*7.1.1 Alley cropping*

Alley cultivation is a simultaneous AFS of trees with annual crops, consisting of rows of trees, usually 4–6 m apart between rows x 2 m between trees, interspersed with annual crops between rows of planting (**Figure 6**). Trees are pruned before planting and branches are left in alleys to incorporate organic matter into the soil and in turn suppress weeds. In this AFS, conveniently, the trees are of nitrogen-fixing species (Fabaceae such as *Erythrina* spp., *Gliricidia sepium,* and *Leucaena leucocephala*), mainly in soils of low fertility, where the nitrogen content (N) is low. The main intention of alley cultivation is the recycling of nutrients to maintain or increase crop yields through soil improvement, weed control, and erosion control.

Reminding that the main mechanisms of gain of N in the soil are: (a) N contributed with the rainfall; (b) N from non-symbiotic fixation; (c) N from symbiotic fixation; (d) N provided by organic fertilizers; and e) N from the mineralization process from fresh remains (vegetable and animal), in this case, the fallen leaves and branches from the trees. Therefore, this is a production system that adapts well to low fertility soils in degraded areas and to dry and semi-arid areas, since it favors the restoration of fertility and physical conditions of the soil. In addition, producers can obtain from trees other products such as poles, firewood, fodder, green manure, and atmospheric nitrogen fixation. The latter has current importance because the action of reducing nitrogen fertilization is a way to reduce nitrous oxide emissions into the atmosphere, so it is considered a way to mitigate climate change. In areas, with steep slopes, the

#### **Figure 6.**

*Left: Alley Cropping of banana (Musa paradisiaca) with rows of Moringa oleifera, Caribbean region of CR; and Right: Organic banana system, rows of Musa AAA subgroup Cavendish) intercropped with a nitrogen-fixing tree (Erythrina berteroana), a timber tree (Cordia alliodora), and cocoa (Theobroma cacao), Caribbean region of CR. Photos: R. Russo.*

rows of trees can be established in contour lines as a living barrier for water conservation and to deter erosion. In addition, they are a way of conserving the soil that does not require physical conservation structures.

## *7.1.2 Crops under the cover of forest curtains*

This category includes any form of short-cycle agricultural monocultures or polycultures such as corn, beans, onions, celery, lettuce, tomatoes, coriander, and other horticultural species, in association with windbreaker curtain-like trees in windy areas, multiramified live fences, or rows of trees in contour lines in hillside areas. All these alternatives that integrate crops with the planting of trees are a form of conservation and restoration of degraded areas, which contribute to conserve biodiversity and water resources. Crops undercover, forest.

## *7.1.3 Trees with perennial crops*

The simultaneous association of trees and perennial crops is a common practice in CA. The most prominent examples are coffee and cocoa crops under shade. The beneficial effects of shade trees, particularly *Fabaceae*, on coffee were recognized and described at the beginning of the last century [8]. Cocoa, unlike coffee, adapts to fertile inshore sites (from 0 to 700 meters above sea level); while coffee is a crop in higher areas. These AFSs with shading trees are more sustainable alternative to perennial monocultures because they give added value in terms of diversifying production, providing habitat for greater biodiversity, favoring soil conservation, and serving as protection of water resources. All these elements are important when contemplating the recovery of degraded areas.

## *7.1.4 Coffee and cocoa plantations under shade*

These systems simultaneously combine trees with perennial crops, such as *Coffea arabica*. The main crop is interspersed with the trees that contribute with environmental services, additional products, soil improvement, microclimate beneficial to the crop, and serves as a tutor or support for vine crops such as *Piper nigrum* or *Vanilla planifolia*.

Coffee (*C. arabica*): Shaded coffee is perhaps the oldest and most important crop, as it is estimated that it covers seven hundred thousand hectares in CA, of which more than 80% are AFS and most of it is grown by small-scale farmers on farms no larger than 5 ha [31–33]. Permanent shade trees can be timber (*C. alliodora*, *Cedrela odorata, Swietenia macrophyla, Dalbergia retusa*, *Tabebuia donnell-smithii*, *Schizolobium parahybum, Grevillea robusta*, also*, Terminalia amazonia*, *Gmelina arborea, Eucalyptus* spp., among others; also fruit trees (*Citrus* spp., *Inga edulis, I. vera, Persea americana*, *Macadamia* spp., *Psidium guajava*), or multipurpose trees (*Erythrina poeppigiana*, *E. fusca*, *Gliricidia sepium*; *Leucaena leucocephala*), *among others* (**Figure 7**) Also, the temporary shade of banana and plantain (*Musa* spp.) is in the early stages of the establishment of the system. In all cases, shade trees play an important role, in light regulation by the various layers or strata of crown trees. Aspects such as planting densities of shade trees, and regulation of shade by pruning or pollarding of branches have sound importance; given that coffee cultivated under excessive shade produces fewer coffee grains and increases in production can be favored with the management

#### **Figure 7.**

*Left: A coffee plantation (Coffea arabica) shaded with a nitrogen-fixing tree (Erythrina poeppigiana) just totally pollarded, in Tres Ríos, CR; and Right: View of a coffee crop associated with Eucalyptus deglupta located in Juan Viñas, CR.*

of the shade, through pruning of the trees, which allows air circulation and greater penetration of light [34]. A coffee AFS with shade trees of *E. poeppigiana* annually pollarded (pollarding is the pruning of all branches at a certain height of the tree trunk) located in Tres Rios, CR and a SAF of coffee associated with *Eucalyptus deglupta* located in Juan Viñas, CR, are presented in **Figure 7**.

