Abstract

The use of advanced planting material (APM) in oil palm allows for more vigorous palms in the field, which have the potential for a higher initial accumulated yield than plants coming from traditional nurseries. The most important factor in nursery plant growth was the length of the nursery stage. However, in order to achieve vigorous growth it is necessary for the plants to receive as much sunlight as possible, which can be achieved by using a bag spacing proportional in length to plant time in the nursery. The idea in keeping a good deal of space between the plants is to reduce etiolation.  Palms taken from the nursery at 18 months, having been spaced at 137 cm, showed, after 37 months in the field, a significantly higher yield (6.3 t/ha of fresh fruit) than those resulting from traditional nursery procedures (13 months of age, in bags spaced at 90 cm).

The use of larger-than-standard bags may aid in the production of better developed plants in the nursery; however, the positive effects are not always clearly seen during the field stage.  The use of high doses of fertilizer in the nursery stage improved growth in some treatment groups. However, this effect disappeared over time in the field, and was not reflected in the yields. These aspects (bag size and nursery fertilization) need to be studied further. A light pruning of the APM before transplanting to the field facilitated handling notably reduced transplanting stress.

The advantages in growth and production with the use of APM were maintained in this experiment until the plants had been in the field for six years, at which point data were no longer collected. During this period, these plants produced a total of fresh fruit 7.35 t/ha higher than that of the control palms.

Introduction

The return on investment in a new oil palm plantation begins after an unproductive period which can last for two to three years. This period can be shortened in several ways:

• Using an early-producing genetic material
• Using good agronomic practices in the field
• Maintaining, in the case of the renovation of a plantation, the oil palms for a prudent period of time after the new planting, and
• Using vigorous nursery plants in an advanced state of development (Ducket 1989; Hartley 1988; Hashin et al . 1987; Khoo and Chew 1976).

The third option runs the risk of favoring certain pests and diseases (Turner 1981) and causes some difficulties in the elimination of the old plantation, once the new planting has been accomplished.

The best-developed nursery plants show a short unproductive period, produce more during their first years, and show larger and higher quality bunches (Khoo and Chew 1976). The planting of nursery material of 10 months of age or younger is counterproductive, in that palms of questionable quality (which would probably have been weeded out with more time in the nursery) may be transferred to the field. Furthermore, these small plants will remain exposed in the field for a longer time and are more susceptible to damage by various pests like the beetle Strategus aloeus , rats, and other animals, such as cows and pigs, which are a serious problem on some plantations.

Previous experiments in Malaysia showed that it was possible to obtain plants with better vegetative development by increasing the space between bags and extending the nursery period.  Positive effects were also obtained by using larger bags and giving the plants an extra dose of fertilizer (Ducket 1989; Hartley 1988; Hashin et al . 1987; Naseeb et al . 1987,1991).  Pruning the plants before transplanting them to the field made the process easier and reduced transplanting stress (Hashin et al . 1987).

Various experiments were started in Costa Rica in 1987 in order to evaluate these techniques under local conditions. Initial results have been published (Chinchilla et al . 1990; Umaña et al . 1990; Chinchilla et al . 1992). Two such experiments were planted in the field in 1989 using 18-month-old nursery material. The results published refer mainly to the behavior of the plants during the nursery stage and the first months after transplanting to the field. In the present study, a follow-up on the field stage is made for these experiments begun in the nursery stage in December, 1987. The objective has been to determine the long-term effect in the field that various nursery treatments had on the growth and yield of plants.

Methodology

The nursery experiment included 16 treatment grouped in a factorial arrangement, according to a random complete block design, with 12 replications. Each plot was made up of 25 plants, with nine central palms.  The experiment used two bag-spacings (90 and 137 cm in triangle), two bag sizes (40x53 cm and 51x61 cm), two fertilizer levels (Table 1), and two pruning levels (0% and 30%, done one week before transplanting to the field).

A control group was planted in normal-sized bags (40x53 cm), spaced at 90 cm, and was taken to the field at 13 months of age, along with the other treatment groups, which at that time had spent approximately 18 months in the nursery.  The plants sown were five Deli x AVROS crosses, in which approximately 76% came from two specific crosses.

