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Essay on Agroforestry
Essay # 1. Introduction to Agroforestry:
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India is endowed with a variety of soils, climate, biodiversity and ecological regions. About 228 million ha (69 per cent) of the country (329 million ha) fall within the dry land. The majority of cultivated area is rain fed with enormous unexploited agricultural production potential. An area of 46.70 million ha has been estimated under wastelands during 2008-09 which is 14.75 per cent of the total geographical area of the country (Wastelands Atlas of India 2011).
At present, wood fuels account for 20-30 per cent of all energy used in India and more than 90 per cent of wood fuels are consumed in the domestic sector. These situations pose threat to crop yields and warrant for an alternate land husbandry and crop diversification for sustainable production. There is a great risk of growing food grains in degraded and culturable wastelands.
The ever growing demands of the increasing population for food, fodder, fuel wood, fruit, fibers, timber, pulpwood, etc. requires emphasis on checking land degradation for which agroforestry practices are considered a most vital technology and a potential farming system for minimizing the land degradation.
The apparent high potential of agroforestry systems are its applicability to control soil erosion, soil improvement, creating congenial and conducive microclimate for tree and understory crops and reduction in the accumulation of greenhouse gases in the atmosphere. Agroforestry has generated rather high levels of enthusiasm in recent years concerning with rain fed land use and sustainable resource management system.
It has the most apparent potential in rain fed areas and in resource limiting small holding farming systems where monoculture agriculture may not be the most feasible or desirable, based on the principles of self-maintenance.
Keeping in view the increasing human and livestock population and decreasing per capita availability of land and grazing resources, there is an urgent need for the development of location specific agroforestry system at culturable wastelands and degraded lands, which will not only fulfill the futuristic requirement of wood, food, fodder, fuel wood, etc. but also conserve and provide solution to sustainably use the land resources.
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Therefore, the agroforestry should be considered as a dynamic, ecologically based natural resource management system that can sustain small holder production through the integration of trees in farm and/or in rangelands for increased social, economical and environmental benefits.
Essay # 2. Concept of Agroforestry:
The gap between demand and supply and land degradation processes could be mitigated through diversification of agriculture by adopting alternate land use system by introduction of woody perennials in agricultural land as well as in degraded lands where woody species can only be grown successfully for their reclamation and further used for cultivation of arable crops.
In this context, the concept of ‘Agroforestry’ comes in handy in fulfilling these deficiencies through integration of forestry with agriculture for increasing productivity per unit area per unit time. Agroforestry, as the term, is used for growing of woody perennials in close association with agricultural crops.
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It is a land use system that involves trees, arable crops and/or livestock seeking positive synergism on the same land unit in space or time. Agroforestry in arable lands can help substantially in meeting such demands and solve some of our pressing problems besides achieving national target of 33 per cent area under tree or forest cover.
Agroforestry is not a new system or new concept, the practice is age old but the term is definitely new. People are rising together woody perennial species, crops and animals, traditionally on the same farm. The practice of mixed farming developed over centuries for meeting most of the requirement of a family. Modern Agroforestry establishes a symbiosis among agricultural crops, woody species and livestock. In other words, these are complementary and beneficial to each other.
Essay # 3. Definition of Agroforestry:
i. One of the earliest definition of agroforestry is that of Bene et al (1977) as well as King and Chandler (1978) which defined agroforestry as a sustainable land management system which increases the overall yield of the land, combines the production of crops (including tree crops) and forest plants and/or animals simultaneously or sequentially on the same unit of land and applies management practices that are compatible with the cultural practices of the local population.
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ii. Nair (1979) defined agroforestry as a land use system that integrates trees, crops and animal in a way that is scientifically sound, ecologically desirable, practically feasible and socially acceptable to the farmers.
iii. One of the simple definition of agroforestry is that of Lundgren and Raintree (1982), who defined agroforestry as a collective name for land-use systems and technologies where woody perennials (trees, shrubs, bamboos, palms, etc.) are deliberately used on the same land management units as agricultural crops and/ or animals, in some form of spatial arrangement or temporal sequence.
