Pineapple experiments in Zanzibar

Abstract

In a previous report* covering the first and second harvesting seasons, the results of a" manurial and a spacing trial on pineapples, conducted at the Kizimbani Experiment Station, were described. The results of the third and fourth harvesting seasons of these trials are now available and the present article reviews the findings over the four-year period. One of the aims of the experimental programme on pineapples being carried out at Kizimbani is to study methods whereby pineapples can be grown in continual cultivation On the same land. This kind of cultivation markedly, influences experimental results from two main causes. Firstly, the stimulating effect of a treatment which produced a heavy harvest is followed in the next year by an adverse effect in that more of the plants which received the treatment become" ratoons" than do those in the non-treated areas and the" ratoon" plants do not bear so well in the second year as original plants which have not yet fruited. Care must be taken therefore in distinguishing between a treatment effect which is merely hastening the harvest and the more valuable effect of both hastening and increasing the harvest. The second cause is that yield apparently diminishes with continued ratooning, apart from the effects of soil exhaustion. The manner in which repeated cropping produces this result is not yet clearly understood, but the habit of growth of the plant may afford a tentative explanation. Each ratooning sucker becomes progressively further detached from the soil as suckers sprout from the axils of the parent plant and frequently become recumbent under the weight of their fruit. After a few years it becomes necessary to remove all the old root bases and reset the last generation of suckers firmly in the soil. This, apparently, has a stimulating effect on fruit (yield, number and total weight), although if the majority of suckers are replanted in the plot the effect may be similar to the establishment