218 CHEMICAL FERTILIZERS 



manuring for root crops is profitable, and the fertilizing 

 ingredients in the crop so obtained return to the manure 

 heap once more, and build up the whole fertility of the farm. 

 Starving the root crops or green fodder is a very bad system 

 of farming. The amount of nitrogen in manure that the 

 swede crop can take is limited, and about fcwt. of sulphate of 

 ammonia, in addition to farmyard manure, is as much as 

 it is worth giving. In addition 4-5 cwt. of basic slag or 

 superphosphate may be used. Where no farmyard manure 

 is available, 4 cwt. of superphosphate, 2 cwt. of fish meal and 

 | cwt. of sulphate of ammonia is a good dressing. The sul- 

 phate of ammonia may be applied as a top dressing at the 

 time the plants are singled. Care must always be taken with 

 regard to turnips and swedes that the land is not deficient 

 in lime, and it is therefore good policy to use basic slag in 

 place of superphosphate on some occasions. Finely ground 

 rock phosphates do remarkably well for the swede crop 

 (see p. 187), and it is therefore highly probable that mix- 

 tures containing much insoluble phosphate and a little soluble 

 phosphate will, in the future, become more popular. Roots, 

 cabbages or other fodder crops which are grown on an exces- 

 sive amount of nitrogen, make inferior foods. 



Mangolds. Mangolds respond to very large quantities of 

 nitrogen, and nitrate of soda is particularly valuable ; potash 

 is also necessary, but phosphoric acid is of less importance. 

 Resulting from the large amount of water needed for growth, 

 it is necessary that much farmyard manure should be used 

 to obtain a good soil texture. Farmyard manure is not 

 sufficiently rich in potash, and extra potash fertilizers are 

 almost always necessary. With 15 tons of farmyard manure 

 per acre, 3-4 cwt. of kainit and 1-2 cwt. of fish guano 

 should be sufficient. After singling, top dressings of nitrate 

 of soda and salt may be used to the extent of 2-3 cwt. 

 Slag has proved better than superphosphate in the northern 

 counties ; in the midlands, superphosphate has produced 

 the better results. On the light soils at Woburn up to 6 cwt. 

 of salt per acre has proved beneficial, and even quantities 

 as large as id cwt. of salt per acre have been used. 



