SOILS FERTILIZERS. 425 



not include the basicity due to bases of iron and aluminum. The basicity meas- 

 ured is due to carbonate and easily decomposed silicates of lime, magnesia, and 

 the alkalis. 



"(2) Fifty gm. of soil were digested with 100 cc. tentli-normal nitric acid 

 for one-balf bour. and 20 cc. of tbe filtrate titrated with caustic soda and 

 methyl orange. 



"(3) After the titration in (2) phenolphthalein was added and the titration 

 continued until the solution became slightly colored. The difference between 

 methods (2) and (3) consists in the fact that (2) includes basicity due to iron 

 and aluminum in addition to lime, magnesia, and alkalis, while (3) includes 

 only lime, magnesia, and alkalis." 



In connection with the pot experiments the method of procedure was as 

 follows : 



'■ Five hundred gm, of the soil were placed in a 500 cc. precipitating jar and 

 100 cc. of water poured on the surface of the soil. A test tube perforated at 

 the bottom reached to the bottom of each jar. The soil was thus ventilated at 

 the bottom, as in the pot experiments. The jars were kept in a dark cupboard 

 at the room temperature and did not receive any further addition of water dur- 

 ing the period of experiment. At the end of the time they were weighed, mixed 

 thoroughly, and portions taken for analysis. . . . The results of the analysis 

 were calculated to the original weight of the soil. 



" Vegetation experiments were made on the same soil in galvanized iron pots 

 8 in. in diameter and 8 in. deep with a 1-in. side tube (Wagner pot). The pot 

 was ventilated from the bottom, a layer of gravel was first introduced, and 5 

 kg. of soil were weighed into each pot. Each pot received 2.5 gm. acid phos- 

 phate and 1 gm. potassium sulphate. The corn planted was grown for various 

 periods in the different soils. The period of growth was the same, how- 

 ever, as the length of time during which the soil was allowed to nitrify in the 

 jars. The effect on plant growth of other additions to the soil was studied at 

 the same time. Most of the tests with nitrogen were made in duplicate. 



"At the end of about 9 weeks the corn was harvested, dried, and subjected to 

 analysis." 



It was found in these experiments that soils vary considerably in ability to 

 produce nitrates, but to a much less extent in their capacity to produce active 

 nitrogen. Whjle an excess of water may entirely prevent nitrification, it re- 

 tarded the production of active nitrogen to a much less extent. 



" No relation conld be observed between the increased production of nitrates 

 due to calcium carbonate, and the acidity or basicity of the soils estimated by 

 the methods described, though the greatest increase was effected on the most 

 acid soil. 



"Although the addition of carbonate of lime increased the pi'oduction of 

 nitrates in most of the soils, the production of active nitrogen was affected 

 thereby only to a slight extent. 



" Magnesium carbonate was less favorable to nitrification in the soil tested 

 than calcium carbonate. 



" Nitrification was much greater in a limed acid soil than in the unlimed 

 acid soil. 



" Phosphoric acid and potash had little effect upon the production of active 

 nitrogen, thongh in some cases nitrification was affected considerably. 



" The formation of ammonia begins rapidly, and a large proportion of the 

 change takes place the first week, under Texas conditions. Nitrification began 

 the second week and reached its maximum in the third. 



65623— No. 5—09 3 



