eChapters

Introduction

The agriculture remains largest public sector wherein 60% of labor forces are engaged. The farmer-based website aims at providing a hassle-free platform to the farmers who don’t have any organized to sell their agricultural products at the most effective prices are hosted. The crop production and agricultural production system has wide diversity to converge the merchandise or byproduct to the top users in novel manner in terms of profit generated by the farmers. The hassle has given to the agricultural system from Government side from growers to the consumers for fresh with standard price. The agricultural produce is accessible online for customer easiness to obtain the produce. All the agricultural produce i.e. fruits, vegetable, cereals and pulses and plenty of more is obtainable online in preset day agriculture. The farming produces including harvested moreover as dairy based products directory developed by different company’s direct purchases from farmers. The positioning propounds e-commerce in agriculture and has tremendous value to farmers, wholesalers or retailers. “This could be a cutting-edge technologies using social computer far superior to anything within the marketplace,” the web site is under continuous process of improvement and development to form it the most effective and user-friendly, and therefore the makers are hospitable any reasonably suggestions. Indian Gross Domestic Product (GDP) grew at 7.3 percent at the moment (2016-17), the agriculture sector remained stagnant at 0.2 percent, with the farm production trailing at 1.7 percent only. This clearly observed the underlying rural distress and farmers facing difficult times. In such a scenario, such a large amount of attempts like ‘doubling the farmers income’, Kisan Bazar so on are the initiative within the right direction, providing farmers with a platform of agri-marketing sector to achieve the buyer directly, without a requirement of an intermediary. They will now sell their products at the simplest prices and this may bolster the agricultural economy without intervention of middle-man.

Many farmers/ wholesalers / retail chains of agri-based industries are trying to find this type of solutions within the country and abroad.

Introduction

The ancient agriculture as an each class of advice has been well connected into several subcategories. As such, the advice under centennial sub-category has been divided to a few references, in adjustment with proper specification not to access only the aggregate of the publication. However, the information on past day agriculture to attending for data has been collected from the adapted references. There are several pictures assuming seeds of cereals and legumes and those of a collection of agricultural tools and implements begin in archaeological excavation and office texts. These are mentioned to advance how accurate to accept in aggregate of every fragment of advice and verify it from added sources more than one. The painstaking and thorough going work have revealed the state of agriculture during the period under study and its gradual development through the ages. The recorded findings are no doubt those have not been comparable with present-day agriculture. The awareness of the people engaged in agriculture regarding the types of food-crops to be grown, the animals to be domesticated and reared for agricultural operations as well as sources of food and nutrition, the design and preparation of tools and implements for agricultural operations and machineries for food processing unfolds gradually with experience gathered in course of time. The agriculture in past period wherein the population was predominantly pastoral and agricultural such great strides were noticeable in the pursuit of agricultural sciences with a sound traditional and scientific practice. Therefore, the recognizable endeavor throughout the period gives sufficient reasons to be proud of cultural continuity towards agricultural heritage.

Introduction

In India, the history of agriculture dates embarrassed to Indus natural depression Civilization Era and even before that in some locations of Southern India. Today, India ranks more familiarized in surface area output. Agriculture and related sectors like biology and fisheries accounted for 137% of the value concerning 500^th of the manpower in 2013. The livelihood buildup of agriculture to India’s value is steady breakdown with the country’s broad-based livelihood growth. Still, agriculture is demographically the broadest and highest livelihood across and plays a strong role within the all-inclusive socioeconomic attachment of India. India exported $38 billion service of scientific discipline on-line symbols, authentic it the seventh larger scientific discipline business person used to and therefore the sixth larger web businessperson, plenty of its agriculture exports serve developing and developed nations as in 2013. Indian agricultural/horticultural foods squarely determined and exported to further more than 120 countries, primarily within the geographical area, environmental region, SAARC countries, the EU and United States. As per FAO (2010), agriculture statistics India is that the world’s larger agent of in great quantity of fruits and vegetables, milk, spices, base crops that as jute, staples as millets and vegetable oil seed. India is that the further larger agent of wheat and rice in the world.

India stratified within the world’s five larger producers of over 80^th of scientific order ending things, as well as in large numbers banker’s invoice crops feels affection for unusual crops including cotton, in 2010. India is one in every of the world’s five larger producers of farm animal including dairy products and plenty of meat, with one in every of the quickest advanced rates, as of 2011.

