By Jean Ollivier and R. Bourdeix, 2018
Note from R. Bourdeix, September 2019; The experience described under was conducted in the rich volcanic soils of Madang in PNG. It seems that in the case of poor coral soils (low attols), the technique of replanting the new coconut palms under the old one is not so good, because the old coconut palms continue to use the nutriments available and strongly compete with the new one, but this need to be further developped. See expeiments conducted in French Polynesia in the 1980's.
Replanting is a very effective way of protecting the environment and natural resources, by using existing infrastructures and limiting plantation extensions on newly cleared forest. In most producing countries, the population of coconut palms is growing old, and ways of replacing them are rarely implemented to ensure that production is maintained and the future of the industry and its profitability are safeguarded. Rehabilitating/replanting coconut plantations and adopting appropriate intercropping systems is one of the main challenges to be taken up for the future of coconut in the Asia-Pacific region. On the other hand, total replanting is out of the question for smallholdings, where farmers are often against felling coconut palms so long as they are still yielding, and where only lightning or senility may possibly lead to felling.
Note from R. Bourdeix, September 2019; The experience described under was conducted in the rich volcanic soils of Madang in PNG. It seems that in the case of poor coral soils (low attols), the technique of replanting the new coconut palms under the old one is not so good, because the old coconut palms continue to use the nutriments available and strongly compete with the new one, but this need to be further developped. See expeiments conducted in French Polynesia in the 1980's.
Replanting is a very effective way of protecting the environment and natural resources, by using existing infrastructures and limiting plantation extensions on newly cleared forest. In most producing countries, the population of coconut palms is growing old, and ways of replacing them are rarely implemented to ensure that production is maintained and the future of the industry and its profitability are safeguarded. Rehabilitating/replanting coconut plantations and adopting appropriate intercropping systems is one of the main challenges to be taken up for the future of coconut in the Asia-Pacific region. On the other hand, total replanting is out of the question for smallholdings, where farmers are often against felling coconut palms so long as they are still yielding, and where only lightning or senility may possibly lead to felling.
Rehabilitation/replanting trial
In 1997,
the PNG Cocoa and Coconut Research Institute (PNG CCRI) launched a
rehabilitation/replanting trial at the Stewart Research Station, 40 km north of
Madang city. The trial was located in a plot previously planted with cocoa
trees in the 50s and 60s under the shade of old local tall type coconut palms
planted in 1935, and Leuceana. Over the last ten years, the cocoa trees have
disappeared through lack of upkeep, leaving a mixture of forest regrowth,
Leuceana, bamboo and creepers growing up the coconut palms.
Land
preparation
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| View of the experiment conducted from 1997 at the Stewart Research Center, Papua New Guinea |
It consisted in manual felling of the regrowth in 1997. The plant
debris was burnt on site, then the interrows were cleared of old coconut stems
and other residues, which were placed in windrows down the old coconut rows. A
Pueraria phaseloides cover crop was used to cover the surface of the trial.
Hybrid coconut planting
Lining for
hybrid coconut planting (in treatments involving replanting) was carried out
down the middle of the interrow of the old coconut palms, which were originally
planted at 115 palms/ha. The hybrid seedlings (Malayan Red Dwarf x Rennell
Tall) were planted 7 m apart, to obtain a density of around 165 palms/ha. The
same crop management sequences were applied in each treatment (cover crop,
circle upkeep and localized chemical weeding).
Experimental design
The
experimental design considers three main treatments for old palm felling,
compared to a control without replanting, with a fertilization or no
fertilization subdivision for each treatment and the control. The trial
comprises five replicates. The felling treatments are as follows:
- P0: total felling of old palms at the time of hybrid replanting
- P3: old palm felling deferred for 3 years after replanting ;
- P6: old palm felling deferred for 6 years after replanting
- C: control with neither replanting nor old palm felling.
Felling in
treatment P0 took place in December 1997. The palms were first poisoned by
injecting 50 ml of a neat monosodium methylarsonate (MSMA) solution into the
stem of each palm. Once the crown had disappeared, the stems remained upright
and gradually rotted. Felling in
treatment P3 was carried out from July to November 2000, by sawing and chopping
the lower section of the stem into 9 meter lengths for use as coconut
wood. Treatment P6 is scheduled for 2003
Fertilization
The young
coconut palms receive (subdivision F1) or do not receive (subdivision F0)
mineral fertilizers. The choice of fertilizers and rates applied is based on
the initial results obtained in a reference fertilizer trial. Although
applications in 1998 involved nitrogen (N), phosphorus (P), potassium (K), and
chlorine (Cl), only N and Cl were used in subsequent years. The fertilizers
were applied to the foot of the underplanted hybrids in treatments P0, P3, and
P6, and in the middle of the interrow for C, the control.