This definition implies that:
a. Agroforestry normally involves two or more species of plants (or plants and animals), at least one of which is a woody perennial.
b. An agroforestry system always has two or more outputs.
c. The cycle of an agroforestry system is always more than one year.
d. Even the simplest agroforestry system is more complex, ecologically (structurally and functionally) and economically, than a monocropping system.
iv. According to Lundgren (1987), agroforestry is a collective name for all land-use systems and practices where woody perennial plants are deliberately grown on the same land management unit as agricultural crops and /or animals, either in a spatial mixture or in temporal sequence. There must be significant ecological and economic interactions between the woody and non-woody components.
v. Young (1989) proposed and defined agroforestry as a collective name for land use system in which woody perennials (trees, shrubs etc.) are grown in association with herbaceous plants (crops, pastures) and /or livestock in spatial arrangement or rotation of both and in which there are both ecological and economic interaction between the trees and non-tree components of the system.
vi. Sanchez (1995) defined agroforestry as a collective name for land use system and practices in which woody perennials are deliberately integrated with crops and/or animals on the same land management unit.
vii. It has been argued that the above definitions are not sufficiently dynamic and the following alternative has been suggested by Leakey (1996): Agroforestry is a dynamic, ecologically based, natural resource management system that, through the integration of tree in farmland and rangeland, diversifies and sustains small holder production for increased social, economic and environmental benefits.
A scientific definition of agroforestry stresses on two characteristics common to all forms of agroforestry and separates them from the other forms of land use, namely:
i. The deliberate growing of woody perennials in the same unit of land as agricultural crops and/or animals, either in some form of spatial mixture or sequence.
ii. There must be a significant interaction (positive and/or negative) between the woody and non-woody components of the system, either ecological and/or economical.
All agroforestry systems possess theoretically three attributes which are:
(1) Productivity:
Agroforestry systems mostly aim to maintain or increase production as well as productivity of the land.
(2) Sustainability:
Agroforestry can maintain and conserve fertility of soil and sustain the production.
(3) Adoptability:
Traditional agroforestry practices already been accepted and adopted by the farming community but improved agroforestry system should be encouraged to adopt.
Agroforestry also has four traits, i.e. ‘4I’:
i. Intentional
ii. Intensive
iii. Interactions
iv. Integrated
These traits describe that agroforestry practices are intentional combinations of trees with crops and/or livestock that involve intensive management of the interactions between the components as an integrated agro ecosystem. These key characteristics differentiate agroforestry from other farming or forestry practices.
Essay # 4. Classification of Agroforestry Systems:
In the early stages of agroforestry development, several attempts were made to classify agroforestry systems. However, the most obvious and easy-to-use criteria for classifying agroforestry systems are the spatial and temporal arrangement of components, importance and role of components, production aims or outputs from the system and the social and economic features.
They correspond to the system’s structure, function (output), socioeconomic nature, or ecological (environmental) spread. These characteristics also represent the main purpose of a classification scheme.
Therefore, agroforestry systems can be categorized according to these sets of criteria:
i. Structural Basis:
It refers to the composition of the components, including spatial arrangement of the woody component, vertical stratification of all the components and temporal arrangement of the different components.
ii. Functional Basis:
It refers to the major function or role of the system, usually delivered by the woody components (these can be of a productive, service or protective nature, e.g., soil conservation, windbreak, shelterbelt, etc.).
iii. Socioeconomic Basis:
It refers to the level of inputs of management (low input, high input) or intensity of management and commercial goals (subsistence, commercial and intermediate).
iv. Ecological Basis:
It refers to the environmental condition and ecological suitability of systems based on the assumption that certain types of systems can be more appropriate for certain ecological conditions i.e., there can be separate sets of agroforestry systems for arid and semiarid lands, tropical highlands, lowland humid tropics, etc.