Introduction

The specific agricultural systems and landscapes have been created, shaped and maintained from generation to generations of farmers and herders based on diverse natural resources, using locally adapted management practices. Indian heritage is unique and prestigious than any other civilization in this world. We must feel proud being a citizen of India for its rich cultural heritage. Agriculture in India has a long history from Neolithic age of 7500-4000 B.C. People changed their life style from nomadic hunter of wild berries to cultivator of land. Agriculture is gifted from the wisdom and teachings of great saints. The knowledge achieved and techniques adopted have been passed down through generations. The traditional farmers have developed the eco-friendly farming systems and mixed farming, mixed cropping, crop rotation etc type of systems were practiced by them. The older generations of the farmers of India passed the depth of knowledge and experience of great epics of ancient India.

Indian agriculture heritage is known as unique and prestigious than any other civilization in this world. Its rich cultural heritage in India has a long history from Neolithic age of 7500-4000 B.C. People changed their life style from nomadic hunter of wild berries to cultivator of land. Agriculture is gifted from the wisdom and teachings of great saints. The knowledge achieved and techniques adopted in generation to generations. The traditional farmers have developed the eco-friendly farming systems and mixed farming, mixed cropping, crop rotation etc type of systems were practiced but the older generations of the farmers of India passed the depth of knowledge and experience of great epics of ancient India and its consequence has come up in present day agriculture.

The preservation of wild animals was maintained and hunting as a sport by the ruler was considered as detrimental to proper development of the character and personality according to Manusmriti, 2^nd Century BCE. In the Puranas (300-750 AD), the names of the experts in animal husbandry were found like Shalihotra on horses and Palakapya on elephants. More than 75 plant species was mentioned in the four Vedas. Satapatha Bhrahamna mentioned over 25 species, and more than 320 plants were found in Charkaa Samhita (300 BC) an Aayurvedic treatise. Over 750 medicinal plant species were recorded in Susruta (400 BC). Rigveda (4000 BC), the oldest book, referred a large number of poisonous and non poisonous aquatic and terrestrial, and domestic and wild creatures and animals. About 500 species of plants were written in Puranas. In the Rigveda, it has been mentioned about the hundreds and thousands of cows, horse drawn chariots and race courses where chariot races were held; camels yoked to the chariots; sheep and goats offered as victims for worship, and the use of cloths made from wool. The famous Cow Sukta indicated that the cow also became the basis of rural economy. Sukta is also worshiped as the mother of the Vasus, the Rudras and the Adityas, and also the pivot of Immortality. Rigveda, which is the most ancient literary work of India, believed that Gods were the foremost amongst agriculturists. According to the thesaurus, “Amarakosha” which was written by the Jain or Buddhist scholar Amarasimha in Sanskrit, Aryans were agriculturists. Agriculture, cattle rearing and commerce were the essential subjects of the king that must be learnt. This was prescribed by Manu and Kautilya. The most ancient literature available in India was “Vedas” which includes the four Vedas (rig, yajur, sama, atharvana), nineteen Brahmanas.

Abstract

Rhizobia are soil bacteria that fix atmospheric dinitrogen after establishing symbiotic relationship inside the root nodules of legumes (Fabaceae). Plant Growth Promoting Rhizobacteria are the group of bacteria which thrive in the rhizosphere region and enhance the plant growth through direct & indirect mechanisms. Pulses are being inoculated with specific rhizobial strains to have better nodulation in India. The native rhizobial strains from the root nodules of legumes from different agroclimatic zones of Odisha was isolated, characterised and screened for PGP activities. Out of all eleven isolates showed similar characteristics with the family Rhizobiacae. Among them six isolates contained nif-gene and PGPR activity (B2, B4, B5, B6, B7 and B8) were applied to seeds, that helped in faster germination and better elongation of root and shoot. The observations were statistically significant.

