was evidently drawn from the more insoluble phosphates. 



"Carbonate of lime caused a gain in phosphoric acid taken up. In 

 all cases the gain ranged from 5 per cent on soil No. 895, with single 

 application of lime, to nearly 95 per cent on soil 1145 with double 

 application of lime. Except in two instances, the gains were consider- 

 able. THE EFFECT OF LIME HAS BEEX TO DECIDEDLY 

 lA^CREASE THE ASSIMILABILITY OF PHOSPHORIC ACID. 



"The phosphoric acid absorbed by the plants from the soils depends 

 not only on the form of the phosphoric acid in the soil, but also on the 

 presence of other substances such as carbonate of lime and organic 

 matter. Soils 895 and 1145 are acid, but the carbonate of lime had no 

 greater effect upon their phosphoric acid than on soils 892 and 893, 

 which are not acid. 



"It is, of course, impossible to state definitely whether the phosphoric 

 acid was rendered more available, or whether the crops took up more 

 phosphoric acid because the conditions were made more favorable by 

 the addition. The effect, however, is the same, viz., Til ROUGH THE 

 ADDITION OF CARBONATE OF LIME TO THE SOIL THE 

 PLANTS CONSUMED MORE PHOSPHORIC ACID." 



THE SUBSTITITION OF ( AIJ IIH ( AHIMJNATK 1 (H{ IM>I ASH IX 



FKKTIMZKH MIXTIKES 



Since the. presence (jf lime carlxnialc in llic soil seems to prevent the 

 formation of the insoluMr pliosphales of iron and aluminum, the wis- 

 dom ii\' mixing the soluble phosphates with calcium carbonate before 

 placing tbcm in soils heavily charged witli iron and nhiminnm oxides 

 becomes ai)parenf. 



As an average result of twelve years exjicrinicntal tests with reverted 

 bone black fsoluljle phosphate) the Pennsylvania Experiment Station 

 obtained a liigber yield of corn, oats, and w Ik al than fi-om the acid |)hos- 

 phate api)lied to tlic soil in its normal condition. The acid |)bosphate 

 in tlif hone black was caused 1o revert by mixing it with (piick lime 

 twelve hours In^forc applying it to the .«Joil. 



In Jannary, 1915, Dr. Charles E. Thorne, of the Ohio Kxperinient 