Several agroforestry systems have been evolved for different areas and one system differs from the other in respect of structure, function, arrangement of components and composition. Nair (1985) classified the agroforestry systems based on nature of components, structure, function, socio-economic and ecological factors, etc.
(A) Structural Classification of Agroforestry Systems:
The structure of the system can be defined in terms of its components and the expected role or function. However, it is important to consider the arrangement of components in addition to their type.
In this structural classification, the type of component and their arrangement both are important consideration. Hence, on the basis of structure, AF systems can be grouped into two categories: classification based on nature of components and arrangement of components.
(1) Classification based on the Nature of Components:
Based on the nature of components, AF systems can be classified into the following categories:
i. Agrisilvicultural systems
ii. Silvopastoral systems
iii. Agrosilvopastoral systems
iv. Other systems
i. Agrisilvicultural Systems:
It refers to combined production of agricultural crops and trees including shrubs/vines and forest crops. This system involves the conscious and deliberate use of land for the concurrent production of agricultural and forest crops both.
Based on the nature of the components this system can be categorized into various forms:
a. Improved fallow species in shifting cultivation
b. The Taungya system
c. Multispecies tree gardens
d. Alley cropping (Hedgerow intercropping)
e. Multipurpose trees and shrubs on farmlands
f. Crop combinations with plantation crops
g. Agroforestry fuel wood production
h. Shelter-belts and Wind-breaks
i. Soil conservation hedges etc.
ii. Silvopastoral Systems:
It refers to combined production of trees and fodder crops/grasses and/or animals. This system deals with combined cultivation of timber yielding tree and fodder yielding tree plus grasses and/or animals.
This system is further classified into three groups:
a. Protein bank
b. Living fence of fodder trees and hedges
c. Trees and shrubs in pasture
iii. Agrosilvopastoral Systems:
It refers to combined production of trees, agricultural crops and pasture and/or animals for production of food, fodder, timber and also grasses/grazing.
iv. Other Systems:
The following systems can be included in this category:
a. Apiculture with Trees:
In this system, various honey (nectar) producing tree species frequently visited by honeybees are planted on the boundary, mixed with an agricultural crop. The main purpose of this system is the production of honey. Species preferred are Eucalyptus spp., Litchi, Mangifera indica, Madhuca indica, etc.
b. Aquaforestry:
In this system, various trees and shrubs preferred by fish are planted on the boundary and around fish-ponds. Tree leaves are used as forage for fish. The main or primary role of this system is fish production and bund stabilization around fish-ponds. Species preferred are Salix spp., Eucalyptus spp., Syzygium cuminii, Terminalia arjuna, etc.
c. Multipurpose Wood Lots:
In this system, special location-specific MPTs are grown mixed or separately planted for various purposes such as wood, fodder, soil protection, soil reclamation, etc.
Following are common agroforestry systems/practices prevailing in different agro- ecological regions of India classified on the basis of the nature of components.
(i) Agri-silviculture (forest trees + crops)
(ii) Boundary Plantation (trees on boundary + crops)
(iii) Block Plantation (Block of trees + Block of crops)
(iv) Energy Plantation (trees + crops during initial years)
(v) Alley cropping (hedges + crops)
(vi) Agri-horticulture (fruit trees + crops)
(vii) Agri-silvi-horticulture (forest trees + fruit trees + crops)
(viii) Agri-silvi-pasture (forest trees + crops + pasture or animals)
(ix) Silvi-olericulture (forest trees + vegetables)
(x) Horti-pasture (fruit trees + pasture and /or animals)
(xi) Horti-olericulture (fruit trees + vegetables)
(xii) Silvi-pasture (forest trees + pasture and / or animals)
(xiii) Forage forestry (forage trees + pasture)
(xiv) Shelter belts (trees for wind protection + crops)
(xv) Wind breaks (rows of trees + crops)
(xvi) Live fence (shrub and trees on boundary)
(xvii) Silvi or Horti-Sericulture (forest trees or fruit trees + silkworm)
(xviii) Horti-apiculture (fruit trees + honeybee)
(xix) Aqua-forestry (forest trees + fishes)
(xx) Homestead (multiple combinations of forest trees, fruit trees, vegetables etc.)
