306 



EXPERIMENT STATION RECORD. 



VARIATION OF THE FICU'RES. 



As illustrating the variation in the composition as well as in the 

 total amounts of the ash, on the basis of Wolff's compilation, the fol- 

 lowing- table is presented: 



Variation in reported ash analyses. 



Although a part of this variation may be traced to errors in the 

 determination of the ash, the variations aside from this are unusually 

 large, and the averages calculated from these figures can be of little 

 value. In the case of winter- wheat straw, for example, the individual 

 analyses run all the way from one-half the average figure to double 

 that value, as shown by the following: 



Variation in composition of asJi of winter-wheat straw. 



The average is only a ver}^ general indication which can only 

 approximate the truth when based on a very large number of determi- 

 nations on samples of different origin and harvests, in which case the 

 variations offset each other in a large measure. 



CAUSES OF VARIATIONS IN THE AMOUNT AND COMPOSITION OF ASH. 



Among the factors, aside from individuality, which influence the 

 variation in composition of vegetable materials may be noted the 

 influence of (1) the stage of growth, (2) the soil, (3) the fertilizers, (4) 

 the available moisture, and (5) the thickness of the stand. 



INFLUENCE OF THE STAGE OF GROWTH. 



It is evident that the percentage of ash in the plant is not uniform 

 during its growth, since the assimilation of the ash elements from the 

 soil and the increase of organic matter in the plant do not always take 



