18 BULLETIN 353, U. S. DEPARTMENT OF AGRICULTURE. 



Extreme care in sampling has kept the probable error very low on 

 the single sample, so that it is nowhere excessive, but replicating the 

 sample three times reduces the probable error 51.5 per cent, while a 

 rephcation five and six times reduces the probable error over single 

 samples 55.1 per cent and over three replications only 7.4 per cent. 

 It does not seem necessary, therefore, in practice to rephcate more 

 than three times. Single samples, however, can not be considered 

 safe when there is wide variation within the plat unless extreme care 

 is used to make the sample composite and representative of the entire 

 area. 



MOISTURE PERCENTAGES IN GREEN FORAGE AND IN FIELD-CURED FORAGE, AS SHOWN 



BY SAMPLES. 



Farrell, in an article in the American Journal of Agronomy,^ sug- 

 gests the desirabiUty of expressing alfalfa-hay yields in terms of green 

 weight. In the article referred to above, he reports 76.5 per cent of 

 moisture lost in air drying, which would be approximately equiva,lent 

 to 79 . 5 per cent of total moisture. The average percentage of moisture 

 m the 23 analyses of green alfalfa reported by Jenkins and Winton ^ 

 was 71.8. 



At Arlington Farm, Va., green alfalfa averaged 75.2 per cent of 

 moisture in 20 samples. This percentage is probably near the aver- 

 age for moderately thrifty alfalfa grown without irrigation in the 

 Central and Eastern States. Alfalfa grown under irrigation and cut 

 when one-tenth in bloom at Chico, Cal., averaged in 1914, 76.9 per 

 cent of moisture. In 1911 McKee ^ found at this station as the 

 average of 28 determinations in alfalfa not quite in bloom 85.8 per 

 cent of moisture. The 1914 results indicate that the condition of 

 growth affects the moisture content very decidedly. Owing to excessive 

 heat and scarcity of water, the alfalfa used for the 1914 samples was 

 less vigorous than that of 1911 and correspondingly less succulent. 

 These differences indicate very clearly the danger of basing yields on 

 the green weight, as suggested by Farrell, or of using some arbitrary 

 percentage of moisture in making corrections on the green weight. 

 Samples should always be taken in experimental work when the crop 

 is harvested and the amount of moisture in the forage at that time 

 determined from them. Field-cured alfalfa at Chico in 1914 had 22.3 

 per cent of moisture, while Jenkins and Winton ^ report as the average 

 of 21 analyses only 8.4 per cent. The samples of Jenkins and Winton 

 had probably dried out to some extent after being brought into the 

 laboratory. 



1 Farrell, F. D. Basing alfalfa yields on green weights. In Jour. Amer. Soc. Agron., v. 6, no. 1, p. 42-45, 

 1914. 



2 Jenkins, E. H., and Winton, A. L. A compilation of analyses of American feeding stuffs. U. S. Dept. 

 Agr., Office Exp. Stas. Bui. 11, p. 22-75, 1892. 



■> McKee, Roland. Arabian alfalfa. In V. S. Dept. Agr., Bur. Plant Indus. Cir. 119, p. 25-30, 1913. 



