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Preface Mineral nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, and other micronutrients are essential for plant growth and food production. They ultimately contribute towards adequate nutrition for human beings. Presently, we face a glaring contrast of insufficient use of nutrients on one hand and excessive use on another. Nutrient Use Efficiency (NUE) represents a key indicator to assess progress towards better nutrient management. A goal for a 20% relative improvement in NUE by 2020 would lead to an annual saving of around 20 million tons of nitrogen, and equate to an initial estimate of improvement in human health, climate and biodiversity worth around $170 billion per year.  Humans have been altering the world’s biogeochemical cycles for many millennia to ensure food and energy security. Many of these anthropogenic activities modified the nutrient cycles of major and micro nutrients of the world.  The scale of these changes has massively accelerated since the industrial revolution throwing the equilibrium into disarray. The rates of anthropogenic carbon dioxide and other green-house gas emissions have increased substantially since 1750 (IPCC, 2007). The greenhouse gases include both methane, especially from fossil fuel sources and livestock, and nitrous oxide, which is particularly emitted from agricultural soils.

Plants require altogether 17 essential elements to nourish themselves and to complete their reproduction and life cycle. Among them nine elements are required in large amounts for their growth, the so called macro nutrients like C, H, O, N, P, K, Ca Mg and S.  The former three elements (C, H and O) are available to the plants through air and water over which we have relatively little control either in their application rates or uptake into plant system.

Soil is a major source of nutrients needed by plants for growth. The three main nutrients are nitrogen (N), phosphorus (P) and potassium (K). Together they make up the trio known as NPK. Other important nutrients are calcium, magnesium and sulfur. Plants also need small quantities of iron, manganese, zinc, copper, nickel, chlorine, boron and molybdenum, known as trace elements because only traces are needed by the plant. The primary nutrients are nitrogen, phosphorus and potassium, because they are required in larger quantities than other nutrients. These three elements form the basis of the N-P-K label on commercial fertilizer bags. As a result, the management of these nutrients is very important. However, the primary nutrients are no more important than the other essential elements since all essential elements are required for plant growth. Remember that the ‘Law of the Minimum’ tells us that if deficient, any essential nutrient can become the controlling force in crop yield.

To meet the food needs of the burgeoning population, India will need to produce 300 million tonnes of food grains by 2020. At present more than 75% of the total food grains produced in the country are of rice and wheat. Use of nitrogenous fertilizers has contributed much to the remarkable increase in production of rice and wheat in India that has occurred during the past three decades. During the last half-decade or so while fertilizer N consumption is touching new heights, the production of both rice and wheat is showing a trend of plateauing. In fact, fertilizer N efficiency of food grain production expressed as partial factor productivity of N (PFPN) has been decreasing exponentially since 1965. The PFPN is an aggregate efficiency index that includes contributions to crop yield derived from uptake of indigenous soil N. fertilizer N uptake efficiency, and the efficiency with which N acquired by the plant is converted to grain yield. A decrease in PFPN occurs as farmers move yields higher along a fixed N response function, unless other factors shift the response function up. In other words, an initial decline in PFPN is an expected consequence of the adoption of N fertilizers by farmers and not necessarily bad within a system’s context

Introduction Agricultural lands in India have mostly low native soil fertility. On these soils there must be a regular application of nutrient inputs through chemical fertilizers and/or organic manures for a successful and sustained crop production to replenish soil nutrient reserves depleted by crop removal and other losses. It is essential to recognize that even in agricultural production systems with relatively low productivity level, the quantity of nutrients available for recycling through plant and animal residues is not enough to compensate the amount being removed by crops. Under these circumstances mineral fertilizers play a key role in those areas having low fertile soils by increasing agricultural production to meet out growing food demand. Chemical fertilizers are the major contributors as source of plant nutrients to enhance crop production and also to maintain soil productivity.

Phosphorus (P) is a critical nutrient in crop production, due to its low bioavailability in soils (Feng et al., 2004). Phosphorus is the vital component of DNA, RNA, ATP and photosynthetic system and catalyses a number of biochemical reactions from the beginning of seedling growth through to the formation of grain and maturity. Many factors influence soil P availability like type of parent material from which the soil is derived, degree of weathering and climatic conditions. In addition to this, erosion, crop removal and phosphorus fertilization and soil phosphorus levels also affect P availability in soil. Rock phosphate is the key raw material used for manufacturing phosphatic fertilizers on which the food production depend.

