4 8 



consequently the feeding value, of the roots is affected very 

 greatly by differences in manuring. As the root crops are 

 in the great majority of cases grown for consumption on the 

 farm, it is the feeding value rather than the market value 

 that must be taken into account. 



EFFECT OF SULPHATE ON YIELD. 



At Rothamsted, as far as weight of roots per acre is con- 

 cerned, nitrate of soda gave better results on mangels grown 

 continuously on the same land than ammonia salts. The 

 following table gives the weight of roots per acre per annum 

 on the average of seventeen years 1876 to 1892 produced 

 by the manurings mentioned : 



TABLE XXV. 



These figures again illustrate the principles we have 

 noticed in the case of the corn crops. The addition of 

 nitrogenous manure gave in each instance a large increase ; 

 and again we see that, while superphosphate and nitrate of 

 soda give about the same return as those manures with 

 potash in addition, when ammonia salts take the place of 

 nitrate, potash manuring seems essential for a full crop. 



EFFECT OF SULPHATE ON FEEDING VALUE. 



When the amount of food for stock per acre is considered, 

 we find different results according to the treatment of the 

 crop as regards farmyard manure. As mangels are com- 

 paratively seldom grown without farmyard manure, and as 

 it is well established that they make use of it as well as, or 

 better than, any other crop, we will first deal with the feed- 

 ing value of the crops at Rothamsted to which farmyard 

 manure was applied. The most important food constituent 

 of the crop is sugar, the percentage of which, and quantity 

 produced per acre, on the plots manured with farmyard 

 manure, on the average of four years, 1877 to 1880, are given 

 in the following table. 



