80 THE CHEMISTRY OF THE FARM 



bined phosphoric acid of the soil. On exhausted land 

 it is generally impossible to obtain a crop without the 

 use of a phosphatic manure, which is generally drilled 

 with the seed. Superphosphate or basic slag may be 

 used for this purpose. 



Mangels have far deeper roots than turnips, and 

 also a longer period of growth. They have a great 

 capacity for drawing food from the soil, including 

 nitrogen, potash, and phosphoric acid. "When carted 

 off the land they are probably the most exhaustive 

 crop that a farmer can grow. As mangels have not 

 the same difficulty that turnips have of attacking the 

 combined phosphoric acid of the soil, phosphatic' 

 manures are, in their case, of much less importance. 

 Nitrate of sodium, when applied alone to mangels, 

 •generally produces a great effect on the crop ; this is 

 not the case with turnips, which require phosphates 

 as well as nitrogen in their manure. 



As both turnips and mangels consume extremely 

 large amounts of plant food, a liberal general manuring 

 with farmyard manure is, in most cases, essential for 

 the production of a full crop ; but the special charac- 

 teristic of the manure for turnips should be phosphatic, 

 and of that for mangels nitrogenous. When large 

 crops are to be grown potash manure must not be 

 omitted. With an abundant supply of nitrogenous 

 manure the proportion of leaf is increased, and the 

 maturity of the root delayed. A heavily-manured 

 crop should be sown early. Late-sown crops of 

 roots should receive a smaller proportion of nitrogen 

 in their manure. 



When beetroot is grown for sugar it is essential to 

 produce small roots; heavy manuring is therefore 



