Under what tree spacing should pastures be established? Presently, as indicated in Section 2.11, the coconut grower wishing to maximize pasture growth as well as yields of copra should use the least number of palms per hectare required to realize this goal (Whiteman, 1980). For tall varieties recommended spacings range from 7 × 7 m to 9.1 × 9.1 m and palm densities from 120 to 200 trees ha-1 (see Table 37). Where pastures are established under palms at closer spacings and higher densities then light transmission values and pasture/animal production will be lower!
However, earlier reports by Child (1974), Liyanage (1955) and Plucknett (1979) had described “group”, “bouquet” and “hedge” planting systems to allow more space for intercrops.
Table 265. - Summary of Growth Responses, TNC Content and Mortality of P. malacophyllum and P. wettsteinii to Shade and Defoliation
|Sh/Rt||RGR||Till no.||LAI||TNC g/m2||Mortality %|
Sh/Rt = shoot/root ratio
Till No. = tiller number/plant
TNC = total nonstructural carbohydrates
RGR = Relative growth rate (g/g/wk)
LAI = leaf area index
Figure 250. - Pasture species screening trial under young rubber, Pikun Thong Research Centre, near Narathiwat, Thailand.
Significantly, a report by Manthriratna and Abeywardena (1979) demonstrated not only the influence of spacing on yield in terms of nuts palm-1 (see Table 266), but also that the same tree density can be achieved by various planting systems with little effect on the mean coconut yield palm-1 and therefore ha-1 (see Table 267).
Thus in Table 267 in Group C with a density of approximately 175 palms ha-1, the mean yield per palm is of the same order of magnitude whether the system of planting is almost square (a rectangularity of 1.04) or highly rectangular (2.67).
For intercropping (in this case with pastures) a rectangular system with a wide between-row spacing has many advantages over the square system. Thus for Group C in Table 267, 12.19 m × 4.57 m (40 feet × 15 feet) and 6.62 m × 7.59 m (25 feet × 24 feet) gives the same density and the same yield per palm, but the more rectangular system would be superior for intercropping. The number of nuts palm-1 decreased with increasing density with 83 nuts palm-1 at a density of 128 palms ha-1, 68 nuts palm-1 at a density of 175 palms ha-1 and 54 nuts at a density of 239 palms ha-1. Coomans (1974) found a similar trend in lvory Coast stating that “the competition factor, which represents the fall in yield per tree when the density of a unit is increased, is mainly a function of the water supply” and suggested that the choice of planting density should take into consideration the mean water deficit of the area. Manthriratna and Abeywardena (1979) indicated that “it would be extremely difficult to partition the effects of various factors, such as light intensity, water availability and nutrient supply whose combined effect would manifest itself in the growth and yield of the palms at the different densities of planting. In Sri Lanka, in those regions where serious water deficits are not encountered, it would appear that competition for light may be the decisive factor which determines the success or failure of coconut holdings planted at the different densities”. Manthriratna and Abeywardene (1979) indicated that the planting of coconuts in avenues or hedges, with rows oriented east to west, is much more suitable for intercropping (Hartley, 1977, concluded that a rectangular spacing of oil palm at 6.4 × 12.8 m resulted in a fruit bunch yield only slightly lower than the normal planting density and allowed elephant grass to be grown in the wide interrow areas). Wickramaratne (1987) also suggests that a rectangular system is best for intercropping and a triangular system for coconut monocropping.
Table 266. - Mean yield of nuts palm-1 year-1 (Manthriratna and Abeywardena, 1979)
It is noted that the Coconut Research Institute of Sri Lanka (Anon., 1987) recommends planting densities according to agro-climatic zone (and rainfall) with higher densities in the dry zone where intercropping is not recommended (see Table 268). However, given the low nut production per tree likely to result it is not clear why high planting densities are recommended for the drier areas (Blaak, personal communication).
The economics of the different planting systems are presented in Table 269, where the different planting systems giving the same plant densities are grouped together. Yield of nuts ha-1 year-1 and the profit indicate that the high density systems give both a high yield as well as high net profit. Manthriratna and Abeywardena suggest that the choice would appear to be between 9.14 m × 4.57 m (30 feet × 15 feet) and 7.62 m × 5.48 m (25 feet × 18 feet), with the former being favoured in terms of intercropping needs. It is also possible that when the returns from the intercrop are considered a lower planting density of 175–200 palms ha-1 and 35 or 40 feet × 15 feet might be the preferred spacing.
What other evidence is there that traditional spacings designed for monocrop coconuts are being modified to give more emphasis to intercrops?
