118 



RESULTS WITH TURNIPS 



1861-70, the addition of 400 Ibs. of ammonia salts to super- 

 phosphate and alkalies increased the crop by an average of 

 only 2 tons of roots and 8 cwts. of leaves. The turnip and 

 swede are not crops which flourish when grown year after 

 year on heavy land like that at Rothamsted, and the produce 

 of the plots consequently became very small. The evil 

 arising from the gradual exhaustion of the humus in the soil 

 was clearly shown in the later swede experiments, when 

 manuring with rape-cake proved far more effective than 

 manuring with ammonia salts, a result which has not appeared 

 in field experiments with any other crop at Rothamsted. 



In the Rotation field at Rothamsted good crops of swedes 

 are obtained, and the beneficial effect of nitrogenous manures 

 is strikingly shown. The rotation is the usual one of swedes, 

 barley, clover or fallow, and w T heat. The average of eleven 

 crops of s\vedes, on the portion of the field from which all the 

 produce is carted, is as follows : 



TABLE XXXIX. 



AVERAGE PRODUCE OF SWEDES IN ELEVEN ROTATIONS AT 

 ROTHAMSTED. 



Thus while the permanently unmanured land produced 

 barely one ton of roots, a purely cinereal manure, consisting of 

 3^ cwts. of superphosphate, with, in the later years, salts of 

 potash, soda, and magnesia, produced more than 8 tons, a result 

 which remarkably illustrates the ability of the turnip crop to 

 obtain nitrogen from exhausted land if only it is supplied with 

 phosphates. 



The mixed ammonia salts and rape cake supplied 141 Ibs. 

 of nitrogen, and consisted of 200 Ibs. ammonia salts, and 2000 



