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Spatial variability in soil parameters including nutrients has been attributed to the parent material, topography, landforms, cropping pattern, fertilization and manuring practices.. Blanket nutrient recommendations further widen the variability and enhance the risk of soil degradation in terms of soil organic carbon and nutrient mining, acidity, green house gas emission, water and environmental pollution. Unfavorable economics on account of blanket recommendation, adversely influence farmers to increase investments in new crop management technologies. This results in low farm productivity and poor soil health, that jeopardize food security and agricultural sustainability.

Earth provides enough to satisfy every man’s need but not every man’s greed.
—Mahatma Gandhi
The term ‘environment’ is derived from French word ‘environner’, which literary means ‘to surround’ or ‘to encircle’ i.e. everything either living (plants, animals, microbes) or nonliving (soil, water, air, temperature, humidity etc.) surrounding us makes our environment. The universe is full of uncountable number of stars, planet and satellites, which has specific type of environment but earth is the only known planet in the universe that contains life supporting environment. The earth environment is a collective term for the nature or ecosystems, that we use and benefit from on a local, national and global scale. The earth ecosystems provide number of benefits called ecosystem services, free of cost.

In agricultural systems, water quality is usually determined to  assess its suitability for irrigation and/or its use for aquaculture. Analysis of irrigation water is carried out, to know their nutrient load, suitability for irrigation purposes in general and to salt sensitive crops in particular, and their significance as nutrient suppliers as in practical crop production (Tandon,1993). For aquaculture, on the other hand, maintenance of pond environment for survival and growth of aquatic lives, forms the major purpose of such exercises. While both the assessments are mostly governed by some common variables, a few additional attributes are also used for identifying the water quality for these two different purposes. The most important characteristics, that determine the quality of irrigation water are:

Plant analysis includes tests on fresh tissue in the field and analysis of total nutrients in plants in the laboratory. Plant analysis is based on the relationship between nutrients in a plant and nutrient availability in a soil. Plant analysis is not a direct method of soil fertility evaluation, but it can serve as a valuable supplement to soil testing in the task of soil fertility evaluation. Plant analysis is useful in confirming nutrient deficiencies, toxicities and imbalance and identifying hidden hunger. Plant analysis generally provides more current plant-based information than soil testing, entails more effort in terms of sampling, sample handling and analysis and, perhaps, expensive.

A. Soil Sampling

Soil is a store house of several nutrients. These are present in available and reserve forms and a dynamic equilibrium always exists between these forms of nutrients in soil. If the available form of a given nutrient element is depleted by crop uptake or by any other means, there will be immediate replenishment from the reserve source. In this context, it is also appropriate to note that soil is not an eternal source of plant nutrients. In a bid to produce more, soils are exploited very badly and they are gradually becoming deficient in several nutrients. There are several soil related constraints coming in the way of achieving sustainability in crop production.

Soils of India vary widely among different regions. The first soil map of India was prepared and classified on the basis of existing knowledge of Russian pedological principles. Govind Rajan (1971) and Govind Rajan and Rao Gopal (1978) have discussed in detail the later developments on the preparation of soil map of India and giving the equivalents of different soil groups in US Comprehensive System of Soil Classification. Soil resource mapping was initiated in 1986 and in a span of 10 years (1986-1996), a detailed database in terms of soils, their area and extent, characteristics and grouping following soil taxonomy (Soil Survey Staff, 1999) was created. The present chapter on “soils of India-nutrient status and management concerns” takes into account the following aspects:

Plant nutrient disorders result from nutrient imbalances in soils. Nutrients are considered essential for plants, when it satisfies the following criteria (Arnon and Stout,1939):
    1.    The deficiency of the nutrient element makes it impossible for the plant to complete its life cycle
    2.    The deficiency of the element is specific and can be corrected only by supply of that element
    3.    The element is directly involved in the nutrition of the plant

Soil is the most precious basic natural resource, on which depends the security of food, nutrition, income, biodiversity, livelihood and environment. But, its indiscriminate and unscientific management is a major threat to sustainability of agriculture. Over the years, there is a loss in the productive potential of soils, which is attributed to imbalance in nutrient use, mining of nutrients from soil, poor replenishment, loss of carbon, pollution, decrease in biological activities, waterlogging, soil salinity etc. Thus, land use is not commensurate with land capability.

In this section we shall discuss diseases that do not involve any parasitic etiology. Such diseases are now more appropriately called ‘Disorders’. The disorder may be of many kinds but all of them have adverse effects on the normal physiology and total performance of the crop host. They are therefore, more often called ‘Physiological disorders’. Lack of proper soil and environmental conditions, nutrient status, irrigation factors and other parameters for successful crop cultivation may result in such disorders.

3.1 Damping-off Disease of Seedlings

The disease is quite common in nurseries or seedbeds all over the world. It is virtually a serious threat to almost all the nursery crops of vegetables and other crops including tomato, chillies, cauliflower, cabbage, brinjal, cucurbits, tobacco and a number of other crops. The economic importance of the disease is more because it takes the toll of precious seedlings in the very initial stages of the crop cultivation. The seed can become infected with a fungus which may cause darkening and softening of the seed leading to its decay. Similarly, seedlings may also be infected while sprouting or even after emergence. The disease is more serious in heavy soils with poor drainage. Abundant soil moisture with 90-100% humidity and temperature around 200C is favourable for the disease.

