eChapters

3.1 What is environment ?

The word environment is derived from a French word “environne” means to encircle or surround. Environment is defined as the circumstances or conditions that surround an organism or group of organisms. It is also defined as the complex of social or cultural conditions that affect an individual or community. Since humans inhabit the natural world and they build social, cultural and technological world, all constitute important parts of our environment.

Abiotic Environment

The physical or abiotic environment includes all those physical and non-living chemical aspects, which exert an influence on living organisms. The abiotic components are soil, water, air and energy from various sources. These provide both habitation and raw material for the synthesis of organic food.

1.1 Man’s place in Nature

All religions of the world share the view that man is the supreme being among God’s creations. He is the only one among many creatures to enjoy nature’s beauties and bounties. Nature is given to him so as to make responsible and judicious use of it. No religion justifies the most destructive attitude the modern man has developed towards his environment. All religions urge man to treat nature as a God-given gift, stating that God is omnipresent in the manifestations of the nature. It is irreligious for man to expect miracles and exploit the environment. Man must be confronted with the reality that struggle is essential for life rather than “struggle for existence.”

In nature, microbes are found as a mixed population. The types that encounter the most favourable environmental and other growth conditions emerge in abundance while others that find the environment less favourable are fewer in number. However, for any kind of study on them or for their use as a pure species, they have to be separated from other species. The nutritional media or culture media are different for different species. As the medium is specific for certain species, it checks or restricts the growth of other microbes for which it may not be suitable. However, some growth of and contamination by unwanted species may occur.

Biofertilizer is still an unclear term. It can be easily found that biofertilizers are identified as plant extract, composted urban wastes, and various microbial mixtures with unidentified constituents, and chemical fertilizer formulations supplemented with organic compounds. Likewise, the scientific literature has a very open interpretation of the term biofertilizer representing everything from manures to plant extracts.  Quality control of biofertilizers involves several major aspects such as isolation and identification of various strains, screening of the pure isolated strains, fermentation and quality control and finished product.

14.1 Introduction

The green revolution brought amazing consequences in food grain production but with insufficient concern for agricultural sustainability. The availability and affordability of fossil fuel based chemical fertilizers at farm level in India have been ensured only through imports and subsidies which are largely dependent on GDP of the country. Dependence on chemicals for future agricultural needs would result in further loss in soil health, possibilities of water contamination and calculated burden on the fiscal system. Indiscriminate synthetic fertilizer usage has polluted the soil, water basins, destroyed micro-organisms and eco-friendly insects, made the crop more susceptible to diseases and depleted soil fertility at the primary levels as of today (Pindi, 2012). India is an agricultural based country.

Earthworms have been on the earth for over 20 million years. In this time they have faithfully done their part to keep the cycle of life continuously moving. Their purpose is simple but very important. They are nature’s way of recycling organic nutrients from dead tissues back to living organisms. Many have recognized the value of these worms. Ancient civilizations, including Greece and Egypt valued the role earthworms played in soil. The Egyptian Pharaoh, Cleopatra said, “Earthworms are sacred.”

Most trees legumes thrive in tropical regions but N2 fixing non leguminous trees are prevalent in temperature conditions. Callatiam and coworkers from U.K. cultivated Frankia for the first time in 1978 in pure culture. A number of non-leguminous shrubs and trees as Alnus, Myrics, Hippophae, Casuarina and Elaeagnus are nodulated by N₂ fixing Actinomycetes, Frankia with Frankiaceae (Actinomycetes), the only acyinomycete reported to fix nitrogen to date. The so called actinorhizal plants include 7 orders, 8 families, 17 genera and 173 species of dicotyledons plants reported by Gaur, (2010), whereas 200 plants and 23 genera were reported by Diagne et al. (2013). Some of the important non-leguminous families and genera are given in Table 12.1.