All the palms, with the exception of the control group, were maintained in a pre-nursery for approximately two and a half months. The nursery period, therefore, lasted 15 and a half months. Transplant to the field was carried out during the last week of May, 1989, at which time the rainy season in the area of study had already begun (Coto, southern Pacific, Costa Rica).

In the field, the plants were set up in a factorial design, which included the four factors evaluated in the nursery: spacing, bag size, fertilization, and pruning. These factors were distributed as a complete random block, with six repetitions. Each plot was made up of 25 palms (nine central), planted nine meters apart in a triangle pattern (143 palms/ha).

Routine measurements of vegetative growth (Corley and Breure 1981) were taken at one to two months intervals during the nursery phase, and every six months in the field. The yield components were taken weekly.

Results and discussion

Vegetative growth: nursery stage

After plant age (18 months vs. 13 months), the most important factor in achieving better vegetative growth was larger bag spacing (137 cm vs. 90 cm), followed by larger bags (51 x 61 cm vs. 40 x 53 cm) ( Table 2 ). The seemingly better vegetative growth in the nursery, associated with the higher levels of fertilizer used, disappeared with time in the field, and was not reflected in the fruit yield. A similar situation was observed by Hashin et al . (1987). However, the optimum fertilization for each nursery depends on the kind of soil used, the use of an inert material or filler in the bag, and possibly on the particular type of genetic cross.

An interaction observed between fertilization level and bag size must be taken into account when defining the fertilization recommendations: plants in large bags with the least fertilizer resulted in relatively poor growth. Furthermore, the plants with the lowest doses of fertilizer in combination with small bags showed growth similar to that of plants with double the base fertilization in both types of bags. The highest dose of fertilizer stimulated a notably better vegetative growth with both types of spacing used.

The positive effect of the larger bag size showed a clear tendency to fade out in the field stage. However, the combination of large bags with the least spacing (90 cm) adversely affected growth, both in the nursery and in the field.  This reaction began around 10 months of age in nursery plants ( Fig. 1 ), at which time a reduction in leaf area growth rate was also observed.  The apparent negative effect of the larger bags, spaced at 90 cm, on certain vegetative variables is probably related to a more vigorous initial growth in these plants, which then leads to earlier competition for sunlight. However, the reason for this behavior, which lasted until the field stage, could not be determined.

The leaf area index increased more rapidly in the plants spaced at 90 cm, particularly those in smaller bags, which indicates an early accumulation of leaf area in these treatment groups.  This lead to a greater etiolation, which occurred mainly after the plants were one year old.

Vegetative growth: field stage

The effect of some agronomic nursery practices on vegetative growth could be seen even six years after transplanting to the field. The most important factors were time in the nursery and degree of separation of the bags. The majority of the growth variables in the different evaluations over time were significantly better in the plants which had spent 18 months in the nursery in comparison with the control palms, which spent 13 months in the nursery.

There was also better growth in the plants spaced at 137 cm in comparison with the controls of 90 cm ( Table 2 , Fig. 1 , Fig. 2 and Fig. 3 ). The benefits during the nursery stage of a larger bag size and a higher fertilization disappeared during the first months after transplanting to the field.

However, the combination of large bags with spacing of 90 cm in the nursery had negative effects on vegetative development in the nursery stage stage, as well as in the field. This has also been reflected in a lower fruit yield in these plants. Bags much larger than standard would only be justified in nurseries which will be maintained for at least 18 months, and in which ample spacing between plants is employed.

A light prunning of foliage in the nursery plants (30% of the foliage one week before field trasplant) facilitated management of the plants and seemed to reduce transplanting stress. There was no measurable affect of pruning beyond the first year in the field. However, excessive foliage pruning in nursery palms can adversely affect the initial growth of the plants in the field, as well as their precocity. This kind of pruning must be avoided.

