Vermicompost for Sustainable Agriculture and Bioconversion of Terrestrial Weed Biomass into Vermicompost

Abstract

Organic fertilizers are alternative to chemicals used in agriculture which enhance soil quality, prevent harmful chemicals entering into food chain, improve health and contribute to sustainable future socially, economically and ecologically. Vermicompost is a nutrient-rich organic fertilizer which promotes plant growth and improves soil quality. Vermicomposting is an economically feasible and environment friendly technology in which organic wastes are bio-converted into value added product and various organic wastes are used in this process. Terrestrial weeds are the plant species which grow on land and invasive in nature. These plants are responsible for various nuisances in the environment, agriculture and society. The weed biomass generated after various management methods are considered as organic waste. The terrestrial weed biomass is a possible option for the production of vermicompost. In this chapter scope of vermicompost for sustainable agriculture, the vemicomposting mechanism and the bioconversion of terrestrial weed biomass into vermicompost have been discussed.

1. Introduction

Chemical fertilizers are used for a long period for nutrient supply in soil but inadequate amount and prolonged used of these chemicals proved to be detrimental for the environment and whole of ecosystem. Beneficial soil microorganisms as well as other biota have been disturbed due to continuous applications of chemical fertilizers. Therefore the needs of environment friendly and ecologically sustainable alternative have been realized. Organic fertilizers are always considered more sustainable practice of agriculture rather than chemical fertilizers [1]. Organic fertilizers have many advantages over chemical fertilizers. The demands for food is very high in current time with rapid increase of population all over the world specially the developing countries. The non-availability of land for growing crops led to the higher demand for application of chemical fertilizers which increased the crop production to fulfill the demand. But various adversities are associated with these chemical fertilizers and have shown direct impacts on soil, water and air. The runoff from agricultural areas caused eutrophication in nearby water bodies. The properties of soil are dramatically altered by the application of these chemicals, Rapid depletion of soil nutrients and soil water retention capacities are evident from various studies [2].

Organic farming relies on efficient utilization of local resources, and application of advanced sustainable technologies. The various management practices adopted in organic farming helps in soil improvement and better nutrient supply. The sustainable development to secure future generation is based on the concept of organic farming. Organic farming has various potential including soil fertility re-storage, sustainable agricultural produce, biodiversity mainatenance, food security and economic benefit to the marginal farmers. The research is oriented towards how organic farming is a solution to global food security and sustainable development. The international organizations are involved for policy development for cost-effective and sustainable strategies for stable food production. The major challenge is to shifting towards organic supplements and curbs the chemicals used in agriculture for a better and healthy environment [3]. Vermicomposting is a technology for the production of organic manure with the help of earthworms. Organic matters are degraded biologically resulting into a more stable compound called vermicompost rich in nutrients. There are various benefits of application of vermicompost to the soil as well as environment [4]. Various organic matters are utilized for the production of vermicompost and further research is going on to investigate the potential of various natural organic resources in the production of vermicompost [5, 6, 7, 8, 9, 10]. Weeds are those unwanted plants that grow on any ecosystem disturbing the native plants and environment. Weeds which grow on land are termed as terrestrial weeds. Various management practices are adopted like mechanical, chemical, biological to remove and control these weeds in any forest or agricultural land. Terrestrial weed biomass is discarded as a waste after various management methods [11]. In the recent time utilization of terrestrial weed biomass for the production of vermicompost is documented in various researches [9, 11, 12, 13, 14]. In the current chapter the role of organic fertilizers for sustainable development as an alternate superior solution to chemical fertilizers has been discussed. Various benefits of vermicomposting technology for the production of organic fertilizers and the potential of terrestrial weed biomass as a feedstock for the production of nutrient rich vermicompost is also illustrated.