(2) Classification Based on Arrangement of Components:
The arrangement of components i.e. trees, shrubs, crops and/or animals or multispecies combinations involve in the dimensions of space and time.
i. Spatial Arrangement:
Spatial arrangements of plants in an agroforestry mixture may result in dense mixed stands (as in home gardens) or in sparse mix stands (as in most systems of trees in pastures). The species (or species mixtures) may be laid out in strips of varying widths either on boundary or inside the fields.
ii. Temporal Arrangement:
Temporal arrangements of plants in agroforestry may also take various forms. An extreme example is the conventional shifting cultivation cycles involving 2-4 years of cropping and more than 15 years of fallow cycle.
Similarly, some silvopastoral systems may involve grass leys in rotation with some species of grass remaining on the land for several years. These temporal arrangements of components in agroforestry are termed coincident, concomitant, overlapping (relay cropping), separate and interpolated.
(B) Functional Classification of Agroforestry System:
The production and protection are theoretically two fundamental attributes of all agroforestry systems. This implies that agroforestry systems have a productive function yielding one or more products that usually meet basic needs, as well as a service role (i.e., protecting and maintaining the production). Productive functions of agroforestry systems are producing one or more products for food, fodder, manure, fuel wood, etc.
Protective functions of agroforestry systems are protecting and maintaining production systems by the system functions e.g. wind-break, shelter-belt, soil conservation, moisture conservation, soil improvement, shade (for crop, animal and man). However, the emphasis on production of outputs should not diminish the importance of sustainability.
(1) Classification Based on Ecological Grouping:
Agroforestry system characterizations pertain to specific ecological conditions of different geographical regions. The most famous and intensive effort in describing several existing agroforestry systems were made by Nair (1985).
Based on the major agro-ecological zones, agroforestry systems are grouped into the following categories:
i. Humid/Sub-Humid Lowlands:
This region is characterized by hot humid climate for all or most of the year and evergreen or semi-evergreen vegetation. The lowland humid and sub-humid tropics (commonly referred as the humid tropics) are by far the most important ecological regions. Because of climatic conditions that favour rapid growth of a large number of plant species, various types of agroforestry plant associations can be found in areas with a high human population, plantation of crops with combinations and multilayer tree gardens, trees on rangelands and pastures, etc.
ii. Semi-Arid/Arid Lands:
This region is characterized by less rainfall confined to 9-21 days in July-September, 2-4 wet months, solar radiation incidence (400-500 cal/cm2/day), high wind velocity (20 km/hour), high potential evapotranspiration (6 mm/day) and high mean aridity Index (70-74.8 per cent).
iii. Highlands:
Variable rainfall, degraded and shallow lands at high altitude to deep rich soils in valleys and great climatic variations are the features of highlands. This area is a storehouse of great biological diversity. The Himalayan region is an excellent example of this type of area. Agroforestry has long encompassed many well-known land-use systems practices.
A system based on the nature of the components and their major functional characteristics for specific purpose appears more logical, simple and practical purpose oriented approach to classification of Agroforestry systems. Again, the choice for a system may be based on many interacting considerations – social, ecological and economical. The right choice for the right situation is necessary.
(C) Classification Based on Socio-Economic Condition:
Socioeconomic criteria such as scale of production, level of technology, input and management have been used as a basis for classifying agroforestry systems.
Based on such socioeconomic criteria as scale of production and level of technology input and management, agroforestry systems have been grouped into three categories:
i. Commercial System:
The major aim of the system is production of the output (usually a single commodity) for sale.
ii. Intermediate System:
Intermediate agroforestry systems are those that are intermediate between commercial and subsistence scales of production and management, i.e. production of perennial cash crops and subsistence crops undertaken on medium-to-small-sized farms.
iii. Subsistence System:
Subsistence farmers those who produce most of what they consume, or consume most of what they produce.
