Carbon Sequestration Opportunities in the Agricultural Land of Nepal

Authors

Roshan Babu Ojha is a Soil Scientist at the Nepal Agricultural Research Council who is currently studying for a PhD at The University of New England, Armidale, Australia (Biography)

Malcolm McEwen is a freelance Soil Scientist and Environmentalist trading as Persephone Habitat and Soil Management . He is the Admin and principle Editor of this site. (Biography)

1) Background

Nepal is divided in four agro-ecozones (Terai, Siwalik, Middle mountain/mid-hill and High Mountain) ranging in elevation from 60 meters above sea level (masl) in the south to 4800 masl in the north. The northern elevation extends up to 8848 masl which is rocky and snow covered. Terai (a part of Indo-gangetic plain) is flat land extending from 60-300 masl. Siwalik is extended from 900-2000 masl. The Middle mountain/mid-hills zone is represented by gentle to steep sloping land extending from 1500-2700 masl (Chalise et al., 2019). The High Mountain zone is steeply sloping land extended from 2,000-4,800 masl. Around 27% of the total land is suitable for cultivation and 20% of land is under cultivation. Forest and shrubs, occupying approximately 40% of total land area, extend from Terai to high-Mountain. Pasture land is mainly limited to high-Mountain and represents 12% of the total land area.

1a) Current Cropping Systems

Farming is dominated by traditional integrated cereal (rice, maize, millet, mustard and wheat) with livestock (cow, buffalo and goat) systems (Gauchan and Yokoyama, 1999). Terraces on the hill slopes is also a key feature of Nepalese agriculture (Jodha, 1992; Partap, 1999). This can be further differentiated with the lower Terai dominated by a rice-wheat based cropping systems, the mid-hills region dominated by maize-based cropping systems and the high mountain region dominated by pastoralism. (Gauchan and Yokoyama, 1999

1b) Abandoned Land

Approximately one third of the cultivable land in Nepal has been abandoned over the last 30 years (Gautam, 2004; Jaquet et al., 2015; Khanal and Watanabe, 2006; Seddon et al., 2002) and whilst land abandonment issues have occurred throughout the country it has been particularly prevalent in the mid-hills zone (Paudel et al., 2019). Within the Kaski district of Nepal 40% of households abandoning at least one parcel of land for two consecutive years and 28% of the all plots being consistently uncultivated and left fallow (Khanal, 2018). Further studies have identified that abandoned crop lands were subjected to degradation through soil erosion, landslides, and terrace collapse (Khanal and Watanabe, 2006).

1c) Causes of Abandonment

The abandonment of land has become an increasing problem as the inability to produce a viable income from agriculture has, through internal migration and emigration, led to rural depopulation. Historically traditional cropping systems emerged out of the need to provide sustenance for the farmer and immediate family with little or no requirement for the generation of income through the cultivation of cash crops. However with the increased desire for consumer goods, energy and transport networks the need to finance this changing lifestyle has also emerged. The existing agricultural systems of Nepal however have failed to adapt to these needs. Minimal attention has been paid to adapting and modernizing agriculture to take advantage of emerging markets, technological developments and export opportunities in response to the growing social changes with most farming enterprises still cultivating traditional crops and using simple tools and draft animals in the tillage of land. Where attempts have been made to adapt lack of cultivation knowledge and use of appropriate tools has resulted in low yields and little income generation. This has been compounded by a failure to educate farmers in the cultivation of new crops and the adoption of appropriate technology to cultivate those crops.

2) Difference and Role of Soil Organic Matter (SOM) and Soil Organic Carbon (SOC)

Soil organic matter (SOM) also, and more commonly referred to as humus is the fully or partially decomposed remains of microbes, animal and plant material. Humus is dynamic in nature and is important in the mineralization of plant nutrients and the maintenance of soil and ecosystem health. Comprised largely of short lived material it contributes to both the labile (active) pools of C, which persist from a few days to several years and the longer lived recalcitrant (stable) pools that can persist for several centuries and contribute to the mitigation of CO2 in the efforts to tackle climate change.

