May, 1912.) 



429 



Scientific Agrieuliure. 



appear to affect the argument which 

 follows, though doubtless reducing the 

 possible crop of cacao on different plots 

 by different amounts. 



We come now to the question of the 

 treatment of shade on the different 

 groups of plots. At the beginning of 

 1902 the whole estate was simply a jungle 

 of Albizzias, Dadaps and Arecanuts, 

 besides coconuts and other trees, beneath 

 which the cacao, which suffered severely 

 from canker, produced an almost neglig- 

 able crop. Clearing operations were 

 vigorously prosecuted during 1902 and 

 1903, with the result that groups A and 

 B were practically cleared of excess 

 shade by the end of 1902, and group 

 by the end of 1903. Treatment of canker 

 by excision and spraying was also under- 

 taken on all three groups. 



As regards the further treatment of 

 shade, the following statement quoted 

 from my earlier Circular applies to 

 groups A and B equally, but not to 

 group C "In 1904 dadaps (Erythrina 

 lithosperma) were planted over the 

 whole area at the rate of 300—400 to the 

 acre. These should have been kept 

 closely lopped, but were allowed to 

 get out of hand and to become closely 

 crowded in 1906. With this fact the 

 comparatively poor crop of 1906-07 may 

 perhaps be associated. During 1907 the 

 greater number of the dadaps were 

 cut down, leaving only 30-40 per acre 

 for purposes of shade. The crop for 1908- 

 09 was the second best on record. The 

 same dadaps have continued to stand up 

 to the present date as a source of lofty 

 and even shade." 



On group C dadaps were similarly 

 planted at the rate of 300-400 per acre in 

 1904-05, all such operations being per- 

 formed somewhat later on group C than 

 on groups A and B. None of the 

 dadaps planted were ever felled, with 

 the result that a condition of excessive 

 shade prevailed from 1908 onwards. By 

 1910 the dadaps themselves began to 

 suffer from close planting, and both 

 dadaps and cacao are now in a miserable 

 condition. 



The average crops per acre from groups 

 At Bi and C. over a series of years are 



shown in the accompanying table, and 

 the variations in crop are also shown 

 graphically in the accompanying dia- 

 gram. It is obvious that the curves re- 

 presenting the crops from groups A and 

 B are closely similar, and we may con- 

 sider these first, reserving group C for 

 later discussion. 



The initial condition of the unmanured 

 plots B was distinctly superior to that 

 of the manured plots A as shown by 

 the crops for 1903. By 1904, however, 

 this difference was obliterated, and in 

 1905-06 the manured plots yielded an 

 appreciably higher crop than the un- 

 manured. Subsequent to 1906 the aver- 

 age crop from the manured plots fell 

 below that of the numanured plots by 

 an amouut nearly equal to the difference 

 in 1903, and the superiority of the un- 

 manured plots has since been maintained 

 to about the same extent. The natural 

 conclusion is that the manures applied 

 during the first three years of the ex- 

 periment had a beneficial effect upon the 

 crop, but that after this the addition of 

 still more manure was useless or even 

 prejudical so far as the yield is concern- 

 ed- It is clear, however, from the dia- 

 gram that the main variations in the 

 crop both from group A and from group 

 B are due to some other cause. 



Over Ceylon generally the crop of 

 cacao gathered in 1906-07 and exported 

 in 1907 was the largest ever recorded. 

 On groups A. and B. at the Experiment 

 Station the crop shewed a very marked 

 falling off. The only condition to which 

 this falling off can be attributed is the 

 dense condition of shade which was then 

 beginning to prevail. 



In 1907-08 the general Ceylon crop fell 

 off greatly, but the crop gathered on 

 groups A and B at the Experiment 

 Station showed a marked increase. The 

 shade was reduced to normal proportions 

 early in 1907, so that the cacao had the 

 benefit of increased air and light during 

 the whole of this crop season. 



Prom 1908 onwards the shade on these 

 plots was kept in a normal condition, 

 and the variations in the crop obtained 

 from groups A and B are found to 