Observations carried outA leaf analysis was carried out in 1996 on a representative sample of the old palms (before the trial was set up), then in 2000 on the palms felled in plots P3. The underplanted hybrids were sampled in 1999 and 2000. Observations of vegetative growth and production Vegetative growth and flowering was monitored while the hybrids were young. Three variables were observed every six months: girth 20 cm from the ground (G), the number of fronds emitted in the six months between two inspections (NFE) and the length of frond rank 4, 9 or 14 (FL). Flowering was observed every 3 months, from the start of flowering. On the old palms, the number of nuts produced was recorded palm by palm every month from the start of the trial. The nuts are grouped by sub-plot, husked and the weight of split husked nuts was recorded. Copra weight after drying is recorded at regular harvesting intervals, so that the ratio of copra weight to husked nut weight, without water, can be calculated.
Econometric measurements.
Working time, hired labour costs and input costs were recorded between 1997 and 2000, covering trial setup, the immature phase of the hybrids, but also production costs for the copra harvested from the old palms, thereby enabling an initial economic approach to the different strategies envisaged. Daily working time was measured for all activities, and expressed as the number of days' work (man-days corresponding to 5 to 6 hours of effective work). Only work specific to dehusking in the field was paid according to output and based on split husked nut weight. The data first expressed in Kinas (local currency) were converted into US dollars taking a mean annual Kina-US$ exchange rate.
Results and discussion
The cost of rehabilitation per hectare over the first three years (cleaning of the growth, preparation of spacing, setting up and maintenance of the legume cover) amounted to US $422. This cost is associated with a load of 108 working days (of which almost 60% in the first year) and 5.7 hours of mechanical work.
The cost of replanting per ha on the three years (supply of plants, linning, holing, planting of hybrid and maintenance of the rings) amounted to US $325 and correspond to a workload of 40.6 man days (md) of which half is performed in the first year. For the treatment of P0, an additional cost of US $49 with 6.5 md for poisoning the old trees.
For the first three years, the cost rehabilitation/replanting per hectare amounts to US $746 if old trees are maintained and US $795 trees are poisoned, against US $422 for the only rehabilitation . When practised, fertilization induced an additional cost of $120 US/ha.
The high variability in the size of the nuts harvested from old trees, related to the genetic determinism and probably to the physiological age of the trees,explain that high number of nuts the preparation of a ton of copra (around 6 200 nuts) . This factor and the residual density (which affects the cost of collection) are very important issues in terms of workload and cost of processing the nuts.
Thus, the cost of collection, processing and transport of the ton of copra is very high: US $158 against US $86 for young hybrids in production achieved in another experiment on the station.
Comparison of the economic performance of the different solutionsIn order to estimate the economic performance of each treatment, it has been conducted an economic simulation over a period of 9 years which corresponds to three times the time step chosen for the felling of old trees. Thus, on the period considered, the first three correspond to actual values observed, the data of the next six years are extrapolated according to a theoretical hybrid and old trees production scheme .
Production accumulated over 9 years varies from 6.8 t/ha in the case of C treatment (only rehabilitation without replanting) up to 26.6 t/ha, being 4 times more, in the case of a replanting with fertilization and maintenance of the old trees for 6 years. Profitability compared the eight different scenarios over a period of 9 years shows a net margin which varies, depending on the case, between - $ 647 and + $ 2 346.
Negative margins are found in the case of rehabilitation alone, the worst case being that of the rehabilitation with fertilization. Indeed, fertilizer not showing a positive effect on the production of old trees, this additional cost does not give place to any increase in the crop.
The
strongest lines are observed in the case of replanting with fertilizers with hybrid
coconut trees, the margin being optimal where the old trees are kept over a
period of 6 years.
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However, the cumulative net margin suggests a positive in the 6th year for replanting P3 and P6 systems, which is an advantage in terms of cash, while we expect the 7th year to be positive for the P0 system.
