62 EXPERIMENTS UPON WHEAT 



to February, was above or below the average, we obtain a 

 similar result. In fifteen seasons with a low winter percolation 

 averaging 5 '02 inches, there was an average crop on the 

 selected plots of 31 '5 bushels per acre ; in the other nineteen 

 seasons of high percolation, 9 '43 inches, the average crop on 

 the same plot was only 26'8 bushels. Although of course the 

 weather later in the season has a great effect in determining 

 the wheat crop, it is yet evident that the most critical period of 

 its growth lies in the first four months, when the foundation of 

 roots is being laid. 



On the whole, it will be seen that the great differences of 

 manuring to which the Rothamsted plots have been subject 

 for so long a period have a much greater effect on the gross 

 amount of crop than on the quality of the grain. Space does 

 not admit of a discussion of the detailed analyses of the crops, 

 but they show similar results in regard to the comparative 

 stability of the nature of the grain. Fluctuations in the amount 

 of the crop due to season or manuring are reflected to a much 

 smaller degree in the composition of the grain ; the composition 

 of the straw, however, shows wider variations, induced by the 

 differences in the manure applied. 



II. WHEAT AFTER FALLOW, AND IN ROTATION. 



Since the year 1856 two half-acre plots in the Hoos field 

 have been cropped in alternate years with wheat without 

 manure ; every year one of the plots is in wheat while the other 

 is being fallowed, so that the wheat crop always succeeds a 

 year's bare fallow. 



The accompanying Table (XXIV.) shows the average 

 produce, grain and straw, on the cropped plot following fallow, 

 compared with the crops on the plot in Broadbalk, which 

 is continuously cropped without manure. It will be seen that 

 the produce of wheat after fallow is considerably higher than 

 when it is grown continuously, 16'6 against 12*2 bushels per 

 acre ; but if reckoned as produce over the whole area, half in crop 

 and half fallow, the whole acre grows much less both of grain and 



