1906.] 



Bare Fallows. 



5 



since the land becomes saturated repeatedly by the winter rain- 

 fall, but in more arid countries it often makes all the difference 

 to the crop. In parts of California, for example, it is possible to 

 take a crop like wheat only every other year without irrigation, 

 the bare fallow in the intermediate years being necessary to 

 collect the rain for a full yield. 



The chief gain, however, from a summer fallow lies in the 

 way the nitrates are made and stored up in the soil for the 

 benefit of the ensuing crop. The Rothamsted experiments 

 illustrate the increase thus produced, for there one plot grows 

 wheat every year without manure, and the second is divided 

 into two portions, one of which is fallowed while the other is 

 cropped every alternate year. The yield is as follows : — 





Wheat every year. 



Wheat after fallow. 



Grain. 



Straw. 



Grain. 



Straw. 





Bushels. 



Cwt, 



Bushels. 



Cwt. 



Average crop per acre per 











annum, 1856-1902 



12.7 



10*0 



i7'i 



14-2 



This shows a considerable gain for fallowing, but it must be 

 remembered the land in the second case is only cropped every 

 other year, hence the production per acre under cultivation is 

 only half as much, or 8| bushels per acre per annum. 



As the benefit of fallowing depends upon the formation of 

 nitrates during the summer and their retention for the next 

 crop, it follows that heavy rain during the winter may wash 

 -them entirely away and leave the land no richer. This fact is 

 plainly seen if the results given above are divided into two groups 

 according as the autumnal rainfall, September to December 

 inclusive, is above or below the average : — 





16 Seasons of 

 less than, average 

 rainfall. 



1 



16 vSeasons of 

 more than average 

 rainfall. 



Rainfall (Sept.— Dec.) 



Percolation through 60 in. soil 

 Total produce (wheat after wheat) 

 Total produce (wheat after fallow) 

 Percentage increase due to fallow 



8-88 in. 

 4*03 in. 

 1,810 lb. 

 2,743 lb. 

 51-5 



13-66 in. 

 8*92 in. 

 1,627 lb. 

 1,757 lb. 

 7-9 1 



