Keywords

1 Introduction

Increasing burgeoning population necessitate the food requirement that leads to increasing pressure on natural resources i.e., forests and soils resulted various anthropogenic activities such as deforestation and illicit felling of trees for agricultural land expansion, practices of intensive farming systems by higher synthetic inputs and in parallel promotion of several industrial developments have various deleterious released greenhouse gases (GHGs) into the atmosphere causing global warming and climate change (Meena et al. 2022; Yadav et al. 2022; Jhariya et al. 2022). On other side, the practices of intensive agriculture enhance the food products by intensifying soils through heavy synthetic inputs which satisfy the food requirement of burgeoning populations but nutrient availability in fruits and foods are low which affects the people’s health and livelihoods (Banerjee et al. 2020). No doubt, food availability is more but irrespective of nutrient availability and quality under the practices of intensive agriculture system which is treated as unsustainable land use systems that affects both food and environmental security. In this context, both agroforestry systems (AFs) and horticulture-based farming systems (HBFs) are good strategies to improve peoples and environment health by providing quality and nutritive foods and absorption of atmospheric carbon (C) through C sequestration. Definitely, agroforestry will stand for climate change mitigation by sequestrating more to more C from the atmosphere through the process of C sequestration and maintain ecological stability (Nair et al. 2011; Raj et al. 2020a, b). The storage and sequestration potential are reported maximum in the region characterizing high rainfall of humid tropic and observed in between 0.3 and 15.2 Mg C/ha/year (Nair et al. 2011). Similarly, HBFs is not less and gain a wide recognition in term of climate change mitigation by high potential of C absorption and maintaining a greater stability of C balance in the environment along with sustainability in both agriculture and natural resources.

Agroforestry is well-known sustainable land use and location specific farming system and proven itself for diversified products, higher productivity from better interaction in tree-crop-soil combination, better soil health & quality, maintaining food and nutritional security (FNS), improving farmer’s health and wealth through diversified products, and overall climate security through the better potential of C sequestration in the tropics (Jhariya et al. 2019a, b). A schematic model of agroforestry technology is depicted in Fig. 7.1.

Fig. 7.1
An illustration exhibits an overview of an agroforestry technology. The compounds are tree, crop, and pasture and livestock's. The interactive models are agrisilviculture, agrosilvopastoral, silvipastoral, and other systems. The scope, benefits, potential, and limitations are listed below.

A schematic model of agroforestry. (Compiled from: Raj et al. 2020a, b; Banerjee et al. 2020; Jhariya et al. 2015, 2019a, b)

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Adoption of ecological and sustainable based intensification in AFs and HBFs can operationalized these farming practices in more efficient in term of intensifying ecosystem services by enhancing biodiversity with less synthetic inputs and less emission of GHGs into the atmosphere that helps in producing diversified multiple products with nutrient rich food and fruits which maintains people’s health and environmental quality (Jhariya et al. 2015; Singh and Jhariya 2016; Roy et al. 2022). In this context, this chapter describes the scope, possibilities, adoptability and conceptual framework of different models in agroforestry and HBFs along with its C sequestration potential in the tropics of the world. Moreover, soil fertility, rhizosphere biology and nutrient sink capacity through the potential of C sequestration in both AFs and HBFs are also discussed. In nutshell, this chapter is designed to gather a comprehensive detail regarding various models of agroforestry and HBFs, its C sequestration capacity, related improvement of soil health and quality and overall its role in maintaining food, nutrition, health and climate security as well as sustainability.

2 Carbon Sequestration: Global Overviews & Historical Development

Indeed, a question always triggered among the scientific community “is C a friend or foe?”. However, various thoughts and wisdoms are arising on this topic but it is clear that C represent itself as an important constituent of the existing ecosystems that found in different forms especially carbon dioxide (CO2) and directly or indirectly connected with delivery of important ecosystem services for wellbeing of humans and environment (Raj et al. 2019a, b). Movement of C (i.e. C cycling) along with other material and gaseous cycling (water, phosphorus, nitrogen and sulphur) intensify the ecosystem services through enhancement of biodiversity (both flora and fauna), biomass accumulation, improving net primary productivity, climate moderation, etc. But now, the day came and the efficiency of C cycling along with others are greatly affected due to several anthropogenic activities which directly or indirectly ruin our environment through depriving ecosystem services (Samal et al. 2022). Emissions of excessive C in the form of CO2 into the atmosphere are a greater challenge of all developed and developing countries. However, we can say C is a “friend” for somewhat extent but its excessive form of emissions and unbalance proportions in the environment put to rethink over it and consider it as “foe”.

In the past especially before the pre-industrial era, the proportion and percentage of CO2 was optimum and balanced among the varying components of environment but now it is rising and today, an unstoppable emission of C (in the form of CO2) into the atmosphere is becoming global concern for all researchers, scientists, stakeholder, policy makers, etc. due to its characteristics of GHGs.

Emission of GHGs has become a hot topic for all researchers and policy makers at global level. Gases such CO2, methane (CH4), nitrous oxide (N2O), ozone (O3) and water vapor (H2O) are considered as GHGs which is continuously emitted by several industrial developments, faulty land use practices, intensive farming systems in agriculture, heavy use of transportation systems, electricity consumptions and various commercial and residential activities that have deleterious impact on biodiversity which causes jeopardizing of our environment and ecosystems services. However, declining fruits quality due to lesser nutrients content, shortage of food-grain production, unexpected and untimely fruits and food production, insect pest emergence in agriculture, forestry and fruits orchards, depleting soil nutrients, less nutrient use efficiency, and overall morphological, physiological and anatomical disorders in plants are continuously observed due to emissions of various GHGs from different sectors which affects our dreams of FNS and climate security. In this context, storage and sequestration of C in environment and its components (lithosphere, hydrosphere and biosphere) are playing an important role in C balance and biomass productions (Awasthi et al. 2022; Manral et al. 2022; Thakrey et al. 2022). However, C sequestration in varying natural resources such as forest, agriculture, agroforestry, soils, etc. are a great topic to discuss which helps in better understanding and exploration of C sink capacity in the era of global warming and climate change (Prasad et al. 2021a, b; Meena et al. 2021).

Consequently, soil C sequestration gained an important attention by policymakers, national and international organization over the world. For example, “The year of soil” and “Decades of soil (year in between 2015 and 2024)” are important declaration of which the first was made by United Nations (UN) in the year 2015 and second was made by International Union of Soil Sciences (IUSS), respectively. However, the same IUSS has declared World Soil Day (WSD) with the simultaneous effort of Thai government on the occasion of World Congress of Soil Science in the year 2002. Moreover, the year 2015 was also remarkable for C sequestration due to approval of “4 per thousand” concept/resolution in the occasion of COP21 that was held in Paris. Although, the concept behind this resolution was sequestration of C in the soil ecosystem must be in depth of 40 cm with 0.4% rate in per year. That was something remarkable. However, maintaining global food and climate security along with promotion of sustainable development are defined objectives of C sequestration.

