FERTILIZERS AND PLANT PRODUCTS 175 



Cotton having a somewhat shorter period of growth, 

 and producing a seed rich in mineral matter, needs the 

 application of larger quantities of fertilizers. Phosphates 

 and organic nitrogen manures are very valuable for this 

 type of crop, and sulphate of ammonia can be also used 

 profitably here. 



Tea being a perennial crop has rather more resemblance 

 to hay than many of the other types of crop. Whilst a 

 certain amount of nitrogenous manure is desirable, excessive 

 amounts tend to produce an inferior quality of leaf. Some 

 of those who experimented in the use of sulphate of ammonia 

 obtained rather unsatisfactory results at first. The reason 

 for this was that excessive quantities were supplied in an 

 unsuitable manner. Where an ample supply of organic 

 manures can be obtained, sulphate of ammonia is not 

 so necessary, but in many situations small and cautious 

 applications of sulphate of ammonia will probably be found 

 useful (see Bald, p. 177). 



Coffee is a somewhat exhaustive crop, and requires 

 a fair amount of nitrogen, phosphates, and potash. 



Succulent Crops. — The general effect of nitrogenous 

 manuring is to delay the ripening of the plant, and to produce 

 a large quantity of green material. Nitrogenous manures 

 tend to produce large quantities of succulent matter, but 

 do not tend to produce flowers, fruit, and seed. 



These manures are, therefore, especially valuable for 

 such crops as lettuces, cabbages, mangolds, tea, etc. The 

 phosphatic manures are generally characterized by the 

 production of deep roots, and it is for this reason that 

 the shallow-rooted crops need considerable quantities of 

 phosphates, because they have no deep root system to go 

 after plant food, and require something to strengthen this 

 system. Potash manure tends rather to the production 

 of seeds and flowers, but does not help root development to 

 any very large extent, but it has no delaying action, in the 

 same way as the nitrogen. Development of deep roots will 

 also depend upon the position of the water supply. Deep 

 water will encourage deep rooting, and surface water will 