Besides the leaf emission rate, the rest of the growth variables have been consistently superior in the palms of advanced nursery material when compared with the control palms. It seems obvious that the age at which the palms are transplanted is a determining factor in field growth. However, there are other elements of nursery plant management that determine to a large extent the potential for growth and production in the field. In this respect it was noted that some variables of the control palms (13 months in the nursery) tended to turn out the same in the field as the 18-month palms that came out of the nursery etiolated (spaced at 90 cm). However, the nursery plants apaced at 137 cm (18 months old) maintained their growth advantages during the entire period of field evaluation ( Fig. 2 and Fig. 3 ).

Etiolation and transplant stress

Palms spaced at 137 cm (specially in large bags) showed the highest rachis elongation rate during the first monts in the nursery. However, beginning when the plants were approximately nine months old, the effect of competition for light became more and more evident in the plots spaced at 90 cm, which was associated with an increase in the rachis elongation rate, which was higher than the other treatment groups, and which led to severe etiolation in these plants ( Fig. 1 ).

During the nursery growth evaluation 482 days after planting, the greatest average rachis length (165.5 cm vs 129 cm in palms spaced at 137 cm) was observed in palms planted in small bags, spaced at 90 cm, receiving high doses of fertilizer. At that time, there was no statistical evidence that this was affected by bag size or fertilization, but there was for distance between bags.

The etiolated palms were less vigorous and the new leaves broke easily during transport, planting, and in the following days. Rougher treatment during the handling of these palms could be part of the reason that they needed a longer recuperation period in the field. The slow establishment in the field of these etiolated nursery palms was seen in the depressed appearance and the funnel shape of the upper leaf crown. This effect, which lasted several months in some plants, is due to the fact that the leaves initially produced in the field are of equal length or shorter than those from the nursery.

The indicator variables of etiolation during the stage of greatest competition for light in the nursery were greater rachis and leaflet lengths, as well as fewer leaflets per linear meter of rachis. However, these same characteristics, when measured in new leaves produced in the field after transplanting (in palms already freed from the competition for light), were indicative that the plant had been capable of successfully establishing itself and had reinitiated its growth after having overcome transplant stress.

Thus, the advanced planting material, more vigorous in the nursery and less affected by etiolation, once in the field produced longer new leaves, with longer leaflets, and fewer leaflets per linear meter of rachis than the 90 cm palms, which were more etiolated in the nursery ( Fig. 1 and Fig. 4 ).

Plants from an advanced stage nursery, due to their weight and size, may be mistreated during transport to the field for planting. However, palms spaced at 137 cm in the nursery may suffer less transplant stress that their etiolated counterparts.

Clearly, the control plants suffered the least transplanting shock. They maintained a fairly constant rate of increase in rachis (and leaflet) length after they were taken from the nursery to the field ( Fig. 1 and Fig. 4 ). This contrasts with the 18-month-old plants in which an initial reduction in growth rate during the first months after transplant was observed.

If a greater number of leaflets/meter of rachis is used as a criterion for stress in the field, the nursery treatment that caused the most transplanting shock was the combination of smaller bags, less space, and the absence of pruning: 118.6 vs. 97.5 leaflets/meter in the opposite combination of these factors, six months after transplant.

The control plants also showed an initially higher leaf emission rate (LER) in the field.  In the case of advanced planting material, besides having an initially lower LER, the rachis and petiole growth rates were also lower during the first months after transplanting ( Fig. 1 , Fig. 3 and Fig. 4 ).

Precocity and initial yield

Ten months after transplanting to the field, the nursery palms spaced at 137 cm had an average of three times more female inflorescences in anteses and bunches than the palms spaced at 90 cm in the nursery (1.4 vs. 0.4 bunches). The palms pruned before transplanting had significantly fewer bunches than those not pruned (0.5 vs. 1.1 bunches). Although this early negative effect in pruning did not show up later in the accumulated yield, it is an indication that excessive pruning could be detrimental to the plant and to its early yield potential.