The case described here reveals that, from a total abandon starting point, the old coconut stand by applying simple rehabilitation techniques, there is a perceptible positive effects on production
Old trees in the second year after rehabilitation. The increase of the production of the old trees in 1999 can be explained by better nitrogenous nutrition related to the good effect of the cover plant and less competition with aggressive weeds.
The natural thinning that occurred over time, reducing the initial density, promoted the production of residual trees. This production still relatively significant (0.6 to 0.9 t of copra per ha per year) confirms that in a very favorable local pedo-climatic context the coconut is a very rustic plant, with long economic life, able to produce even after a long period of neglect.
The production of the old trees of the P3 treatments and P6 is not different from that of witness C, suggesting that the agroecological local conditions permit, at least in the period of 2 years, a high density of trees that can go up to 240 trees/ha.
During the first two years after replanting, the competition between the young and old trees is not significant and lets assume that both populations can co-exist without apparent damage on the growth of young or on the production of the old palms. It remains to determine how much of time this situation can be sustained without damage to the development of young plants.
However, the simulation conducted shows that, in the conditions of the experiment, with a residual density of old trees reduced to around 70 trees/ha and high cost of collection and processing operations because of the low ratio of copra/nuts, it is not economic to exploit such a coconut grove
as results show negative net margins -$108 and - $647 for respectively CF0 and CF1 treatments/
It might be otherwise if the residual density was higher, making less expensive the collection costs, or if the harvest round was less frequent.
The P6F1 system shows the highest productivity (+ $2,346) with a net margin positive in the fourth year and a positive cumulative net margin + $422 after 6 years. It is followed by the P3F1 system + $2,122 but with a positive net margin in the fifth year and a cumulated net margin of + $ 149 in the fifth year. The P6F0 system comes in third + $2,065 with a cumulative positive net margin in sixth year + $401. The P0F0system gives the lowest productivity of the replanted systems + $1,646.
From an economic point of view and in the conditions of the trial, it appears that,among the strategies of rehabilitation-replanting, P0F0 treatment is the less powerful model in terms of net margin. If from an agronomic point of view it improves somewhat the growth and the precocity of youth trees, it is unlikely that the effect is important and durable enough to cover the loss of income in the early years. It could however be otherwise if the wood of old felled coconut trees could be valued on a market sufficiently remunerative. Such market requires further investigation in the use of the coconut timber and coconut heart in order to complete the economic strategies balance sheets..
Moreover, the solution of the poisoning of old trees presents a risk in some situations: coconut decaying timber left standing can lead to the development of the larval and the outbreak of the dynastides( Oryctes spp.), causing substantial damage to the replanted young trees but also on neighbouring adult trees.
In Papua New Guinea, the large accentuated ageing proportion of coconuts poses the problem of the sustainability and the renewal operation would ensure the future of this industry and to maintain a satisfactory share of the coconut in the diet of the population.
If the village sector the replanting of coconut trees is not yet key issue, it's going to be in the medium term. Replanting is already an issue for the old colonial plantation established before the second world war and which are redistributed to small planters.
In some areas (such as the small islands for example), the land pressure is strong and the possibility of extending the culture is limited, if not zero. In that case strategies and techniques of replanting are relevant. Replanting is an effective way to protect the environment and natural resources, using existing infrastructure and limiting the extension of crops on high conservation value land.
Total replanting is not a solution for a smallholder, often reluctant of cutting of a coconut tree as long as it continues to produce, and only lightning, disease or senility will cause its death. Decide a propitious moment for replant strongly depends on various factors: variety, residual density, productivity and market of products or by-products of the coconut.
In the conditions of the experiment, the resumption of maintenance and the restoration of the nitrogen fertility by the introduction of a legume cover allowed to significantly increase the production of the old coconut trees. However, the only rehabilitation does not ensure the profitability of the system if it is not associated with a replanting policy.
So, the high producing hybrid coconut com- plantation is an attractive way to rehabilitate old plantations. The growth of young coconut does not appear to be affected by competition from the old trees, especially during the first two years of growth. This lets the producer continues to harvest copra and ensure an income while guaranteeing the future by establishing a young coconut stand that generates revenue from the fourth year.
Other associations of crops under coconut palm systems can be compared with the various scenarios described here, but often these other systems are more consumers in working time do not always have organized supply chains to ensure the flow of products. Also, efforts should be made to optimize the use of land occupied by the existing coconut trees often placed in favorable infrastructural conditions and access to the market for the sale of the copra or fresh coconuts.
