Permaculture Designers Manual
CHAPTER 10 –
THE HUMID TROPICS IN PERMACULTURE
Section 10.10 –
Themes on a Coconut or Palm Dominant Polyculture in Permaculture
There are many considerations to bring to the planning of a coconut or palm-dominant polyculture; they can be dealt with in the following themes:
- Structure and Zoning;
- Species Selection;
- Re-working Old Plantations;
- The Effects of Plantation Monoculture.
Any humid tropical polyculture that duplicates or imitates the normal structure of a tropical forest is likely to succeed.
The structure of the system refers to the final cross-sectional appearance of any polyculture.
Near large markets, or mass transport systems, it is quite feasible to introduce large tree species into the palm system and to use the fruits and nuts as a supplementary market crop.
Around villages, a far more complex and species-rich approach is needed, with fuel, fodder, structural materials and basic foods, oils, and medicines in a complex intercrop.
Remote from settlement or market, some livestock ranging (pigs, cattle) can be contemplated, with the intercrop selected to assist animals on range over dry periods, as ground forage or as a drop from fodder trees such as figs, breadfruit, papaya, or Inga edulis.
Proximity to village or settlement decides species complexity and (by implication), structure, in that labor-intensive systems are best placed close to the village.
Zoning out, we might place:
- Productive trees in palms (total species: 6-12) Figure 10.31.A;
- Palms within crop and avenue cropping between palms (total species: 30-35) Figure 10.31.B;
- Animal forage and free range in palms (total species: 8-20) Figure 10.31.C;
- Village garden and trellis, roof crop, greens (total species: 100-150) Figure 10.31.D;
- Fuel-wood in dwarf palm (total species: 3-4) Figure 10.31.E;
- Forest and tree reserves.
It is in and around the village that small livestock, fungi culture, paddy crop and terrace is appropriate.
CRITERIA FOR SPECIES SELECTION
For any one site a selection of species that go with a palm polyculture has to be made.
Some criteria are:
A mosaic of the full range of food, craft, and medicinal plants is needed. Special intensive crops such as fungi, paddy and even algae can be planned. Experimental plots can be located here. (Figure 10.32)
Species are selected according to a general zoning/use-plan.
It is helpful if:
- Species are suited to soils;
- A mosaic approach is indicated based on soil drainage and nutrient status;
- If the site is complex, then so should be the main crop;
- Species are locally acceptable or are very similar to local types;
- New introductions need trials and instruction as to processing;
- Species chosen have a wide potential for processing;
- Coconuts have hundreds of known products or uses; this gives market flexibility;
- Species do not become rampant (unless they are controlled by livestock or cultivation);
- There is good information, some varietal types and assured yield or low management input for the species used;
- Species are compatible, such as those listed herein;
- Species serve a present and future essential use (as thatch, fuels, oils, dry-stored food).
Considerations for Varietal Selection
For coconuts and many other species (guava, yam, taro, banana, papaya) there are dozens of varieties developed for quite specific sites, soils, microclimates or uses.
There are coconut palms ideally suited to oil production, while others produce very fine quality cup copra for temple use and others are ideal for shredded coconut, coconut milk, fresh nut markets and so on.
There are dwarf, medium-height and tall varieties. The former are ideal for village surrounds, especially on windy areas (where there are dozens of deaths each year from falling coconuts).
Dwarf varieties (Philippine, Samoan) are easily accessible, have large nuts, good eating characteristics and will not damage people or buildings if the nuts fall.
Pest resistance and soil type must also influence cultivar selection.
In older plantation areas, selected and well-tested local species will be available. For areas with no plantation history, it is perhaps wise to build up a small arboretum of many varieties and select a range of cultivars suited to the end-product aims.
In every country, the cooperation of local agricultural authorities and their assistance with varietal selection will be needed.
Once a nursery is established (either as large containers or open bed planting, later as field plantings where rainfall permits), the site planning can go forward, but every plantation needs a mulched, shaded nursery, no matter how modest.
Shade is most cheaply provided by light-foliaged legumes at wide spacing (e.g. Acacia, Albizzia).
As almost all coconuts must be seed-grown, we can expect a variation in all crop characteristics, subject to later selection, culling and new selections for site.