3 Agroforestry System and Horticulture Based Farming Systems (HFS): An Ecological Perspective

Of all-natural resources, agroforestry is more dynamic and diversified farming system which designed to make ecologically more stable and sustainable that comprises three elements (tree, crop and livestock’s) in complex manner, able to sustain and feeds by diversifying productions, intensify ecosystem services, maintaining soil, food, nutrition and climate security along with enhancing both socioeconomics and other environmental benefits (Leakey 1996). The practices of AFs are widely recognized by farming communities due to its numbers of positive signs such as a greater tree-crop-livestock’s interactions, sustainable land management practices, multifarious benefits, biodiversity management, varying ecosystem services, economically viable, socially acceptable, maintaining soil health and quality, enhancing flora and fauna populations, and improving food, nutritional and climate security that promotes ecological sustainability in the tropics (Cole 2010). AFs delivered various ecosystem services along with multiple products and tangible and intangible benefits such as timber, fuelwood, fodder for livestock’s and NTFPs (non-timber forest products) are considered as tangible (direct) benefits whereas biodiversity enhancement, soil fertility improvement, watershed management, FNS along with climate security are represented as intangible benefits (indirect benefits). However, due to scanty of quality and nutritive food and fruits HBFs is practiced by integrating various fruit tree species, vegetables, flowers and others. It does not only help in diversifying the nutritive and quality fruits but also maintain the health status of peoples and environment. Similarly, the horticultural land systems are developed by incorporating mixed horticultural vegetable, fruits, flowers and spices crops and these are categorized into fruits namely banana (Musa paradisica), pineapple (Ananas comosus), Mandarin orange (Citrus reticulata), passion fruit (Passiflora edulis), cashew nut (Anacardium occidentale), etc.; vegetable crops namely cowpea (Vigna unguiculata), cabbage (Brassica oleracea), French bean (Phaseolus vulgaris), radish (Raphanu ssativus), mustard (Brassica nigra), ash gourd (Benincasa hispida), cauliflower (Brassica oleracea var. botrytis), pumpkin (Cucurbita pepo), tomato (Solanum lycopersicum), chow-chow (Sechium edule), brinjal (Solanum melongena), okra (Abelmoschus esculentus), colocasia (Colocasia esculenta), etc.; different spices crops such as turmeric (Curcuma longa) and ginger (Zingiber officinale), etc.; and flowers namely orchids (family, Orchidaceae), rose (Rosa chinensis) and anthurium (Anthurium andraeanum), respectively. Further, various fruit trees that used in HBFs in different agro-climatic zones of India is depicted in Table 7.1 (Singh and Jhariya 2016).

Table 7.1 Fruit tree used in horticulture-based farming systems (HBFs) in India
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4 Agroforestry Systems in the Tropics of Developed and Developing Countries

The area of AFs is not confined and limited but it spreads up to 1023 m ha globally (Nair et al. 2009a, b) of which India covered 25.32 m ha (Dhyani et al. 2013) whereas 8.0 million ha area was covered by homestead garden in Southeastern Asia (Kumar 2006) and in the U.S.A. around 235.2 million ha area was covered by silvopastoral system, hedgerow cropping, windbreaks and other riparian buffers (Nair and Nair 2003). Similarly, as per CAFRI (Janshi) and Bhuvan LISS III, around 13.75 million ha area covered under AFs in India (Rizvi et al. 2014).

Agroforestry is practicing in the tropic from a time immemorial and committed for multifarious benefits through delivering a better ecosystem services which is possible by adoption of wide array of scientific practices and management to understand better tree-crop-animal’s interactions along with promising soil and climate security. In turn an improved soil quality and better environment can enhance the agroforestry performance in the tropics. In this context, a model is developed for understanding the synergy exists between environment and soil for agroforestry performance in the tropics which is depicted in Fig. 7.2 (Sun et al. 2017). It is quite interesting to know that, AFs is very flexible, location specific and can adopt easily in the varying regions of the tropics (tropical, temperate and humid regions); although it can be modifies by varying biophysical, topography, socioeconomics and climatic situations but wherever adopted it work more efficiently. Of the tropics, tropical region comparatively more promising in term of suitability, adoptability and diversity of agroforestry models than humid and temperate regions. However, many models have been developed and distributed constantly in both developing (Asian and African continent) and developed countries (European continent) of the world due to its decade of development (King 1987). Similarly, feasibility and interactions among tree-crop-animals, natural resource availability, land features, soil (edaphic) characteristics and climatic situations decide the type of agroforestry models viz., agrisilvicultural, silvipasture and agrisilvopastoral, etc. varied from arid to humid tropics which is depicted in Table 7.2.

Fig. 7.2
An illustration presents the performance of agroforestry in the tropics. The system deals with woody perennial trees, herbaceous crops, and pastures and livestock. Synergy between soil and environment leads to better scientific and management practices, resulting in better agroforestry performance.

Synergy between environment and soil for agroforestry performance in the tropics. (Compiled from: Sun et al. 2017)

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Table 7.2 Agroforestry models in different tropics of the world
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5 Carbon Sequestration Potential in Different Agroforestry Models

Sequestering atmospheric C and its fixation into both vegetation and soil helps in mitigating the global issue of climate change besides adding biomass into the woody vegetation. However, C sinks potential of AFs depend on nature and types of woody perennial tree species and associated herbaceous crops that represents tree-crop interactions and their management practices. Likewise, C allocation pattern in different components of tree species are also varies for example, the value of C content in tree branches was similar to stem but higher than root part which is followed by foliage and stem bark whereas the same C value was similar in Acacia nilotica, Eucalyptus tereticornis, Butea monosperma and Azadirachta indica followed by Dalbergia sissoo = Albizia procera, and Anogeissus pendula = Emblica officinalis respectively (Prasad et al. 2010). Similarly, Murthy et al. (2013) have estimated around 12–228 and 68–81 Mg C/ha of agrisilvicultural system practicing in humid tropical lands and dry lowlands of S-E Asia. Also, C sinks capacity of AFs in different world are depicted in Table 7.3. In general, agroforestry potentially sequesters more C and gain higher biomass as compared to other sole based cropping (mono-cropping) and tree plantation systems. Moreover, C sequestration potential in tropical agroforestry systems (TAS) are varies from 12 to 228 Mg/ha and as per this estimates the projected C sequestration value is 1.1–2.2 Pg in terrestrial ecosystems by next coming 50 years through the practices of AFs in the coverage area of 585–1215 × 106 ha of the total earth surface (Albrecht and Kandji 2003). Similarly, integration of some nitrogen (N) fixing leguminous trees-crops-grass are also a better option for C storage and sequestration along with enhancing the N availability, fertility, and health status of both vegetation and soils in the legume-based AFs (Verchot et al. 2011; Montagnini and Nair 2012). Legume based agroforestry models helps in minimizing N2O and CO2 emissions into the atmosphere and makes them balance in environment for better ecosystem and ecological sustainability. This will help in mitigating climate change issues and maintains the health of overall agroecosystems (Jhariya et al. 2018). Similarly, the silvopastoral system has potential to enhance greater biomass rather than sole based system. For example, the value of overall biomass was higher by 35.0% in silvopastoral system (Azadirachta indica + Cenchrus ciliaris) rather than neem sole based system. This would help in better understanding of silvopastoral potential role in biomass enhancement along with several other ecosystem services for better ecosystem (Mangalassery et al. 2014).