For efficient nutrient use, most important factors are the timely supply/recycling of adequate amount of nutrients to the production system and its retention and release by soil for timely and ready availability in the root zone for its mobility to the plant in the presence of optimum moisture content in the soil. For keeping the applied nutrients retained in the root zone one has to reduce the soil erosion and leaching losses through technologies available in hand which include direct measures of soil and water conservation and maintain the soil aggregation and porosity through suitable tillage and organic residue recycling. For movement of nutrients into plant system we need to ensure optimum soil moisture content through water management.

Meeting food demand and escalating food prices are serious issues, as current food scenario indicate that crop demand will increase by 100 to 110% from 2005 to 2050 at global level (Tilman et al., 2011). Precision use of fertilizer is the crucial for achieving sufficient food production for growing population. It is costly input to produce and apply, both financially and environmentally. Fertilizer consumption measures the quantity of plant nutrients used per unit of arable land.

Preamble Crop nutrient management in the climate change scenario is carried out with the basic understanding of nutrient concentrations in soils, plants and their transformations but these strategies might not apply under changed climate conditions where there is an overall change in the environment. It is understood that nutrient acquisition by plants from the soil is closely associated with overall biomass and strongly influenced by root foraging area. It is speculated that change in soil factors due to climate change could restrict root growth and nutrient stress would also occur. Plant size may also change but nutrient concentration may not change; therefore, nutrient removal will scale with growth. The interaction of mineral behavior in the soil with global climate change variables is poorly understood.

The concept of sustainability in agricultural system All forms of production systems exist today, from nomadic herding to continuous, intensive monocrop systems. Their distribution is determined by soil and climate conditions, and by social and economic factors. In very general terms, as one moves from drier to wetter areas, pastures and animals become less important, and trees more so. Population density is greatest where soils are most fertile, and management systems the most intense. Most production systems have evolved so that they are sustainable in terms of the environmental conditions prevailing at the time—including the level of demographic pressure.

Since the 1960s, the world population has doubled from three to seven billion, and this trend will persist in the coming decades. Because of this rapid expansion, a massive increase in crop production is required to meet the food and energy demands of future generations. Potassium is the third important plant nutrient after nitrogen and phosphorous. It is seventh most abundant element in the lithosphere. Being chemically active metal, it is never found in its pure elemental state in nature. Potassium (K) plays a particularly crucial role in a number of physiological processes vital to growth, yield, quality, and stress resistance of all crops. The K content of Indian soils varies from less than 0.5–3.0%. The average total potassium content of those soils is 1.52% (Mengel and Kirkby 1987).

Nanotechnology is a field of study which deals with materials at nano-scale like nanometer which is one billionth of a meter (1 nm = 10-9 meter). At nano-scale, physics, chemistry and biology converge towards the same principles and tools. Nanotechnology is domain in science and technology, which is multidisciplinary in nature and any scientist, engineer, medical doctor can do research on nanotechnology. Presently, it is more of a science and less of a technology because of a lack of proper tools for studying the properties of nano-material. Nano-particles (NPs) are materials that are small enough to fall within the nanometric range, with at least one of their dimensions being less than a hundred nanometres. This reduction in size brings about significant changes in their physical properties with respect to those observed in bulk materials. The presence of naturally occurring NPs is implicated in interplanetary and interstellar space (Hochella Jr, 2002) as well as our earth in which life from the beginning has evolved in their presence (Becker and Reitmeijer, 2006). Currently it is observed that NPs can be synthesized from many biological organisms including plants.

Through green revolution, we have developed high yielding varieties albeit with high nutrient requirements putting much more reliance on chemical fertilizers. The major challenge facing plant biology right now is to improve crop production and to feed an expanding world population. This is against a background of pressure on agricultural land use and climate change having negative impacts on growing conditions. The adverse effects of agriculture, and specifically fertilizer use, include damage to the environment, a large carbon footprint for the manufacture and use of agrochemicals, and the utilization of non-renewable resources. One solution is to increase the area of land for agriculture, as well as increasing production while maintaining the current rate of inputs; however, this is predicted to have substantial negative impacts on the environment (Tilman et al., 2002), is unsustainable in terms of phosphate use, and would have a huge economic footprint in terms of energy demands for nitrogenous fertilizer production. The challenge is to increase yield, decrease inputs, and improve resistance to abiotic and biotic stresses. Improving crop nutrient use efficiency ideally requires an understanding of the whole system, from the macro (agro-ecosystem) to the molecular level.