Cocoa (*Theobroma cacao*) farming in CA is practiced by small farmers extremely poor (indigenous people, Afro-Caribbean, and mestizo), living in remote zones. Cocoa is cultivated at 100–800 m altitude in small plots (1.2 ha/farm) with low yields: 75–150 kg/ha/year in zones with frosty pod rot (*Moniliophthora roreri*) and with poor management; and 200–350 kg/ha/year where there is frosty pod rot and minimal management (**Table 1**). Cocoa trees are typically spaced at 4 × 4 m (625 plants/ha) in most countries. Most farmers have two or more cocoa plots per farm. Cocoa trees are 4–6 m tall and are associated with shade trees at a density in the range of 85–166 trees/ha. Most shade trees are planted, and some species are selected from the natural regeneration. Shade trees are used for timber (*Cordia alliodora, Cedrela odorata*), fruit (*Musa spp., Citrus spp*., avocado (*Persea americana*), coconut (*Cocus nucifera*), peach palm (*Bactris gasipaes*), mango (*Mangifera indica*), and shade providers (*Inga* spp., *Gliricidia sepium*). Shade tree canopies usually have three vertical strata (low <10 m, medium 10–20 m tall, and high >20 m tall) [35, 36].

#### *7.1.5 Agroforests*

The concept of agroforests, despite being traditional systems, has been incorporated more recently into the definitions and classifications of FAS. Agroforests are areas with a predominance of trees and shrubs or communities that resemble forests, where there are plots or clearings with agricultural practices along with structures typical of natural forests due to their floristic composition and their multiple stratifications. An example is the so-called *Quesungual* agroforestry system (SAQ ), or *Kuxur Rum*, an agroforestry modality that was practiced ancestrally by the Mayan cultures and is still carried out in some regions. This system is reported to be practiced in countries such as Guatemala, El Salvador, Honduras, and Nicaragua. It consists of pruning selected trees in an area of natural forest (usually secondary) up to the middle of the trunk, without damaging the roots, and planting corn in the clearings or gaps with greater solar radiation [37]. It should be noted that in the case of Honduras, after Hurricane

*Agroforestry: An Approach for Sustainability and Climate Mitigation DOI: http://dx.doi.org/10.5772/intechopen.105406*

#### **Figure 8.**

*Cocoa (Theobroma cacao) agroforest in rehabilitation with a shade of numerous tree species, Changuinola, Panama.*

Mitch, in the areas where SAQ was practiced, such intense damage was not observed. Studies carried out in southeastern Honduras, on hillside land with slopes greater than 12% (approximately 80% of the country's area); have shown this system reduces the vulnerability to climate change of smallholder subsistence farmers, and that it has great potential to improve livelihoods and help to adapt climate changes on tropical slopes; it is a good option to mitigate greenhouse gases, and in turn, it performs other services for a better sustainable agricultural use [38]. Other examples are cocoa agroforests in the area of the binational Sixaola River basin between CR and Panama (**Figure 8**).

#### *7.1.6 Silvopastoral systems*

Silvopastoral Systems (SPS) are agroecosystems in which a tree component is deliberately associated with an herbaceous one (natural or improved pastures) and a livestock production component (domestic animals) in the same site so that there are biological interactions between both to maximize the land use. In other words, they temporarily and spatially combine the maintenance of pastures (natural or cultivated ones) with livestock production activities, along with tree species. To this the silvopastoral practices can be added, in which the woody component does not need to be in the same site as the animal component because forage can be transported; such as the case of forage banks or living fences, which are pruned, and the forage produced by the pruning is supplied to confined animals [39, 40]. The limits, inputs, outputs, components, and interactions are shown in **Figure 9**. Silvopastoral systems found most frequently in CA are: (a) trees in pasture lands, including grazing in secondary forests and fallows; (b) grazing in forest and fruit plantations; (c) living fences; (d) perimeter shelterwood; and (e) fodder banks or crop and utilization of forage trees and shrubs. Tree species identified in pasture lands in CA are diverse and are according to the characteristics of vegetation, climate, and altitude of each region. In most cases, the trees are from natural regeneration and have been allowed to grow in densities that do not affect pasture growth, in a range from 10 to 70 trees per hectare but can reach up to 100 trees; with a basal area (BA) ranging from 1 to 7 m2 /ha, although some authors mention that is possible to have up to 200 trees/ ha [42]. Among the most frequent tree species found in animal production systems is *Cordia alliodora, Cedrela odorata, Enterolobium cyclocarpum, Pithecolobium saman,* 

**Figure 9.** *Interactions in a silvopastoral system. Source: taken from [41].*

*Guazuma ulmifolia, Tabebuia rosea, Pterocarpus rohrii*, *Pentaclethra macroloba, Mangifera indica*, *Gliricidia sepium* in the lowlands (up to 600 masl); and *Citrus* spp*., Platymiscium dimorphadrum, Persea americana, Inga* spp*., Psidium guajava*, *Bursera simaruba, Brosimum alicastrum, Alnus acuminata;* in midlands and uplands (600–2000 masl).