Even if we grow from root tips in tissue culture, meristem and single-cell mutations are very high.
In seed-grown crop, we might expect about one in twenty trees to show some very different characteristics and of these perhaps one-third will be favorable for site, giving a limited set of new characteristics for selection.
Thus, it is unlikely that a seed-grown or a culture grown palm plantation will demonstrate a very uniform genetic resource and this will later lead us to “cull and select” options in management.
This indicates a need for initial over-planting to allow for a 2-4% cull within the first 7 years when we can make a fair estimate of vigor, nut production, bearing and pest resistance and another 2-4% cull in years 7-14, when the tree is mature.
Final culling (14-60 years) should be in the nature of a replant and renewal process. Culling and replanting in palm crop can be a continuous process, so that plantation vigor (and overall design) is updated.
Species Suited to Co-processing
In a special plantation intended for (e.g.) ethanol or biogas fuel production, the same ferment and distillation equipment will serve a complex of crops that can form a “special use” polyculture.
Similarly, wetlands suit many swamp palms (Nypa, Maurantia), taro, rice, and Azolla fern or blue-green algae complexes, where the fern acts as nitrogenous mulch and the palms as deep nutrient pumps for the paddy crops.In alcohol oriented (fuel) palm crop, interplant of cane sugar, century plant (Agave), beet or sorghum sugar may add to the total sugar crop and suit the processing or distillation unit, while oil palms may be inter-planted with mustards, sunflower, rapeseed, etc. to take advantage of oil press equipment and to increase honey production for bees, which themselves increase oilseed crop.
Thus, special site conditions, investment in processing equipment or special end-use may dictate special plant assemblies in the site mosaic.
PATTERNING OF PALM POLYCULTURES
Pattern and Water Run-off
Many sites on clays and clay-loam soils benefit from earth sculpturing for run-off absorption.
On extensive sites and on clays over limestone or dolomite, absorption swales may be the only practical broad scale irrigation method.
In fact, any leveling or sub terracing of land helps water infiltration. Palms and trees appreciate ground water reserves.
A hillside patterned as per Figure 10.33, suits clump plantings of palms. Swales are illustrated and exemplified in Module 9.
Planting Patterns of Palms (Clumps vs. Grids)
Without altering too much the appearance, spacing and amounts of coconuts, Figures 10.34 A-C illustrates some of the possible plantation layouts.
While A and B are “normal”, C arises from several independent observations I have made on densely-planted coconuts.
Ten to twelve coconuts planted in a circle and each only a few feet apart, do in fact quickly adopt a divergent growth habit something like that in Figure 10.35.
Not only do nut counts compare favorably with trees planted on a square grid pattern and nuts drop cleanly to the ground, but a third (probably more important) factor emerges, to do with mulching.
Coconuts in plantation mulched with their own fronds and husks show better growth and bearing, but in normal plantation, husks are left at one tree in 10-30, because the labor of first gathering and then distributing the mulch is too great.
However, with the circle clumps, it is easy to both gather and husk the coconuts in one place and thus mulch the base of all trees, conserving water and returning nutrients to every tree.
A little care in turning husks face-down prevents mosquito breeding in the mulch heaps.
Any other nutrient (manure, blood and bone) is equally easily applied to clumps.
Clumps also form more suitable trellis for vanilla, black pepper and other vine crop. They are also very economical for watering and the circle leaves large areas of ground free (although lightly shaded).
The wide spacing of circles enables replanting to take place in discrete sets of 10-12 palms without gross linear disturbance to the system as a whole.
Although I originally saw such clumping as a convenient way to apply mulch, it later became clear that broad areas of clear ground for grazing and intercrop are also available.
Such patterning frees up to 60% of the ground area, as against 30% for linear planting. Clump planting is ideal for run-off harvesting of water in circular swales (Figure 10.33) or in coconut-circle pits.
As for the spacing of palms in lines, a very good rule is to space at twice the frond length for that site plus two feet. This allows full crown development without abrasion damage to the fronds from wind-sway.
Intercrop spacing is as usual: cacao 2x3m, banana 3x3m, cassava 1x1m, maize 1×0.5m in rows, citrus 9x9m and so on (local agricultural people can advise).
Coconuts on new sites are normally 6x6m.
