2.9 Plot size and shape

Conventionally, progenies are arranged in plots of 4 x 4= 16 palms. Recently, Breure & Konimor (1992) presented evidence that the expected response to selection of 16-palm plots is greater than with plots of a smaller number of palms. The plot is the experimental unit to compare progenies, so the average yield per plot is needed to estimate General Combining Ability (GCA) values. Carrying bunches to a central point for weighing is not convenient, mainly because the stacked fronds in the interrow do not allow for the easy movement of workers. Recording yield per palm is therefore preferred. The possibility of identifying outstanding tenera for clonal propagation is an additional advantage. Individual palm recording also permits more careful checking harvesting standards and loose fruit collection.

Experiments to compare sources of planting material are usually laid down in commercial estates. It is therefore more convenient to weigh the bunches per plot in bulk; moreover, data processing is simplified as plot yields are immediately available. This method of bulk recording becomes practical when all palms of one plot are bordering the same interrow path for transporting the bunches to the road (harvesters x path).

An inspection path is usually established in the centre of the field, parallel to the collection roads, to improve supervision.

For convenience of carrying bunches, the distance between collection roads is about 250 m. There are thus 27 palms between roads, assuming the usual distance of 9 m between palms.

The layout of harvesters x paths and inspection paths makes it convenient to establish the progenies in two half-rows (27 palms per plot), as shown in Fig. 1.

Progenies may differ considerably in vigour, and thus mutual shading, which may create a bias in evaluating their yield potential, particularly if derived from distinct sources of parent palms. The effect of mutual shading can be diminished by grouping the progenies according to sources of planting material and, within these sources, to the height and mean leaf area established in the nursery.