THE MANURING OF THE CANE. 



order of availability. Of the organic forms of nitrogen Stubbs ranks castor 

 pomace first, followed by dried blood and fish scraps. 



Choice of Nitrogenous Manures. As a general principle it 

 has become accepted that sulphate of ammonia is the better material to use on 

 soils containing a high percentage of calcium carbonate, since in such soils 

 conditions are generally favourable for nitrification. On the other hand it is 

 believed that in the absence of this body or on soils which are of an acid 

 reaction that nitrate of soda is the preferable source. The idea, however, that 

 nitrification is essential to the assimilation of nitrogen by plants must now, 

 however, be definitely abandoned, as a whole series of experiments, initiated in 

 1887 by Pitsch and terminating with those of Miller and Hutchinson in 1909, 

 have shown conclusively that plants can assimilate ammonia compounds 

 directly. 



The long continued application of ammonia salts to certain soils may 

 result in an acid reaction therein with consequent sterility ; such a result has 

 been observed in light sandy soils at the Woburn Experimental Station. On 

 the other hand, the long application of sodium nitrate may result in the 

 deflocculation or puddling of the clay of soils, rendering them mechanically 

 quite unfit for cultivation. 



So far as tropical cane experiments and experience go the mass of 

 evidence seems to be divided ; but Harrison 14 is, however, of opinion that the 

 heavy clay soils of British Guiana have benefitted rather than not by the long 

 continued application of ammonium sulphate; this he is inclined to attribute in 

 part to the alkaline nature of the sub-soil water. In Java too, sulphate of 

 ammonia forms the source of available nitrogen. In the Hawaiian Islands 

 nitrate is extensively used as a stimulant, though ammonia salts form a part of 

 the high grade fertilizers also used ; in Egypt and in Mauritius, nitrates 

 are also extensively employed. 



The organic forms of nitrogen are used with a different object to the more 

 readily available, and their use as the sole source of nitrogen seems confined to 

 Louisiana, where the simultaneous production of cotton seed meal may account 

 for this preference. 



At the moment of writing nitrate of lime is being extensively advertised, 

 and this material may well become the most eflicient source of nitrogen for the 

 cane, but experiments with it are as yet imperfect. 



Specific Action of readily available Nitrogen. The 



action of ammonia as an early cane manure is thus explained by Geerligs : 

 Its application causes the sap to rise in the cane ; the leaves are unable to 

 elaborate this sap, and consequently the development of the undermost buds 

 is forced (tillering or suckering) ; the number of canes in a stool is thus 

 increased ; it is essential that favourable weather follow this forcing, else the 

 young shoots will wilt and die. 



71 