Essay # 5. Importance and Impact of Agroforestry:
i. Increased per unit production due to introduction of trees.
ii. Growth of trees or woody perennials conserves soil and soil moisture.
iii. Agroforestry improves soil fertility and can improve productivity by increased output of tree products, improved yields of associated crops, reduction of cropping system inputs and increased labour efficiency.
iv. Provides more diverse products and services.
v. Provides higher revenue due to sale of tree products.
vi. Reduced pressure on remaining natural forests for wood, fuel wood and other forest based products and pressure of grazing.
vii. Enhanced microclimates by increase in atmospheric humidity (10-20 per cent).
viii. Reduces wind velocity by 40 per cent.
ix. Protects field crops against the scorching and desiccating conditions.
x. Trees supply cheap fuel wood, fodder, small timber, poles.
xi. Helps in reducing carbon loss from soils by sequestrating CO2 from atmosphere.
xii. Reduction of run-off, nutrient leaching and soil erosion by tree roots and stems.
xiii. Enhances recycling of nutrients and nutrient pump due to deep and tap rooted trees.
xiv. Addition of soil nutrients through litter fall and their decomposition.
xv. Improves soil physical and chemical conditions through the accumulation and decomposition of organic matter.
xvi. Reduced chances of total crop failure which is common to monoculture system.
xvii. Increase in farm incomes due to improved production and sustained productivity.
xviii. Help in improvement of rural living standards from sustained employment and recurring incomes.
xix. Improvement in nutrition and health due to increased quality and diversity of food outputs.
x. Better protection of ecological systems.
Essay # 6. Scope of Agroforestry:
Agroforestry has great potential to rehabilitate and reclaim degraded lands for sustainable production. It is one of the important alternatives farming system for improvement of degraded sites as it can play a very vital role in utilization of all the natural resources in a most effective manner for sustainable crop production by maintaining the long term production potential of land.
It is an important tool for arresting land degradation and amelioration of lands. It is a land management system that optimizes the overall land productivity and reduces resources depletion through the utilization of positive interaction between crop-tree-animals in its temporal and spatial dimensions.
Agroforestry can be seen as phases in the development of productive agro-ecosystem and an alternate land use system, wherein, farmers can manipulate and manage their land by growing trees for the service or products.
Demands of our rising population for food grains, fuel wood, timber, fodder, etc. are increasing day by day and the present availability and supply are in short. Moreover, over 200 million people, mostly poor, are highly dependent on forests for meeting their subsistence and livelihood needs. The above needs cannot be fetched from the traditional farming practices.
An alternative land use system has to be evolved to fulfillment of needs of escalating population and solve the land and climatic degradation. The agroforestry practice is the answer to release the pressure on land up to some extent. Agroforestry is a valuable and viable tool for increasing the tree cover as well as to meet the demand for wood and food.
The several agroforestry practices already proved that it can meet out the demands of timber, fuel, fodder, non-timber minor forest produce and medicinal and aromatic plants. The sustainable development and management of these lands through agroforestry innovations not only meet the multiple needs for food, fodder, fuel wood, fibre, fertilizer, NWFPs, medicinal and aromatic plants etc. but also ensure economic and environmental security for human beings by synchronization of proper land uses.
Agroforestry is the only realistic approach and tool to conserve natural resources and to meet the target of increasing forest cover to 33 per cent from the present level of 23.81 per cent.
The increasing pressure on land as well as on forests, rising demand for fuel and fodder and finally the requirement of timber for multifarious purposes have strengthened the need of agroforestry as an alternate land use system especially at natural resource conservation front. Today, the main concern of agroforestry is to ensure optimum use of natural resources and develop viable multiple use alternatives which can improve the overall economic condition of the farmer.
It is also important that the system what we are developing and promoting must be sustainable. The purpose of growing trees with crops and/ or animals in interacting combination has variety of objectives including biological control of soil erosion, where the emphasis is now forced upon.