Access and Mulch Provision
Sensible roads or grass access ways are necessary for gathering or handling heavy crop and some provision for these must be made even where horses or donkeys with panniers are used.
More importantly, a careful assessment of mulch sources is essential wherever mulch-loving crop (avocado, banana) or mulched short-term crop (dry land taro, ginger, yams) are planned.
A layout such as Figure 10.36 ensures mulch sources for the system itself and for short-term crop.
Natural fall from palm fronds and husk or nut shell will line mulch about one in 8-12 rows of palms with about 2m wide x 0.5m high mulch beds.
In clumps, 10-12 palms will provide about 0.5m deep of mulch for the inner circle of mulch.
This is easier to gather and keep in place in windy areas.
The addition of bananas, especially with avocado, has become standard in many plantations, as the banana plants at harvest (with root mass) provide about 25 ton/ha of organic matter, a key resource for a healthy fruit and palm crop (Penn, J.., New Scientist 20 May ’85).
Small tree legumes (Cassia, Calliandra, Leucaena) can also help. Bananas in legume crop may be regarded as “pioneer” mulch in grassland reclamation.
The layout in Figure 10.36:
- Reduces the labor of harvest by providing regular access;
- Provides sources of mulch for short-term crop;
- Enables mulch accumulation by long-term crop as interplant.
Earth Shaping for Intercrop
Earth shaping is worthwhile for several reasons, not only to assist water infiltration and run-off, but to give a free root run, to retain mulch in wind, to affect better drainage in over-wet areas and to provide microclimate benefits with respect to wind shelter and ground warmth.
Briefly, earth MOUNDING for root crop and cucurbits is beneficial in humid tropics, and earth TRENCHING is best in dry tropics.
Earth working is discussed in Module 9, but some relevant data is given here.
Ridges of 0.5 x 1m increase yields in cassava, sweet potato, potato and yam crop.
Mulch and green crop can be grown between the ridges.
Pineapple and ginger also prefer ridges in wet areas.
In Figure 10.38, Leucaena intercrop for mulch is on mounds, while maize and green mulch (beans) occupy hollows.
Ridges permit deep mulching for low crop such as pineapple, the mulch being applied between ridges.
Yield Over Time
Plantation can be cropped with short-term grains for a season or two, but by years 2-4, the palm fronds (of linear plantings, not so much of clumps) cause mechanical damage and obscure the ground after years 4-6, a stem forms and from 6-14 years complex perennial intercrop (not short-term grains) can be placed in linear systems in clump systems, the early ground effect is less marked. (Figure 10.39)
Nair (1975) gives convincing economic analyses for coconut.
He shows a 50% increase in yield for irrigation alone and a trebling of the yield for complex intercrop of two or more species, effectively doubling the cash returns to the grower on the same area.
Costs of irrigation and intercrop (plant or animal) never exceed returns if care is taken to select beneficial plant and animal species for available soil, water supply and climate.
Often, the cheapest irrigation system is to pattern the ground to hold wet-season run-off for tree crop use in dry seasons.
On Nair’s analysis, where 1 unit = 4 rupees, the net income from coconut was as Table 10.2.
Adding three species and increasing net yield by 3-9 times increases costs by 3.1 times.
This is a clear implication for small holders that much less area, polyculture, would give as much return (3 to 8 times) for far less (as expense is also a function of expanded area under crop).
Irrigation of any sort is obviously a key factor.
There would be no point, however, where more species added, even if very carefully selected, would push labor, harvest and control costs past sensible limits, as per the schematic in Figure 10.40.
So it is also clear that a complex polyculture must be managed by many more people if expanded to a wider scale.
RE-WORKING OLD PLANTATIONS
People, who inherit or buy old stands of coconut, or other palm crop, need to undertake clearing and replanting programs for renewal if the stands are 60+ years of age.
This is an ideal time to re-assess the potential for intercrop, to assess local processing potential and to use the trunks, fronds, sugars and palm heart products of the over-mature palms for mulch, food and structural material.
If hurricanes have stripped the old crop, it is also timely to assess the placement of windbreak for future plantation and to place Casuarinas, Acacia, Albizzia, bamboo, or tough Prosopis species to afford greater shelter and to fix nutrient in the crop or to provide forage for grazers such as pigs, cattle, tortoise, or game birds (turkey, geese)
The cleaning of old trees should be carefully planned to give a maximum return and to correct placements in older plantations.
