1^1^ 



UiU 



A FORTNIGHTLY REVIEW 



OF THE 



IMPERIAL DEPARTMENT OF AGRICULTURE FOR THE WEST INDIES. 



Vol. XV. No. 366. 



BARBADOS, I\rAY 6, 1916. 



Price \d. 



Method in Manurial Experiments with 

 Trees. 



■T reliable tiguret- are wanted as to the effect 

 of manuring, it is of the greatest impor- 

 (tance to conduct experiments, and to inter- 

 pret the results on a rational— or what is the 

 same thing — on a scientific basis. It is impossible 

 to arrive statistically at the truth without doing 

 so. The only thing we can expect to learn without 

 employing special scientific methods is the visible 

 effects of manures. That can be done by applying 

 manure to one part of the field or orchard, and by 

 leaving the remainder untreated. The treated portion 



of the crop may, as a result, look better, and may look as 

 if it would give increased yields. Such visible effects 

 can generally be trusted, especially with orchard crops, 

 and are of value. But as soon as we wish to start 

 weighing and measuring, we encounter difficulties 

 because it is not easy to decide when an increased yield 

 is due wholly, or in part, to the manure applied, or to 

 something else as, for instance, climatic changes, soil 

 differences, or the constitution of the different plants. 



It is proposed to confine attention in this article 

 to methods employed in manurial experiments with two 

 orchard crops — coco-nuts and cacao. The methods 

 described are those employed at the present time in 

 the West Indies and British Guiana. For the sake of 

 brevity and convenience, the methods will be expressed 

 by means of formulte. These are quite simple expres- 

 sions, although they may appear complicated at first 

 glance. 



Before proceeding to do this it will be useful, 

 perhaps, to paint out; some of the features of manurial 

 experiments with trees which differentiate them from 

 manurial experiments with annual crops. In manurial 

 experiments with trees the following points have to be 

 taken into account: (1) The life of a tree is lengthy 

 and has three periods, (a) the vegetative period, that is 

 the period until it comes into bearing, (b) the bearing 

 period, and (c) the period of decline during which the 

 yield tends to fall off. We must not compare the 

 effects of manures on trees in different periods of 

 development. (2) The number of trees per acre is 

 comparatively small; from this it follows that the 

 individuality of a tree may exert a great influence. 

 (8) Apart from ordinary individuality, there may 



