88 



CHAPTER VI 



GRAMS OF MINERAL MATTER IN ONE LEAF. 



One fresh cane leaf contains 

 One fresh trash leaf contains 



Silica 



Carbon 



Iron oxide 



Alumina 



Lime 



Potash 



Soda 



Phosphoric anhydride 



Sulphuric anhydride 



Carbon dioxide . . 



Chlorine 



Water 



Deduct oxygen equal to chlorine 



Nitrogen ., 



If this manner of regarding the cane as a growing organism is correct, it may 

 lead us to modify some of our ideas concerning the manuring of sugar canes, and 

 may account for the better result obtained by applying considerable quantities 

 of nitrogen in one dose at an early stage, and for the smaller results obtained from 

 the use of such a slow-acting manure as dried blood." 



Very early experiments dealing with this point were made as long ago 

 as 1877 by Rouf 15 in Martinique. He harvested, weighed and analysed a 

 crop of cane month by month. His results transposed into pounds per acre 

 are given below, together with the conclusions drawn : 



1. The absorption of minerals commences as soon as the development of 

 the plant allows, but evidently it is much more active if the plant finds the 

 necessary fertilizing principles at its disposal, and above all if the climatic 

 conditions are favourable. 



2. The progress is moderated from the sixth to the ninth month ; then 

 the march of the elements rises to the tenth and eleventh month, the time of 

 the maximum absorption. At this period the total weight of stalks and 

 leaves is a maximum ; the cane has absorbed all the minerals and nitrogen, 

 and the weight of dry matter also is the maximum. By the tenth month 

 the cane has absorbed a maximum of the following elements : phosphoric 

 and sulphuric acids, potash, soda and silica. At the eleventh month the 

 elements which lagged behind are absorbed up to the maximum ; these are 

 lime, magnesia and nitrogen, and the elements which first reached a maximum 

 have begun to be eliminated. In the twelfth month, the elimination of the 

 last three elements begins and continues for all until the cane is ripe. 



3. The cane should be manured early so as to place at its disposal 

 necessary food, and to accelerate the elaboration of sugar. 



4. The elimination of the excess of potash, chlorides and soda from the 

 stalk and their transport to the top and leaves are ended when the cane is 

 ripe. In the top of the cane are accumulated alkaline chloiides, glucose, 

 albuminoid and pectic bodies. 



The return of plant food to the soil by the plant as it ripens indicates the 

 agricultural economy of harvesting the crop at its period of maximum 

 ripeness as less plant food is then removed. Rouf s analyses bang out this 

 point very clearly. 