Table 7.3 Carbon sinks capacity of agroforestry systems in different world
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In nutshell, AFs represents itself as a C farming system due to its huge potential in capture and storage of C in both vegetation (tree-crop) and soils which requires a good management practices to improve C sink capacity that helps in producing higher biomass and maintain C balance in ecosystem for better environment and ecological sustainability (Jhariya et al. 2019a).

6 Soil Carbon Sequestration in Agroforestry Systems: A Global Scenario

Soil, as we call “soul of infinite life”. Yes, it is true and can’t be denied due to sustaining whole life by supporting biodiversity (tree, crop, animals and other natural resources), anchoring tree roots, harboring various soil inhabiting flora and fauna including beneficial micro-organisms, stores essential nutrients, maintain rhizosphere populations, and deliver multifarious ecosystem services to maintain ecosystem structure. However, better management practices in AFs and soils could be helpful in enhancing C value through effective sequestration process (Raj et al. 2020a, b). Addition and decomposition of litter fall, twigs, barks and other tree’s fallen residues/materials can enhance the C content value that directly and indirectly increase the population of earthworm and soil inhabiting beneficial microorganisms and their interactions will improve the fertility and health status of soils (Bertin et al. 2003). Moreover, tree species, their types, nature, tree-crop interactions, shedding leaf litters, its texture and decaying rate along with agents that involve in decompositions will surely affects the extent of C accumulation, sink capacity and C release into the soils. Similarly, management practices in AFs also add some inputs in C addition which reflects health status of soils (Jhariya et al. 2019b). However, tropical soils contributed higher biomass, more C contents and diverse form of microorganism as compared to temperate soils. Thus, soil C-sequestration value in different AFs in the world is depicted in Table 7.4.

Table 7.4 Soil carbon-sequestration value in different agroforestry systems in the world
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Moreover, integrating tree with some pasture/grass species (known as silvopastoral system) are gaining wide recognition for reclamations of degraded land and having great potential of C sink either into vegetation and soils that help in biomass increment and improvement of soil fertility. Silvopastoral system can store more organic C into the soils through greater potential of C sequestration. In addition, integrating leguminous N fixing multipurpose tree (MPTs) with some valuable pastures could be a great option to minimize GHGs emission and climate change mitigation along with diversifying products (as timber, fuelwood, fodder for livestock’s, etc.), intensifying ecosystem services and maintain N and C status into the soils for better ecosystem. Therefore, this system can be going in the direction of improving higher biomass, soil organic C and N availability. Legume trees such as Acacia species and subabul (Leucaena leucocephala) have great capacity to capture and fix C into soils that can be stored in the form of soil organic carbon (SOC) as a pool which improve the fertility and health status of tropical soil (Cadisch et al. 1998). Moreover, combination of Leucaena leucocephala and Dalbergia sissoo could potentially sequester more C as compared to sole based plantation system that can help in combating global warming and climate change issues (Sheikh et al. 2015). Similarly, integrating legume trees with eucalyptus tree-based plantation were worked more effectively in term of storage and sequester of C into the soils (Kaye et al. 2000). However, many studies were conducted for better understanding of the potential role of silvopastoral system (rather than monocropping/sole based cropping system) in SOC enhancement through better C sequestration as compared and its role in climate change mitigation. For example, the value of SOC was increased from 36.30% to 60% in silvopastoral system (Azadirachta indica + Cenchrus ciliaris) rather than sole cropping system (Mangalassery et al. 2014). Moreover, C sinks value in soil of different silvopastoral systems are depicted in Table 7.5. As per one estimate, well managed silvopastoral model has potential to sequester approximate 0.012 TgC/ha and predicted value is 0.6 TgC/ha up to the year 2040 by converting 630 m ha degraded croplands/grassland system into AFs (Kirby and Potvin 2007; Ghosh and Mahanta 2014).

Table 7.5 Silvopastoral systems and its carbon sink value in different parts of the world
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7 Horticulture Based Farming Systems (HFS) in the Tropics

If we look on the statistical figure on horticultural productions and land use systems then we see around 300 m MT of productions was reported through horticulture which is quite higher than 275 m MT of agricultural grains productions. This higher production promotes per capita consumption of variety of vegetables and fruits over the period. Of this figures, perennial horticultural crops produced around 214 MT/yr from 12.1 Mha areas of which fruits, plantation crops, spices and nuts contributed 6.1, 3.2, 2.6 and 0.14 Mha areas, respectively. These figures pull the attentions of growers towards perennial horticultural crops and related land use systems due to higher production systems, maximum area coverage, low inputs of energy and water than other annual field crops in agriculture and AFs (Ganeshamurthy et al. 2020). Although, HBFs/fruit based AFs comprises various models such as agri-horticulture system (agricultural crops and fruit trees/vegetables/spices/flower crops), horti-pastoral system (Integration of different fruit trees/vegetables/spices/flower crops with livestock’s/pasture), agri-horti-silviculture system (integrating three components of agricultural crops, different fruit trees and trees other than fruits), multitier horticulture system, different horticultural land use systems and homestead gardening practices that are mostly widespread in humid, arid and semiarid tropics of the world.

HBFs are playing an important role in providing various nutritious and quality fruits and vegetables and having potential to cover minimum dietary needs of both vegetables and fruits /day/capita which is 220 and 85 gram per head per day rather than available 80 and 60 gram, respectively (Roy 2011). Some fruit trees like guava (Psidium guajava), Indian gooseberry or amla (Emblica officinalis), plum (Prunus domestica), mango (Mangifera indica), apple (Malus domestica), papaya (Carica papaya) and Citrus species, etc. are very commonly used in different agroclimatic zones of India. As per Singh and Malhotra (2011), in rainfed regions horticulture crops add additional income along with maintaining food, nutrition and climate security.

