452 Journal of Agricultural Research voi. xiir, No. 9 



Harbor, Mich., was tested during the season of 1914-15. In these 

 experiments but one application of the boron-treated manure was made, 

 and the observations extended over only one season. The manure was 

 applied to the soil at the rate of 16 tons per acre. The amount of boric 

 acid calculated to have been added to the soil is given above. 



Experiments were inaugurated in 1914 on the experimental farm of 

 the Bureau of Plant Industry at Arlington, Va., and on the farm of the 

 Bureau of Animal Industry at Bethesda, Md. The Arlington experi- 

 ments extended over two seasons ; those at Bethesda over three seasons. 

 The manure was applied to the soil at the rates of 16, 24, and 40 tons 

 per acre. (The percentage of boric acid in the different plots is given 

 on p. 451.) Nine plots were used at each place: Three for borax-treated 

 manure, three for colemanite-treated manure, and three for untreated 

 manure. In all cases the boron was well incorporated with the manure, 

 and the mixture then stood in piles for 10 days before it was spread on 

 the plots. The ground was lightly plowed, harrowed, and rolled. Dif- 

 ferent vegetables were grown on the plots the first two seasons. Rye 

 was grown the third season on ail plots at Bethesda.^ 



In order to obtain additional information in regard to the length of 

 time that boron can be detected in soils, samples of soils which had 

 received applications of boron-treated manure in 191 4 and which had 

 been tested for soluble boron in 191 5 were taken in 191 6 from the plots 

 at Orlando, Fla., New Orleans, La., and Dallas, Tex. 



EXPERIMENTAL METHODS USED 



Boron was estimated in the plants and soil as boric acid, with the 

 methods described by one of the writers (2). This procedure involved 

 the use of strips of curcumin paper, and a comparison of the color 

 obtained from extracts of the ash of the plants and fruit and extracts 

 and fusion mixtures from the soil, with the color from standard solutions 

 of boric acid. Both total and acid-soluble boron were estimated in the 

 soil. 



The methods of the Association of Official Agricultural Chemists - for 

 solids, total nitrogen, and for nitrogen as ammonia on distillation with 

 magnesium oxid were used. The Folin and McCallum aeration method 

 for ammonia ^ and the aluminum-foil reduction method for nitrates ^ as 

 adopted by the American Public Health Association were employed. 



1 The cooperation of Dr. E. C. Schroeder, of Bethesda, and of Messrs. Butterfield and Criswell, of the 

 Arlington Farm, was of great assistance. 



2 AssooATioN OF OFFiaAL Agriculturai, Chemists, report of the committee on editing tent- 

 ative AND official methods OF ANALYSIS. 381 p., 15 fig. Baltimore, 1916. 



3 Folin, Otto, and McCallum, A. B. on the determination of ammonia in urine. In Jour. Biol. 

 Chem., V. 11, no. s, p. 323-525- 1912- 



* American Public Health AssoaATioN. Laboratory Section, standard methods for thS 

 BXAMINATION OP water AND SEWAGE, ed. 2. 144 p. New York Bibliography, p. 70-74, 137-140. 1912. 