Nutrient supply is one of the major inputs for agricultural crop production in a sustainable manner. The factor productivity of inputs especially the fertilizers in agriculture was found to be in a declining phase during the last four decades. This had a detrimental effect on annual compound growth rate of major crops as wells on soil quality. The current status of nutrient use efficiency in different cropping system is low in case of major macro nutrients likes Nitrogen (30-50%) and Phosphorus (15-20%). Because 50-70% of the nitrogen applied using conventional fertilizers, with particle size dimensions greater than 100 nm, is lost to the soil due to leaching, nutrient utilization efficiency (NUE) by plants is low. Attempts to increase the NUE in conventional fertilizer formulations have thus far resulted in little success. On the other hand, the emerging nano strategies indicate that, due to the high surface area to volume ratio, nano fertilizers are expected to be far more effective than even polymer-coated conventional slow-release fertilizers. In this context, nanotechnology offers an important role in improving the nutrient use efficiency of agricultural systems.

In plants, mineral uptake is the process in which minerals enter the cellular material, typically following the same pathway as water. The most normal entrance portal for mineral uptake is through plant roots. Some mineral ions diffuse in-between the cells. In contrast to water, some minerals are actively taken up by plant cells. Mineral nutrient concentration in roots may be 10,000 times more than in surrounding soil. During transport throughout a plant, minerals can exit xylem and enter cells that require them. Mineral ions cross plasma membranes by a chemiosmotic mechanism. Plants absorb minerals in ionic form: nitrate (NO3-), phosphate (HPO4-) and potassium ions (K+); all have difficulty crossing a charged plasma membrane. It has long been known plants expend energy to actively take up and concentrate mineral ions. Proton pump hydrolyzes ATP to transport H+ ions out of cell; this sets up an electrochemical gradient that causes positive ions to flow into cells. Negative ions are carried across the plasma membrane in conjunction with H+ ions as H+ ions diffuse down their concentration gradient.

Nutrient use efficiency of crops is being improved through temporal and spatial management of the form and amount of nutrient inputs as being demonstrated by various agronomic practices. In addition, understanding of the genetic basis of nutrient efficiency would lead to the development of nutrient use efficient varieties thus reducing the application of nutrients. Earlier studies on genetics of nutrient use efficiency were limited as increasing productivity with heavy nutrient inputs was the main focus. But in the backdrop of environmental degradation due to the excessive nutrients and its impact in climate change, nutrient use efficiency in crops is need of the hour for sustainable and eco-friendly agriculture.

Low bioavailability of phosphorus (P) in soils is one of the major limiting factors influencing crop production throughout the world. Plants, however, are known to possess potential adaptive mechanisms at morphological, physiological, biochemical, and molecular levels to overcome P deficiency (Vance et al., 2003). Such adaptive mechanisms mainly include an increase in total root length and root hair growth (Bates and Lynch, 2000), enhanced organic acid (Singh and Pandey, 2003), acid phosphatase (Pandey, 2006) and ribonuclease (RNase) secretion into the rhizosphere (Hocking, 2001), increase in expression of proteins such as phosphatase, inorganic phosphate (Pi) transporter, RNase and phosphoenolpyruvate carboxylase (PEPcase) in plant tissues.

World population is expected to cross 8.5 billion by 2025 and it will be a gigantic task to produce enough to meet the future food demand by growing same set of crop varieties on anticipated reduced area. Most of the land that could be brought under cropping has been utilized with exception of some land in Sub-Saharan Africa and South America (Borlaug and Doswell, 1993). Therefore, it is warranted to produce more from less land, less water and less inputs which can be achieved by enhancing the efficiency of production system by devising more efficient crop management practices and developing input use efficient cultivars.

The diets of over two-thirds of the world’s population lack one or more essential mineral elements. This can be remedied through dietary diversification, mineral supplementation, food fortification, or increasing the concentrations and/or bioavailability of mineral elements in produce (biofortification) involving aspects of soil science, plant physiology and genetics underpinning crop biofortification strategies, as well as agronomic and genetic approaches currently taken to biofortify food crops with the mineral elements most commonly lacking in human diets: iron (Fe), zinc (Zn), copper (Cu), calcium (Ca), magnesium (Mg), iodine (I) and selenium (Se).