Abstract

Phosphorus is the second important key element after nitrogen as a mineral nutrient in terms of quantitative plant requirement. Although abundant in soils, in both organic and inorganic forms, its availability is restricted as it occurs mostly in insoluble forms. The dynamics of phosphorus in soil is closely related to the dynamics of the biological cycle in which microorganisms play a central role. They also participate in the cycles of the most important macro and microelements such as phosphorus besides their major role in the decomposition of plant residues, creation of humus and maintenance of stable soil structure. Microorganisms affect the amount of phosphorus accessible to plants by means of mineralization of organic phosphorus compounds, immobilization of available phosphorus and solubilization of non-soluble phosphorus minerals such as tricalcium phosphate. Mineralization is catalyzed by microbiological enzymes phosphatases secreted by a diverse group of bacteria, fungi and other groups of microorganisms. Organic phosphorus mineralization in soil depends on several soil and environmental factors such as temperature, pH, soil moisture, degree of aeration. In this chapter the major emphasis is given on the transformation of P through microbiologically involving different enzymes and also the microorganisms involved in the process. Emphasis is also given on the factors that have profound influence on the microbial transformation of P in soil and ultimately making it available for plant uptake. This chapter also focuses on the mechanism of P solubilization, role of various phosphatases, impact of various factors on P solubilization and potential for application of this knowledge in managing a sustainable environmental system.

Abstract

Agriculture provides food, feed, fiber and many other desired products for survival of human beings in the world. Modern agriculture emphasizes on use of hybrid seeds, high yielding varieties and chemical fertilizer to increase the crop productivity within a short period. Indiscriminate use of synthetic fertilizers has led to environmental pollution and deterioration of soil health, which results in depletion of essential plant nutrients and organic matter in soil. On account of the environmental hazard and soil infertility, biofertilizer concept was developed. Biofertilizer are natural fertilizers including bacteria, fungi and algae alone or in combination that augment availability of nutrients to the plants. However, due to its short shelf life period it may not be a suitable candidate for modern agriculture. Thus, it is the need of the hour to develop an economic and eco-friendly nano-biofertilizer for sustainable agriculture.

Abstract

Potassium (K) is the third most essential macronutrient element for plants. More than 98% of K in agricultural soils are remained as insoluble organic and inorganic compounds or complexes that are unavailable for plant uptake. Nutrition of crop plants are heavily relied on application of expensive inorganic chemical fertilizers, which is a potential cause of environmental pollution. An eco-friendly alternative strategy for plant K nutrition could be the application of K solubilizing bacteria (KSB) as biofertilizer. Plant and soil-associated bacteria from diverse taxonomic genera such as Bacillus, Pseudomonas, Acidithiobacillus, Paenibacillus, Flectobacillus, Arthrobacter, Enterobacter, Sphingomonas, Paraburkholderia etc. have shown high K solubilizing activities and promote plant nutrition in K deficient soils. The mechanisms involved in their activities include acidolysis, chelation, exchange reactions, and enzymatic degradation of insoluble K minerals and other K complexes. However, inconsistency in the efficiency of KSB-based biofertilizer for crop production in diverse ecological settings is still a big challenge. Recent genomics, post-genomics and CRISPR-Cas genome editing approaches seem to be useful for a better understanding the underlying mechanisms of KSB and development of highly efficient K fertilizers for promoting sustainable agriculture. This chapter comprehensively reviews current updates of KSB-based biofertilizer and their potentials for promoting sustainable crop production. The role of genomics and post-genomics approaches for better understanding of the mechanisms of the functions of applied KSB-based biofertilizers in the crop field and mitigation of the existing inconsistency in the efficiency of KSB-based fertilizers are also discussed.

Abstract

Potassium is a very essential nutrient element that is required for proper health, growth, functioning and productivity of plants. However, up to 98% of this very important mineral is held up in insoluble, unavailable forms in the soil and with only approximately 2% soluble form available for plant use. Biofertilizers add nutrients to the soil for plant use by some mechanisms like the breakdown of phosphorus, potassium, fixing nitrogen, and also synthesizing some substances which in turn enhance plant growth. These processes take place naturally. Microorganisms that solubilize potassium have demonstrated an increased potassium uptake by plants when added as bio-inoculants consequently resulting in increased yield by these plants. This article reviewed the methods of isolation of potassium solubilizing bacteria and fungi and their use as biofertilizers. Data are presented showing summary of researches conducted on potassium solubilizing microorganisms and their findings. Figures on production efforts of biofertilizers in India per year and by states are also added.

