EFFECT OF FALLOWING 



63 



straw than where the crop is grown year after year on the same 

 land. A given area of land would therefore be more productive 

 when cropped every year than if the crop were alternated with 

 fallow. The superior yield of the portion in crop after a 

 fallowing may to some degree be attributed to the greater 



TABLE XXIV. Wheat without Manure. Grown continuously (Broadbalk 

 Field], and in alternation with Fallow (Hoos Field). Average Produce 

 per acre, 57 years (1856-1912). 



freedom from weeds, but in the main it is due to the pro- 

 duction of nitrates in the soil during the summer when it is 

 fallow, a process which is much stimulated by the stirring 

 and aeration the soil receives. The success of a fallowing 

 depends upon these nitrates remaining for the succeeding crop, 

 since they are not retained by the soil they may be entirely 

 washed out by heavy autumnal rains. 



That the autumnal rainfall is the great factor in determining 

 whether a bare fallow shall be profitable or not to the following 

 crop, may be well seen by comparing the crops yielded by 

 these plots with the rainfall and percolation which took place 

 during the autumn previous to each crop. 



The percolation through 60 inches of bare soil for the four 

 months September to December inclusive, as measured by the 

 drain gauge, amounted on the average to 6 '45 inches for the 

 seasons 1870-1901. If, then, we divide the years into two 

 groups according as the autumnal percolation is above or below 

 the average, and allot to each year the crops on the continuous 

 wheat and wheat after fallow plots for the harvest following 

 the given percolation, we shall obtain the average results shown 

 in Table XXV. and illustrated in the diagram Fig. 9. 