Under natural conditions, the largest source of labile carbon (C) inputs to the soil is root exudates (Bertin et al., 2003; Hutsch et al., 2002; Kuzyakov 2002). Roots exude a variety of low-molecular weight organic compounds, including sugars, amino acids, organic acids (Bertin et al., 2003), but also contain hormones, vitamins, amino compounds, phenolics and sugar phosphate esters (Uren, 2001). These compounds are rapidly metabolized; for example, Hutsch et al., (2002) found that 64–86% of maize root exudates were respired by soil microorganisms. The effect of root exudates depends on the distance that they can diffuse away from rhizoplane (Gupta and Mukerji, 2002).

Introduction   Climate change is a result from emission of greenhouse gases (e.g. CO2, CH4, N2O, etc.) that will cause atmospheric warming (IPCC, 2007). Climate change may be due to natural internal processes or external forcing such as modulations of the solar cycles, volcanic eruptions, and persistent anthropogenic changes in the composition of the atmosphere or in land use. Human induced changes in atmosphere composition are a major concern. Burning of fossil fuels, like oil, coal, and natural gas is adding CO2 to the atmosphere.

Introduction The term nitrogen use efficiency, (NUE) is widely used in research to cover problems in use of N in crop production systems. It describes N input/output ratio at different scales starting from farm levels to regional levels. An analysis of of NUE is helpful to analyze possible options for improving NUE in different crops and cropping systems. NUE at crop scale may be defined as the ratio between the yield and the N uptake by the crop. This ratio is sometimes called as the physiological NUE or utilization efficiency. High NUE can be achieved by high harvest index and a high productivity of dry matter per unit N uptake. The second component of NUE is the ratio of plant N uptake to the potentially available N. This ratio is called uptake efficiency or available N use efficiency. Enhancing the uptake efficiency of the crop is possible through enhancing the physiological uptake efficiency of the roots, enhancing root length density and matching the N supply and demand of a particular crop.

Introduction The soil is the largest terrestrial pool of organic carbon, about 1150 Pg (1Pg = 1015 g) compared with about 700 Pg in the atmosphere and 600 Pg in land biota (Lal and Kimble,1997). Organic carbon level of soils reaches a fixed equilibrium that is determined by a number of interacting factors such as precipitation, temperature, soil type, tillage, cropping systems, fertilizers, the type and quantity of crop residues returned to soil, and the method of residues management. In the temperate climate, it may take about 50 years for the organic carbon of soils to reach a new equilibrium level following a change in management. However, this period is much shorter in a semiarid and arid climate and also in tropical climate like India.

Introduction Organic matter in soil is the key to soil health. SOM improves many physical, chemical, and biological characteristics of the soil, including water holding capacity, cation exchange capacity, pH, buffering capacity, and chelating of micronutrients. Furthermore, well decomposed SOM improves soil structure by increasing aggregation, enhances biological activities in the soil, slowly releases nutrients, and suppresses some diseases. A loss of SOM can lead to soil erosion, loss of fertility, compaction, and general land degradation.

Introduction Our soil resource is generally taken for granted for many uses. Most people don’t realize the importance of the resource and that it is fundamental for farming/agriculture. Without high quality soils, agriculture production cannot be achieved on a sustainable basis to meet ever growing demand. Thus, conservation agricultural practices are capable of improving soil health by increasing organic carbon, aggregation, improving infiltration and minimizing erosion losses.

Introduction Use of FYM, crop residues, leaf fall, root deposition etc. has been part and parcel in agriculture. These material undergoes microbial decay over the time slowly and the major portion of it finds way back to the atmosphere. Not only that, residue burning traditionally provides a fast way to clear the agricultural field of residual biomass, facilitating further land preparation and planting. However, in addition to the loss of valuable biomass and nutrients, biomass burning leads to release of toxic gases including GHGs.

According to Planning Commission Report (2014), India generates about 62 million tons of municipal solid wastes (MSW) every year from urban cities. There has been a significant increase in municipal solid waste generation in India in the last few decades. This is largely due to rapid population growth and economic development in the country (Annepu, 2012). Solid waste management (SWM) has become a major environmental issue because of serious environmental implications like global warming (through green house gases emission) and contamination of toxic pollutants (like heavy metals) in surface and groundwater bodies. Solid waste management is one of the essential services to be provided by municipal authorities in the country to keep urban areas clean. Out of total waste generated in India, only 12.45% waste is scientifically processed and rest is disposed in open dumps (CPCB Report, 2013). Although, incineration of solid wastes is being followed in many places for energy production, composting is considered most environment friendly method of SWM as it promotes recycling of nutrients in crop production.