2. Organic fertilizers as an alternative to chemical fertilizers

Heavy input of synthetic chemicals like herbicides, manure, pesticides in commercial agriculture includes ample amount of cash outpouring. Conventional agriculture practice always leads to pollution, soil degradation and health issues [15]. As a plant grows, the major essential seventeen elements along with other are taken up from the soil. The nutrient supply is the major role of soil and as these elements becomes in short supply than restoration is required in the soil for sustainable agriculture. Chemical fertilizers are used to replenish the soil for centuries. But the efficiency of these fertilizers is very low. Around 80–90% of the fertilizers are not assimilated by the plants after application to soil. The remaining fertilizers acts as contaminant and intrude into the environmental bodies [16]. The soil is capable to produce crops in sustainably but the application of various synthetic chemicals led to loss in soil fertility in different parts of the world. There is a huge gap between nutrient supply and nutrient demand. The nutrient in fertilizers was globally supplied in 2014 was 240 million tons while requirement of nutrient was 284 million tones. This results into scarcity in crop production [17]. On the other hand the heavy metals are present in chemical fertilizers and prolonged use of these results into adverse impacts on soil property. Plant metabolism is also affected by the accumulation of heavy metals and becomes fatal. The various contaminants from enters into food chain due to application of chemical fertilizers leading to bioaccumulation. The aquatic life of nearby water bodies are at high risk due to eutrophication [18]. Eutrophication is caused by runoff during rain and sometimes irrigation. Nitrogen and phosphorus are the major elements which mostly affect water bodies. Nitrogen in other forms like ammonia finds its way to atmosphere considered as one of the greenhouse gases. Negatively it contributes to global warming. Therefore all these chemicals are harmful to the surrounding ecosystem as well as human, plant and animal health. The mismanaged application of chemical fertilizers in excessive quantity often results into contamination. These contaminants accumulate in water; air and soil negatively affect the environment thus impedes sustainable production of food [19]. With growing demand the transition was seen in last decades from traditional practices to modern practices in agriculture. The prerequisite of inorganic fertilizers was very high wide-reaching to increase agricultural production. The stipulated demand increased for various essential elements in soil from 2015 to 2020. In the coming 5 years the overall fertilizer consumption will be very high. But eventual application of chemical fertilizers increases the chance of environmental contamination. These chemicals also contain heavy metals and other radioactive compounds becomes fatal when enters the food chain and also a major foundation for contaminants which exist in soil and environment for a longer period [16]. Generally by the composition the inorganic fertilizers more or less remain same as compared to organic fertilizers. However organic fertilizers always have advantages over chemical fertilizers both economically and ecologically. In the recent time amendment of soil with organic supplements is gaining tremendous response for the management of soil nutrients and sustainable agriculture [20].

Organic fertilizers are prepared from various organic resources and nutrient composition varies based on the characteristics of the used feedstock [11, 21, 22]. In the recent time on large scale production and application of organic fertilizers have been promoted worldwide. But the resources to prepare organic fertilizers are limited and difficult to meet the demand. Biodegradable organic matter is the major feedstock for organic fertilizer preparation. Organic matters are considered easiest way for nutrient recycling in soil and plants. They act as soil conditioner and dependency on chemical fertilizers is reduced. If the application is adequate with proper guidance to the farmers then small amount of organic fertilizers is enough to meet the requirement of essential elements for drop growth [16, 23]. Among the various advantages of organic fertilizers the major contribution is the supply of macro and micro nutrients, improvement in soil properties, increase in plant nutrient uptake efficiency, increase microbial interaction and also in a barren land it acts as a better amendment to revitalize infertility of the soil. Therefore a mass movement is required to shift in the application of organic fertilizers prepared from various organic sources. The application of chemical fertilizers as in conventional agricultural practices must be discouraged to avoid deterioration of food quality, human as well as soil health [16].

The nutrient level in organic fertilizers is very high. They are considered good soil amendments and also involves in various disease control in plants. Bacterial augmentation, promotion of plant growth, reducing population of nematodes has been observed during application of organic fertilizers. The increased microbial population and improved organic content in soil result into continuing reimbursement in soil fertility. The crop cultivation in organic way always retains stable pH and more exchangeable minerals for plant uptake [24]. The prevention of harmful impact of inorganic fertilizers and long-standing protection to land is possible by the application of organic manure. Organic fertilizers are generally free of toxic elements and heavy metals. The carbon linkages in these fertilizers make the nutrient ions release slower which consequently perks up the soil physical properties like aeration, water retention and sustainable nutrient supply. This helps in better plant growth [25].

