Evolving a Polyculture in the Humid Tropics in Permaculture

Permaculture Designers Manual




Section 10.9 –

Evolving a Polyculture in the Humid Tropics in Permaculture

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If, as is often the case, we start to evolve a Permaculture on grasslands or compacted soils, then the very first step is to thoroughly plan the site and rip, swale, pit, or dam every area to be planted, thus ensuring maximum wet season soil water storage to carry over to dry periods.

This process should commence at the highest point of the property and around the house or village site.

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On these loosened soils and in mulched swales, a mix of tree legumes, fruits, bananas, papayas, arrowroot (Canna), cassava, sweet potato and comfrey can be planted.

There should be one such plant every 1m-1.5m, with Acacia at 3mx3m spacing, banana at 2x2m, fruits 5x8m, palms 10x10m and the smaller species as gap fillers.

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As well, all larger planting holes should be seeded with nasturtium, Dolichos, Haifa clover, broad bean (fava), buckwheat, Umbelliferae (dill, fennel), lupin, vetch (hairy or woolly), dun peas, chilies, pigeon pea or any useful non-grass mix available and suitable to climate and landscape.

The end aim is to completely carpet and over shade the ground in the first 18-20 months of growth.

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Ideally, dense plantings of this type should be grass or hay mulched, using monsoon grasses, Swamp grasses and later the tops of arrowroot, comfrey, banana, Acacia and green crop.

Later still, shade-loving species such as coffee and dry taro can be placed in any open spots.

It should include; paths for access, openings for annual crop, bee plants on the edges, flowers and fire-resistant “wet” ground covers such as comfrey.

Tradescantia, lmpatiens and succulents can be placed as time goes on, while the fruit trees are kept free of grass and mulched by cutting out crowded Acacia and banana as mulch.

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It is far better to occupy a quarter hectare thoroughly than to scatter trees over 2ha as production is higher and maintenance less, moisture is conserved, and frost excluded.

As for species richness or species per hectare, this can be very complex and dense near the village or home, and simplify to well-tested species of high yields as distance from the home increases.

Any trellis crop should be first placed to shade the home, livestock or to make fences and only later placed on Acacia or other legumes as they age.

The number of productive, managed and effectively-harvested species in a polyculture is decided by a complex of these factors:

1. The number of people responsible for managing one or two of these crops or animal species (labor).

   2. The proximity of the complex to village or settlement (zoning).

   3. The relative cost-benefit balance on increasing inputs to optimum levels (fiscal economics).

   4. The need for effective plant guilds (harmonious ecological assemblies).

   5. The method or marketing and processing (whether these can cope with complex product).

   6. The total area which is controlled. Larger areas demand increasing simplicity, at a cost to factor 4 above.

   7. The maturity or stage of evolution of the plant system. Older systems provide more niches, younger systems more regular product.

In practice, the gardens, walls, roof areas, trellis systems and compounds or villages are the most complex and rich areas of cultivated species.

We can manage and find uses for some 200-400 species in such situations, of which the following usage classes are dominant (some very useful species fall into 3 or more of these classes:

Potential Species

Basic food species                                     70-90
Mulch and fodder provision                   10-30
Medicines and biocides                           20-50
Structural and craft                                      5-20
Culinary herbs                                            20-30
Beverages and export specialties           10-15
Fuelwood and coppice                             12-30
Special uses, sacred uses                          8-15

Total cultivated species                       155-280

Plus wild-gathered species                     40-80

Total special utilized in a             195-360

complex village situation


While a complex polyculture of many hundreds of species delights both the naturalist and (in food plants) the householder or villager and the benefits to settlements are numerous, it becomes difficult to control an extensive rich polyculture and collect it.

Our very complex polyculture works best at small scale and with close attention from people.

The depopulated, dehumanized and now almost deserted wasteland of modem agriculture is unable to cope with any but the most basic and simple intercrop systems, thus sacrificing yield, quality, stability and inevitably people.

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Thus, if we analyze the dollar economics of such systems, there will be an optimum number of species for broad scale cash yields.

If we analyze for total nutrition and total yield (ignoring the dollar returns), a different and richer species assembly will be indicated.

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While the fiscal return peaks at about 6 to 8 species in a system, the nutritional total yield system peaks at 50 to 100 species, well-distributed over all seasons.

These two factors (extensive vs. intensive and fiscal vs. nutritional) must be defined by ourselves for our needs and will have a profound effect on design.

What we may arrive at is a sensible zoning or species richness close in and a concentration on less species of high value as we extend the system. It is in the garden, however, that we may learn the value of such successful extension without sacrificing large amounts of energy and capital.

Thus, our gardens are trial areas for the outer zones.



(Figure 10.30)

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Even in established polyculture, particularly in plantations, it is good to re-survey the site with special attention to:

  • Main access and harvesting ways;
  • Earth shaping for rainwater harvest and specific crop;
  • Sufficiency of mulch;
  • Best water and irrigation strategies;
  • Better village planning;
  • Improved or more sophisticated site processing for market.

These are the main factors that can reduce work or increase yields and commercial values.