Table 267. - Yield per palm as influenced by density and rectangularity (Manthriratna and Abeywardena, 1979)
|Group||Inter-row spacing (ft)||Intra-row spacing (ft)||Rectangularity|
|Density palms ha-1||Mean yield nuts palm-1|
In Tanzania, the coconut extension service has in recent years recommended a move away from the traditional 9 or 10 m spacing to a 9 × 15 m spacing because surveys of farming households showed that the expansion of coconut planting was not limited by the availability of land, but by shortages of labour (Behrens et al., 1993; Diehl, 1993). Food crops have priority for the smallholder and in order to get more farmers to plant coconuts the solution was to plant them at wider spacings to benefit food crops, with permanent intercropping benefitting the coconut palms through better maintenance of the intercrop (and therefore the coconuts).
Table 268. - Coconut Planting Density by agro-climatic Zone, Sri Lanka (Anon., 1987)
|No. of palms ha-1*|
* Square, rectangular and triangular systems of planting can be used. When intercropping the rows with wider spacing should preferably be aligned east-west.
Jayasooriya (1990) suggests that the concept of Coconut Based Farming Systems has initiated a new era in coconut development, with a move away from the traditional monocrop coconut system (and traditional coconut spacings). In Sri Lanka (Anon. 1989) the Coconut Research Institute has undertaken trials with a hedge planting system of 30 × 18 feet (9.14 × 5.48 m) and an avenue system of 10 × 5 m or 200 trees ha-1 in the drier parts of the Intermediate Zone (Liyanage and Dassanayake, 1993). Liyanage and Dassanayake (1993) suggest that in future replanting or new planting programmes avenue planting system should be adopted (e.g., 10 × 5 m, 12 × 5 m, 15 × 5 m) with wider rows in east-west direction to facilitate light penetration.
Table 269. - Economics of different planting systems (Manthriratna and Abeywardena, 1979)
|Palms ha-1||Yield ha-1 annum||Income ha-1 annum*||Cost of** fertilizer|
|Cost of*** picking|
|40 × 21||128||10,589||6,353||448.00||61.44||5,843.56|
|35 × 24|
|40 × 18||150||11,237||6,742||525.00||72.00||6,145.00|
|35 × 21|
|30 × 24|
|40 × 15||175||11,979||7,187||612.50||84.00||6,490.50|
|35 × 18|
|30 × 21|
|25 × 24|
|35 × 15||200||12,447||7,468||700.00||96.00||6,672.00|
|30 × 18|
|25 × 21|
|30 × 15||239||12,948||7,769||836.50||114.00||6,818.50|
|25 × 18|
* Calculated at the rate of Rs. 600/-per 1,000 nuts.
** Calculated at the rate 3.50 per palm (3 kg per palm + cost of application).
*** Picking and collecting charges 8 cents per palm per pick.
In Indonesia on new plantings it is recommended that young coconuts be planted at 5 × 12 m, giving a tree population of 160 palms ha-1 and wide inter-row areas for cultivating other crops (Darwis, 1988). Darwis (1990) indicates 'the coconut plant spacing for intercropping purpose is not the same as for monoculture coconut, both in triangle and square spacing. The coconut plant spacing for intercropping purpose uses the fence system, 5 m × 12.5 m so that coconut population is 160 plots ha-1. The direction of coconut rows from east to west enables optimal use of the sun radiation, minimizing shading of the intercrops.
In Papua New Guinea while coconuts were traditionally spaced at 7 × 7 m to 9 × 9 m some new plantings have been spaced as wide as 12 × 12 m to accommodate intercrops such as cocoa (Ovasuru, 1988).
In Thailand, Dootson et al. (1987) indicated that the current spacing recommendation of 8.5 m triangular may prove to be a compromise between the optimum for monoculture (of hybrids) and the lower density appropriate for intercropping.
In Ivory Coast trials showed that “a density of 120 trees ha-1, which can simplify intercropping, produces as much as the usual density of 160 trees ha-1 up to 14 years” (Anon., 1992c).
In Vanuatu, according to Evans et al. (1992), increasingly under conditions of depressed copra prices some commercial smallholders are showing interest in planting coconuts at lower densities so that the more productive improved pastures can persist under grazing.