3. Organic fertilizer for sustainable development

Organic food is in high demand due to consciousness for health among the consumers and concern for environment to meet sustainable development goals. Therefore most of the marginal growers are inclined towards organic farming. The research, promotion, marketing along with education and training for organic farming has been stimulated in various sectors all over the country. Organic farming includes good soil health, crop protection, organized plantation, health benefits and sustainable land use for agriculture. In both developed and developing nations organic farming plays a crucial role in maintaining healthy environment. The reduced level of greenhouse gas emissions, efficient energy use and protection of biodiversity as well as ecosystem in developed countries is the outcome of organic farming. On the other hand in developing countries it promotes high yield with economic benefits, sustainable utilization of resources and also maintains biodiversity [26]. The practical applicability of organic farming mostly depends on the farmers. Untill 2012 organic food shares US$ 60 billion of the global food industry. Organic farming is not about more nutrient supply to soil rather it concentrates to minimize loss of nutrients and proper soil management with sustainable nutrients supply. Retention and recycling of nutrients is the major goal of organic farming. Organic matters supply these nutrients in a healthy manner and prevent soluble nutrients to leach out [27]. The term sustainable development was first conceptualized in the Bruntland Commission Report in 1987. Sustainable development describes development as without compromising the future generation to fulfill their own needs while meeting the needs of the present generation. Keeping it in view, for the benefits of existing and future generation around 150 global leaders adopted a global agenda to achieve sustainable development by 2030 through 17 primary sustainable development goals (SDG) for transformation a better future. All these goals targets for an equitable society and mitigate climate change [17]. The SDG also includes zero hunger, good health and well being. Organic farming is vital to achieve these goals. The change in agricultural pattern is always suggested for food security and feeding ever expanding global population sustainably. Organic farming is always kept as topmost solution for this by various scientific reports [28, 29, 30]. According to [17] organic agriculture is a holistic approach for better soil quality, biodiversity, proper biological cycle and overall healthy agro-ecosystem. This can be accomplished by using any biological resources despite of synthetic chemicals. This is the base for organic movement throughout the world [31, 32, 33]. The principles lie on good health and ecology makes the root for organic farming to grow and gain popularity across the globe. Organic farming stands as a sustainable approach that reduces green house gas emission as a mitigation measure to climate change. Organic food production as a safety concern influences both consumer awareness and consumer purchase. In USA alone organic products shares 5.3% of the food market with $47 billion in 2016. In developing country like India organic market shares in 2015 $104.5 billion. Organic farming is always beneficial to the marginal farmers with who follows traditional approach with no chemical applications. This results into large scale organic production. On the other hand it provides economic benefits, health and environment, protection of biodiversity by the implication of traditional knowledge. The adaptation to climate change is possible through organic farming as it is concordant to traditional farming and more resistant to disease and extreme climate. The motto of SDG is to make the world poverty liberated and sustainable. This makes organic farming as a fundamental strategy for the well being of the planet. Organic farming is a combination of tradition and scientific innovation for the benefit of environment and maintaining a healthy relation of the organisms involved. This totally brings to an end of synthetic chemicals considered as a curse to environment [15]. In this context, organic fertilizer is a boon to organic farming as well as sustainable development [34, 35]. Organic matters are the major source for organic fertilizers. Addition of organic source to soil is always beneficial to maintain soil fertility. The various organic sources are still under investigation which can be utilized to prepare organic fertilizers. The green waste are considered biodegradable wastes and generated from various sources. The biomass of various organic wastes can be turned into wealth with proper technology to prepare organic fertilizers. In the following part of the chapter one of such technology and a possible source for organic fertilizer has been discussed in brief.

4. Vermicompost as nutrient rich organic fertilizer

Composting is a process in which biodegradation of organic matter takes place in an aerobic environment. There is various composting process and is one of the traditional practice for organic waste management. Over the time composting techniques have been evolved with various advanced engineering. Vermicomposting is an extension of composting technology in which earthworms are involved in the degradation process. Earthworms consume organic matter and accelerate degradation process. At the end nutrient rich vermicompost considered as one of the finest organic fertilizer is obtained [12]. Vermicompost is termed as black gold. Application of vermicompost has various benefits including promoting soil health and plant growth [36, 37, 38]. Being organic in nature is always superior to the other synthetic chemicals. The demand for vermicompost production is rising in global market. The outcome of vermicompost never harm human health and always safe for consumption. The environmental issues are always resolved by the application of vermicompost. The technology itself for vermicompost production is environment friendly and economical. The zero pollution and low cost of vermicomposting technology makes it advantageous over other fertilizer production technologies [11]. At present for a sustainable future adoption of an eco friendly and economical technology is very much important. Vermicomposting has the potential to mitigate all the problems related to health, environment and society. The organic waste generation is becoming a major problem all over the world and their ultimate fate is the waste stream. The burning also releases harmful elements to the atmosphere as well as destroys overall physical properties of the soil. The proper waste management through utilization of these bio wastes as organic fertilizer for organic farming is possible [39]. This may set a benchmark as the most significant approach for sustainable development.

The importance of earthworms for the biodegradation of organic waste was first observed by Charles Darwin which became the base for evolution of modern sustainable technology called vermicomposting for organic waste management [12]. Vermicomposting have evolved in more scientific way by different researchers [40, 41, 42, 43, 44]. There are various benefits associated with vermicompost. Vermicomposting is considered more advantageous than traditional composting process [11]. The particle obtained after breakdown during vermocomposting is more homogenous and uniform with earthy manifestation than heterogeneous mixture obtained during composting process [45]. The release of nutrients is slow during application of vermicompost to the soil. This benefits the easy uptake of nutrients by plants and also increases water holding capacity of soil [39]. Vermicomposting highly influence the soil physical properties. The soil porosity, aeration and temperature are well maintained during application of vermicompost. Soil microbial activity is also enhanced and replenishes nutrient content in soil in significant way which gradually promotes healthy plant growth [36]. Bulk density of soil is also observed to be reduced due to enhanced microbial activity resulting into increased porosity. The oxidation potential is also enhanced during vermicompost application to the soil. Vermicomposting of different organic wastes with different earthworm species results into nutrient rich eco-friendly vermicompost. The nutrient content is significantly high in vermicompost produced from various feedstocks and acts as a soil amendment for organic farming [9, 20]. The nutrients are released into more exchangeable format during stabilization process of organic waste making these elements readily available to plants in final vermicompost [12].

