1918.] SOILS FERTILIZERS. 819 



in the acid silt loam soil. In neutral and acid soils made strongly alkaline with 

 magnesium carbonate the increase In number of B. azotobacter was much greater 

 than in the untreated soils. 



The data in general show that magnesium carbonate was superior to calcium 

 carbonate or limestone in stimulating the reproduction of bacteria in acid silt 

 loam and acid sand soil.s. As_a rule the smaller applications gave better re- 

 sults than the larger. 



A Ust of 64 references to literature cited in the article is given. 



Nitrification as a measure cf the availability of different forms of calcium 

 carbonate when employed as correctors of soil acidity, P. S. Bubgess {Soil 

 Sci., 4 (1911), No. 4, pp. S27-3S6, fig. 1 ) .—Experiments conducted at the 

 Hawaiian Sugar Planters' Experiment Station with coral sand and finely- 

 ground coral limestone are reported. 



It was found that " where no additions of nitrogen are made, coral .sand and 

 ground coral limestone are about equally effective in enhancing the nitrification 

 of an acid .soil's own organic nitrogen. After neutralizing Hawaii acid soils, the 

 average amounts of nitrate formed over a period of five months under optimum 

 conditions are comparatively small. The increment of gain in nitrate formed 

 over the soil exactly neutralized, due to adding twice the amounts of lime re- 

 quired (either as coral sand or as gi'ound limestone), is too slight to warrant 

 double applications. Twice the required amounts of coral sand effect a greater 

 increase in nitrate produced over the soils exactly neutralized than do twice 

 the amounts of flnely-gi'ound coral limestone. 



" Where coral sand was used in sufficient amounts to bring the soils to exact 

 neutrality, the following percentages of gain over the soils to which no lime in 

 any form was added, are indicated: No nitrogen added (soil's own nitrogen), 

 486 per cent ; dried blood nitrogen added, 165 per cent ; and ammonium sulphate 

 nitrogen added, 398 per cent. Where finely-ground coral limestone was used 

 to neutrality, the following percentages of gain over the ' no lime ' cultures are 

 indicated: No nitrogen added (soil's own nitrogen), 518 per cent; dried blood 

 nitrogen added, 235 per cent ; and ammonium sulphate nitrogen added, 608 per 

 cent. 



" Comparing the average percentage of increased nitrate production due to 

 neutralizing exactly the soil with coral sand with that brought about by the 

 addition of finely-ground coral limestone, where both ammonium sulphate nitro- 

 gen and dried blood nitrogen were supplied, we have, as a general average over 

 the entire incubation period of five months, an increase of 281 per cent due to 

 sand applications and an increase of 421 per cent due to ground limestone appli- 

 cations. From these figures a simple ratio shows that, when lime availability is 

 measured in the soil by enhanced nitrification, 1 ton of the finely-ground lime- 

 stone is practically equivalent, in neuts-alizing soil acidity, to 1.5 tons of the 

 best grade of coral sand." 



The principles of the liming of soils, E. C. Shorey (U. S. Dept. Agr., Farm- 

 ers' Bui. 921 (1918), pp. SO, figs. 6). — This presents information regarding the 

 materials used in liming and their preparation, together with a discussion of 

 the changes, so far as they are known, which are brought about in the soil by 

 lime. The relative merits of different forms of lime and the factors which 

 determine their use in farm practice are fully explained. A list of terms com- 

 monly used in the di.scussion of liming is included. 



The use of lead for stimulating grovrth in plants, A. Stutzek (Jour. Landw., 

 64 (1916), No. 1-2, pp. 1-8; abs. in Jour. Chem. Sac. [London], 110 (1916), No. 

 648, I. p. 704; Internat. Inst. Agr. [Rome], Internat. Rev. Sci. mid Pract. Agr., 

 8 (1917), No. 6, pp. 844, 845; Chem. Abs., 11 (1917), No. 8, p. iOr)8).~" Experi- 

 ments carried out in 1914 and 1915 on the action of aqueous solutions of lead 