In Tonga, Thompson (1988) mentions that “traditionally coconut trees used to be planted on a 10 × 10 m grid pattern. In relatively recent times the Tongans of their own volition changed these spacings to 5 × 15 m to let more light into the interiors to enable more crops to be grown beneath the coconuts”. A spacing of 60 × 15 feet (18.27 × 4.57 m) was indicated by Havea (1988) and spacings of 13.6 × 6.06 m (118 palms ha-1) and 14.5 × 6.06 m (111 palms ha-1) mentioned by Lavaka (1988). Opio (1990a) refers to the practice of “hedge planting” which has been introduced in recent years to minimize the problem of poor light penetration so that continuous intercropping can be undertaken at any stage of development of the coconut trees. Hedge planting is based on wider spacing between the rows and closer spacing between the plants. He mentions that while there is no significant difference in plant population per unit area compared to the conventional spacing of 9 × 9 m, yields from hedge planting are generally higher (see Table 270), sometimes by as much as 25%. This is mainly because inter-cultivation encourages adoption of appropriate technology and improved husbandry practices. Hedge planting also allows for continuous inter-cultivation, which minimizes the problem of land shortages, encourages intensive land utilization and increases the productivity of land under coconut.
Table 270. - Comparative yield levels for selected local talls under conventional spacing and hedge planting in Tonga
(spacing 9 m × 9 m)
(spacing 15 m × 5 m)
|% increase in Yields|
|Average No. plants ha-1||124||133|
NA - Not available.
Observation based on 15 farms in Tonga, Hedge planting was first introduced in Tonga in 1976 by the Department of Agriculture to encourage continuous intercropping.
Figure 251 illustrates the 15 × 5 m hedge planting system used in Tonga where the valuable export crop squash is grown between coconut rows. With the collapse in the export of copra and coconut oil, coconuts are used mainly for domestic consumption. Figure 252 illustrates another planting system which is being tried out where clumps of four coconut palms are established in rows 15 m apart under senile tall palms. Tonga appears to have pioneered the practical work on coconut spacing for intercropping, however, there is much to be learned from past and on-going work with other tree crops such as rubber (see Abdullah et al., 1992; Eng, 1992 and Horne, 1993), Pinus radiata (see Bird et al., 1992; Hawke, 1991; Knowles, 1991), Douglas fir (see Sharrow, 1991) and slash pine (see Lewis and Pearson, 1987). As well as the hedge planting systems already tried in Tonga double-row hedge planting systems, such as those described previously in this chapter should be tried and careful consideration should be given to the use of wider spacings when establishing or replanting coconuts where intercropping is to be undertaken.
Shelton (1993a) suggests that establishment of pasture with plantation tree crops may not be sustainable unless there is a radical alteration of tree-planting configurations to improve the long-term light environment.
Figure 251. - The 15 × 5 m coconut hedge planting system, Tonga.
Figure 252. - A ‘group’ planting coconut system under trial in Tonga.
The effect of hedgerow planting systems on species selection
If hedgerow planting systems are adopted so that light transmission conditions in the inter-row areas are in excess of 80 or 90% throughout the life of the coconut trees then the need to identify shade tolerant species will be less of a priority. As such, species which have already been identified and are in widespread use in open areas, can be recommended and selected according to the particular environmental and socio-economic conditions and likely management levels. Although for the immediate future, in the large majority of coconut areas planted at traditional spacings, the need for shade tolerant species remains, many coconut plantations comprise ageing stands of lower-yielding trees which have thinned over the years and which will need replacing (e.g., in the Philippines according to Ontolan (1988) it is estimated that 55% of the more than 300–400 million coconut palms are older than 40 years and 27% are beyond 50 years). With generally low productivity and profitability decisions will have to be made about whether to diversify and intercrop or replant with pure coconut stands. In Vanuatu, according to Evans et al. (1992), increasingly under conditions of depressed copra prices some commercial smallholders are showing interest in planting coconuts at lower densities so that the more productive improved pastures can persist under grazing.
If new coconut layouts are adopted this will have implications not only for pasture species but also for stocking rates, grazing systems and the management and economics of the whole integrated system.
10.6.3 Development of (coconut) multicropping systems where various management options are modelled to maximize returns for the grower
Opio (1990b) described an intercropping/rotational grazing model (see Figure 253) which on the basis of cashflow analysis gave much better returns in terms of gross revenues and returns to labour than monocrop coconuts. Although the return to labour and benefit/cost ratio figures for hybrid coconut are relatively high in Table 271, the fact that data for hybrid coconuts were not available beyond year 14 meant that Opio was uncertain of the calculated figures and ignored this option in evaluating the systems. While Local Tall coconuts and cattle had a better return to labour figure than Local Tall alone, the returns to labour from rotational grazing and intercropping with taro and kava were higher than the minimum wage of WS$ 0.60 hour-1 and this system would provide a reasonable alternative use of land during what traditionally would have been a fallow period with a significant increase in income. Whether the light in years 8 to 16 actually falls as low as 20% is doubtful, but the approach adopted by Opio is worth following up. (In 1993 taro in W. Samoa was devastated by taro blight (Phythophthora colocasiae)).
