III.] 



EFFECT OF SEASON AND MANURING 



83 



grain to be formed from the reserve materials already 

 stored up in the plant, another attempt is made to turn 

 out a standard product. 



Even on the Rothamsted plots, where the differences 

 in the supply of nutrients are extreme and have been 

 accumulating for fifty years, the composition of the 

 grain changes more from one season to another than 

 it does in passing from plot to plot. Table XX 1 1,, for 

 example, shows the percentage of nitrogen in the 

 wheat grain and straw, from several plots differing in 

 their nitrogen supply in two sharply contrasting 

 seasons. 



Table XXII.— Composition of Wheat Grain and Straw as 



AFFECTED BY MANURING AND SEASON, BROADBALK FiELD, 



Rothamsted (1852 and 1863). 



Of course very great differences in " quality " may 

 be entirely passed over in a crude chemical analysis 

 which merely determines the amount of such ultimate 

 constituents as nitrogen, phosphoric acid, etc. For 

 example, high nitrogen content is generally associated 