Soil organic carbon (SOC) is the part of the SOM comprised of just carbon. On average SOM is composed of 58% of SOC. Carbon stored in the soil, in the form of SOC, is the second largest global Carbon reservoir (Lal et al., 2015). A significant component in maintaining soil ecosystem function (Adhikari and Hartemink, 2016; Janzen, 2006; Lal, 2019) it is further necessary in maintaining the physical, chemical and biological properties that contribute to soil fertility, soil sustainability and food security (Lal, 2004; Lal et al., 2015; Wiesmeier et al., 2019).

2a) Current Status in Nepal

Soil organic carbon (SOC) is an essential soil component to maintain and restore soil quality and ecosystem function (Janzen, 2006; Lal et al., 2015; Wiesmeier et al., 2019). Past policies in Nepal, (i.e.The National Agriculture Policy (NAP) 2004 included in the Agriculture Perspective Plan (APP) 1995-2015) focused on chemical fertilizer distribution and subsidy schemes but failed to address the potential or importance of organic fertilizer and SOC in the maintenance of soil and crop health. As a consequence the use of chemical fertiliser at the expense of organic fertilizer has led to significant oxidation and loss of Soil Organic Matter (SOM) in the croplands of Nepal with SOC having declined to 1% (ADS, 2015).

2b) Existing Government & Agency Policy Objectives

The importance of SOC to increase agricultural productivity and sustainability has been identified in the Agriculture Development Strategy (ADS, 2015-2035). The former National Agriculture Policy (NAP) 2004 and the Agriculture Perspective Plan (APP, 1995-2015) largely focused on increasing agricultural production through seed and fertilizer development at the expense of organic manures which in turn has led to an increase in soil erosion, nutrient mining, and chemical pollution of water bodies by agro-chemicals. With the decline in SOC having now been realized a target to increase Soil Organic Matter from 1% to 4% over the next 10 years has been set. To meet this target, the Ministry of Agricultural Land Development (MoALD) has a policy to increase SOM through the promotion of the organic farming, improved use of manure, on-farm composting, vermi-composting, and the subsidizing of commercial organic fertilizer. However few government programs have yet been started to address organic farming and organic fertilizer production at the farm scale.

2c) Current inputs of SOC

Addition of organic material is one of the most effective ways to add carbon to cultivated soils. However most organic inputs contribute the labile form of carbon (Paul et al., 2001) which is mineralized according to first order kinetics. This results in an annual loss of approx. 50% of the carbon added with, after four years, only 6% of the additions remaining. This though can be offset by regular timely additions (annually or every three years) which, over the long term result in a net balance being achieved.

2c i) Farm Yard Manure

In integrated livestock farming systems Farm yard manure (FYM) is the most commonly used bulky organic fertilizer. Combined with mineral fertilizer FYM can increase labile carbon by 75% and water soluble carbon by 110% (Brar et al., 2013). The stable carbon fraction is higher in farm yard manure and straw residue incorporation than green manure addition (Chaudhary et al., 2017).

In most studies addition of Farm yard manure significantly increases SOC sequestration and SOC stock but the amount of farm yard manure use in the studies is far from the realistic dose applied by the farmers. Practically, it is not achievable in farm level to maintain the FYM dose (3-4 t FYM ha-1 on dry weight basis) as recommended by the studies (Gami et al., 2009).

2c ii) Crop Residues

Residues such as crop stubble, cereals straw, leaves and roots which are not removed from the field after harvest add small amounts of SOC and further provide other physical, chemical and biological benefits. Residue retention similarly increases soil organic matter levels (Gupta Choudhury et al., 2014; Lugato et al., 2014; Rasmussen et al., 1980) and can have beneficial effects on microbial communities (Zhao et al., 2016). However, both the quantities and stability of crop residue carbon are low and thus the benefits are minimal on their own.

3) Future Opportunities to Increase SOC

In order to meet the Agriculture Development Strategy (ADS, 2015-2035) target of increasing SOM to 4% over the next 10 years and with the greatest degradation and highest productivity occurring on the Terai and mid-hill regions, specific management strategies for the Terai, mid-hill and high mountain regions should to be developed. These strategies should similarly address agricultural development and education.