Abstract

Nitrogen (N₂) is an essential nutrient for every organisms. It is the building block of many biological molecules. Atmosphere contains 79% of N₂ gas which cannot be used by plants directly as it is chemically inert. Many diazotrophs like bacteria and cyanobacteria have the capability to convert atmospheric dinitrogen into a usable form by means of Biological nitrogen fixation (BNF). N₂ fixation is generally three types i.e. Asymbiotic, Associative and Symbiotic. Asymbiotic N₂-fixation also known as free living N₂-fixation is under taken by some bacteria and cyanobacteria. In associative N₂-fixation, some bacteria fix nitrogen in association with root of some grasses and cereal plants. In symbiotic nitrogen fixation, Rhizobium form root nodule in legumes and fix atmospheric N₂ and convert it into the ammonia (NH₃) by the help of Nitrogenase enzyme. This oxygen sensitive enzyme consist of two components i.e. di-nitrogenase (MoFe protein) and di-nitrogenase reductase (Fe protein) which are highly conserve in sequence and structure. The N₂ fixing genes e.g. nod gene (nodulation gene) and the nif gene (nitrogen-fixing gene) are located in the plasmid which is also called mega plasmid. Symbiotic association between legume and rhizobium have agronomic importantance and reduce the use of N-fertilizers or even avoided. The long term use of the nitrogenous biofertilizer in the agricultural field is a promising approach to develop and fulfil N₂ demand of the growing crop without causing any environmental hazard.

Abstract

Sustainable agriculture is vital in today’s world as it offers the potential to meet our agricultural needs, something that conventional agriculture fails to do. Current soil management strategies are mainly dependent on inorganic chemical fertilizers, which caused a serious threat to human health and environment. To overcome the ecological problems resulting from the loss of plant nutrients and to increase crop yields in the absence of resources for obtaining costly fertilizers, microscopic organisms that allow more efficient nutrient use or increase nutrient availability can provide sustainable solutions for the present and future agricultural practices. Microbial populations are instrumental to fundamental processes that drive stability and productivity of agro-ecosystems. Several investigations addressed at improving understanding of the diversity, dynamics and importance of soil microbial communities and their beneficial and cooperative roles in agricultural productivity. Thus the technique, which uses microscopic organism as biofertilizer, is environment friendly and ensures safe and healthy agricultural products. In this chapter we aim to provide a brief overview of potential use of biofertilizer for attaining sustainability of agro-ecosystem.

Abstract

In recent years, significant studies have been carried out on Plant growth promoting rizhobacteria (PGPR) to replace the usage of pesticides and fertilizers to improve the plant health. Plant growth promoting rizhobacteria (PGPR) is a group of rhizosphere bacteria, which are symbionts to plants and influence their growth by providing plant growth promoting substances. Different bacterial genera act as plant growth promoting rizhobacteria (PGPR): Pseudomonas sp., Rhizobium sp., Azotobacter sp., Bacillus sp. Pseudomonads are gram negative rods, aerobic, fluorescent, motile and are able to produce siderophores which influence plant growth. There are multiple potential traits offered to the plants by plant growth promoting (PGP) Pseudomonas sp. are (1) Biocontrol agent against plant pathogens (2) Induced systemic resistance, which is a defense mechanisms in plants preceding to pathogenic attack (3) Influence of plant growth promoting (PGP) Pseudomonas sp.on agricultural crops (4) Siderophores, which are low molecular, high affinity iron chelating compounds which benefits the plants to acquire iron molecules (5) Nitrogen fixation (6) Phytoremediation of heavy metals (7) Solubilization of inorganic phosphates (8) Secretion of plant hormones (9) Bacteriocins(10) Antifungal factors (11) Antibiosis traits and (12) Endophytic PGP Pseudomonas sp.

