ROTATION OF CROPS, 215 



were fed or retained on the land ; the corresponding amounts 

 of total produce being 5348 lb. and 5658 lb. Or, taking the 

 produce on the bean and clover portions, there were 28| 

 bushels of grain where the roots had been removed, and 3 If 

 bushels where they had not been removed, the corresponding 

 amounts of total produce being 4841 lb. and 5307 lb. Lastly, 

 with the mixed manure, including nitrogen, the average pro- 

 duce was, on the fallow portions, 31£ bushels after the 

 removal of the roots, but only 30| where they had not 

 been removed, the amounts of total produce being, however, 

 5808 lb. and 5883 lb. On the bean or clover portions, the 

 results were 32f bushels where the roots were carted, and 33£ 

 bushels where they were not removed ; and the amounts of 

 total produce were 5847 and 5932 lb. 



.Reference to the average produce of the last two courses, 

 the tenth and eleventh, the wheat years of which were of 

 more than average productiveness, shows, in the case of the 

 manured plots, more striking difference in the amount of the 

 fourth crop due to the removal or the retention on the land 

 of the constituents of the first crop — the roots. The roots of 

 those courses were, however, more than average in amount. 



The results, both with superphosphate alone and with the 

 mixed manure, afford, therefore, distinct evidence of the effect 

 of the removal or otherwise of the first crop of the course — 

 the turnips — not only on the second and third crops, but on 

 the fourth crop — the wheat — also. 



The next point is to illustrate the difference of effect on the Effects of 

 other crops of the rotation, on the one hand of the growth and l ^™ l ™j? 

 removal of the highly nitrogenous leguminous crop, and on fallow on 

 the other of fallowing which removes nothing; and first as ^^ s ^f 

 to the wheat, which we are now specially considering, and ceeding 

 which immediately succeeds the leguminous crop or the cro P s - 

 fallow. 



A careful examination of the average results over the eight 

 courses (second to ninth) will show that, both without manure 

 and with superphosphate alone — that is, under conditions of 

 exhaustion, especially of available nitrogen — the wheat crops 

 were in every case higher after fallow, with its supposed 

 accumulation, than after the leguminous crops, which removed 

 much more nitrogen than the succeeding wheat would require. 

 On the other hand, on the mixed manure plots, where the 

 condition of the land, and especially its nitrogenous condition, 

 was not exhausted, but fairly maintained — there was even 

 rather more average produce of wheat after the removal of 

 the highly nitrogenous leguminous crops than after the 

 accumulations of the fallow. 



It is unsafe to form general conclusions from the results of 