3a) Land Management strategies

Opportunities to increase SOC in agricultural lands exist through the adoption and promotion of better pasture and tilled land management practices and utilization of existing infrastructure. These include seeding pasture with deeper rooted and beneficial species, better utilization of field boundaries and terrace walls, adoption of green manuring and on farm composting of organic wastes prior to incorporation into the land.

3a i) Pasture Management

With the majority of pasture existing in the higher elevated regions and representing 12% of the total land area consideration and research into suitable perennial and deep rooted species that contribute both to the health of livestock and increase SOC should be undertaken. The same should be performed at the lower altitudes in order to similarly improve stock health and productivity and sequester carbon. At present we are working with ADAOS to devise a strategy to integrate improved habitat and pasture management for the preservation and maintenance of traditional Nepali cattle.

3a ii) Field Boundary and Terrace Wall Management

Field sizes in Nepal are relatively small and so have a much larger ration of boundary to cultivated land than found elsewhere. Similarly, the predominance of terrace farming generates a large surface of terrace wall representing as much as 50% of the total land area (Sedi reconnaissance). These boundaries and terrace walls are currently utilized in the production of forage for housed cattle however colonization is largely left to natural processes resulting in the establishment of poor quality and non-forage value plants (weeds) that require maintenance and can damage the terrace walls. Through the deliberate seeding of more productive less damaging plants to both the boundaries and the terrace walls would result in better forage and higher productivity of cattle. Furthermore these boundaries offer the opportunity to cultivate biomass and oil bearing plants such as Jatropha or Tree borne oilseed (TBO’s) for the production of bio-fuels. With Nepal having no fossil fuel reserves utilization of boundary and terrace walls for biomass and biodiesel crops could thus contribute greatly to the development of a domestic fuel industry that reduces pressure on natural forest land, provides fuel security and promotes wider sustainability objectives (SDG’s). Is furthermore another area of research and development that we intend to investigate and promote. (link to biodiesel page)

3a iii) Green Manure and Under Sowing

Cropping systems in Nepal range from constant all year round production (mustard, maize, rice) to single annual crop (rice) production. With the former one harvest is followed by the addition of small amount of fresh FYM incorporated with the sowing of the following crop and little of no subsequent weed management resulting in dirty (weed infested) crops producing low yields. With the latter land is left fallow between crops and is similarly naturally colonized by poor value plants utilized for rough grazing. In both cases the use of green manures both as standing crops and as an under-sow for incorporation following harvest and prior to re-sowing would provide additional Carbon inputs and improve subsequent crop productivity and grazing value.

3a iv) On farm Composting

On farm composting of FYM and organic residues remains one of the best ways to provide SOC to the soil and utilize available nutrients for subsequent crops. The current practice of using fresh FYM whilst more beneficial than not does however have detrimental effects as available nutrients, in particular nitrogen, are utilized by micro-organisms in order to decompose the material. Similarly, residues that are not incorporated are often removed and burned. These residues could be utilized along with the FYM in compost production so as to produce a more stable beneficial product with higher fertilizer value. We are currently developing a three stage composting system with ADAOS to produce high quality stable compost for use in crop production and as an ingredient in the manufacture of potting media for the production of nursery plants (link to compost post)

3b) Supplementary Opportunities

In addition to improved land and on farm management strategies opportunities to gather non-farm based (i.e. wood mill and forestry residues) and off/post farm residues (processing and restaurant waste) for either composting or biochar manufacture exist. Similarly abandoned and marginal land could be utilised to produce green material for direct incorporation into cultivated land or for compost feed stock. There further lies an opportunity to add significant amounts of SOM and SOC through the development of nursery production to supply seedling plants for field cultivation. Each module may hold as much as 10g of SOC thus every 10,000 seedling plants grown in soil-less media could add 1 ton of SOC to a parcel of land.

3b i) Composting of off farm and non-farm derived organic wastes

Organic wastes derived from domestic and commercial operations as well as forestry residues and saw mill wastes (i.e. wood shavings, bark) offer a route to recover significant quantities of carbon for either composting or the manufacture of biochar. Similarly invasive water weeds such as water hyacinth could be utilized in both composting and biochar manufacture. Currently wood waste from saw mills is being used as a compost ingredient at ADAOS and we are similarly looking at opportunities to collect restaurant waste from Lakeside for compost manufacture as well as the water hyacinth that annually chokes the Fewa lake.

