Chapter 4
Agroforestry

4.8 Multistory agroforestry

A multistory agroforestry system has at least three "stories" or "layers" of intercropped plants of different heights.

Each layer partially shades the layer below it. A mature, complex agroforest does not leave enough light at the ground level for Imperata to return.

The diversity of crops in multistory agroforestry reduces risk. If one crop fails or if prices drop for one crop, the farmer still has other crops for subsistence or cash. Because the farmer still has other intermingled crops, the agroforestry farm is not likely to be abandoned. Even if it is neglected, a mature agroforest will not revert to Imperata grassland.

Multistory agroforestry is commonly developed by small farmers as they:

• Plant nurse trees for shade-tolerant crops like coffee and cacao.

• Make productive use of space between and under cash crops like rubber and coconut.

• enrich fallows with species like rattan and yams.

• establish a variety of low-input, low-maintenance tree crops.

4.8.1 Crop combinations

There are many possible crop combinations that can be used in multistory agroforestry. In general, plants and crops used will include at least three heights, and will include plants that grow in direct sunlight and plants that grow in partial or full shade (see table next page).

Note that many large trees need shade when young but love sun when old. Also note that some species, like mango, cast heavy shade and few plants can grow under them. Species like Paraserianthes falcataria cast a lighter shade and are more suitable for multistory agroforestry.

Plants of different sizes, needing different levels of light

(See additional species in Appendixes D and E)

4.8.2 Planning ahead: ecology and economics

Ecology. For any crop combination that you consider, predict how the multistory agroforestry system will grow and change over time. Each year, some plants will become less productive, and others will grow and cast additional shade. Plan the development of the multistory agro forestry system so that:

• The first plants established are adapted to full sunlight.

• The first cropping system includes Imperata control measures.

• Plants that can give shade are planted before plants that can tolerate shade or require shade.

• Plants that enrich the soil are planted before plants that require improved soil conditions.

• Plants that require sun are not planted where other plants will shade them before they mature.

• Medium-sized and large trees will have room to grow and will not become too crowded later. Think ahead to the width of the tree's canopy when it is mature. Consider whether the trees around it will also grow tall and wide; if they will crowd it, they should be harvested or never be planted at all.

• All growing space is used: crops fit together vertically (tall, medium, and short), horizontally (all planting spots occupied), and underground (deep-rooted and shallow-rooted plants).

Economics. Any farming system requires planning to diversify products and spread labor and income through the year. The first crops planted should provide food or income within 3-4 months (for example, sweet potato). Choose crops that give both subsistence produce and cash income. Plant trees that bear different fruits at different times of the year. A multistory agroforest will change every year for the first several years, with changes in labor requirements and products. Plan ahead.

4.8.3 Examples

Strategy: Nurse tree and shade-tolerant crops. Fast-growing nitrogen-fixing trees can be planted first to improve site conditions. This approach is often used for crops like coffee on poor sites, where nurse trees are valued for shade and soil enrichment throughout the life of the coffee crop.

1. Plant nurse trees (Section 4.7). Naturally occurring trees can also provide shade; assisted natural regeneration techniques may also be used (Chapter 5).

2. Intercrop annual crops (Section 4.4.2). Choose an intercrop each planting season that is adapted to current sun or shade conditions.

3. Plant shade-tolerant trees. After one year or when the nurse trees provide enough shade, plant shade-tolerant trees. Plant them 3-4 m apart from each other, or at the recommended spacing for the tree crop. Plant them 1 -2 m away from the nurse trees.

4. Fertilize, prune and weed as for other tree crops (Section 4.6).

5. Prune nurse trees. When nurse trees are providing too much shade, cut branches and use the leaves as mulch.

6. Thin trees. Watch for adjacent trees with canopies starting to grow into each other. Also watch out for sun-loving trees that are being shaded by less valuable trees. One by one, remove weak or lower-value trees to make space for healthy or higher-value trees. Be careful not to damage other trees when cutting. The remaining trees will grow faster.

7. Enrich with other crops. Plant shade-tolerant crops for food and cash income.

Nurse tree system, southwestern Sumatra.

This system evolves into a permanent complex agroforest. Damar trees (Shorea javanica) produce a commercial resin.

Strategy: Rapid establishment of both sun-loving and shade-tolerant tree crops. Plant annual crops first. Cultivate and weed to keep Imperata out. Plant sun-loving plants at the same time. Plant bananas, papayas and other such plants for quick shade (and early production). Plant shade-tolerant trees and shrubs and crops in the shade of the bananas and papayas. By the time the bananas and papayas go out of production, the sun-loving crop trees will be large enough to provide shade.

Coconut-based system, Cavite, Philippines

This system can be further enriched with the addition of root crops, multipurpose trees, black pepper, and fruit trees. Similar systems have been used to establish coconut in Imperata grasslands.

Strategy: complex agroforests. Many indigenous people care for nearly permanent tree gardens or agroforests with many species. These agroforests usually have no apparent planting pattern and may seem complicated. However, even complex agroforests can be successfully established in Imperata grasslands.

Rubber agroforest, South Kalimantan, Indonesia.

Farmers settled Tiwingan Baru, South Kalimantan, in 1975, in the middle of Imperata grasslands with very poor soils. Within a generation, farmers successfully established wide areas of agroforest using the following cropping pattern.

The most important fruit and nut trees planted were candlenut (Aleurites moluccana), mango (Mangifera indica), and durian (Durio zibethinus); other species included petai (Parkia spp.), coconut (Cocos nucifera), rambutan (Nepihelium lappaceum), cloves (Eugenia aromaticd), and kuini (Mangifera odorata).

Important factors in these farmers' success have been:

• Prior experience with tree crops and agroforests.

• Community cooperation in controlling swidden fires.

• Access to markets.

• Secure land tenure.

In other communities with access to markets and secure land tenure, extension assistance and community organization for fire control could likewise help rehabilitate Imperata grasslands.

Footnote__________

* Although fanners commonly use cassava as a rubber intercrop, the practice is not recommended because unharvested cassava is a host for white root fungus.