This system not only control physical erosion but also reduces losses of soil organic matter and nutrients. Today, the potential of agroforestry for soil conservation is generally accepted and widely propagated. The system also helps in reduction of atmospheric carbon by sequestering in tree and biomass development.
Essay # 7. Selection Criteria for Suitable Agroforestry Trees:
Tree species that are chosen to be grown in conjunction with agricultural crops should have inter alia the following characteristics:
i. Identifying the proper species suited to the soil and site conditions
ii. The selected species should be capable of providing the desirable products and services
iii. Species adoptability and compatibility with the companion crop
iv. Tree species should be fast to medium growing
v. High value that a slower growth rate is acceptable
vi. Single stemmed with clear bole and tall
vii. Amenable to early wide spacing
viii. Deep-rooted with tap root system so the trees do not compete with companion crops for moisture and nutrient
ix. Drought resistance or capable of growing on a wet site
x. Trees should have a low crown diameter to bole diameter ratio
xi. Light branching in habit
xii. Produce a light rather than a heavy shade
xiii. Phyllotaxis should permit the penetration of light to the ground
xiv. Tree phenology should be advantageous to the growth of the annual crops
xv. Litter fall and litter decomposition rate should have positive effect upon the soil
xvi. Tree should have efficient nutrient pump system
xvii. Preferably leguminous and nitrogen fixer and MPTs
xviii. Possess self-pruning properties
xix. Tolerance to relatively high incidences of pruning
xx. Marketability of products (wood, fruit, fodder, fuel, etc.)
Tree Characteristics for Agrisilviculture System:
i. Tree species medium to fast growing
ii. Straight, single stemmed with clear bole and tall
iii. Low crown and less branching habits
iv. Good survival and adaptability
v. Tap and deep rooted species with efficient nutrient pump
vi. Preferably leguminous and nitrogen fixer and MPTs
vii. Less competitive with associated crops for water, light and nutrient
viii. Resistance to disease and pests
ix. Trees should not act as a common host for diseases and pests
x. Tree species medium to fast growing
xi. Crown should be round with medium diameter
xii. Multiple stemmed and upright branch angle
xiii. Ability to produce green fodder during lean period
xiv. Leaf should have high palatability and good nutritive value
xv. Preferably leguminous and nitrogen fixer
xvi. High coppicing power and liable to high lopping and pollarding habits
xvii. Deep rooted with efficient nutrient pump
xviii. Hardy and tolerance to adverse environments
xix. Resistance to disease and pests
xx. Trees should not act as a common host for diseases and pests.
In reality, no individual tree can be successful for all sites and can provide all type of services. However, the tree should be selected which has high adaptability to site, provide early and economic returns, multiple uses, maximize land use in time and space, complimentary to the system and non-competitive with associate crops or/and other component of agroforestry system.
The suitable tree species to be used in agroforestry largely depend on soil and site conditions, nature of agriculture/horticultural crops, objectives of farming and agro-climatic conditions, market demand, industrial demand and need of the farmer.
Essay # 8. Multipurpose Tree Species in Agroforestry:
The multipurpose trees are woody perennials that can provide multiple products and services in agroforestry systems. They may supply food in the form of fruit, fodder, leaves and at same time supplying wood, fuel wood, fiber, flosses, fertilizer (add nutrients to the soil) and supply some other products (silk, gum, lac etc.).
In short it can be said that multipurpose trees are those trees which provide multiple products and perform various functions and the trees have a greater impact on a farmer’s well-being because they fulfill more than one basic need.
The MPTs can be integrated with agroforestry or any other form of tree farming system to improve total biomass and yields, to diversify products, to increase economic resiliency and to improve farm viability and sustainability in the long-term.