11.1 Introduction

Our Country is a fast developing nation for the overall development and has proved that the country which was known for a begging bowl for food grains has turned up towards self-sufficiency and also has excess production to feed the present level of population. From about 50 MT of food grain production in 1950-51, harvest in 2010-11 reached over 241 MT, highest ever along with high production of fruits, vegetables, milk, egg and fish. This increased food production in the country has mainly been achieved through productivity gains, as the net sown area has remained static for the last four decades.

Phosphorus is the second important key element after nitrogen as a mineral nutrient in terms of quantitative plant requirement (Donahue et al., 1990), which is required in optimum amount for proper growth of plants and soil micro-organisms. Being a constituent of ATP, it is involved in various processes such as cell division, energy transduction through photosynthesis and biological oxidations and uptakeof nutrients. The average soil contains 0.05% phosphorus, but only one tenth (1/10) of this is available to plants due to its poor solubility and chemical fixation in soil (Barber, 1984). About 98% of Indian soils have inadequate supply of available phosphorus (Ghosh and Hassan, 1979). A survey of Indian soils showed that out of 363 districts, only 2.2% were high, 51.5% medium and 46.3% were low in phosphorus content (Ghosh, 1982).

BGA belong to a class of prokaryotic photosynthetic microorganisms also known, as cyanobacteria are capable of fixing atmospheric nitrogen aerobically. Most abundantly found in tropical zone, never form fibrous growth and are enveloped by a sheath. The trophic independence of algae for C and N makes them responsible for a natural fertility buildup of rice field soils. The nitrogen fixing ability of BGA was first recognized by Frank and Prantil in 1889. The occurrence of the BGA in the rice field was reported by FE Fritsch in 1907.

Azospirillum is a spiral-shaped nitrogen fixing bacterium. It also produces hormones and vitamins. Important species are Azospirillum brasilense and Azospirillum lipoferum. It is widely distributed in soils and grass roots.The genus Azospirillum belongs to family Spirillaceae with four commonly available species viz. A. brasilence, A. lipoferum, A. amazonense and A. halopraeferens or A. seropedicae (Fig. 8.1).

The first species of the genus Azotobacter, named Azotobacter chroococcum family Azotobacteriaceae, was isolated from the soil in Holland in 1901. Azotobacter represents the main group of heterotrophic free living nitrogen-fixing bacteria principally inhabiting neutral or alkaline soils. Azotobacter chroococcum and Azotobacter agilis were studied by Beijerinck (1901). In subsequent years several other types of Azotobacter group have been found in the soil and rhizosphere such as Azotobacter vinelandii, Lipman (1903); Azotobacter beijernckii, Lipman (1904); Azotobacter paspali, Döbereiner (1966), Azotobacter nigricans, Krasil’nikov (1949); Azotobacter armenicus, Thompson and Skerman (1981); Azotobacter salinestris, Page and Shivprasad (1991). A. paspali while A. agilis was categorized  under the genus Azomonas (Table 7.1).

Azolla is a free-floating water fern that floats in water and fixes atmospheric nitrogen in association with nitrogen fixing blue green alga Anabaena azollae. Azolla fronds consist of sporophyte with a floating rhizome and small overlapping bi-lobed leaves and roots. Rice growing areas in South East Asia and other third World countries have recently been evincing increased interest in the use of the symbiotic N2 fixing water fern Azolla either as an alternate nitrogen sources or as a supplement to commercial nitrogen fertilizers. Azolla is used as biofertilizer for wetland rice and it is known to contribute 40-60kg N/ha per rice crop. The agronomic potential of Azolla is quite significant particularly for rice crop and it is widely used as biofertilizer for increasing rice yields. Rice crop response studies with Azolla biofertilizer in the People’s Republic in China and in Vietnam have provided good evidence that Azolla incorporation into the soil as a green manure crop is one of the most effective ways of providing nitrogen source for rice.