7.1 Agrihorticulture (Crops + Fruit Trees)

This system comprised a simultaneous integration of agricultural crops (both annual and perennials characteristics) and fruit trees/vegetables/flower/spices, etc. in unit land and widespread in the marginal and dry areas of different agroclimatic zones mostly dominant in India, Sri Lanka, Nepal and Bangladesh (Pant et al. 2014). In this context, the recommended combination of agriculture crops with horticulture trees under agri-horticulture model in HBFs prevailed in dry region of Rajasthan is depicted in Fig. 7.3 (Bhandari et al. 2014). Also, Table 7.6 showing varying tree-crop combinations of agri-horticulture system is practiced in different agro-climatic zones of India (NRCAF 2007). However, this system consists short duration of juvenile fruit and vegetable plants which is sometimes combined with other MPTs, therefore it produces other products like good quality timber, fodder, fuelwood, NTFPs in addition to food grains and horticultural produce. That’s why, farmers mostly prefer agri-horticultural system rather than agri-silvicultural system due to less juvenile phase, high nutritive and quality fruits, vegetables and spices, and having good economic returns in short durations in agri-horticultural system (Kareemulla et al. 2002).

Fig. 7.3
A chart exhibits the agri-horticulture technique in H B Fs integrated in dry areas. The growing conditions of the crop include irrigated conditions having irrigated lands, rainfed conditions having rainfall of 150 to 300 millimeters, and rainfed conditions having rainfall of 300 to 500 millimeters.

Agri-horticulture model in Horticulture based farming system in dry region of India (Bhandari et al. 2014)

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Table 7.6 Varying tree-crop combinations of agri-horticulture system practiced in agro-climatic zones of India (NRCAF 2007)
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7.2 Hortipastoral (Fruit Trees + Pasture/Animals)

This system is highly recommended on degraded and wasteland areas due to its great reclaiming potential along with supplying nutritive and quality fruits, vegetables, highly palatable leguminous fodder/pastures (to livestock’s) that maintains health status of farmers and animals (Kumar et al. 2011). However, various form of horti-pastoral models are existing namely Aonla (Emblica officinalis) based hortipastoral system for conservation purpose of soil and water, Bael (Aegla marmelos) based hortipastoral system, Tamarind (Tamarindus indica) based hortipastoral system, etc. spreads in the rainfed regions, custard apple (Annona sp.) based hortipastoral system, Kinnow (Citrus nobilis × C. deliciosa) based hortipastoral system distributed in the partial irrigation system, etc. that enhance the biodiversity, improve ecosystem services and maintains income and health status of poor farmers and local communities in the tropics (Kumar et al. 2009).

7.3 Agrihortisilviculture (Crops + Fruit Trees + Tree Other Than Fruits)

The model itself represents an integration of three components such as agricultural crops, different fruit trees/vegetable crops and trees other than fruits respectively. This system nurtures all the biodiversity and maintains health, wealth, and food and climate security in every aspect. “Is this system being more diversifies, secure and sustainable than others in HBFs?” The answer is “yes” because having more components represents more diversity which intensified ecosystem services along with other multifarious tangible (timber, fuelwood, fodder, NTFPs, etc.) and intangible benefits in term of money, health, microclimate amelioration, soil health and quality through fertility improvement and climate change mitigation through C sequestration, etc. The peculiar significance of this system having higher possibility of income generation through mature fruit trees rather than monsoon dependable agricultural crops.

8 Carbon Footprint of Agriculture Versus Fruits and Vegetables Crops

The horticultural land use systems comprise various fruits and vegetable crops are having less contribution in GHGs emissions; for example, low GHGs emissions were observed in potato and other root vegetable crops due to high productivity potentials. However, Joshi et al. (2009) have predicted the annual demands for different vegetables and its contribution in global warming potential (GWP) are 127.01 Mt and 21.7 Mt CO2 eq. whereas fruit crop like apple (Malus domestica) has 86.0 Mt of annual demands and 30.7 Mt CO2 eq. of global warming potential (GWP) by the year 2020–2021. The estimated figure indicates an apple has less demands but higher contribution in GWP as compared to vegetable crops. However, agricultural food crops have more in demands and GWP value as compared to fruits and vegetables. For example, the demands (Mt) and GWP (Mt CO2 eq.) values of wheat, rice and pulses are 83.0 and 29.1, 173.0 and 246.3, 16.0 and 15.5, respectively by the year 2020–2021. These figures are enough to say about comparative studies on demand and GWP of horticulture (fruits and vegetables) versus agricultural food crops.

Similarly, many authors have quantified GHGs emissions and related GWP (global warming potential) contribution by various agricultural and horticultural crop production through a series of field experiments at IARI, New Delhi and according to them, the vegetables crops such as potato, cauliflower and brinjal contributed in CO2 emissions (g/kg) are in the order of cauliflower (13.3) > brinjal (12.5) > potato (10.0) whereas overall maximum potential in global warming (CO2 eq.) are observed in brinjal (31.1) followed by cauliflower (28.2) and least value in potato (24.9), respectively. Similarly, the value of N2O was similar as 0.1 g/kg whereas CH4 was zero among these horticultural crops. The horticultural fruit crops such as banana, apple and other spices contributed in CO2 emissions (g/kg) are in the order of spices (100) > apple (41.7) > banana (10.0) whereas overall maximum potential in global warming (CO2 eq.) are observed in similar fashion i.e. spices (845.0) > apple (331.4) > banana (71.6) respectively. Similarly, the value of N2O was highest in spices (2.5) followed by apple (1.0) and least value (0.2) observed in banana whereas CH4 was zero among these horticultural crops (Majumdar et al. 2002; Bhatia et al. 2004; Chhabra et al. 2009; Pathak et al. 2009).