3b ii) Biochar

Biochar, anoxygenic pyrolysed charred materials, have considerable agronomic (Biederman and Harpole, 2013), and environmental benefits including C sequestration (Schmidt et al., 2011), and mitigation of greenhouse gas emissions (Gurwick et al., 2013).

Biochar addition can have considerable long-term stability (Lehmann et al., 2009) and significantly increase the stable C sequestration in soil. Depending upon feedstock the half-life of biochar in soil varies from a few months to hundreds of years but with the proportion of labile C (3%) to recalcitrant C (97%) the contribution is chiefly in the long term (Wang et al., 2016) . Smith et al., 2010 similarly identified that the C decomposition in biochar is slower indicating that biochar additions are a potential means for long-term storage of carbon. Furthermore Woolf et al. (2010) estimated the net reduction in greenhouse gas emissions by sustainable biochar production could be as much as 1.8 Pg CO2-C annually whilst Weng et al., (2017) noted that additions of biochar improved root growth with newly derived root carbon increasing by 20%. (Link to Biochar Page)

3b iii) Abandoned land: Utilisation for green manure and compost feed stock production

With upwards of 30 % of agriculture land being abandoned and little prospect of that land being bought back into production in the short term it could be utilized to produce green manures for incorporation into operational lands or for the production of feed stocks for nearby compost operations. Such an utilization would be extremely beneficial to on farm composting of FYM which is absent of bedding material and so lacks sufficient structure to be effectively composted.

3b iv) Module raised plants in soil-less carbon rich substrates

We are currently developing a nursery operations at ADAOS (link to page) for the production of seedlings raised in potting media derived from the worm worked compost and coir. Each module contains up to 10g of SOC in the form of humus (SOM) made from FYM, grass cuttings and wood shavings. As yet we are unaware of any research undertaken to calculate the amount of of SOC such a system would add to a field but estimate that at a planting rate of 100,000 seedlings per hectare the total input could exceed one ton of carbon per hectare. As the material has been both composted and worm work it is highly stable and may have a longevity in excess of 10 years.

4) National and Global benefits

In addition to contributing to the aims of Nepal’s Agriculture Development Strategy (ADS, 2015-2035) the above recommendations also provide the opportunity to contribute to wider National and International Objects, in particular the Sustainable Development Goals (SDG’s) of the United Nations Development Program (UNDP)

The Sustainable Development Goals (SDGs), also known as the Global Goals, are 17 integrated objectives that aim to balance social, economic and environmental sustainability. They were adopted by all United Nations Member States in 2015 as a universal call to action to end poverty, protect the planet and ensure that all people enjoy peace and prosperity by 2030. Specifically we hope, through the above measures to address:

  • Goal 7 & 9 Affordable and Clean Energy & Industry, Innovation and Infrastructure through the generation of biomass and biodiesel fuel industries in Nepal.
  • Goal 4 & 8 Quality Education & Decent Work and Economic Growth through horticultural and soil management programs.
  • Goal 13 Mitigating climate change through carbon sequestration
  • Goal 15 Life on Land through habitat management and creation
  • Goal 17 Partnerships to achieve the Goals. Starting with ourselves, a team that originates from and is spread over four continents.

Whilst similarly working towards and in partnership with the other 10 Goals (No Poverty, Zero Hunger, Good Health and Well-being, Gender Equality, Clean Water and Sanitation, Reduced Inequality, Sustainable Cities and Communities, Responsible Consumption and Production, Life Below Water, Peace and Justice Strong Institutions,)

5) Way Forward

Increasing carbon in croplands has multiple soil crop and environmental benefits. To achive both the domestic targets and global goals consideration should be given to fully integrating all possible options to sequester carbon into Nepals agricultural soils. Similarly priority should be given to the re-utilization of abandoned croplands for the accrual of Carbon either within the land it self or for use in active farming operations. Through our work with ADAOS and other ongoing projects we are developing mechanisms to promote and educate land owners and farmers in sequestering carbon and improve productivity in crop production in order to achieve the Nepalese Governments agricultural and environmental targets.

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