Introduction

Given that Deli x AVROS crosses are the most popular materials in commercial oil palm plantations, it is useful to have data on vegetative growth for reference purposes, in order to assess the performance of any other commercial plantation using this type of genetic material. The aim of this paper is to present the growth curves of a particular Deli x AVROS cross, whose development was followed during 14 years after planting in the field. These data does not necessarily represent the average performance of any given Deli x AVROS cross, or even the average performance of the commercial lots of the plantation where it is grown. The plot studied was chosen simply because there was a large amount of information available. These growth figures (or the yield figures corresponding to another commercial Deli x AVROS plot) do not claim to be optimal for the age of the palms.

We studied the vegetative growth of 79 palms of a cross known as C9258, planted in 1986, which forms part of a breeding experiment (CB862A). Some of the information on bunch yield comes from a commercial Deli x AVROS plot (126 ha) planted in the same year. The yield data shown in some tables and figures corresponds to whole bunches. The data pertaining to loose fruits are shown in a separate table.

The information presented corresponds to plots located in the Coto area, in the south west of Costa Rica. Soils are alluvial (Fluvaquentic Eutropept). Average annual rainfall is 3934 mm, with a period of lower precipitation between December and March ( Table 1 ). Annual mean temperature is 27°C (maximum 31.6 and minimum 22.1°C). The average number of sunshine hours per day is 5.7 (3.9 in July and 8.3 in February).

Results

Vegetative growth. Stem height increased in an almost linear manner with palm age (r² = 0.99). The average increase was 62 cm/year ( Fig. 1a ). For most other growth variables, the model that best fitted in with the data was y = ax² + bx + C, where x is palm age. The determination coefficient was normally greater than 0.90, except for the number of leaflets in a linear meter of rachis (r² = 0.80), and the number of leaves (r² = 0.84) ( Fig.1a , Fig.1b , Fig.1c ). The number of leaflets per linear meter of rachis, the number of total leaves per plant and the leaf emission rate decreased with palm age.

Plants were left to develop between 39 and 40 leaves up to eight years of age, but this number gradually decreased to only 34-35 leaves per plant, which may indicate over-pruning of these palms ( Fig.1c ). However, the number of leaves that a palm retains is also associated with the fall and eventual presence of a plateau in the number of bunches harvested after plants reach 10 years of age ( Fig. 2 ). Other growth variables also tended to stabilize after 10 years, and this indicates that variations between years was reduced.

This study does not include data on stem diameter, an aspect that was considered in a previous paper (Ramírez et al. 2002). Mean values and the standard deviations for each of the growth variables appears in table 2 .

Yield. The yield data for the cross C 9258 comes from only 79 plants ( Table 3 ). More realistic data comes from a commercial lot, also planted with a Deli x AVROS material (several crosses) in 1986.

During the first five years of the commercial lot, bunch yield increased with palm age (2.9 - 24.7 t/ha of fresh fruit bunches). From this point on, yield variation with age was less pronounced (minimum 18.7 and maximum 29.3 t/ha FFB).

Yield cycles were observed from the fourth year on, and these repeated themselves every 4-5 years. The smallest difference between two consecutive peaks was 1.9 t, and the largest was 8.1 t FFB/ha/year.

The number of bunches produced per palm increased between the second and the fourth year (from 1100 to 2817 bunches/ha/year), then decreased until the eight year, and finally stabilized at between 884 and 1580 bunches/ha/year ( Fig. 2 ). Mean bunch weight increased almost linearly with palm age ( Fig. 2 ).

The average increase was 1.3 kg/year (r² = 0.93). Mean bunch weight varied with the season of the year: bunches were smaller during the drier months (December to March: 14.8 - 15.7 kg), and larger during the wet season (15 - 17.3 kg). The increase in bunch weight during the wet season may be due to better pollination during the dry season.

The percentage of loose fruits before and during harvesting ranged from 8.5 to 10.1 % during the period of the study ( Table 4 ).

References

Corley, R., Breure, C. 1981. Measurements in oil palm experiments. Harrisons and Fleming Advisory Services. 33 p.

Hartley, C. 1883. La palma de aceite. CECSA, Méjico. 958 p.

Ramírez, F., Chinchilla, C., Bulgarelli, J. 2002. Low soil P-content associated with a reduction in trunk diameter in oil palm. ASD Oil Palm Papers (Costa Rica) 23: 20-26.

Richardson, D.L. 1986. Morfología, crecimiento, floración y rendimiento de la palma aceitera. ASD de Costa Rica. Documento interno. 186 p.