Abstract

Soil salinity is one of the major environmental stresses affecting crop productivity and soil health drastically, particularly in arid and semi-arid areas. Most of the vegetable crops being salt sensitive, grow poorly in saline and alkaline soils. Soil salinity affects crops mainly due to the osmotic stress and excessive accumulation of toxic ions (Na⁺, Cl^-, and SO₄ ^2-), whereas alkali soils are generally characterized by poor physical conditions due to high concentrations of bicarbonate (HCO₃ ^-) and carbonate (CO₃ ^2-) as well as high exchangeable Na⁺. Excessive concentrations of sodium chloride (NaCl) in soil or irrigation water can induce several morphological, physiological, and biochemical responses in plants leading to stunted growth and yield. This is due to osmotic (i.e., water deficit) and ionic (i.e., Na⁺ and Cl^-) effects on nutrient uptake/translocation and metabolic processes such as nitrogen assimilation, photosynthesis, and protein synthesis. Plant growth promoting microbes (PGPMs) are considered as promising tools to overcome the limitations of salinity on crop growth and productivity. Many PGPMs can enhance tolerance of crops to salt stress by increasing nutrient uptake through better solubilization of nutrients like phosphorus and zinc, and also by production of small peptides, volatiles and metabolites with hormone activities such as indole-3-acetic acid or auxin analogs in the rhizosphere. This chapter discusses the benefits of PGPMs in plant adaptations to salt stress conditions.

Abstract

Agriculture is one of the most important factors contributing to the economic growth of India. Out of the 329 million hectares of India’s geographical area, about 114 million hectares are under cultivation. There are 17 essential elements required for proper plant growth. Of the mineral elements, the primary macronutrients (nitrogen, phosphorous, and potassium) are needed in the greatest quantities and are most likely to be in short supply in agricultural soils. Secondary macronutrients are needed in smaller quantities, and are typically found in sufficient quantities in agricultural soil, and therefore do not often limit crop growth. Micronutrients, or trace nutrients, are needed in very small amounts and can be toxic to plants in excess. Silicon (Si) and sodium (Na) are sometimes considered essential plant nutrients, due to their ubiquitous presence in soils.

The economy of India thrives on agriculture, the most practiced occupation in the country. Agricultural fertilizers are essential to enhance proper growth of plants and crop yield. Recently, farmers have been using chemical fertilizers for quicker and better yield. But these fertilizers endanger ecosystems, soil, plants, human and animal lives. In contrast, naturally grown biofertilizers not only give a better yield, but are also harmless to humans. This chapter aims to study the biofertilizers play a key role for enhancing economic development of sustainable agriculture (EDSA) in comparison to chemical fertilizers. Biofertilizers improve the crop yields, plant resistance, soil health, profit to farmers, and the benefit to cost ratio of biofertilizers were higher than chemical fertilizer, proved that the biofertilizers would lead to better sustainable economic development for the farmers and their country.

Abstract

The concern of global food security is growing day by day as the agriculturally available land is reducing each day with the expansion of industrialization and urbanization. During the course of urban and industrial development, crop production is greatly affected by global warming, contamination of hazardous materials, salinity and drought. To combat against such adversities, scientists have taken several additives measurement like development of transgenic crops, application of indigenous plant growth promoting microbes etc. for sustainable agriculture. Use of plant growth promoting microbes is getting popular day-by-day as they occupy a privilege niche with the autochthonous flora of specific environment. For the expanse of food and shelter, the microbes supply a wide range of plant regulators (e.g. auxins, cytokinins, gibberellins, ABA, phenols, NH₃ etc.), antibiotics, alkaloids, steroids, terpenoids, diterpenes, enzymes (e.g. cellulases, lipases, proteinase, esterases etc.) etc. for overall development of the plant. Apart from growth promotion, it also protects the plants against pathogenic invasion creating a competition with pathogens for nutrition and habitat. In near future, formulation of different plant growth promoting bacteria (like alpha- Azorhizobium, Azospirillum, Ancylobacter, Rhizobium, Bradyrhizobium, Sinorhizobium, Novosphingobium sp., beta- Burkholderia sp., gamma- Acinetobacter, Aeromonas, Azotobacter, Enterobacter, Klebsiella, Pantoea, Pseudomonas, Stenotrophomonas sp. Proteobacteria, Bacillus sp., Paenibacillus sp. and Actinobacteria- Microbacterium sp. etc.) and fungus (Aspergillus, Trichoderma, Penicillium etc.) may reduce the use of pesticides and chemical fertilizer to promote greener ways of crop production.

