566 



The Supplement to the Tropical Agriculturist 



so prevalent that in May, 1902, when the sys- 

 tematic treatment was begun, over 90 per cent 

 of the trees on the whole station were diseased. 

 By vigorous measures this number had been 

 reduced below 10 per cent on the experimental 

 plots by the end of 1903. Nevertheless, through- 

 out the experiments the loss of crop from this 

 scourge represents a considerable item. The 

 total crop from each plot from 1903 onward is 

 recorded in a comprehensive table from which 

 we quote as follows ■ — 

 Total Number of Pods Produced by Each 

 Plot from 1903-1911. 



go 



Plot. '1 reattnent. 



1903. 



1905-06. 



1908 09. 



19X011. % 



rage 

 d to 















Ave 

 late 













1905-11. 





1 Unmanured 



9311 



15459 



16163 



7402 



11 75^ 



9'0 



2 I nmanured 



7087 



13036 



14758 



7750 



9026 



7 - 4 



3 Lim ■ once 



6223 



11773 



90B1 



6360 



7341 



5-7 



4 Cattle manure 



4563 



10251 



8888 



50J3 



6478 



5'0 



5 Lime forked 



3225 



8?ea 



6751 



4^87 



5676 



4'4 



6 Lime Unforked 



2523 



9151 



7145 



5326 



6330 



4'9 



7 Basic slag and 















ammonium 















sulphate 



2777 



10952 



7531 



5401 



6836 



5-3 



8 Kainit 



2685 



8653 



7239 



54^0 



6245 



4-8 



9 Bone dust 



2256 



8274 



8193 



6666 



7191 



5-5 



10 (Jnmanured 



3662 



10276 



7952 



6417 



7392 



5'7 



91a Potassium 















chloride 



4232 



14094 



11614 



6992 



9189 



7.1 



946 Potassium 















sulphate 



4523 



14688 



9770 



5770 



8715 



6-7 



95a Sodium 















nitrate 



4230 



12S24 



8398 



4614 



7090 



5-5 



9:6 Ground- 















nut cake 



4432 



12628 



88S1 



4544 



7358 



57 



96a Concentrated 















superphos- 















phate 



3108 



12270 



8952 



4582 



7391 



5-7 



9(i6 Precipitated 















phosphate 



4330 



9058 



9380 



5192 



6?95 



5'3 



98 Fish manure 



887 



5677 



7966 



7981 



69S9 



5-4 



99 Blood meal 



668 



6530 



4969 



4414 



5285 



4'1 



100 Castor cake 



1125 



6718 



9827 



5292 



6360 



4-9 



101 Basic slag and 















potassium 















Sulphate 



2155 



6149 



8735 



5436 



6091 



4-7 



107 Basic slag, 















castor cake, 















and potassium 













sulphate 





10600 



9057 



6334 



7833 



6-0 



108 Ground nut 















cake and 















potassium 















sulphate 





9684 



7744 



6805 



7307 



5 6 



109 Potassium 















nitrate 





8890 



4961 



4340 



5564 



4-3 



110 Basic slag 





10956 



5950 



4542 



6386 



4-9 



111 Ammonium 















sulphate 





11268 



9311 



693C 



8284 



6-3 



Average 



3622 



10038 



8H6S 



5822 



7198 



5-5 



Average calcu- 















lated to cwt. 



2-8 



7'7 



67 



4-5 



5.5 





The recovery of the cacao from its initial en- 

 feebled condition was marked by an increase in 

 the general crop, which rote to a maximum in 

 the season 1905-06 in the case of practically all 

 the plots ; but the crop of 1906-7 was compara- 

 tively poor. In 1904 dadaps were planted over 

 the whole area at the rate of 300—400 to the 

 acre. These should have been kept lopped, but 

 were allowed to get out of hand and to become 

 closely crowded in 1906. With this fact, says 

 Dr. Lock, 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 tor pur- 

 poses of shade. The crop for 1908-09 was the 



second best on record. The same dadap trees 

 have continued to stand up to the present date 

 as a source of lofty and even shade. Dr. Lock 

 gives a complete list of the manured plots with 

 a description of the treatment which each one 

 has received. The general method of applica- 

 tion of all the fertilizers was to scatter the 

 manure in a circle round each tree and fork it 

 lightly into the soil. At the beginning of the 

 experiments the diameter of the circle was from 

 three to four feet, bat this was gradually in- 

 creased to six feet, at which point the various 

 circles generally met, the average distance 

 between the trees being approximately twelve 

 feet.' More recently the manures have been 

 applied in straight lines between the trees. 

 Speaking generally, the soils of these plots are 

 distinctly favourable for the growth of cacao, 

 their mechanical condition especially being 

 excellent. Arranging the plots in order of 

 average crop gathered for 1905-11, Dr. Lock 

 shows as the first remarkable result that the 

 unmanured plots 1 and 2 come out easily at the 

 head of the series. There is no exact record 

 of the treatment of these two plots prior to 

 1903. They are, however, situated adjacent to 

 the cattle sheds, and it is understood that the 

 plots received large quantities of dung in the 

 form of a mulch. We have independent reasons 

 for regarding surface mulching as a specially 

 valuable treatment for cacao, and we know 

 from the results of the Rothamsted experiments 

 that the effect of dung may persist in the soil 

 for an indeterminate number of years. Dr. 

 Lock has, therefore, little reason for surprise 

 at the position taken by these two plots; 

 but, after a series of interesting comparisons, 

 he comes to the conclusion that of all fertilizers 

 continuously applied, the best resultiis obtained 

 from those which contain phosphoric acid, 

 especially when this constituent is combined 

 with nitrogen in such a form as bone-dust or 

 fish manure. He says we may even go so far as 

 to express the opinion that either of these ferti- 

 lizers will probably yield a profit when applied 

 to old cacao. There is no direct evidence that 

 the application of any other form of manure 

 leads to a profit. With regard to the above, 

 Dr. Lock asks : To what are we to attribute a 

 result so entirely contradictory of those ob- 

 tained in the West Indies ? We have no data; 

 he says, from which to ireply to this question, 

 but it is evident that extreme caution must be 

 used in attempting to apply the results of 

 the experiments of this nature. It is hoped 

 that future experiments with young cacao will 

 lead to more definite conclusions. Beside can- 

 ker fungus, squirrels are said to levy a consider- 

 able toll on the cacao crops at the Experimental 

 Station. They eat holes in the ripe or nearly 

 ripe pods and remove the contents. Tables are 

 given showing an annual average destruction of 

 528 pods by squirrels and of 725 pods by canker 

 fungus — which means a loss of nearly a hundred- 

 weight of cocoa beans. Dr. Lock winds up his 

 report with an exhaustive summary and dis- 

 cussion in which he states that the differences 

 of crop which can be attributed to the action 

 of definite chemical constituents are extremely 

 slight, and it seems clear that the continued 

 application of most artificial manures to a 