As it may take 8-15 years to rework a neglected, old plantation, the process can be staged and tuned as trial systems.
In many areas, the old palms are tapped for sugar before removal, and the palm hearts eaten or sold as “millionaire’s salad” (although palms planted specifically as young heart crop have a very good yield, can be close-planted, and are a crop themselves).
Good managers may be about the business of replacing, replanting or re-grouping the plantation at a rate of 4% or so per annum, giving a slow but constant renewal and culling as needed.
The new trees also give an opportunity for field-testing selections from the nursery beds. It is generally agreed that coconut is over-mature in 40-80 years, when nut yield falls from optimum 45 per tree or so to 15 or less. Excellent trees bear 60-100 nuts per year.
Uses of Palm Trunks
The trunks of coconut are a good resource; not only do they provide an excellent building material, but (stacked in open box fashion) they make baskets to hold mulch on land for the growing of yams and vines. (Figure 10.42)
In the shallows of tropical seas or lagoons, they form a frame for coral to cement together, sheltering crayfish, crabs, and fish.
The trunks hold silt and sand in reclaiming new lagoon areas or in creating stable planting ledges in “hurricane garden” hollows cut into coral sands, on the sides of gleyed or plastic-lined surface ponds on islands or as an aid in retaining bank stability and plant establishment on slopes.
Palm trunks can also be used to create planting benches on pits on coral islands.
Pit base; taro, mint, parsley and kangkong.
Sides: cassava, papaya, yam and banana. Spoil: sweet potato (mulched). Figure 10.41
THE EFFECTS OF PLANTATION MONOCULTURE
Plantation crop in the tropics may bring with it all the evils of monoculture and especially those of poisonous sprays, which not only affect the workers themselves but infect all streams and eventually town water.
These sprays drift over adjacent properties, making livestock unsellable and poison the landscape generally.
Plantations almost invariably erode the landscape, pollute rivers, estuaries and corals with silt and sprays and exhaust soils.
They centralize power and corrupt local politics, often funding repressive politicians.
Their products are of low nutrition and contain high levels of residual chemicals.
Perhaps worst of all, plantations almost always displace local self-reliant crop and replace it with “company store” dependency.
Cures are available. Firstly, plantations can be locally managed by worker cooperatives, as in some Sri Lankan tea plots.
Here, at least, the workers have a say in and profit from their labor. This does not necessarily alter many of the ecological factors, however.
Secondly, plantations need not exist, as the same area of crop can be produced by smallholders and processed centrally.
This is a further improvement, as quality can be rewarded and good ecology instituted.
Such an approach needs shared research, market and processing systems.
Thirdly, the plantation itself can adopt two reformatory practices:
- Good ecological management through the use of polyculture systems, soil building, organic fertilizers and biological control of pests.
- The “common work” approach, where workers lease secondary or tertiary crop in, around and under the main crop or lease rights to the processing of the main crop residues.
Modern analyses (computer modeling of intercrop) show that intercrop and polyculture raise employment and income and plantation itself should be designed specifically to allow intercropping throughout the life of the palm.
It is quite feasible for people to extend specific successful crop mixes from their home gardens to more extensive situations, thus giving a surplus for trade.
Money is then gained as a result of extending a stable and tested polyculture rather than by imposing a monoculture on an unsympathetic and fragile landscape.
No landscape or soil can maintain long continued monoculture production of crops, as even tree crop is susceptible to disease in this situation.
The approach of extending small and successful trials is basic to success.
Broad scale trials have unstable effects (social and ecological) from the beginning and success is rarely achieved as a result of such an approach.
However, it must also be recognized that complex small systems may work well simply because they are close by and many such systems cannot be scaled up to large acreages as a totality.
Size itself creates new factors or cost, control, market and labor requirements.
Plantation and mono-crops have the undeniable advantages of ease of harvest and predictability, neither of which are necessarily the best criteria for human centered benefits.
Malnutrition and low socioeconomic status are common factors in the human populations of the wet tropics and criteria such as full nutrition and enhanced self-reliance are where we should be concentrating for the tropics.