The multiple products and functions of multipurpose trees can be summarized as follows:
i. Food (fruit/vegetables/root/shoot/oil)
ii. Wood /timber
iii. Small wood
iv. Fuel wood
v. Fodder
vi. Tannin/dyes/gums
vii. Wood pulp
viii. Litter/green manure/ mulch
ix. Pest control
x. Living fence
xi. Medicinal uses
xii. Honey and nectar production
xiii. Shade
xiv. Wind resistance (to use as a component in a windbreak)
xv. Erosion control
xvi. Nitrogen fixation
xvii. Soil fertility improvement
xviii. Shade and shelter to wildlife habitat
The most important benefit of multipurpose trees planting and integrating in other forms of tree farming system is that they can provide an assured amount of insurance in the event of agricultural crop failure or market fluctuation.
The desirable characteristics of MPTs to be considered while choosing the tree species are:
i. Easy establishment and management
ii. Easy adaptability to local climatic condition
iii. Fast growing
iv. Short rotation
v. Preferably nitrogen fixing ability or leguminous species which can contribute to soil nutrients
vi. Deep root system to draw nutrients and water from lower soil layers
vii. Easy availability of quality planting stocks and easy propagation
viii. Provide fodder and green manure
ix. Tolerance to drought and minor injuries and withstand against flood
x. Resistant to insects, pests, diseases and strong winds
xi. Multiple uses, high demand and value of the produce
xii. Meet out the multifarious needs of farmers
Essay # 9. Soil Fertility Improvement in Agroforestry:
Tree legumes (nitrogen fixing trees-NFTs) are especially valuable trees integrated into an agroforestry system especially in subtropical and tropical agroforestry to restore nutrient cycling and fertility self-sufficiency. Nitrogen is an essential nutrient for plant growth and NFTs are a major source of nitrogen in tropical ecosystems. In legume, nitrogen fixation starts with the formation of a nodule.
A common soil bacterium, Rhizobium, invades the root and multiplies within the cortex cells. Nitrogen fixing trees (NFTs) are trees and shrubs that have the ability, through a symbiotic association with certain soil bacteria, to take nitrogen from the air and use it for growth. NFTs can make substantial contributions to nitrogen inputs.
The major group consists of leguminous tree species nodulating with Rhizobium, Brady rhizobium, etc. these include many of the most widely used MPTs such as Acacia, Erythrina, Gliricidia, Leucaena and Sesbania species. In addition, a limited number of non- leguminous genera such as Alnus and Casuarina species nodulate with Frankia.
The NFTs can be integrated into a system in many different forms like plantings, alley cropping, contour hedgerows, shelter belts, live fencing, protein bank, etc. Apart from productive system, they can serve many functions: microclimate for shade-loving crops like coffee or citrus, support for vine crops like vanilla, pepper, and yam, mulch banks for home gardens and living fence and fodder sources from around fields.
The nutrient cycling consists of inputs into (gains), output from (losses) and internal turnover or transfer within the system. The paths of these gains, losses and transfers are also similar: inputs come through fertilizer, rain, dust, organic materials from outside the system and N2 fixation (for N) as well as weathering of rocks (for other elements); the principal outputs are derived from erosion, percolation (leaching), crop harvest (for all nutrients), denitrification and volatilization (for N) and burning (for N and S).
Forest ecosystems represent closed and efficient nutrient cycling systems, meaning that they have high rates of turnover and low rates of out puts or losses from the system. In other words, they are self-sustaining. On the other hand, common agricultural systems are often open, meaning that the turnover within the system is relatively low and losses as well as inputs are comparatively high.
The sources of nutrient addition in agroforestry system that should be taken into account are:
i. Trees: Litter (leaf fall/pods/fruits + small twig etc.)
ii. Crop: Manures and fertilizers, mineralization, N-fixation, weathering, crop litter, etc.
iii. Rainfall also accounts for nutrient additions via through fall, stem flow and atmospheric dust
Essay # 10. Agroforestry Models for Different Agro-Climatic Zones of India:
Agro-climatic region is the land unit in terms of major climate, superimposed on length of growing period (moisture availability period) and an agro-ecological zone is the land unit carved out of the agro-climatic region, superimposed on the landform, which acts as a modifier to climate and length of growing period.