9 Carbon Sequestration Potential in Horticulture Based Farming Systems/Fruit Based Agroforestry Systems

It is well known fact about the potential of horticultural based land use systems in C sequestration than the other farming technology i.e. agriculture and AFs in the tropics. However, perennial crops contributed major role in CO2 sequestration than annual crops. In this context, a study has been conducted on varying horticulture-based farming systems and it was observed that C sequestration potential was maximum in mango-based land used systems followed by cashew (Anacardium occidentale), rose (Rosa chinensis), vegetables and medicinal and aromatic plants-based land used systems. In addition, higher inputs of plant residues into the soil of perennial systems resulted into less CO2 emission than other annual crops in agriculture systems. Somehow, perennial horticultural based farming systems helps in gaining economic benefits through C credits. Therefore, applying an effective strategy of better C management and soil health improvement would be helpful in enhancing C sequestration technology in both perennial based horticulture systems and AFs (Ganeshamurthy et al. 2020). Similarly, many studies have been conducted on different horticulture-based models for C storage and sequestration. C sequestration capacity varies as per varying horticulture land use systems. For example, agri-horticulture model has been proven a better farming practice for mitigation of CO2 and having higher economic gain with C credits as compared to other practices like agriculture, silvopastoral and varying land use practices of forest ecosystem in the Himalaya regions (Rajput et al. 2017). Horticultural orchards having greater capacity to enhance C storage value in subsoil region than other AFs due to deep rooting characteristics in perennial orchard system. An attempt has been made to justify the question “Is species associations affect the C sequestration potential?” Indeed, the potential of C storage and sequestration will vary as per varying combinations of plants, its types, nature and including management practices in climatic situations. In this context, the highest C sink value (140.1 t ha−1) was observed in the combination of Cocos nucifera (coconut tree) and Syzygium cumini (Jamun) which is followed by139.0 C t ha−1 in Cocos nucifera + Mangifera indica and least value has been observed in Cocos nucifera + Garcinia indica (Garcinia) as 132.2 C t ha−1 whereas coconut sole plantation reported only 98.2 C t ha−1, respectively (Bhavya et al. 2017).

As we know, horti-silviculture systems are ecologically sound and diversified horticulture-based farming systems which can withstand in less moisture condition in dry region of the tropics. C sink capacity and sequestration of horticulture-based farming systems in this region will helps in enhancing C stocks in both vegetations and soils in various farming models. However, C sink capacity in any systems depends on nature and type of plant species and its sink potential in any farming systems. Various studies have been conducted on this topic; for example, Singh and Singh (2015) reported C sink values in the form of biomass C, soil C which was compared with total C values in the various tree combinations of horti-silviculture systems vs. sole tree systems in the dry region of Rajasthan. According to the study (Singh and Singh 2015) the C sink value in soil ecosystem was higher as compared to biomass C. Also, C value was observed higher value in tree combinations in horti-silviculture systems than sole tree systems due to greater diversity and sink potential of horti-silviculture rather than single cropping systems. Nutrient losses through leaching would be less in tree combinations in horti-silviculture systems due to closed type of nutrient cycling. Therefore, different trees combinations including fruit trees in horti-silviculture systems are used for a comparative study on C sink potentials in both soils and vegetation as biomass C. In this context, comparative studies of soil C and total C sink in horti-silviculture vs. sole tree systems in dry regions of Rajasthan (India) are depicted in the Fig. 7.4.

Fig. 7.4
A horizontal double bar graph plots the studies for tree combinations in horti-silviculture systems versus sole tree systems. Total carbon has the highest value for cordia myxa + prosopis cineraria at 5. Soil carbon has the lowest value for sole A. excelsa at 0.2. Values are estimated.

Comparative studies of soil carbon and total carbon sink in horti-silviculture vs. sole tree systems in dry regions of Rajasthan (India) (Singh and Singh 2015)

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From the Fig. 7.4, it clearly demonstrates that maximum total C value (soil + biomass) was 5.07 Mg/ha reported in the combination of Cordia myxa + P. cineraria based AFs due to greater potential of C sequestration. Therefore, the capturing and storing of atmospheric C depends on tree-crop combination, its type of interaction, nature of species, feasibility of combinations and related management practices that affect the potential of C sequester into both vegetation and soil components in horticulture-based farming systems. This can be justified by Yadav et al. (2015) which demonstrated that the combination of pear (Pyrus communis) and wheat (Triticum aestivum) had maximum value of biomass (38.0 Mg/ha), C storage (17.0 Mg/ha) and C stock equivalent CO2 (62.3 Mg/ha) respectively rather than sole wheat cropping system. This result represented that combination of fruit trees with the crops having more value of biomass and C than sole based cropping system. Secondly, type and nature of horticulture tree and crop combinations and their interactions deliver the potential of biomass and C sequestration. In the same study, it found that the combination of pear and wheat has maximum rate of biomass (12.0 Mg/ha/yr), C storage (5.3 Mg/ha/yr) and C stock equivalent CO2 (19.6 Mg/ha/yr) which is followed by other less valuable interactive combinations of apricot (Prunus armeniaca) + wheat having 11.5, 5.2 and 19.0 Mg/ha/yr, respectively. Thus, fruit trees under HBFs showed a significant improvement in enhancing total biomass and C sink value which needed more study for better understanding the interactions and its positive impacts on our environment.

10 Soil Carbon Sequestration in Horticulture Based Farming Systems (HBFs)

Horticulture based land use systems has proven itself a good C farming system due to greater potential of tapping, sequestration and storing of atmospheric C into soil that helps in reclamation of degraded lands by improving productivity along with diversity enhancement which maintains ecological sustainability (Wang et al. 2010). Especially, perennial horticultural crops having higher potential in C sequestration than agriculture and AFs (majorly annual crops) in the tropics (Shrestha and Malla 2016; Janiola and Marin 2016; Chandran et al. 2016; Bhavya et al. 2017).

However, Bhavya et al. (2017) has emphasized the importance of perennial crops in horticulture land use systems and according to the study; emission of CO2 was less due to higher input of residues into the soil in perennial systems rather than other annual crops. Also, the C sequestration potential of different horticulture land use systems (4 years old) were reported and found in the ranked of mango-based orchard > cashew-based orchard > rose (Rosa chinensis) block plantation > vegetable-based block plantation > medicinal and aromatic based block plantation, respectively. Therefore, both soil C stock and CO2 sequestration value (Mg/ha) were calculated at different depths in varying cropping systems of horticulture land use practices which is depicted in Table 7.7. Thus, perennial horticulture-based farming systems showed greater potential in C sequestration and higher soil C stocks which would be helpful in enhancing soil fertility and health (Chandran et al. 2016).

Table 7.7 Soil carbon storage and carbon dioxide sequestration value (Mg/ha) under different horticulture land-use systems
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11 Soil Organic Carbon (SOC) & Soil Fertility in Horticulture and Other Farming System

Indeed, a great synergy exists between SOC and fertility status of soils. SOC plays an important role in global C cycle, promotes efficient nutrient cycling and maintaining soil fertility along with ecological sustainability (Lenka et al. 2017). If we compared perennial horticultural system with other annual farming system then it is clearly demonstrated that perennial systems are more efficient in C sequestration and maximum SOC than other annual cropping system that helps in enhancing soil fertility, health and mitigate our changing climate. Similarly, the value of total soil organic carbon (TSOC) was highest (29.0 Mg C/ha) in Psidium guajava followed by Syzygium cumini (27.3 Mg C/ha), Litchi chinensis (26.0 Mg C/ha), and least value (19.2 Mg C/ha) in Mangifera indica whereas the value of OOC (oxidizable organic C) was recorded maximum (26.0 Mg C/ha) in Psidium guajava followed by both Syzygium cumini and Litchi chinensis having same value (25.1 Mg C/ha)and least (16.5 Mg C/ha)was observed in Mangifera indica, respectively on reclaimed sodic soils of perennial horticultural land use systems in the tropics (Datta et al. 2015).