For two months (26 and 27 months after transplanting to the field), yield of the 90 cm plots (plants from bags spaced at 90 cm in the nursery) was more than that of the 137 cm plots (spaced at 137 cm in the nursery). The control plots also surpassed the production of the 137 plots during part of the initial period. Thus, accumulated yield (fresh fruit) from the control group 28 months after transplanting surpassed that of the 137 plots by 1.58 t/ha. However, two months later the yields had leveled off. From that moment, the 137 plots produced significantly more than the controls. At 37 months after field transplanting, the 137 plots had produced an equivalent of 6.04 t/ha more fresh fruit bunches than the controls ( Table 3 , Fig. 5 ). After this period, the yields were similar in the 90 plots, the controls, and the 137plots. However, the initial advantage obtained from the 137 plots has always been maintained, or rather has improved slightly with time. 72 months after transplanting, the accumulated yield of the 137 plots was 7.35 t superior to the control group, but only 2.2 t superior to the 90 plots ( Table 3 ).

The yield advantage is obtained in the 137 plots during harvest peaks, especially the first one ( Fig. 6 ). Furthermore, these plots maintained higher yields than the control and the 90 plots for 4-6 months even after the peak production month ( Fig. 6 ). This implies less abrupt fluctuation in yields, which is an additional advantage of an advanced stage nursery. This behavior is an indication that the annual yield fluctuations in oil palms can be softened through agronomic practices. In this case, the most vigorous palms have more trunk reserves which will permit them to maintain greater production for a longer time.

The higher fresh fruit production in the 137 plots was associated, during the last years of evaluation, with a greater average bunch weight, even though the number of bunches tended to be smaller than in the 90 plots ( Fig. 7a and Fig.7b ). This implies yet another advantage of the 137 material, as a smaller number of heavier bunches means a savings in harvest costs.

Accumulated production was not influenced by bag size or by nursery fertilization taken separately. However, the negative effect of the nursery combination of large bags spaced at 90 cm has been maintained ( Fig. 8 ).

Bunch components were analyzed only once, when the plants had been in the field for 34 months. To do this, random bunches were taken in all the plots according to the nursery treatments. The comparison of bunch components did not indicate the existence of significant differences between fruit obtained in the 90 plots and that from the 137 plots ("t" de Student, P = 0.05). However, there was a tendency for certain variables, including oil in the mesocarp, to be greater in the 137 plots.

Conclusions

A fundamental objective in all commercial use of oil palm is the recovery of the investment in the shortest time possible. This can be achieved, in part, by producing better nursery plants that have the capacity to establish themselves rapidly in the field, and that have the potential to reach high levels of fruit production during the first years. The results of these tests demonstrate the advantages of prolonging the normal nursery period and providing each plant with the opportunity to receive as much sunlight as possible, with the aim of achieving more vigorous growth.

A traditional oil palm nursery consists of plants developed in bags, aproximately 40 x 53 cm in size, spaced on the corners of an equilateral triangle with each side being 90 cm or less. The plants are maintained in these conditions for approximately 12 months before being moved to the field.

The concept of advanced stage nursery implies extending the nursery stage to 18 months or more (Ducket 1989; Hashin et al . 1987; Khoo and Chew 1976; Naseeb et al . 1987). This requires an increase in the space between bags in order to reduce etiolation. Other practices which seem to help in an advanced nursery are the use of larger bags and an increase in fertilization (Hashin et al . 1987).

Our experience in Costa Rica has showed that the use of an advanced stage nursery gave rise to plants that were more vigorous in the field stage, earlier producing, and with a higher yield potential. Besides these advantages, there seem to be others whose economic consequences must also be considered:

• Yield peaks softened, which means a better distribution of yields over the year.
• Greater global yield with fewer bunches of greater weight, which affects harvest costs
• Reduction of the period of greatest susceptibility to attack by Strategus aloeus , rats, and other animals, such as cows and pigs, as the plants brought to the field are larger and grow faster, and thus escape damage earlier.  In addition, the plant is better able to tolerate damage by S. aloeus and rats because of a greater "base bulb" diameter.

One problem noted with the use of advanced planting material was the risk of causing higher transplanting stress. However, the evidence shows that etiolated plants are more susceptible to mistreating during transplant. Transplanting stress is obviously less in younger palms, but what is not obvious is that this lower stress makes up for the other advantages of more vigorous plants.