Table 271. - Benefit-Cost analysis for coconut Local Talls and intercrops in Western Samoa, at 10% discount rate (Opio, 1990b)
|Types of Enterprises||Sum of Net Present Value||Annuity||Return to Labour hour-1||Benefit Cost Ratio|
Figure 253. - Intercropping/Rotational Grazing Model for Coconut Plantation (after Opio, 1990b).
|Key:||T =||Taro/annual crop|
Comparative results of different intercrop/rotational grazing enterprise combination net returns for Fiji are shown in Table 272. The results indicate not only that returns from monocrop coconuts can be increased substantially by intercropping but that intercropping/ rotational grazing of Local Talls (LLT) with taro provided the highest net accumulative return under a coconut based farming system (Opio, 1993). The minimum wage was F$ 0.62 hour-1.
This approach is not new as shown by the work of Garrett and Kuntz (1983) on black walnut (Juglans nigra L.) in USA, which lends itself especially well to multicropping due to the high value of its wood and the production of a nut crop with intercrops providing early financial returns which can serve to offset establishment costs and provide a sustained income throughout the rotation period. With black walnut planted at 12.2 × 12.2 m Garrett and Kuntz (1983) compared four multicropping management regimes (see Figure 254), with nine different management options and illustrated the flow of costs and revenues for a specific management option (Table 273). Just as mentioned earlier for coconuts, rubber, oil palm and forest species, protective fencing was required for walnut seedlings; production of tall fescue and orchard grass was found to be greater beneath the black walnut trees than in the open and shaded plants had improved digestibility! In fact, as early as the late 1930s (Neel, 1939) in Tennessee the effect of shade on pasture had been investigated. In Australia in the 1970s Hawley (1978) noted that integrating sheep with walnuts increased net income ha-1 from A$ 150 to A$ 220.30.
Table 272. - Discounted net returns per ha under coconut based farming system in Fiji (mature Local Talls (LLT) at 10 per cent discount rate) (1987 prices). Opio (1993).
|Year||Mono LLT||LLT/Taro||LLT/Cocoa||LLT/Kava||LLT/Cattle||Intercropping/Rotational grazing||Mono cocoa||Pasture|
|10 years accumulated|
|Av. return to labour/man hour|
* Kava is a three to five-year semi-perennial crop, thus a three year cropping sequence was adopted for this study.
Sources: 1. Department of Agricultural Economics, University of the South Pacific, School of
Agriculture Data Bank, 1990.
2. Annual Reports of the Institute for Research, Extension and Training in Agriculture (IRETA) various issues.
This is an area which urgently requires attention and models with a range of management options should be developed and tested to build on coconut based farming systems work already underway (e.g., Mahmud and Akuba, 1989) and incorporate spacing changes as in 10.6.2 above.
Although a considerable amount of information is available on the coconut system, the long-term systematic investigation of the pasture-livestock-coconut system is lacking in terms of the studies undertaken for example by the Forest Research Institute at Rotorua in New Zealand for Pinus radiata and livestock/pasture integration or at MARDI in Malaysia for rubber and oil palm. The information available on coconut systems tends to come from a series of unconnected studies by individual research workers; perhaps there is need for a university or research institute in South East Asia or the South Pacific to focus on integrated crop-livestock-coconut systems and to carry out a long-term programme of research along the lines of that undertaken for crop-livestock-tree crop systems in other areas.
Table 273. - Cost and revenues for a multicropping management option1 by investment category
|1–80||6.18||Annual property taxes|
|1–80||2.47||Annual tree management|
|10||40.76||Pruning to 2.1 m|
|16||29.64||Pruning to 3.4 m|
|20–30||138.32||Annual nut return|
|31–40||311.22||Annual nut return|
|41–50||242.06||Annual nut return|
|51–60||328.51||Annual nut return|
|61–70||414.96||Annual nut return|
|71–80||501.81||Annual nut return|
|Soybeans||1–10||158.08||Planting and fertilization|
|Winter Wheat||1–10||165.49||Planting and fertilization|
|11–15||88.92||Annual seed return|
|11–15||81.26||Annual hay return|
|Livestock||16||86.45||Perimeter fence construction|
|16–80||2.47||Annual fence maintenance|
|16–80||65.46||Annual livestock feed costs|
|16–80||80.03||Other annual livestock costs|
|16–80||250.09||Annual livestock receipts|
1 Soybeans and winter wheat, 10 years; fescue seed and hay, 5 years; livestock grazing, 65 years;
site index = 19.8; rotation = 80 years; growth rate = 0.85 cm per year; commercial thinning at age 40; black walnut stumpage price increase = 1.5 percent annually above all other costs and prices.
Figure 254. - Alternative black walnut management regimes.