86 CHAPTER VI 



collected from the refuse of old villages and known as " ruins manure," is 

 also used by the fellaheen planters, as well as dove dung, to which a quite 

 fictitious value is attached. 



In Barbados and other islands of the British West Indies pen manure 

 forms an important source of plant food. 



The methods of application differ very considerably. In countries such 

 as Java, Demerara, Mauritius, where there is a cheap supply of labour, the 

 sulphate of ammonia used is placed by hand directly at the foot of the cane 

 stool. A hole may be made in the ground with a crowbar, into which the 

 calculated quantity of manure is placed with a spoon or other measure. 

 Alternatively a ring maybe scratched round the stool over which the material 

 is scattered. In Java exactitude in application has been sometimes carried 

 to the extent of supplying the sulphate of ammonia in the form of tablets 

 of from 7 to lo grams weight. In countries where labour is more expensive 

 the manures are usually broadcasted on the land and incorporated with the 

 soil in the operations of ploughing. The applications may also take place 

 in the furrows as they are opened out to receive the tops as they are planted, 

 or the manure may be placed near the cane row after small ploughs have been 

 used in cultivation. In the Hawaiian Islands it is not unusual to apply 

 nitrate of soda dissolved in the irrigation water. 



The relatively very great quantity of manure used in the Hawaiian 

 Islands calls for comment. Carefully conducted experiments confirmed by 

 plantation experience have there shown that the limit at which the return 

 from manures ceases to become remunerative is much higher than elsewhere. 

 This is all the more remarkable considering the high fertility indicated by 

 analysis and confirmed by the great productivity found in practice on 

 unmanured land. Actually the response to heavy dressings of manure has 

 been found to be the greatest on the richest and most fertile soils. This 

 condition can be readily understood in the light of the law of minimum 

 \cf Chapter V) by realising that on certain soils there are no limiting factors 

 present ; certain of the Hawaiian soils in conjunction with ample irrigation 

 and good tilth very nearly approach this condition. In other countries 

 where such large applications of manure do not give a proportionate increase 

 in the crop, some limiting factor, as for instance lack of rain, may be present. 

 It is also to be remembered that the sugar produced by intensive manuring 

 in Hawaii enjoys protection in the U.S. market, so that pound for pound 

 the sugar produced is more valuable than that grown in unprotected districts. 



Time of Application of Manures.^ — The experimental studies of the manur- 

 ing of the cane have in all cases pointed to the benefit to be obtained from an 

 early application of readily available nitrogen and as a matter of observation 

 it has been found that such canes make a rapid, vigorous growth and are less 

 affected by a drought which may occur after the canes are established. 

 Geerligs explains the specific action of nitrogen as first of all causing the sap 

 to rise in the stem ; the leaves at this stage of growth are unable to elaborate 

 the sap, and consequently a development of the underground buds of the 

 rhizome is forced. This process is known as tillering or suckering, and results 

 in a larger number of stalks to a stool. The influence of nitrogen is, however, 

 more than this. The root system of the cane develops, and thus gives the 

 cane more opportunity to make use of the soil and of the limited supply of 

 soil water during a period of drought. In general plant physiological 

 experience readily available nitrogen leads to large leaf development, and 