Abstract

Microbes are ubiquitously found in the environment. Their interaction with other living organisms could either be pathogenic or beneficial in nature. Soil as a rich source of microbes, researchers have extensively studied the plant-microbe interactions. The soil microbes supply the nutrients deficit plants with essential growth elements such as nitrogen, phosphorous, potassium, etc. and improve the texture and quality of the soil. Due to the destructive nature of chemical fertilizers to soil and environment, it was required to generate a more ecofriendly means of increasing the soil fertility. This led to the development of microbes based biofertilizers. The primary benefit of biofertilizers is to promote a healthy soil environment along with supplying essential nutrients to the plant. Again, biofertilizers can be tailor-made according to the specific plant or the climatic conditions. Fungal and bacteria based biofertilizers, either alone or in combinations are formulated for the plants. Lately, liquid fertilizers are increasingly finding their use in the biofertilizer industry due to their ease in manufacture and prolonged effect on plant growth. The scope of this chapter lays on the currently popular biofertilizers and recent trends in the biofertilizer industry.

The Fertilizer (Control) Order

The Fertilizer (Control) Order (FCO) is a set of legally enforceable executive orders issued by the Govt. of India under the Essential Commodities Act, 1955 passed by the Parliament. This order came into force in 1957, essentially to regulate the sale, price and quality of fertilizers in India. Amendments are made from time to time as per the exigencies and need of the hour and therefore a large number of amendments were made over a period of time. Consequently, after an overall review of the various provisions of the order, a revised Fertilizer (Control) Order 1985, was issued, which came into effect on September 25, 1985. The FCO consists of five Schedules comprising of different activities as mentioned in Figure 8.1, besides forms of registrations and appendices.

Schedule I comprises Part A and B. While Part A contains the specifications of different fertilizers (e.g. minimum nutrient content, maximum moisture content, range of physical parameters, maximum levels of impurities/ contaminants, etc.), that can be marketed in India (no material not performs the specifications as in the FCO cannot be sold as fertilizer), Part B lists the tolerance limits in plant nutrients and physical parameters for various fertilizers. Schedule II encompasses again two parts, with Part A describing the procedures for drawal of samples of fertilizers, and Part B describing detailed methods of analysis of fertilizers.

Schedule III encompasses four parts namely, Part-A, Part-B, Part-C and Part-D. While Part-A contains specifications of different biofertilizers, Part-B contains tolerance limits of biofertilizers, Part-C describes the procedures for drawal of sample of biofertilizers, Part-D describes the methods of analysis of biofertilizers. Schedule IV also encompasses four parts. Part-A contains specifications of organic fertilizers, Part-B contains tolerance limits of organic fertilizers, Part-C describes the procedures for drawal of sample of organic fertilizers, and Part-D describes the methods of analysis of organic fertilizers. Schedule V also contains of four parts. Part-A contains specifications of non-edible de-oiled cake fertilizers, Part-B contains tolerance limits of non-edible de-oiled cake fertilizers, Part-C describes the procedures for drawal of sample of non-edible de-oiled cake fertilizers, and Part-D describes the methods of analysis of non-edible de-oiled cake fertilizers.

Fertilizers have played a pivotal role in enhancing food grain production in India especially after the introduction of high yielding and fertilizer responsive crop varieties during the green revolution era. However, there are certain problems associated with fertilizers because of their relatively low nutrient use efficiency (NUE) or nutrient uptake by crops. The fertilizer use efficiency is 30-50% for N, 15-20% for P, 70-80% for K and 8-10% for S. In case of micronutrients, the use efficiency is only 1-2%. The low NUE is typically the result of higher release rate of fertilizers than the absorption rate by plants, and/or transformation of fertilizers/ nutrients to forms that are not bioavailable to crops.

Application of N and P fertilizers at levels exceeding plant requirements due to low acquisition efficiency leads to significant environmental consequences in many parts of the world due to losses, such as nitrate (NO₃^-) leaching, NH₃ volatilization, and nitrous oxide (N₂O) emission. Excessive use of fertilizer N affects the groundwater. Similarly, excessive use of N and P fertilizers leads to surface runoff which in turn causes eutrophication in aquatic ecosystems. These negative environmental consequences associated with fertilizer inputs further emphasize the need of technological approaches to improve nutrient management in modern agriculture. As such, there is great need in developing innovative fertilizers to minimize the losses of nutrients and increase their efficiencies.

In addition, current agricultural activities contribute up to 20-30% to the annual atmospheric emissions of greenhouse gases (GHGs), such as methane (CH₄) and carbon dioxide (CO₂). Even higher contribution is being noted for N₂O (about 60%), which is a potent GHG and catalyst for stratospheric ozone depletion, with more than 300 times the global warming potential than CO₂. Its emission is closely related to mineral fertilizer input. High fertilization rates lead to N and P losses with negative impacts on atmospheric GHGs concentrations and water quality.

