Based on a field study, Kumar et al.reported that the presence or absence of over-canopy had little effect on the rhizome yield of galangal , a medicinal plant, implying its shade tolerance.Being a shade-tolerant crop, galangal yield remained steady across a wide range of light availability conditions, from full light to a photosynthetic photon flux density as low as 18% of that in the open.Woody perennials such as cacao , cinnamon , clove , coffee and nutmeg , and vines and creepers such as sweet potato and vanilla can also tolerate shade to varying degrees.Species are also grouped into obligate or facultative shade plants and obligate or facultative sun plants based on their light requirements.Nonetheless, rigorous studies on the nature, mechanisms, inheritance, and management of shade adaptability of understory species in CBFS are lacking.Being a single-stemmed woody perennial with oucambium, the palm’s main stem does not develop radially with age.The crowns are likewise rather narrow, measuring 5 to 6 m in breadth.This unique growth form of the coconut palm allows significant light infiltration into the understory in an even-aged stand.A related aspect is the uniform spatial arrangement of the palms.In Kerala, coconut palms are typically planted at 7.6–9 m apart, with a population density of 120 to 170 palms per hectare.Likewise, an average density of 148 trees per hectare was reported from Melanesia’s smallholder coconut plantations.Although designed to meet the growth requirements of mature palms, this wide spacing typically results in inefficient use of site resources and a lack of full site occupancy by the main crop throughout the majority of its life cycle.
In the field study mentioned above, Kumar and Kumar found that understory light transmittance for mixed coconut+multipurpose tree stand ranged between 6 and 75% of that in the open, depending on the time of the day, tree species involved and planting geometry.According to Thomas et al.,4x8ft rolling benches only around25% of the land is properly utilized, when monocropping is practiced in coconut gardens.Furthermore, the grower receives little or no returns from the palms throughout their immature stage, which can last up to 10 years, while the intercrops provide some returns.As a result, mixed species agroforestry systems aimed at increasing spatial and/or temporal complementarities in resource utilization, as well as providing additional returns, have become a unique feature of the coconut-growing regions in the tropics.What explains the functioning of such sophisticated agroecological models is perhaps the “Niche-complementarity hypothesis”.It implies that a bigger suite of species occupying a site may lead to better resource partitioning and utilization making the system more productive than systems involving fewer number of species.Consistent with this, Liyanage and Dassanayake reported increased nut yields when pasture species , black pepper and coffee were inter cropped with coconut.Such beneficial effects of inter cropping have been attributed to improved nutrition of the palm through complementary resource sharing, better retention of soil moisture, reduced weed competition and improved soil quality.
Competition for site resources between coconuts and the associated plants, however, could be a potential problem.Such interactions may be either above ground or below ground.Section 5.1.4 describes the below ground interactions.Furthermore, the nature of inter specific interactions will vary depending on the stage of coconut stand development.A synthesis of the published reports, nevertheless, indicates that growing trees in the inter spaces does not have a strong adverse impact on the yield of coconut palms, except in situations where such trees impede light availability of the palms.Species mixtures generally ensure spatial complementarity in resource use as the components occupy different niches, although the tree-crop interactions may change with time and planting geometry.Although coconut-based polycultural systems are ubiquitous, below ground interactions of woody perennials in such mixed-species systems are rarely studied due to methodological challenges.Furthermore, results from the available studies are also not consistent, implying that the interactions may be either complementary or competitive.Nelliat et al.reported horizontal and vertical stratification of coarse roots in “adequately and separately fertilized multi-storied combination of coconut, cacao and pineapple”.Conversely, Pandey et al.found that the coconut root systems were at close proximity to the intercrops in well fertilized polycultural systems involving three 20-year-old tree species,implying competitive nutrient withdrawal by the coconut palms.Using the 32P soil injection technique, Kumar et al.and Gowda and Kumar investigated root competition in the coconut + dicot MPT agroforestry system.According to Kumar et al., 32P uptake by coconut palm in a species mixture was higher than that of a sole coconut stand, owing to increased subsoil root activity in the former, implying that the coconut root system may grow deeper in mixed-species systems compared to sole coconut systems.Gowda and Kumarexamined root interactions between coconut and dicot trees along a soil fertility gradient.
Notwithstanding major differences in the nutrient status along the gradient as well as dicot tree root characters, uptake of 32P by the coconut palms was not substantially different, signifying non-competitiveness of the associated dicot tree components for P.Nevertheless, the interplanted dicot trees captured significant quantities of the radio-label supplied to the coconut palm, implying a “scavenging effect” by these trees that, in turn, minimizes the potential for lower leaching of nutrient elements.Coconut-based farming systems often involve mixtures of trees that occupy different soil strata and this may entail a certain degree of spatial complementarity in resource use.Occurrence of two or more woody species in mixtures also favors diminished lateral spread and/or facilitates deeper root penetration of the components.In the coconut+dicot tree system investigated by Gowda and Kumar mentioned above, the interplanted dicot trees absorbed considerable quantities of the radio-label applied to the palm, which declined log-linearly with distance from the palms, signifying a substantial potential for “capturing” the lower leaching nutrients, at proximal distances.Proximity of the associated tree component, therefore, is a strong determinant of such plastic responses in tree root distribution.Gowda and Kumar also reported that some dicot species in the coconut+dicot tree mixture developed deeper root systems , while others produced increasingly spreading root systems , denoting that root architecture of mixed tree plantations is species dependent.Thus, there is a need for proper selection of the component crops and their manipulation to optimize productivity in coconut ecosystems.An array of ecosystem services such as provisioning, regulating, supporting, and cultural services are provided by the coconut based multi-strata, multi-species ecosystems.This includes crop species yielding food, fiber, fuel, fodder, timber, medicine, and other basic necessities , besides cash returns.The diverse range of crops integrated into CBFS producing fruits, nuts, drinks , edible oils and cakes, fiber, foliage, timber, bio-fuels, vegetables, spices, and medicinal plants justifies the sobriquet “coconut-based food forests”.The coconut palm also yields organic coconut water, virgin coconut oil, functional foods and health drinks like neera , coconut sugar, cosmeceuticals, oleochemicals, and bio-lubricants and is a popular ingredient in the cuisines of many countries in South and Southeast Asia.Furthermore, the coconut palm produces edible copra for the extraction of coconut oil, as well as desiccated coconut powder, fermented sap, and sap jaggery, among other culinary items.