The rate and dynamics of C sequestration and pool stocks varies as per varying land use practices such as AFs, HBFs, horti-silvi-pastoral system, forestry and another mangrove ecosystem. As per Das and Itnal (1994) the value of SOC increased from 4.2 g/kg to 7.1 and 7.3 g/kg while converting sole cropping to agroforestry and agri-horticulture land use systems of 6 years old. The maximum value of SOC was observed under forest land which was followed by other land use systems in the rank of natural grasslands > varying fruits orchards > Eucalyptus plantation respectively in 30 cm depth of soil ecosystem. Of all these practices, fruit orchards played remarkable role in SOC pools and observed in the rank of apple > mango > litchi > citrus species > guava with respective value of SOC was 105.2, 53.2, 45.5, 43.1, 39.0 ton/ha. Thus, apple orchard has greatest potential of climate change mitigation through highest contribution in SOC pool as compared to other perennial fruit orchards (Gupta and Sharma 2011). However, different horticultural land used systems such as orchards of jamun (Syzygium cumini), Psidium guajava (guava), Litchi chinensis (litchi) and mango (Mangifera indica) have different value of SOC and highest value (133 Mg C/ha) was observed in guava orchard along with maximum (76 Mg C/ha) C content in passive pool which increased with depth in all other land used systems (Datta et al. 2015). Similarly, SOC content was highest (9.5 g/kg) in Vicia faba cover crop management system as compared to 8.7 g/kg in conventional tillage practices under 5 years of Mediterranean vineyards of Sicily at Italy (Novara et al. 2019). Moreover, a dense forest ecosystem has more diverse species which intended to higher sequestration of C than other land use system having sole plantation system. That’s why the value of SOC at 1 m soil depth was maximum (1.29%) in dense mixed forest followed by 1.22% in horticultural plantation system and least value in agricultural system (Koppad and Tikhile 2014).

12 Carbon Sequestration and Nutrient Sink/Input in AFs and HBFs

One question always strikes i.e. “Why horticulture land use systems are preferable for more C sequestration than other farming systems such as agriculture and agroforestry?” However, there is a various vast array of hypothesis behind it but it is clear that perennial horticulture system having more potential of C sequestration that enhance nutrient sink capacity rather than other farming practices. Although, perennial fruits systems contain high biomass C which is 25–100 times higher than agricultural land use system. Hence, perennial horticultural systems are preferable and adopted to degraded and some others vacant land than agricultural crops and AFs. Undoubtedly agroforestry and horticultural systems reduced GHGs emission into the atmosphere and mitigate climate change issue by sequestrating more atmospheric C. But horticulture-based plantation system has proven more C sequestration potential than agroforestry and other farming practices. In this context, many authors have worked out and justify this hypothesis by some practical and research works. For example, a comparative study was conducted on C sink potential in between agroforestry land use system and horticultural land system for offsetting GHGs emissions (Bloomfield and Pearson 2000). By 2050, the potential of C sequestration will be more (16.4 GtC) as compared to 6.3 GtC through AFs in the tropics (Brown et al. 1996) whereas these sequestration value will be 3.5 GtC in horticulture systems as compared to 1.15 GtC in AFs by upcoming 2050 (Trexler and Haugen 1994).

Absorption and fixation of atmospheric C by woody perennials trees and fruits plants in agroforestry and HBFs are proven a better solution for mitigation climate change by reducing the level of GHGs in the atmosphere. However, sequestration of C in soils & vegetation plays an important role in maintaining soil health & quality in AFs & HBFs. Improvement of soil physico-chemical properties is a good indicator for soil health in AFs and HBFs which is itself a complex type of farming systems in which nutrient leaching is less as compared to sole based cropping system due to closed type of nutrient cycling and nutrient pumping is possible through deep rooting system of trees & fruit crops that adds more availability of essential nutrient to plants. Apart from the soil improvement, these systems add more biomass and C input, increase nutrient input, add more organic matter into the soil, efficient nutrient cycling, improve the rhizosphere zone, increase microbial population, minimize soil & water erosion, evaporation and nutrient leaching losses gets checked and overall improvement of micro-climate is observed. In this context, a model (Fig. 7.5) is developed which represents C sequestration and soil health in AFS and HBFS (Sarvade et al. 2019; Shi et al. 2018; de Stefano and Jacobson 2018).

Fig. 7.5
An illustration exhibits the development of the carbon sequestration model and nutrient sink in A Fs and H B Fs. The atmospheric carbon is absorbed by a tree via photosynthesis and leaf and litter input to the tree. The carbon released by root decay into the soil helps to maintain soil health.

Carbon sequestration and soil health in AFS & HBFS (Sarvade et al. 2019; Shi et al. 2018; de Stefano and Jacobson 2018)

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Thus, AFs and HBFs have proven itself as a good strategy for soil, environment and food security. Woody perennial trees in both AFs and HBFs make availability of leaves, twigs and other residues and its decomposition add organic matter into the soils that improve productivity, fertility and nutrients uptake capacity of soils which in turn enhance the C sequestration potential of the systems that improve overall soil ecosystems. In turn, healthy soils having optimum nutrients and water availability and provide anchorage to various models of AFs and HBFs in the tropics that produce healthy, nutritious and good quality food, fruits and maintain FNS in the era of hunger and malnutrition problems. In this context, a model (Fig. 7.6) is developed on soil for sustainability of AFs and HBFs in the tropics (Dollinger and Jose 2018; Colmenares et al. 2020). However, farmers get motivated, take a lesson and adopted the better scientific oriented farming systems which help in building their health, income & livelihoods (Dollinger and Jose 2018; Colmenares et al. 2020).

Fig. 7.6
A cyclic diagram for the development process of soil sustainability in the tropics. It starts with the soil ecosystem, leading to healthy soil, followed by producing good and nutritious foods and enhancing health, resulting in agroforestry and horti based farming systems. It leads to sequestration.

