14 



BULLETIN 353, U. S. DEPARTMENT OF AGRICULTUEE. 



RELIABILITY OF AIR-DRIED SAMPLES. 



The reliability of air-dried samples may be determined in three 

 ways: (1) By a comparison of the percentages of moisture loss in 

 the samples with that in the 100-pound and 500-pound quanti- 

 ties, which, on account of their bulk, approximate field methods; 

 (2) by a careful comparison of the relation between the moisture 

 lost m air drying and the total moisture content as revealed by oven 

 drying; and (3) by noting the variation in the percentage of moisture 

 remaining in the air-dried material. A comparison of the moisture 

 loss in air-dried samples with that in bulk lots of the same material 

 is given in Table II. 



Table II. — Comparison of the loss of moisture in green and field-cured forage when air 

 dried in small samples and in large bulk. 



Place. 



Crop. 



Moisture in green material. 



Moisture in field-cured 

 material. 



Total. 



Loss in 

 samples. 



Loss in 

 bulk. 



Total. 



Loss in 

 samples. 



Loss in 

 bulk. 



Chico, Cal 



Alfalfa 



Per cent. 

 76.9 

 72.0 



58.0 

 71.2 



Per cent. 

 74.5 

 66.3 



50.5 

 54.2 

 65.8 



Per cent. 

 73.0 

 64.3 



49.2 

 58.2 

 60.9 



Per cent. 

 22.3 

 29.0 



20.3 

 43.2 



Per cent. 

 14.3 

 13.4 



7.2 

 20.5 

 26.0 



Per cent. 

 11.5 



Arlington Farm, Va. . . 

 New London, Ohio . . . 



Tall oat-grass and 



orchard grass. 

 Timothy 



13.5 

 10.1 





Sorghnm 



16.8 





do 



22.1 













It will be seen that the losses in the smaU samples of green material, 

 except for those of sorghum at AmariUo, Tex., which were not well 

 cured, averaged from 1.3 to 4.9 per cent greater than it did in the 

 bulk lots. This was to be expected, smce the small sample naturally 

 dries out more completely than the bulk. The difference, however, 

 is slight, and the loss of moisture in the small samples seems to be 

 fairly consistent with the loss which was found in the bulk lots. 



The comparison of small samples with bulk lots of field-cured 

 material is not so favorable to the use of the sample method as in 

 the case of the green material. Table II also shows that the mois- 

 ture loss in the samples, when compared with the total moisture con- 

 tent, is not quite so consistent as the percentage of moisture loss in 

 the bulk lots. 



A better way to determine the reliability of the sample method is 

 by a study of the percentages themselves, especially in the column 

 devoted to percentage of moisture in the air-dry material. The uni- 

 formity of these percentages throughout one crop means that the air 

 drying of samples can be depended upon to bring samples to a nearly 

 uniform moisture content, and this method therefore serves the pur- 

 pose of correcting field weights almost as well as to oven dry the 

 samples. The moisture content of the air-dry samples is not en- 



