THE MANURING OF THE CANE 91 



Lime in Connection with Cane Growing. A study of the analyses of 

 the ash of the cane cannot lead to the conclusion that the cane is a calciophile 

 plant, and Harrison 8 in his resume of twenty-five years' experimental study 

 of the manurial requirements of the cane has come to the same conclusion. 



The benefits that follow the application of lime in many districts where the 

 cane forms the staple crop must not then be considered as due to specific 

 action of this material on the cane, but as due to its general effect in ameliora- 

 tion of the soil. 



The action of lime may be briefly summarized : 



1. Correction of acidity in the soil, whether due to an excess of organic 

 matter or due to long-continued application of ammonia salts. 



2. Amelioration of the physical condition of heavy clays. 



3. Rendering potash available. 



It is now generally considered better practice to apply moderate doses 

 of lime, say 1,000 Ibs. per acre, every five or six years, than to put on 

 heavier applications less frequently. This is the general rule in the Hawaiian 

 Islands, larger applications being only made on a few plantations possessing 

 a distinctly sour soil with much organic matter. However, some heavy 

 clay adobe soils have been treated there with success with as much as fifty 

 tons of coral sand to the acre ; this procedure recalls the system of marling 

 once so prevalent in English agricultural practice. 



The form in which lime is applied is either as the carbonate or as quick- 

 lime. Recent practice inclines very strongly to the use of the carbonate, 

 to the exclusion of the caustic form. In addition, the fineness of division 

 of the lime has been shown to have a very great bearing on its efficiency. 

 The very extensive literature on this important point has been collated by 

 Kopeloff, 18 whose experiments point to ground limestone sifted through 

 mesh 200 to the linear inch as being the most efficient form in which to make 

 the application. 



A point of very great interest in connection with cane growing and one 

 which has not, so far as the writer is aware, been thoroughly investigated, is 

 the " lime : magnesia " ratio best suited for the cane. For cereal crops gener- 

 ally, for rice, and for such as have a large leaf development, evidence has been 

 brought forward by Loew 19 and his pupils that the lime should be in excess 

 of the magnesia in proportion from I 5 to 2 times as great. In the absence 

 of any evidence to the contrary it may perhaps be taken that a similar ratio 

 holds for the cane. That an excess of magnesia has a deleterious effect on 

 the cane has been shown by Eckart, 20 who irrigated cane in tubs with both 

 lime and magnesia chlorides, and found a much better growth when the lime 

 was in excess of the magnesia than when the quantity of these two bodies 

 was nearly the same. 



Quite recently Loew 21 in Porto Rico has gone further into the subject in 

 special reference to the cane ; in that island he has found the soils containing 

 an excess of magnesia over lime. He quotes an instance of a cane soil 

 suffering from acidity, stiffness and an excess of magnesia over lime where an 

 application of 3,000 Ibs. lime per acre increased the yield of cane 57 per cent. 

 He also writes : " The most favourable ratio of lime to magnesia in the soil 

 for cane will very probably be as 2 to I, if both are present in an equal state 

 of availability. This can be inferred from experiments with maize by 

 Bernadini." 