The practice of spacing bags in the nursery at 90 cm can be counterproductive. Too frequently, due to unforeseen circumstances, plants have to be kept in the nursery longer than planned. In this situation, there is the dilemma of whether to separate the bags once the plants are already established (which is not always possible or desirable), or rather to take the risk of being able to remove the plants before they suffer excessive etiolation.

With the first option, an extra cost in incurred, as well as the further mistreating of the plants. If the original spacing is maintained, and the nursery period is excessively prolonged, the result will be very weak, etiolated plants, with low energy reserves, which suffer serious maltreatment during planting.

In an attempt to minimize the problem, severe (and sometimes repeated) prunings are resorted to, the consequence of which is a slow process of establishment in the field and a considerable delay in the beginning of production.  Not having had appropriate spacing, plant age becomes another factor against obtaining a good plant. On the other hand, appropriate bag spacing, planned in advance, allows for unexpected problems to be successfully faced and also for more vigorous plants to be transplanted to the field.

The experiences in Malaysia with different types of advanced nursery material also showed that the use of larger bags aided in the production of better plants. Our data show a tendency for better vegetative growth in the nursery in palms developed in larger-than-standard bags. However, these differences have disappeared during the field stage. Bunch production was not affected by bag size.  On the other hand, the use of large bags increases the cost of materials and labor.  A very apparent negative effect on growth and production was also observed in plants developed in large bags spaced at 90 cm.

As with bag size, the use of high doses of fertilizer in the nursery stage did not provide any added benefit. High doses of unbalanced fertilization can even increase the severity of diseases like antracnosis ( Colletotrichium gloeosporioides ).

It is very probable that larger bags and a balanced fertilization program have a positive impact that could not be determined in this experiment. For example, it is important to know if there is an interaction between different kinds of soils (with different chemical and physical characteristics), genetic crosses, and different fertilization programs. Similarly, bag size and shape could affect plant development, depending on the length of time in the nursery. There are currently various experiments in progress with the aim of clarifying the role of these factors.

References

Chinchilla, C. Ml.; Umaña, C. H.; Richardson, D. L. 1990. Desarrollo de material avanzado de siembra en viveros de palma aceitera. Informe interno, Palma Tica, Programa de Investigaciones en Palma Aceitera. Coto, Costa Rica. 59p.

Chinchilla, C. Ml.; Umaña, C. H. y Richardson, D. L. 1990. Material de desarrollo avanzado en viveros de palma aceitera ( Elaeis guineensis Jacquin). I. Espaciamiento y volumen de la bolsa. Turrialba 40(4): 428-439.

Chinchilla, C. Ml.; Umaña, C. H.; Richardson, D. L.; Castrillo, G. 1992. Material de desarrollo avanzado en viveros de palma aceitera. IV. Tamaño y forma de la bolsa. ASD Technical Papers, Costa Rica. (en revisión).

Corley, R. H. V.; Breure, C. J. 1981. Measurements in oil palm experiments. London, Unilever Plantation Group. 35p.

Ducket, J. E. 1989. A guide to oil palm nurseries. Kuala Lumpur, Malaysia. The Incorporated Society of Planters. 109p.

Hartley, C. W. S. 1988. The Oil Palm. Third edition. New York. John Wiley & Sons, Inc. 761p.

Hashin, M. T.; Tan, T. K.; Yeow, K. H. 1987a. Field evaluation of oil palm advanced planting material. In Int. Palm Oil/Oil palm Conferences, Agriculture (1987, Kuala Lumpur, Malaysia). Proceedings. Kuala Lumpur, Malaysia, PORIM. p. 369-395.

Hashin, M. T.; Yeow, K. H.; Poon, Y. C. 1987b. Recent developments in nursery practice; potting media. In International Palm Oil/Oil Palm Conferences, Agriculture (1987, Kuala Lumpur, Malaysia). Proceedings. Kuala Lumpur, Malaysia, PORIM. p. 369-371.

Khoo, K. T.; Chew, P. S. 1976. Effect of age of oil palm seedlings at planting out on growth and yield. In International Development on Oil Palm. Ed. by D. A. Earp and N. Newall. Kuala Lumpur, Malaysia. The Incorporated Society of Planters. p.107-115.

