116 



THE ROTHAMSTED EXPERIMENTS. 



Influence 

 of fallow 

 on beans. 



Failure of 

 clover 

 grown at 

 short in- 

 tervals. 



crop of either the second or the third period of 8 years. In- 

 deed, on the two manured plots there is an average annual 

 yield of nitrogen per acre over the 4 years of crop during the 

 last 8 years not very far short of the average of the first 8 

 years. Thus, with the purely mineral manure, there is an 

 average annual yield of nitrogen over the first 8 years of 60.2 

 lb., and over the 4 years of crop of the last 8 of 53.3 lb.; and, 

 with the mineral and nitrogenous manure together, over the 

 first 8 years of 69.0 lb., and over the 4 years of crop of the 

 last 8 years, of 57.4 lb. 



That is, with the intervention of fallow, we have, though 

 not good agricultural crops, yet really large yields of nitrogen 

 compared with those obtained in many of the preceding years ; 

 and very large yields without any supply by manure, com- 

 pared with those obtained under the same conditions with 

 any of the %o?i-leguminous crops. It would appear probable, 

 therefore, that if a suitable mechanical condition of the land 

 could have been maintained, fair crops, and large yields of 

 nitrogen, would also have been maintained. 



Upon the whole, then, although the crop practically failed 

 when it was thus attempted to grow it year after year on the 

 same land, it nevertheless accumulated, in its above-ground 

 produce, much more nitrogen over a given area than the 

 crops of the other Orders, but was little benefited by an arti- 

 ficial supply of nitrogen. 



We have now to record a still greater failure than that 

 with beans — namely, when it was attempted to grow another 

 leguminous crop year after year on ordinary arable land — 

 this time Trifolium pratense, or Ked clover. The results are 

 summarised in Table 37. 



The table is headed Eed clover, sown frequently on the 

 same land. The period of experiment was in fact 29 years 

 — from 1849 to 1877 inclusive. But the details, not given 

 in the table, show that although clover was sown fifteen 

 times in the 29 years, in only 7 was any clover crop ob- 

 tained; whilst about one-fifth of the produce of the whole 

 series of years was yielded in the first year, 1849. It is, in- 

 deed, fully recognised that in our own country clover will 

 not grow under ordinary conditions more frequently than 

 once in a certain number of years, which varies according to 

 soil and other circumstances, but is seldom so few as four, 

 and frequently as many as, or more than, eight years. It 

 should be stated that when the clover failed, sometimes a 

 cereal crop, wheat or barley, was sown ; but more frequently 

 the land was left fallow. Further, the amounts of produce 

 entered in the column headed Series 1 are in each case the 