In 1989, the Planning commission of India divided the country into 15 broad agro-climatic zones based on physiographic and climate. The emphasis was given on the development of resources and their optimum utilization in a suitable manner within the frame work of resource constraints and potentials of each region. Similarly, our country” has been broadly grouped into 20 agro-ecological regions.
Essay # 11. Tree-Crop Interactions under Agroforestry System:
In agroforestry systems, very little information is available regarding tree-crop interactions. Agroforestry literatures repeatedly emphasize that the success of agroforestry relies heavily on the exploitation of component interactions. The success of agroforestry relies heavily on the utilization of component interactions.
Interactions refer to the influence of one component of a system on the performance of the other components as well as the system as a whole. Ecologically the types of interactions in two species populations have often been described on the basis of net effect of interactions.
Agronomists and agroforestry researchers have used the terms “below-ground” and “above ground” to describe interactions (mostly competitive) between components for growth factors observed through roots (nutrients and water), and intercepted through leaves (mainly radiant energy).
These interactions were grouped into ‘Tree-Crop Interface’ (TCI) and the ‘Tree-Animal Interface’ (TAI) in all agroforestry systems. In simultaneous agroforestry systems, trees and food crops interact in many ways, leading to positive and negative impacts on the growth of both trees and crops.
The main effects of tree crop interactions are:
i. Negative Effect (or competition) – due to shading, root competition for water and nutrient
ii. Positive Effect (or complementary) – because of litter fall & decomposition and pruning biomass of trees increase C, N, P and other nutrients, deep rooted trees play a role as ‘safety-net’ for leached nutrients in the deeper layer or as ‘nutrient- pump’ for fertile soil.
Essay # 12. Future Prospects of Agroforestry:
Active agroforestry research has been going on for the last three decades wherein, the purposeful growing of trees and crops and/or animals in interacting combination for a variety of objectives has been studied. Concepts and potentials of different agroforestry systems and practices has already been practically proved that agroforestry can increase the productivity of land besides meeting the needs of food, fodder and fuel, especially in third world countries.
The food, fodder and fuel production in developing countries will have to be increased by 60 per cent in the next 25 years to meet the needs of the growing population. The FAO study says that about 80 million hectares of culturable wastelands would have to be brought under cultivation/plantation in the next 25 years.
The study also stresses that the trend of stripping forest cover to meet food/fodder and fuel need must be controlled and efforts be made to increase productivity of agricultural land by advocating agroforestry as one of the most practical way of meeting the needs for food, fodder and fuel.
Coming to recent times, the increasing pressure on land as well as on forests, rising demand for fuel and fodder and finally the requirement of timber for multifarious purpose have reinforced, as never before, the absolute and inseparable nexus between agriculture and forestry.
In fact, the distinction sought to be made between agriculture as related to food, fibre and oilseed crops and forestry embracing tree culture in a general sense is, to a great extent, artificial and not well founded.
For his survival, man has to ensure optimum use of agriculture, grasslands, forests and aquatic bodies, including oceans. Of these, the combination of first three systems i.e. agrisilviculture, silvopastoral and agrosilvopastoral are covered under agroforestry.
Although the term sustainable land use is at present widely used, the precise interpretation of this concept remains problematic. We consider ecological sustainability as one component of sustainable land use. Ecological sustainability refers to the need to maintain the long-term production potential of the land.
Other components of sustainable land use refer to social, cultural and economical aspects, such as the ability of land managers to adopt proper management systems and the equitable distribution of inputs and outputs of production. Agroforestry systems are often claimed to be superior to agricultural systems without a woody component, because of their ability to contribute to sustained production of crops, livestock and wood especially on fragile land and in areas with prevalent low external input agriculture.
The woody plants are assumed to contribute to both protective functions (enhancing ecological sustainability) and productive functions (taking the place of chemical fertilizers). It is also commonly expected that agroforestry can contribute to land rehabilitation and increased production on degraded lands (NRCAF 2007).