212 



THE AGRICULTUEAL NEWS. 



July 4, 1914. 



FRUIT AND FRUIT TREES. 



THE DOMINICA. MANURIAL EXPERI- 

 MENTS WITH CACAO. 



A paper of considerable interest to the cacao industry 

 in general appears in the recently issued number of the 

 West Indian Bulletin {Vol. XIV, No. 2). It is compiled by 

 Mr. H. A. Tenipany, B.Sc,, Government Chemist and Super- 

 intendent of Agriculture for the Leeward Islands. 



During the past eleven years manurial experiments with 

 cacao have been systematically conducted on plots of mature 

 trees situated in the Botanic Gardens, Dominica. Annual 

 accounts of the results of these experiments have appeared 

 in the Progress Iteports on the Botanical and Experimental 

 Stations, but the object of the present paper has been to 

 study the cumulative results in greater detail, particularly 

 in connexion with the influence of various environmental 

 factors on the results in question. 



Although the original series of trials was begun in 

 1902, and has been continued up to the present time, in 

 igOt four additional plots were laid out to afford extra 

 information on points elucidated by the original series. The 

 evidence derived from the additional experiments fully 

 confirms the conclusions drawn from the original series. 

 The manurial treatment which the plots (0-28 to 0'37 acre 

 in area) has received is as follows: Plots C, no manure; 

 plot A, basic phosphate 4 cwt. per acre, sulphate of potash 

 1| cwt. |er acre; plot B, dried blood 4 cwt. per acre: 

 plot E, basic phosphate 4 cwt. per acre, sulphate of potash 

 H cwt. per acre, dried blood 4 cwt. per acre; plot D, 

 mulched with grass and leaves. In the additional series 

 of the experiments, the manurial treatment was: plot F, 

 mulched with grass and leaves; plot G, manured with 

 cottonseed; plot H, no manure; plot I, mulched with grass 

 and leaves. 



In describing the physical characteristics of the soils 

 of the plots, it is shown in the paper by the figures of 

 analysis that these are distinctly light and sandy in type; the 

 underlying subsoil forms a continuation of the top soil, and 

 presents a considerable thickness of coarse sand and gravel 

 through which water percolates freely. During the rainy 

 season the permanent water table usually stands about 8 feet 

 below the surface of the ground. In order to determine 

 what the exact physical character of the soil is from plot 

 to plot, a series of shrinkage determinations was made 

 whereby the approximate amount of agricultural clay is 

 obtained. These have shown, on the whole, that the texture 

 of the soil varies only slightly throughout the plots, except 

 in the case of plot E. 



Turning now to the treatment received by the plots, it 

 should be pointed out first, that the variety of cacao culti- 

 vated on plots A to E is, on the whole, of the Forastero type, 

 with a tendency towards Calabacillo. Plots H and I, on the 

 other hand, are planted with trees of the Amelonado type. 

 The manures and the mulch are applied once a year, usually 

 during the months of May and June. In applying the 

 manures the material is .spread uniformly over the surface of 

 the ground, and then lightly raked under. The mulch is 

 composed largely of grass from the lawns mixed with leaves 

 and pods of the Saman trees (Pithecolobium Saman), which 

 surround and shade the lawn. The mulching material is 

 given at the rate of 5 baskets each containing 20 fb. to 

 every tree. In view of the importance of the mulching 

 methods as demonstrated by these experiments the question 



of the manurial value of various descriptions of mulches is 

 considered in a special section of the paper. 



After having described the meteorological conditions (from 

 which, unfortunately, data concerning relative humidity and 

 wind pressure are necessarily omitted), the author proceeds to 

 describe the methods of the cicao growing in each of the 

 plots. These observations seem to confirm fully the quanti- 

 tative results, and show a gradual transition from highly 

 vigorous growth and good health in the case of the mulched 

 trees down to less vigorous and less healthy condition 

 in the case of the trees that have received no fertilizer. 



The yields recorded from the plots from year to year are 

 treated in the paper graphically. In Plate I the returns 

 from the original series of experiments are displayed, while 

 Plate II gives those obtained in the two additional series. 

 Inspection of the curves shows that while in the case of the 

 No Manure plots, C and H, the returns fluctuate closely 

 around the mean value, those for the plots which received 

 manure show, on the whole, a distinct upward tendency in 

 the earlier years of the experiments, and subsequently settle 

 down to fluctuations around the mean value higher than that 

 of the No Manure plot. .Moreover, when this value has been 

 attained, the annual fluctuations in yields are less marked in 

 the cases where the plots have received a dressing supplying 

 all the various manurial constituents than when the dressing 

 in character is incomplete. 



The important corollary follows, that in applying manures 

 to orchard cultivation under conditions such as those govern- 

 ing these experiments, a period of from three to five years will 

 usually lie required to elap.se before the trees settle to the 

 standard of fertility conditions as the treatment applied. 



In the next section of the paper, data are given showing 

 the mean probable error attaching to the various experiments 

 and demonstrating that the value of this factor is in all 

 cases of such magnitude as to allow of the results adduced 

 being regarded with confidence as indicative of real differ- 

 ences derived from various forms of treatment. 



The chemical characteristics of the soils of the plots 

 bring out the effects of the manurial applications as regards 

 soil composition. In respect of the nitrogen content, the 

 mulched plot B is by far the highest, whilst it is followed by 

 plot E which received the complete manure. Possibly owing 

 to leaching, plot B showed a lower nitrogen content than 

 plot E, though it has received the same manurial treatment. 

 Observations are included in regard to available phosphoric 

 acid and potash The results in relation to organic carbon, 

 on the whole, follow those found in the case of nitrogen, 

 being highest in the case of plot B, and lowest in plots A and 

 C. The question of the relationship of the plots in this 

 respect is considered further at a later stage in the paper. 



The manurial gains and losses which have accrued to 

 the plots are dealt with at considerable length in the paper 

 and bring to light many points of great interest. This and 

 the remaining sections of Mr. Tempanys paper will receive 

 consideration in the next issue of the Agricultural News. 



In the Chamber of Commerce Journal for June 1914, 

 attention is directed to two tropical products of new com- 

 mercial interest: (1) The Philippine oil nut, apparently belong- 

 ing to the Meliaceae, the nuts of which contain 4.5 per cent, 

 of non drying good soap making oil; and (2) some important 

 hardwood timber of the Solomon Islands — Callophylhim 

 inophyllwn, useful for furniture making, and AJzeila hijuga, 

 which appears to be absolutely impervious to tht attacks of 

 white ants. These timbers are becoming recognized on the 

 New Zealand and Australian markets. 