There is great benefit in testing new legumes, tree varieties, and earth shaping systems for optimum yields and in assessing labor, work, social and market factors for future development.

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On a new site, the same considerations hold, but the establishment of windbreaks and any earth shaping is a priority, preceding planting.

There are also essential soil tests for plant nutrients and trace elements, as it is a modest amount of these that give early vigor and early yields.

Intercrop selection is also a priority, sometimes used to shelter a more delicate crop, but also as mulch and nurse crop for nitrogen fixation and for wind, salt or sun damage reduction.


Steps in total planning are roughly in priority:

1. Assess market; future; prices: potential for processing to higher value; labor; shares, legal systems; social necessities and local self-reliance needs.

2. Analyze and get advice on soils and necessary nutrients.

3. Plan ground layout and windbreak, access and water. Detailing can follow later.

4. Plan and carry out essential earthworks.

5. Establish nursery and use selected varietal forms for new or replacement crop.

6. Commence broad scale placements with or after windbreak and nurse crop.

7. Continue by constant assessment, consultation, feedback and innovative trials. Fill niches as they evolve.



Consider only the species we can add to the polyculture to assist in the regulation of problem species (plant and animal).

Some powerful biocides that are found in plants are harmless or short-term and are totally bio-degradable, natural substances.

Classic insecticides are those derived from Chrysanthemum spp. Derris spp (rotenone) and the neem tree (Melia or Azadirachta).

A few of these plants in home gardens and small clumps in crop give a ready source of insect control or control or invertebrates, nuisance fish and amphibian in water.

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Both neem and derris control aquatic organisms; most insecticidal plants are lethal to aquatic species.

Broad scale mosquito control, applied from the air or as ground mists, can combine fats or oils (e.g. lecithin), a poison (neem oil) and an infective agent (Bacillus thuringensissis).

All or these are potentially assisted in pest control by small fish and such insect predators as notonectids (backswimmers) in open water systems.

Ground foragers (chickens, pigs, cattle, large tortoises) eat fallen fruit and larval insect infestations, while leaf foragers (birds, frogs) attend to infestations in the canopy, as do a variety of small skink lizards.

Some lizards (Tiliqua) forage for snails and slugs at ground level, as do ducks.

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Pasture grubs are eagerly sought out by a variety or birds and small mammalian and marsupial insectivores.

Tropical land crabs seek larval insects in mulch and provide useful food themselves.

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Even the problem of kikuyu grass is eased by domestic guinea-pigs on range (in small houses): these free trees from grass competition and provide manures.

Neem tree leaves and oil deter pests in stored foods, and have been so used for centuries in India.

In short, a little research will indicate plants, invertebrates, vertebrates and common harmless substances are of great use in the tropics.

I believe that there are no pest problems that will not yield to our applied commonsense and an integrated natural approach.

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In any tropical tree crop monoculture, soil fungi and nematodes may become persistent pests.

Marigolds (Tagetes) often serve to reduce or eliminate nematodes and Crotolaria as a leguminous green crop traps them in its root mycelia, so both these plants need consideration where nematodes are a problem.

Mulch and green manures (soil humus) often buffer the effects of these and fungal pests, hosting fungal predators.

Palm groves provide sheltered and shaded aspects for both intercrop and livestock.

Chickens (for controlling pests such as rhinocerus beetle larvae), guinea pigs, geese and land tortoises (to reduce grass competition), pythons (for rat and mouse control), owls (the best rodent predator), bees for pollination and all species for their manure value and other possible beneficial additions to the palm/crop/interplant complex, give complex yields as a by-product.

Pigs are ideal scavengers in tree crops below palms and fruit.

Chickens and ducks are especially valuable in weed control in pineapple, ginger and taro and will control comfrey and Tradescantia if needed (the latter plants also control grasses if planted as part of a weed barrier).

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Perhaps the main function of animal species in the tropics is to “recycle‘” plant wastes and to help control the rampant growth of ground cover.

The usual domestic species, often penned, are pigs, chickens, geese, guinea pigs, rabbits, pigeons and milking goats, cattle or buffalo.

Horses and bullocks or oxen perform draught animal functions.

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Moreover, useful endemic animal species (and especially island species of restricted natural range) need to be more widely examined for their particular uses and selected for their functions in a wider set of trials out of their normal range.

In the established tropical system, geese control pond-edge grasses and wallaby or small grazers keep forest clearings and paths open; both are encouraged by feeding-out bran or pollard in the areas to be clipped.

Where no foxes or pythons threaten poultry, flocks of guinea fowl and hens, ducks and bantams perform invaluable pest-control and manure/scavenging roles.

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Where predators are a problem, special housing or pigeons in safe elevated roosts, may be the only way to keep fowl. The effects of electric fences in tropical areas, if not within forest edges, are often nullified by the rank growth of coarse grasses and become inoperative for repelling python, pig, bandicoots and foxes.

For this reason, fence lines must be planted with a dense perennial ground carpet of low herbaceous plants to exclude grasses or over shaded by tree canopies.


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