292 ^ 



THE AGRICULTURAL NEWS 



September 14. 1912. 



FRUITS AND FRUIT TREES. 



A NEGLECTED CONSIDERATION IN 

 CACAO CULTIVATION. 



'The hygrometric state of the air is the most important 

 factor miking for success in a cacao plantation, although it 

 his been the least considered up to the present.' This is the 

 translation of a sentence appearing at the head of one of 

 a series of articles dealing with African cacao that are being 

 published in U Agriculture Pratique des Paya ChawU, the 

 special article emp'oyed in giving the following informa- 

 tion being contained in the issue of that journal for May last. 



As far as the knowledge of the writer is concerned, 

 J. H. Hart was the first to point out that the humidity of 

 the air plays a preponderating part in the growth of cacao, 

 and he states that this opinion is finding confirmation con- 

 tinually in cacao-growing in Africa. Theoretically, the 

 matter may be deduced from the examination of meteorologi- 

 cal observations. On the Gold Coast, as in Nigeria, it is 

 easy to remark the irregularity of th-i rainfall, and the con- 

 siderable deviations in temperature which are the character- 

 istics of the climate of both place.s, particularly as one 

 approaches the north, towards the limit of the zone that can 

 be cultivated. On the contrary, a remarkable constancy is 

 noticed in the relative humidity of the atmosphere, and for 

 the first time an enormous deviation, principally among the 

 minima of the humidit)', between the figures observed for 

 the centres of cultivation of the Gold Coast and Gambaga, 

 .•situated at the extreme north of the Colony, wliere as much 

 rain falls as at Aburi, and where cacao cultivation cannot be 

 carried out. 



In practice, a large number of observations show that 

 the cacao plant suffers very severly from the dryness of the 

 air, and that much of the want of success in cultivating 

 this plant arises from the little care taken by planters to 

 provide in their plantations a sufficient degree of humidity. 

 The chief matters to be considered are as follow.^: — 



(a) Cacao plants in a plantation which readily resists 

 dry weather, thanks to the permeability and the depth of the 

 .soil, suffer damage and lose their leaves immediately after the 

 blowing of the Harmattan (a drying wind), which drives 

 away the moist air and rei)laces it by that which is dry. 

 The plantations situated in the northern parts of the belts of 

 cultivation are particularly exposed to tliis wind. The Har- 

 mattan reaches many points, as far as the coast; this is the 

 case every year at Aburi on account of its altitude. Cacao 



plants and heveas regularly lose their leaves at its first 

 breath. At Lagos, on account of the considerable deforesta- 

 tion, the north-north east wind reaches as far as the lagoon, 

 after having completely swept the centre of cultivation at 

 Agege-Otta. 



It is not necessary for the wind to be violent in order 

 that it may produce its d&maging etfects; plantations 

 •sheltered by strips of forest through which it filters suffer 

 decidedly from it, on account of the slow replacement of the 

 air which a progressive fall of the state of humidity brings 

 about. It is equally remarkable that at Oshogbo, where the 

 dry season sometimes lasts from four to five months, cicao 

 grows well, thanks to a rennrkable constancy in the 

 hygrometric state of the air. 



(b) A plantation in which the trees are planted to(x 

 widely, and where a complete cover has not been formed by 

 the fourth or fifth year, is generally in danger and only 

 gives small yields. 



In felling the forest for clearing, the planter has 

 removed the forest conditions near his plantation; that is to 

 say, he Ims eliminated the regulating factor as regards 

 temperature and the moisture of the atmosphere and the 

 soil. His first care should be to replace the cover in a few 

 years; the prosperity of a cacao cultivation is set at this 

 price. If after the removal of the temporary shade — - 

 bananas in most cases— the soil of the plantation is expo.sed 

 to the sun, the water vapour emitted by evaporation from 

 the soil and by transpiration from the leaves is dissipated. 

 The layer of air which bathes the cacao plants becomes 

 exposed, through this cause, to sudden atmospheric change.? 

 which are inimical to the trees, and loses that moisture^ 

 which it is agreed, should be present in all well-conducted 

 plantations of cacao. 



(c) Verification of the facts is supplied by observing the 

 conditions in the indigenous cacao plantations. In this 

 consideration, those are not included where the trees are planted 

 too thickly; but those, kept in good order, in which there are 

 360 to 6-tO plants to the acre. Under these conditions, the- 

 cover is suflicient without the assistance of shade trees; the air 

 is generally cool and damp during the hottest time of the day. 

 Such cultivations have been observed in the region of Agege; 

 they showed good resistance to the Harmattan and were 

 normally very productive. The leaves of the plants oi» 

 the exterior acquire, besides, special characters under the 

 influence of the sunlight and the wind; they become papery 



