122 



Journal of Agricultural Research voi. xvm, no. 3 



there was at times during the vegetative stage of growth a tendency 

 toward tip burning wherever magnesite was applied. This unfavorable 

 condition, somewhat similar to that observed by Dickson (2), was not 

 noted on the calcite- or dolomite- treated wheat and did not appear to 

 cause permanent injury in any case. 



Table III. — Soluble salts, nitrates, bacterial contents, acidity, and carbon-dioxid content 

 of two acid soih as affected by natural carbonates of calcium and magnesium 



YELLOW CLAY 



Treatment per million 

 pounds of soil. 



Control 



4,000 pounds calcite 



4,000 poimds magnesite. . 

 4,000 pounds dolom^ite. . . 



12,000 ix)unds calcite 



12,000 pounds magnesite. 



Soluble 

 salts, 

 parts 

 per 



million. 



0192 

 272 

 604 

 (6)... 

 424 

 624 



Nitrate (NO3) 

 content, 

 parts per 

 million. 



As 

 sam- 

 pled. 



Trace 



After 

 nitrifi- 

 cation, 



Per- 

 cent- 

 age of 

 carbon 

 dioxid. 



Trace 



184 

 36s 



873 

 842 



Acidity, as cal- 

 cium carbonate 



needed per 



million pounds 



of soil. 



Hopkins 

 method 



S,6oo 

 40 



Jones 

 method 



8,250 

 I.SOO 

 1.250 

 I, 500 

 1, 100 

 750 



Bacterial con- 

 tent, millions 

 per gram of 

 soil. 



Aero- 

 bic. 



3.027 

 7.605 



S-244 

 9.158 



An- 

 aero- 

 bic. 



0. 000 



. 000 



1. 220 



.000 

 I- 133 



Ratio 

 of cal- 

 cium 

 oxid to 

 magne- 

 sium 

 oxid. 



1:3-0 

 1:1.6 



BLACK SAND 



Control 



4,000 poimds calcite 



4,000 pounds magnesite. . 

 4,000 pounds dolomite . . . 



12,000 pounds calcite 



12,000 pounds magnesite. 



448 

 280 

 360 



432 

 1.320 



233 

 91S 



340 



913 



1,000 



1,280 

 2,544 



13. 500 

 6,000 

 5,000 

 5,500 

 I, 500 

 1,000 



2.813 

 10. 583 

 6-833 



16.037 

 S-837 



■907 

 .099 

 . 420 



. 760 

 .62s 



1.0:2. 3 

 I. 4:1.0 

 1.0:4^0 

 1.9:1-8 

 3-4:1-0 

 1.0:7.8 



"Figures calculated to dry basis. 



6 Blanks in dolomite column indicate that no deterjninations were made. 



Table III gives the results of tests on the soils made lo months after 

 the experiments were started, when the pots contained growing clover 

 and wheat stubble. The samples were drawn with Noyes' bacteri- 

 ologists' soil samplers ^ to the full depth of the pots. Nitrates, bacterial 

 numbers, nitrification and soluble salts were determined on the moist 

 samples. Acidity and carbon dioxid were determined on air-dry 

 samples. 



Soluble salts were determined by means of the electrical bridge ^ 

 and show the relative quantities of ionized salts in the soil solution. 

 The nitrates were determined by the modified phenol -disulphonic 

 acid method.^ Nitrification was carried out in tumblers by the beaker 

 method. Carbon dioxid was detennined with boiling hydrochloric 

 acid (specfic gravity 1.115). Acidity was determined by the Hopkins* 



' Noyes, H. A. soil sampling for bacteriological analysis. In Jour. Amer. Soc. Agron., v. 7, 

 no. 5, p. 239-249, fig. 13, pi. 4. 1915- 



2 Davis, R. O. E., and Bryan, H. the electric bridge for the determination of soluble salts 

 IN soils. U. S. Dept. Agr. Bur. Soils Bui. 61, 36 p., 7 fig., 2 pi. 1910, 



8 Noyes, H. A. accurate determination op soil nitrates by phenol disulfonic acid method. 

 /n Jour. Indus, and Engin. Chem., v. 11, no. 3, p. 213-218. 1919- 



< Wiley. H.W. op cit. 