If we consider the economic benefits of vermicompost, in the current time global market for fertilizer is increasing. Farmers are more concentrated in efficient production. Organic fertilizers are always derived from natural sources. Vermicompost is basically a result of bio-conversion of various organic wastes. The improvement in soil quality and healthy crops associated with vermicompost application highly influence the rural economy. The economic profit for any agricultural produce in evaluated on the basis of yield, return and cost–benefit analysis. The nutrient losses from the field are marginalized during any organic application including vermicomposting. The lower emission of pollutants, soil biota conservation, enhanced nutrients is all characterized for economic profit for any marginal farmers using organic manure like vermicompost [20]. On the other hand on site production of vermicompost also requires very low input for installation and the raw material can be easily available without any transportation costs [12]. The rural development is possible through employment generation by small entrepreneur with vermicompost production with readily available resources in and around. The farmers were benefited substantially with organic farming as compared to equivalent economic input in synthetic fertilizers [20].

5. Terrestrial weed biomass as an organic waste for vermicompost

Various organic wastes have been investigated for the production of vermicompost. The unwanted plants in any ecosystem are termed as weeds and terrestrial weeds are those grow on land. The non native species to a particular area causing harm environment and health is termed as an invasive species. These invaders remain persistent in an area and gradually harm the total environment. The weeds particularly invasive in nature and destroys native vegetation. The whole nutrient regime and energy balance is altered by the prevailing of these weed species. The management of these weed species is difficult and complete eradication is not possible [12]. The weed biomass is a potential resource for the production of vermicompost. In the recent time various researches revealed the utilization of terrestrial weed biomass and found significant results while producing vermicompost [11, 12, 13, 14]. Among the most noxious terrestrial weed species mostly investigated for the potential of vermicompost production are Lantana camara, Ageratum conyzoides, Parthenium hysterophorus etc. All of these weeds species are associated with various adversities and management with sustainable technology is very much required. The rapid regeneration capacity and morphologal adaptation make these weeds wide spread to a larger area. Most of these are found in forest, agriculture and urban ecosystem [12]. The weed biomass is easily available near farm area after clearance in abundance and can be easily utilized for onsite vermicompost production without any heavy cost involved. The nutrient rich vermicompost is produced from Ageratum conyzoides without any phytotoxicity. The germination index analysis proves Ageratum conyzoides biomass as an excellent media for plants [14]. The enhanced nutrient content in the bioconversion of Ageratum conyzoides biomass indicates its suitability as a substrate for vermicompost production [12]. The high tolerance capacity makes the weed Lantana camara to withstand any adverse environmental condition. Annually Lantana camara biomasss tons in billion is generated and can be utilized in an extensive way for vermicompost production. The FTIR analysis of vermicompost produced from Lantana camara biomass indicates reduced lignin content and allelopathic elements. Thus the vermicompost produced become eco-friendly and plant friendly [9].

6. Conclusion

Sustainable development depends on the conservation of natural resources and reliance on renewable resources for the future generation. Hunger reduction and food security for all is the major goal of SDG. The consumer consciousness for health and well being is the major driven force for organic movement. The chemicals applied in the paradigm of shift in agricultural activities in recent past have destroyed the food quality, soil fertility and the environment to a large extent. Organic farming is a solution to overcome all of these problems. The organic products are in high demand in both developed and developing nations. It was observed that organic farming is beneficial to the marginal farmers in rural economy and also helps in maintaining a clean environment. Organic fertilizers make organic farming more sustainable. Crop production, soil fertility is also enhanced due to application of organic fertilizers. The role of vermicompost as an organic fertilizer plays a crucial function in sustainable eco-friendly farming with abundant benefits including maintaining soil quality and nutrient supply to the crops in efficient way. Vermicompost application also accounts for pest control, enhanced microbial activity in soil and release of no emission to the atmosphere. Terrestrial weed biomass is seen to be a good resource for vermicompost production. This can be utilized in an efficient way instead of discarding it into waste stream. The proper management of terrestrial weed biomass through vermicomposting can resolve the demand for organic fertilizer globally.

Conflict of interest

The authors declare no conflict of interest.