The role of leguminous plants in improving the soil fertility is known for centuries. The nitrogen uptake in legumes by some unknown process was demonstrated through agronomic experiments by J.B Boussingault in 1838, which was opposed by Liebig and others. The presence of bacteria in the roots nodules of legumes was observed by P.G Lachmann (1858). M. Woronin (1866) further examined and observed them to be rod-shaped and motile.

Under agricultural conditions, the nitrogen removed is usually greater than the nitrogen input. To maintain fertility, nitrogen must be returned to the soil. This takes place mainly by biological nitrogen fixation, which is responsible for the major reduction of dinitrogen to ammonia that is used by the plants. Biological nitrogen fixation accounts for most of the fixation of atmospheric nitrogen in to Ammonium, thus representing the key entry point of molecular nitrogen into the biogeochemical cycle of nitrogen (Fig.4.1). Some bacteria can convert atmospheric nitrogen into ammonium. Most of this nitrogen fixing prokaryote is free living in the soil.

Biofertilizers can be defined as the preparations containing strains of micro-organisms which can augment the microbiological process viz. nitrogen fixation, phosphate solubilization or mineralization, excretion of plant growth promoting substances or cellulose or lignin biodegradation in soil, compost or other environments. Biofertilizers can be divided into nitrogen fixing bacteria, phosphate solubilizing and mobilizing microorganisms and organic matter decomposers as (Table 3.1 and Fig. 3.1):

On the basis of Nitrogen Fixation: On the basis of N₂ fixation, they are divided in to two sub categories as

2.1 Introduction

Microbes are the oldest form of the life on earth. These organisms date more than 3 billion years to a time when they were discovered with oceans. They are so tiny in size that million microbes can fit into the eye of a needle. Without microbes, we can’t live. Thus, understanding microbes is vital to understanding past and future. Microbes play many roles in the earth’s environment recycling dead plant and animal matter through the soil, removing CO2 from the atmosphere by photosynthesis in the oceans and nitrogen from the atmosphere to form nitrogenous fertilizers plants. Microbes play an important role in nutrient recycling, management, organic matter, decomposition and increasing the crop productivity and quality and protection against diseases (Panwar et al., 2009). Over the past century, many of the basic scientific principles of plant nutrition and soil fertility have been explained. In developed countries, inorganic chemical fertilizers have been widely accepted as a major source of improving and maintaining soil fertility.

Agriculture is undoubtedly the largest livelihood provider in rural India. As we enter a new post WTO Scenario and IT revolution, new inventions are happening day by day in every sphere. Agriculture is not culture now, it is agri business! Agriculture constitutes over 25% of India’s GDP. In recent years, much emphasis has been given by the Ministry of Agriculture on commercializing agricultural production in the country. Adequate production and distribution of food has become a high priority and global concern. In the fast changing world and increasing competition in a globalized economy, there is a need for exploiting the available resources to the maximum level and use of best technologies available world over, to cope up with domestic demand of food and also to target export market. This will be particularly relevant in South India, where farmers grow a number of crops, but have technical constraints in enhancing production and productivity because of inadequate exposure to high technology & inputs coupled with advanced production practices, logistics and marketing. In addition, shortage of labour is a major concern for progressive farmers of South India who are ready to offer more wages to labourers. Therefore, they are forced to become machinery-dependent in their farm operations. As a result, Southern India is emerging as one of the hottest destinations as well as a strong market with buying potential for farm machinery and equipment.

The market of organic products is growing globally every year. This organic market expansion makes it possible for farmers to reap the benefits of a trade with relatively high price premiums. Organic farming is carried on in almost all countries of the world. The share of organic farms in overall farmland and in terms of numbers of holdings is growing continuously. The market for organic products is also growing very rapidly, not only in Europe, North America and Japan, where the largest markets are to be found, but also in many emerging economies in transition. In India, an organic movement is now emerging on different levels i.e. producer groups, trainers and advisors, certification bodies and processors and traders.