36 



The Rothamsted Wheat Experiments. 



1844 the land might fairly be considered as, agriculturally 

 speaking, exhausted. Since then the cultivation has been 

 of the simplest description, and no attempt has been made 

 to increase the crop by deep or subsoil ploughing ; the land 

 has, however, been kept free from weeds. A summary of 

 the results, given in four periods of ten years each, is 

 presented in Table IV. 



TABLE IV. PERMANENTLY UNMANURED PLOT. 



The increased yield of grain during the second ten years 

 as compared with the first is attributed to the favourable 

 seasons of the second decade ; the total produce (grain and 

 straw), a much more accurate measure of the available 

 fertility of a soil than is the grain alone, is also slightly 

 higher over the second period than over the first. The 

 decline during the third decade as compared with the second 

 is seen to be very marked, much more so than that of the 

 fourth as compared with the third. But the more recent 

 seasons had been so unfavourable for the growth of wheat 

 that the produce of the fourth ten years cannot be accepted 

 as correctly representing the reduction due to soil exhaustion 

 alone. This is proved by the fact that the produce of the 

 last year, 1883, in a rather better season, was 13| bushels 

 per acre, which closely approximates to the average yield of 

 the forty crops. 



The annual decline in the produce, due to exhaustion 



