A STUDY OF THE FACTORS OF COXTEOL. 85 



kept as a cheek. 2nd ]May, when the cane Avas about 4 inches high, twelve 

 second-stage grubs of Lepidiota frcnchi were placed in each pot, in holes 

 about an inch deep made in the surface of the soil around the sets. On 

 26th November the cane in the check-pot was practically dead, while that 

 in the treated pots was green and almost normal in appearance. On ITtti 

 December the soil was turned out of all the pots. The check had seven 

 grubs, three feeding on set and remains of large roots near top of soil, 

 and four finishing roots below set that had l)een bitten off higher up. AH 

 the megass had been eaten in the treated pots, and the grubs had just 

 begun on the roots of the cane. 



In the second experiment the treatment was much the same, except 

 that the megass was placed nearer the set in each case. On 2-lth ]May 

 five second-stage grubs of Lepidiota frencln were placed in each pot. 

 On 24th October the cane in the check had died after making leaves a 

 foot long. The soil was turned out and four grubs were found, one in 

 stage III, eating in end of set. On 17th December the cane in the 

 treated pots began to shov\f signs of injury. Xo megass was left, and the 

 grubs had begun to eat the roots of the plants. 



While it would hardly be i)ractical to treat canefields with megass, 

 the same end is accomplished by the frequent use of green manures, 

 and the conservation of trash and other refuse from the crops. Proltably 

 there is no treatment more adaptable to grubby soils than that devised by 

 Mr. AVilkinson, as outlined above. 



I have also emphasised surface cultivation mainly because of its 

 value for increasing the vigour of the crop, hence making the plants- 

 more resistant to attack. Furthermore, I was able to show, by an exten- 

 sive series of experiments that I carried out at Greenhills during 

 January and February, 1919 (105). that cultivation was effective in 

 destroying a part of the young grubs. The best results, as one would 

 naturally expect, came from the frequent use of the pony plough, 

 working as near the stools as pos.sible. The ordinary one-horse scarifiers 

 Avere next in the order of effectiveness, and the harrows came last. And, 

 again, in our ^leringa plots we had unmistakalile evidence of the value 

 of cultivation ; for even in the check-plot, which received no other treat- 

 ment than thorough cultivation extending Avell into February, the cane 

 cut a fair crop. 



Fertilisers are important in the growing of any crop, liut this is 

 particularly true Avith sugar-cane, for experiments have demonstrated 

 that a 30-ton crop removes from the soil 102 lb. of nitrogen, 65 lb. of 

 ]iotash, and 45 lb. of phosphate. Land not supplied Avith these elements 

 rapidly becomes depleted, and soon it Avill not produce paying crops. 

 By using lime the natural unavailable potash of clay soils is gradually 

 liberated ; so artificial application of this element is not required so soon 

 on ncAV land. Nitrogen, hoAvever, is highly essential for the maximum 

 profit, especially when Ave consider the stinuilus that it gives to cane 

 being injured by grubs. If sulphate of ammonia is used, it must be 

 applied only after the rains haA^e set in, else its effects are largely lost. 

 The usual practice of applying 2 cAvt. of this salt per acre does not give 

 maxinuim results; it could Avell be d()ul:)led, making two applications, and 

 Avould show a handsome profit. 



I am sorry to repeat, as I have reported previously (108), that. 

 meatAvorks manure appears to make the grubs more destructive to the- 

 cane-roots. In all of our plots AA'here this fertiliser Avas used Ave had a. 