Soil for sustainability of agroforestry and horticulture-based farming systems in the tropics (Dollinger and Jose 2018; Colmenares et al. 2020)

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Das et al. (2020) has reported the maximum value (1.63%) of SOM in livestock’s and horticultural based farming systems as compared to 1.6% in AFs. This is due to ameliorating potential of acidic soils by minimizing Al-toxicity was more in livestock’s and HBFs as compared to AFs. Das et al. (2020) also investigated on nutrient input and according to the study agri-hort-silvi-pastoral systems contributed highest input of exchangeable potassium (K) whereas maximum value of phosphorus (P) was observed in both agriculture and livestock’s-based farming systems due to availability of cow dung and its continuous dressing over time. Therefore, agriculture system contributed more in total fertility build-up followed by agri-horti-silvi-pastoral and livestock’s-based farming systems.

13 Carbon Sequestration and Rhizosphere Biology in AFS and HBFS

Today, the soil ecosystem is gaining high attention and is characterized by vast scientific frontiers in the rhizosphere make a remarkable position and active portion due to stabilizing a link between plant root and soil interface that involves effective biogeochemical processes and maintains ecosystem stability (Hiltner 1904; Hartmann et al. 2008). The major questions are “How the rhizosphere system involve in feeding the world and maintains environmental/ecological sustainability?” and “How plant root system involves in C transfer from atmosphere to rhizosphere?” As we know, rhizosphere exists in between plant root and soil interface that harbor all living microorganisms which makes nutrient availability and transfer. However, plant types, age and varying biotic and abiotic stresses affects rate of loss of C i.e. C transfer which is 40% of total photosynthate is lost through extensive root systems into rhizosphere system that promotes the bacterial multiplication for better growth and development inside this zone. In turn, a healthy microorganism promotes healthier plants through better uptake, storage, nutrient cycling, pathogen suppression and better soil structure. Therefore, rhizosphere promotes microbial productions which intends for healthier and diversified farming systems by healthier soil that leads to high biomass production, quality food and fruit productions along with better C sequestration potentials of systems. That’s why we call “better rhizosphere biology involves in food and environmental security through better C sequestration”. Thus, there is a great synergy between rhizosphere biology and soil-food-climate security.

14 Carbon Sequestration in Relation to Climate Change and Food Security

Carbon storage and sequestration play key role in biomass production (Raj and Jhariya 2021a, b) in term of timber, fiber, NTFPs including nutritive fruits which ensure food and nutrition security under changing climate. Agroforestry system performs unique functions in climate change adaptation and mitigation through C sequestration potential. Food productions in agroforestry system are linked with C storage in term of vegetation and soil biomass (Nair et al. 2009a, b; Niles et al. 2002). However, a climate resilient agroforestry and horticulture-based farming system enhance grains and fruits biomass which ensure food security and its sustainable utilizations among peoples. As per Lal and Bruce (1999), approx. 0.75–1.0 Pg yr−1 of C sequestration has been reported under global croplands ecosystem. Storing C in soil under agroforestry and horticulture-based system play key role in belowground biomass production which also maintain SOC pools. “Soils for food security and climate” are key initiatives of “4 per 1000” which was successfully launched in the year 2015. This initiative under The Paris Agreement has stressed on limiting global warming below 2 °C. This is targeted to enhance SOC sequestration with three objectives including climate change mitigation, adaptation and food security improvement for long term (Demenois et al. 2020). Similarly, integrating perennials crops (cacao and coffee) in agroforestry systems enhance C sinks than sole cropping system. Increasing perennial trees in farms under semi-arid regions promotes agroforestry systems and its C sequestration potential under changing climate (Brandt et al. 2018). Horticulture based mixed farming systems integrated various crops, fisheries and livestock enhance plant productivity along with climate change mitigation and adaptation (Newaj et al. 2016). This system also provides many nutritive food and fruits that ensure food security for healthy ecosystem. Similarly, this system is more diversified which buffer excessive temperature and enhance C sink and biomass production for healthy diets under changing climate (Bailey 2016; Waldron et al. 2017).

15 Agroforestry and Horticulture Role in Food and Nutritional Security Under Changing Climate

As per FAOSTAT (2018), 821, 151 and 613 million of people, including children, and women are undernourished, stunted and suffered from iron deficiency respectively. Whereas 2 billion people including adults are under obese and overweight. These are due to unhealthy, untimely and less nutritive food consumption. At the same time the current food production systems, especially intensive agriculture, contribute significantly to the environmental degradations. Beside the producing nutrient rich crops, the environmental footprint can be minimized by adopting agroforestry and horticulture-based farming system which ensures environmental health as well as global hunger problem under changing climate. In Kenya, women play important role in climate change mitigation by some innovative techniques of rainwater harvesting systems under varying agroforestry system which ensure food and water security by their collective efforts (Gabrielsson and Ramasar 2013). Thus, different agroforestry models and its adoptions provide various ecosystem services including food production and nutritional security through climate change mitigation (Sanz et al. 2017). Moreover, agroforestry systems improve biodiversity, food productivity, and ecosystem restoration under varying climatic situations (Paudela et al. 2017; Newaj et al. 2016). World Bank (2012) reported a global food production must be increased by 70% for upcoming 35 years due to higher demands of food production by 9 billion populations. However, it is still unclear to examine how climate change affects overall plant productivity and food security in agroforestry system. Global climate change decline agroforestry productivity and various ecosystem services particularly in developing countries. However, many developing countries are still facing food insecurity. In this context, adopting sustainable farming system including climate resilient agroforestry technologies and horticulture-based farming system would be helpful in soil-food-climate security for long term (Ospina 2016). However, forest-based farming system including afforestation activities also improves soil, food and environmental security along with other natural resource conservation (Raj et al. 2020a, b, 2022). Climate resilient agroforestry system ensures greater food diversification which provides healthier diet to people. Horticulture based farming system comprises different perennial fruits plants which is highly nutritive and regulate people health and economy. These integrated farming systems maintain soil-food and climate security along with ecosystem health and environmental sustainability.

16 Management Aspects for Improving Carbon Sequestration

As we know, unscientific and faulty land use practices disturb the global C cycle due to imbalance of emissions and sinks of C that affects the status of SOM and related ecosystem services (Jaiarree et al. 2014). A proper land use system always enhances the performance of varying farming systems in storage and sequestration of C along with multiple benefits through ecosystem services. Intensification in agriculture, perennial horticulture and AFs resulted higher synthetic inputs that leads to land degradation and minimizing C stocks in both vegetations and soils. In this context, applying ecological and sustainable intensification in these varying farming practices can intensify ecosystem services through enhancing biodiversity with higher production of food and fruits along with food-soil-climate security through better C sequestration potential (Jhariya et al. 2021a, b).