There is an urgent need to improve NUE in agricultural systems, and to manage biogeochemical cycles in a sustainable way. This includes the development and application of modern technology as alternatives to conventional fertilization. There is a need to reduce the use of fertilizers/nutrients in agricultural systems by increasing NUE. The recent development in smart fertilizer delivery systems including nanofertilizers or the new generation fertilizers is a good alternative to commercially available fertilizers to improve the NUE and enhance resource utilization. Smart fertilizers may be a solution to enhance food production and environmental quality.

Iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), nickel (Ni), boron (B), molybdenum (Mo) and chloride (Cl) elements are known as micronutrients. The micronutrients are also called as trace elements or minor elements as they are required very small quantities by plants. The elements Fe, Zn, Cu, Mn and Ni are known as micronutrient cations and B, Mo and Cl are known as micronutrient anions and they behave accordingly in soils. Among these elements, Fe content in soil as well as plant is the highest and sometimes higher than phosphorus (P) and sulphur (S). In plant, the concentration of micronutrients often found up to 100 mg kg^-1, except that of Fe and Mn which may go up to 500 mg kg^-1 (dry weight basis). Another element, cobalt (Co) is also regarded to be essential for the growth of certain higher plants and animals, and likely to be included in the list of micronutrients. The importance of micronutrients has been realized during the past four decades when micronutrient deficiencies were observed in most of the soils in our country, where intensive agriculture is practiced.

5.1. Importance of Secondary Nutrients in Agriculture

Secondary nutrients such as sulphur (S), calcium (Ca) and magnesium (Mg) are the macronutrients that are required in relatively large amounts for crop growth. Among the secondary nutrients, Ca is the 5^th most abundant element in the earth’s crust while, Mg and S are ranked 8^th and 13^th, respectively. The average S content of the earth’s crust ranges from 0.06 to 0.10%; whereas, Ca in soil solution of temperate region soils is 30 to 300 ppm and soils of tropical areas is 8 to 45 ppm (Tisdale et al., 1997). In case of Mg, its’ concentration ranges from 5-50 in temperate region and 120-2400 ppm in tropical region. The Ca and Mg are the most abundant cations occupying the exchange sites of the soil colloids. Thus, most soils with the possible exception of highly weathered, leached acid soils, contain enough Ca and Mg for crop growth. In soils, occurrence and reactions of S are different from those of Ca and Mg. The plant available S is SO₄^2- ion which is relatively mobile in soil solution. Like nitrogen (N), S is also subjected to chemical and biological oxidation-reduction reactions. On the other hand, Ca and Mg are much more stable and they exist in soil as Ca²⁺ and Mg²⁺ cations and present in association with soil colloidal fraction similar to that of K. In general, Ca and Mg are the most abundant cations occupying in the exchange site.

Secondary nutrients in soils may be lost due to several reasons such as (i) crop removal, (ii) leaching, (iii) erosion, and (iv) volatilization. The amount of Ca and Mg attain importance in areas where soils are either strongly alkaline or acidic. These soils are often deficient in Ca and Mg. The Ca deficiency is most widespread in acidic soils. The alluvial soils of the Indo-Gangetic Plains (IGP), being neutral to moderately alkaline in reaction, have sufficient bases on their exchange complex and Ca deficiency is, therefore, rarely found in these soils. However, alkali soils may contain inadequate quantities of Ca due to dominance of Na⁺ on the exchange complex. Magnesium deficiency is found in sandy soils with low exchangeable Mg²⁺, acid soils and those with high in native or applied K. Alkali soils have high exchangeable Na⁺. The Ca²⁺ is a suitable ion to replace this Na⁺ from the exchange complex when Ca²⁺ is supplied through gypsum (CaSO₄.2H₂O). The replaced Na⁺ forms Na₂SO₄ which is then leached down to remove the salt away from the root zone of the crops. Gypsum also reacts with Na₂CO₃ to form CaCO₃ and Na₂SO₄ which is leached down the profile. A thorough leaching of the soil with irrigation water should be done after application of gypsum to free it from Na₂SO₄.