428 



[May, 1912. 



SCIENTIFIC AGRICULTURE. 



ON THE EFFECT OF SHADE IN 

 CACAO CULTIVATION. 



By R. H. Lock, sc.d. 



(From Circulars and Agricultural 

 Journals of the Royal Botanic Gardens, 

 Peradeniya, Vol. VI,, No. 9.) 



In a recently published Circular * 

 certain views were expressed by the pre- 

 sent writer on the importance of the 

 proper treatment of shade in Cacao 

 Plantations. The conclusion was drawn 

 from more or less general observations 

 that the planting up of shade trees and 

 the cutting out of excessive shade have 

 a far greater effect upon the crop than 

 any amount of manuring whether with 

 artificial fertilizers or with cattle manure. 

 Figures were published which showed in 

 the opinion of the writer that no defin- 

 ite distinction could be drawn between 

 the behaviour of twentyfive different 

 plots, covering an area of 22 acres, some 

 of which had been left unmanured for 

 the previous eight years, whilst others 

 had been treated with large quantities of 

 different specified fertilizers. It is the 

 object of the present note to communi- 

 cate certain definite figures which have 

 a direct bearing upon the question of 

 the treatment of shade. 



The positions of the different groups 

 of plots here described are shown in the 

 accompanying plan. 



The manured plots, described at length 

 in Circular No. 4 of the current volume, 

 bear the following numbers : 3-9, 94-96, 

 98-101 and 107-111. They occupy alto- 

 gether 19 acres. These plots have been 

 treated regularly with various fertilizers 

 since 1903. We will refer in future to 

 the whole group of manured plots as 

 group A. 



The plan shows that the following eight 

 plots, 1 and 2, 10 and 112-116, each an 

 acre in extent, are situated in close 

 proximity to group A, Speaking in 

 general terms they are closely similar to 



* Report on Experiments in Manuring Old 

 Cacao, Circular Vol. VI., No. 4, October, 1911. 



the plots of group A both in respect of 

 the varieties of cacao which occupy 

 them and in the nature of their soil. 

 They have, however, the advantage of 

 possessing a somewhat larger proportion 

 of good Forastero trees as compared 

 with trees of the Old Red variety, and it 

 is believed that plots 1 and 2 received 

 considerable quantities of cattle manure 

 prior to 1902, when the estate was taken 

 over by Government. Since 1902 the 

 treatment of these plots has been pre- 

 cisely the same as that of > the manured 

 plots, except for the fact that they have 

 received no fertilizers of any kind. We 

 will call this group of unmanured 

 plots B. 



We may further describe plots A and 

 B as being situated on the near side of 

 the paddy-field which divides the Experi- 

 ment Station into approximately equal 

 portions. 



On the further side of the paddy-field 

 there is a block of 42 acres (plots 11-52) 

 which was occupied by old cacao in 1903. 

 Subsequently certain of these plots were 

 cleared in order to make room for 

 other products, as follows :— Plots 24 and 

 25 in 1905, plots 11 and 12 in 1908, and 

 plots 13-23 in 1911. The area described 

 was thus reduced in 1911 to 27 acres. It 

 should be pointed out that the plots 

 cleared were among the poorest yielders 

 of the group in question, a circumstance 

 which adds additional weight to the 

 argument which follows. We may call 

 the group of plots on the far side of the 

 paddy-field group C. 



Group C consists of very much poorer 

 cacao than groups A and B. It includes 

 a considerably higher proportion of the 

 old Red variety, and it is interplanted 

 with coconuts to an extent which must 

 have bad a material effect upon the crop 

 of cacao produced. Groups A and B 

 also bear a small number of coconut 

 trees, but not so many as group C. The 

 number of coconuts has remained con- 

 stant on all thiee plots throughout the 

 experiments, and their presence does not 