In nutshell, a better management practices in farming systems are needed for better rhizosphere biology, healthier microbial populations, better nutrient inputs and uptake by plants, soil health fertility improves that results greater potential of C sequestrations, maximize the availability of SOC which helps in maintaining healthier ecosystem performance (Fig. 7.7) (White III et al. 2017; Ahkami et al. 2017). Similarly, tree-crop interaction play major role in establishment and performance of multistoried perennial’s horticulture based farming system and AFs in which management practices must be apply for better understanding of ecological and economic interactions between woody (timber and fruit trees) and non-woody components (annual crops, grasses and pastures, etc.). Therefore, varying components and their interactions provide a scope for number of scientific studies which explores the underlying ecological principles of these farming systems at temporal and spatial scale over the time. Soil management is an important aspect which regulates proper growth and productivity of agroforestry and horticulture systems comprising both annual and perennial crops. Whereas, C sink is possible through healthy soils and healthy soil is possible through better soil management practices. Thus, management must be focused in taking account of soil management which directly correlates with C sequestration that helps in healthy and quality productions in both AFs and HBFs. Conservation tillage, proper mulching, applying cover crops, maintaining soil fertility, nutrient availability, enhancing nutrient use efficiency, water management through better irrigation system, technology for controlling soil and water erosion, etc. are many options that must be follow for better soil C sequestration.

Fig. 7.7
A process flow diagram of rhizosphere biology. It enhances microbial populations with better nutrient inputs and uptakes and better soil health, resulting in maintenance of food and nutritional and maximize the availability. This maintains climate security and improves ecosystem performance.

Rhizosphere biology for better ecosystem performance (White III et al. 2017; Ahkami et al. 2017)

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17 Critical Research Needs for Enhancing Carbon Sequestration in AFS & HBFS

An ample of research has already been conducted that explore the complex nature of horticulture-based farming and AFs having multiple array of significance in term of varying ecosystem services but some parts of research remain unaddressed. For example, research is needed to understand the underlying truth of tree-crop-animals-soil interactions and related productivity, profitability and in accordance of political and social milieu in agroclimatic zones. Similarly, research should be undertaken for development of degraded, waste and salt affected areas through AFs and perennial HBFs in agroclimatic zones of India. Further, a detailed study on C sequestration potential of different woody perennial trees comprising timber and fruit tree are needed. However, many authors have reported the potential C sink value of different trees used in urban forestry, agroforestry, HBFs and other land used practices in the tropics which are depicted in Table 7.8. As per Forrester et al. (2006) some indigenous tree species like neem (Azadirachta indica), Mahua (Madhuca latifolia), peepal (Ficus religiosa) and tamarind (Tamarindus indica), etc. have high potential to sequester more C and fix into them as biomass which also helps in minimizing the pollution in urban and rural areas. Moreover, a critical research is needed to understand the soil genesis and its pedology for better soil health management which is directly link with rhizosphere biology, microbial population, C sequestration potential, extent of SOC, nutrient use efficiency, quality food and nutritious fruits productions and other varying ecosystem services for better environment and ecological stability.

Table 7.8 Carbon sink value in different tree species
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Thus, research should be undertaken in accordance of maximizing potential of C sequestration in both vegetation and soils in agroforestry and horticulture land use systems which can be possible through understanding the interaction magnitude among tillage practices, varying climatic situations and soil types on C sequestration. Also, topics such as (a) exploration the C sequestration potential of various agroforestry and perennial horticulture system in agroclimatic zones, (b) evaluation the synergy between C and soil-crops health & productivity, (c) evaluating the practices of C sequestration for GHGs emissions, (d) horticultural waste based biochar production and its role in C balance and SOC in soils, (e) quantifying the impact of tree pruning for better light penetrations and photosynthesis in varying fruits orchard along with its significant role in retaining soil C through conversion of tree pruned biomass into biochar and its application into the soil and (f) evaluating the significance of conservation practices in both AFs and HBFs beyond the C sequestrations etc. should be addressed.

18 Policy and Legal Framework

As we know, C sequestration is win-a-win strategy to combat global warming and other negative consequences of climate change which already popularized by various government, NGO, national and international organizations and policy maker in the world. Policy must be in frame of conducting more research on C sequestration potential of varying land use farming systems in priority basis. Governance and policy should develop a legal framework on exploration and understanding of C sequestration and SOC pools through better soil management practices in horticulture and AFs in varying agroclimatic zones. Policy should be aimed towards regulating C balance and enhancing C sink into both vegetation and soils to offset GHGs emissions by every practical aspect which would be helpful in maintaining tree-crop-soil health, productivity and climate security for ecological sustainability in long term basis.

19 Conclusion

Today, emissions of GHGs are major challenges and it can be minimized by practices of better horticulture and AFs that not only mitigate the issue of climate change but also helps in maintaining C balance in environment, enhance SOC and nutrients input into the systems, promotes microbial population through better rhizosphere technology, intensify the ecosystem services through enhancing biodiversity, resource use-efficiency, maximize productivity i.e., quality food and fruits that helps in maintaining food-nutrition-climate security. It is now crystal-clear hypothesis and assumption regarding better performance of perennial horticultural systems in C sequestration than other farming practices like agroforestry and annual cropping systems. Also, perennial horticultural land use systems deliver better economic return through C credits. Soil stores much C pools for long time by better soil management practices, healthy rhizosphere biology, less synthetic inputs under eco-intensification practices that all intensify the ecosystem services and whole ecosystem sustainability. Thus, better management of soil and whole farming systems are important for better consequences of C sequestration in term of biomass productions and others uncountable tangible and intangible benefits through ecosystem services which maintains ecological sustainability.

20 Future Thrust

The C dynamic, its source and sink are the key criteria for planning C reduction, emission, financing and trading. The AFs, HBFs and other agroecosystems related land-use are the key concern in terms of food security, climate change and C emission-reduction processes. In this connection proper monitoring, modelling and assessment are needed time to time with upgradation of technology in different land-use to strengthening the knowledge regarding the trends of C emission-reduction. Similarly, the limited studies are available on C sequestration potential of diverse fruit and vegetable-based horticulture land use systems in different agro-climatic zones in India. Surely, it will give a new dimension to study and emphasis should be given on to identify a suitable species and develop a suitable propagation protocols along with better management practices which would help in enhancing C sequestration and productivity of varying perennial fruits and vegetables. Thus, more studies are needed to quantify C sequestration potential and various types of footprints in different land system. Further, various models were properly tested in different agro-climate zone along with varying site conditions for incorporation and promotion of C enrich technology in different plantation activities and government schemes. The potential of C sequestration by various indigenous species and the species having wider ecological amplitude were screened out for achieving the higher C sink and to move forwards with sustainable approach.