Fertility of a soil can be assessed by analyzing various available nutrients present in the soil. Fertilizer recommendations for various crops and cropping sequences can be made on the basis of fertility status of a soil. Besides this, problematic soil can be ameliorated on the basis of soil test values. Among the various steps of soil testing programmes, soil sampling is the most vital step.

Soil organisms play vital role in agri-ecosystem processes such as nutrient cycling, soil detoxification and organic matter decomposition. They also influence water infiltration by improving soil porosity through production of polysaccharides. Rhizosphere microorganisms help plant to acquire macro and micronutrients, produce phytohormones for better crop establishment. Soil microbes process organic matter to provide a balance of minerals and nutrients which are utilized by plants to achieve healthy and vigorous growth. Microbes also colonize on plants parts and offers protection by excluding many plant pathogens. They are the basic indicators of soil fertility and are responsible for maintaining a hospitable environment for crop growth.

A new analytical technique called inductively coupled plasma emission spectroscopy has been used for simultaneous multi element analysis of biological materials and soils (Hou and Jones 2000; Wikipedia, 2010; Bradford and Cook, 1997). This technique offers advantages over AAS and other multi-element methods because matrix problems are eliminated or minimized through use of the high temperature argon plasma. Apart from multi- element capability at all concentration levels, plasmas are noted for relative freedom from chemical and ionization interferences that are common with AAS, and detection limits are equal to or better than AAS, depending on the element to be analyzed. Elements such as Al, P, S and B, which are either poorly measured at low concentrations or not possible by AAS, are readily determined with higher sensitivity by ICP.

Introduction After the Second World War, isotopes have become available in sufficient quantities for use in different fields of scientific research. There has been tremendous increase in the number and scope of applications of these new tools and agricultural research is no exception. During the last quarter of a century, the use of isotopes and radiations has become one of the important tools in the solution of practical problems in the area of soil-plant nutritional studies throughout the world. In India, these studies were initiated as early as 1955 with the establishment of the Radiotracer Laboratory at the Indian Agricultural Research Institute, New Delhi. The use of these nuclear tools got further fillip in our country with the establishment of the Nuclear Research Laboratory at the Indian Agricultural Research Institute, New Delhi in 1968 as a UNDP Project on Nuclear Research in Agriculture, operated by the Joint FAO/IAEA division of the International Atomic Energy Agency. Also, the agriculture division of Bhabha Atomic Research Centre, Mumbai and the special radioisotope laboratories established by several agricultural universities had made significant contributions to the use of isotopes and radiations in agricultural research.

Knowledge of structure is a basic element of biological research. Understanding structures of various degrees of complexity contributes to a better understanding of function, ontogenetic and physiologic processes, as well as phylogenetic relationships. In biological sciences, ultrastructure refers to the nanostructure of a biological specimen, such as a cell, tissue, or organ, at scales smaller than can be viewed with light microscopy. Electron microscopy (EM) has a great impact on our knowledge and understanding of ultrastructure.

About the Editors Dr. R. Elanchezhian was born on 1971 in Vandal village in Sivaganga Distt. of Tamil Nadu. He studied B.Sc. (Agri.) during 1988 to 1992 from Tamil Nadu Agricultural University (Coimbatore), and M. Sc. (Plant Physiology) and Ph. D. (Plant Physiology) in 1995 and 1998, respectively, from IARI, New Delhi. He joined ARS (ICAR) in 1998 and started his career at ICAR-CIARI, Port Blair, Andaman & Nicobar Islands as a Scientist/Scientist Sr. Scale (1998-2006). Then as a Sr. Scientist he worked at ICAR-RCER, Patna (2006-2012). Presently he is working as Principal Scientist at ICAR-IISS Bhopal, Madhya Pradesh, India, since February 2012. During his scientific career at ICAR-CIARI, Port Blair he worked on physiological and biotechnological management of abiotic/biotic stresses in rice, solanaceous vegetables with emphasise on salinity, drought and insect resistance. He has generated promising somaclones of rice and solanaceous vegetables with improved agro-morphological traits besides having moderate tolerance towards salinity and bacterial wilt and insect borer. He was involved in sustainable management of plant biodiversity of A&N Islands including collection, characterization, conservation and enhancement of ecologically and economically important plant species. He has got registered several indigenous germplasms of rice with NBPGR New Delhi. At ICAR Research Complex for Eastern Region, Patna he continued the work on biotechnological and physiological management of abiotic stress tolerance with special reference to submergence and drought stress conditions.