Naseeb, M.; Long, S. G.; Wood, B. J. 1987. Trials on reducing the non-productive period at oil palm replanting. In International Oil Palm/Palm Oil Conferences, Agriculture (1987, Kuala Lumpur, Malaysia). Proceedings. Kuala Lumpur, Malaysia, PORIM. p. 372-390.

Naseeb, M.; Letchumanan, A.; Loong, S. G. 1991. Sime Darby's early experiencies with oil palm advanced planting materials. In Abstracts, 1991 Porim International Palm Oil Conference (1991, Kuala Lumpur, Malaysia). Abstracts. Kuala Lumpur, Malaysia, PORIM. p. 99.

Umaña, C. H.; Chinchilla, C. Ml.; Richardson, D. L. 1990. Material de desarrollo avanzando en viveros de palma aceitera ( Elaeis guineensis Jacquin). II. Condiciones del substrato. Turrialba 40 (4): 440-451.  

Chinchilla, C. Ml.; Umaña, C. H.; Richardson, D. L. 1990. Desarrollo de material avanzado de siembra en viveros de palma aceitera. Informe interno, Palma Tica, Programa de Investigaciones en Palma Aceitera. Coto, Costa Rica. 59p.

Chinchilla, C. Ml.; Umaña, C. H. y Richardson, D. L. 1990. Material de desarrollo avanzado en viveros de palma aceitera ( Elaeis guineensis Jacquin). I. Espaciamiento y volumen de la bolsa. Turrialba 40(4): 428-439.

Chinchilla, C. Ml.; Umaña, C. H.; Richardson, D. L.; Castrillo, G. 1992. Material de desarrollo avanzado en viveros de palma aceitera. IV. Tamaño y forma de la bolsa. ASD Technical Papers, Costa Rica. (en revisión).

Corley, R. H. V.; Breure, C. J. 1981. Measurements in oil palm experiments. London, Unilever Plantation Group. 35p.

Ducket, J. E. 1989. A guide to oil palm nurseries. Kuala Lumpur, Malaysia. The Incorporated Society of Planters. 109p.

Hartley, C. W. S. 1988. The Oil Palm. Third edition. New York. John Wiley & Sons, Inc. 761p.

Hashin, M. T.; Tan, T. K.; Yeow, K. H. 1987a. Field evaluation of oil palm advanced planting material. In Int. Palm Oil/Oil palm Conferences, Agriculture (1987, Kuala Lumpur, Malaysia). Proceedings. Kuala Lumpur, Malaysia, PORIM. p. 369-395.

Hashin, M. T.; Yeow, K. H.; Poon, Y. C. 1987b. Recent developments in nursery practice; potting media. In International Palm Oil/Oil Palm Conferences, Agriculture (1987, Kuala Lumpur, Malaysia). Proceedings. Kuala Lumpur, Malaysia, PORIM. p. 369-371.

Khoo, K. T.; Chew, P. S. 1976. Effect of age of oil palm seedlings at planting out on growth and yield. In International Development on Oil Palm. Ed. by D. A. Earp and N. Newall. Kuala Lumpur, Malaysia. The Incorporated Society of Planters. p.107-115.

Naseeb, M.; Long, S. G.; Wood, B. J. 1987. Trials on reducing the non-productive period at oil palm replanting. In International Oil Palm/Palm Oil Conferences, Agriculture (1987, Kuala Lumpur, Malaysia). Proceedings. Kuala Lumpur, Malaysia, PORIM. p. 372-390.

Naseeb, M.; Letchumanan, A.; Loong, S. G. 1991. Sime Darby's early experiencies with oil palm advanced planting materials. In Abstracts, 1991 Porim International Palm Oil Conference (1991, Kuala Lumpur, Malaysia). Abstracts. Kuala Lumpur, Malaysia, PORIM. p. 99.

Umaña, C. H.; Chinchilla, C. Ml.; Richardson, D. L. 1990. Material de desarrollo avanzando en viveros de palma aceitera ( Elaeis guineensis Jacquin). II. Condiciones del substrato. Turrialba 40 (4): 440-451.