Also available in both domestic and international markets are a variety of value-added products from coconut oil such as soap, body oil and perfumed hair oil, and kernel-based products such as coconut chips, coconut cream, coconut milk powder, white soft coconut cheese, coconut yoghurt and so on.Tender coconut water is a healthier alternative to many carbonated beverages due to its nutritious properties.Apart from being an important dietary component, the coconut palm and the associated species yield diverse range of aesthetic and artisanal products.Coconut wood is an excellent structural material that is used in the construction of buildings, furniture, flooring, and paneling, and the fabrication of high-end products like handcrafted, biodegradable,flood and drain table and sustainable coconut bowls, as well as for the making of charcoal, chemicals, pulp, and paper.In experimental studies, the mechanical properties of coconut wood compared quite well with those of other structural timbers such as teak , wild jack and the like.Coconut wood thus supplements the supply of raw materials for the wood industry and provides low-cost and durable construction materials.Because of its availability and renewability, coconut’s sustainability can add value to this construction material and thus help to conserve the remaining natural forests, by offsetting the pressure on them.Additionally, CBFS provides byproducts such as coconut shells and fibre, which are presumably underutilized but constitute vital raw materials for cottage enterprises.Coconut shell is a useful bio-fuel as well, despite its relevance as an alternative fuel in homes and small businesses.In addition to offering an alternative and better source of fuel than fuel wood and other traditional fuels, using coconut shell as a fuel reduces CO2 emissions and sanitizes the environment of the harmful hard shell.The husk usually forms 35–45% of the weight of the whole nut when ripe.About 30% of the husk is fibre and 70% is coir dust.The industry uses just about 35% of the total husk available, while there is scope for economically utilizing at least 50% of the husk produced.Coir fiber and coir pith are two important products made from coconut husk.The fibers are used for spinning into yarn for manufacturing mats and mattings, ropes, twines, etc.Pith, which is usually mixed with short fifibers and contains mainly lignin, cellulose, and hemicellulose, is used as a manure and has a variety of industrial applications too.Agrobiodiversity being the critical feature of NbS, CBFS offers innumerable opportunities for integrating diverse forms of crops in the same land management system.
Such systems have provided sustenance, nourishment and livelihood security to large segments of Kerala’s rural and peri-urban populations for millennia, as in other parts of South and Southeast Asia.As described in Table 2 and Section 5, many functional groups of plants, such as food crops , permanent plantation crops, medicinal plants, multipurpose trees, and others, are associated with CBFS, implying their potential to conserve biodiversity in managed ecosystems.Such integrated farming systems generally outperform mono specific production systems in all major aspects of multifunctional agriculture, including food security, environmental functions, economic functions, and social functions.The coconut palm is also very resilient as it can withstand natural calamities like typhoons and flooding.In general, woody perennial-based mixed-species land use systems have the potential to address natural calamities such as droughts, floods, and high temperatures as a consequence of climate change.Improvements in soil organic matter status and water holding capacity, and the resultant yield gains, are also integral features of the coconut-based ecosystems.Osei-Bonsu et al.observed higher soil moisture retention in cacao + coconut mixture in Ghana compared to cacao + Gliricidia sepium system.From Sri Lanka, Arachchi and Liyanage also reported improved soil organic matter status, bulk density, aeration, and water content in the soil profiles of acacia and gliricidia interplanted plots compared to that of sole coconut and Calliandra calothyrsus and L.leucocephala intercropped plots.Although global warming and the consequential faster soil organic matter turnover may exacerbate the deterioration of nutrient-poor tropical soils, such obstacles are less likely in coconut-based multi-strata production systems than in mono specific stands, emphasizing the CBFS’s sustainability.Another major characteristic of CBFS is enhanced carbon capture and storage in soil-crop systems, which has the potential to minimize CO2 emissions.This includes carbon sequestration in soil and biomass , as well as the substitution of fossil fuels with bio-diesel made from biomass or coconut oil.However, only few studies have characterized the carbon sequestration potential of coconut-based ecosystems.The available reports suggest that tree plantations signify remarkable carbon pools as trees hold much more carbon per unit land area than other categories of vegetation, and CBFS has huge potential as a carbon sink.Consistent with this, Navarro et al.reported that coconut plantations exhibit high productivity typical of the tropical humid evergreen forest ecosystems.Ranasinghe and Thimothias estimated that the ecosystem carbon stock of CBFS in Sri Lanka ranged from 32 to 72 Mg C ha–1, while the net carbon balance ranged from 0.4 to 1.9 Mg C ha–1 month–1 under various growth conditions.Carbon storage by coconut palms in mixed stands is clearly greater than that of sole stands, especially when the species-mix involves trees.For instance, in a system involving different inter cropped fruit trees such as guava , litchi , sapota and custard apple grown in association with coconut, Manna et al. reported higher soil carbon sequestration for mixed-species systems than sole coconut.Nutrient management of CBFS is yet another important determinant of soil carbon sequestration, and improved nutrient management may augment the carbon sequestration potential.