2.1 Loose Smut of Wheat

The disease is prevalent in all the wheat growing areas in the world. However, it is a serious problem in humid and sub-humid areas. The incidence of the disease is comparatively more in cooler and humid parts of northern India as compared to the drier and tropical parts of the country. Being a simple interest disease epidemiologically, this is a threat to the cultivation of wheat for seeds. The disease is therefore, dreaded by seed growing agencies who have to treat the seeds with costly chemicals.

A disease is characterized by the sum total of symptoms as expressed by the host plant and the signs of the pathogen involved. As stated earlier, it is the core part of disease diagnosis because in every diseased plant there are some symptoms/signs of the problem regardless of the ease in their visibility. Even in latent infections there are certain clues or at least presence of the pathogen inside the host serves as sign of the pathogen. However, the term, ‘disease’ itself refers to an uncomfortable situation of the concerned host. It reflects in the form of reduction in the vitality and performance of the host to varying degrees depending on the quality and quantity of the factors involved in production of the disease. Study of the characteristics of disease is, therefore, important for its quick and accurate identification.

Chemicals in the form of insecticides ,fungicides and herbicides are extensively used in large numbers in agricultural production. Commercial production of some crops would be impossible if chemicals are not used. Small quantities of chemical residues often remain in such crops and the harvested grains and other products. The residues of pesticides  have been observed in small quantities (ppm level) in soil, water, agricultural produce  and even in animal tissues and their products like meat and  milk. They finally reach the consumer, namely, man (and even animals). Even the environment  is  now-a-days polluted with pesticides and other chemicals harmful to the humans. In view of the importance and seriousness of the problem the residues need to be estimated in the food and non-food products to assess their safety. Analytical details of a few pesticide residue procedures are presented below. Specialized texts may be consulted for  more extensive information.

Plant pigments impart colour to the different components like leaves, flowers, fruits etc. They in turn are responsible for the colour of raw food, we eat. Pigments like chlorophyll, anthocyanins, flavonoids, tannins, xanthones etc. are the different pigments that are present in plants. The primary function of pigments in plants is photosynthesis, which uses the green pigment chlorophyll along with several red and yellow pigments that help to capture as much light energy as possible. Chlorophyll is green in colour. Carotenoids like a, b, and g, carotenoids are yellow in colour. Lycopene is red in colour. Flavones and falvonols are also yellow in colour. Anthocyanins are purple and magenta in colour. Other functions of pigments in plants include attracting insects to flowers to encourage pollination. The assay of pigments is mostly based on their native colour.

Sixteen chemical elements are known to be important to a plant’s growth and survival. The sixteen chemical elements are divided into two main groups: non-mineral and mineral.  The Non-Mineral Nutrients are hydrogen (H), oxygen (O), and carbon (C). These nutrients are found in the air and water.
  
In a process called photosynthesis, plants use energy from the sun to change carbon dioxide (CO₂ - carbon and oxygen) and water (H₂O- hydrogen and oxygen) into starches and sugars. These starches and sugars are the plant’s food. Since plants get carbon, hydrogen, and oxygen from the air and water, there is little the farmers and gardeners can do to control  how much of these nutrients a plant can use.

Alkaloids are of plant origin and are alkaline in reaction. They contain N as part of a hetercyclic ring. They exhibit pharmacological activity. Presently more than 2000 alkaloids are known. They have a lot of uses in medicine and as  flavoring agents, psychoactive agents, pain killers and as pesticides.

Certain constituents associated with plants are toxic. When such items are consumed by men and animals, they become hazardous. Mold growth on food items may be the cause of toxicity. Some of them are called mycotoxins. Aflatoxins are the best examples of such a group of compounds. Sometimes processing also produces some toxins. Fumigants, smoke and some metals (mercury, lead, cadmium, arsenic etc.) used for such purposes are some such toxic constituents. Pesticides used in protecting the crops and grains during storage remain on the items and the residues are hazardous.

Phenol is normally a benzene ring containing an –OH group, and hence an aromatic alcohol. The term “phenolic” refers to similar aromatic compounds with one or more -OH groups. Phenolics constitute one of the most widespread classes of secondary metabolites. Commonly talked about class of compounds like anthocyanins, flavonoids, lignins, tannins, coumarins and chalcones are all phenolic substances. Phenolics are water insoluble substances. However, the water solubility increases with the increase in the number of -OH groups. Phenolics absorb electromagnetic radiation strongly. Many of the phenolics absorb in the visible part of the spectrum (Ex. anthocyanins) and are coloured. Phenolics are produced in plants by 1. Shikimate pathway through phenylalanine (C₆-C3) and 2. Acetate/malonate pathway.

Vitamins are essential organic nutrients required by an organism in small quantities. They are essential since they cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. The term vitamin does not include other essential nutrients like dietary minerals, essential fatty acids, or essential amino acids which are needed in larger quantities than vitamins. The term vitamin is derived from “vitamine,” coined in 1912 by the Polish biochemist Funk. The name is from vital and amine, meaning amine of life. Thirteen vitamins are generally recognized presently. Vitamins are used in small quantities by an organism to keep it in a healthy condition.

Nucleic acids were first discovered in 1868 by Friedrich Meischer. Nucleic acids are high molecular weight polymers that are present in our cells. They store and transfer genetic material from generation to generation. Knowledge of how genes are expressed and how they can be manipulated is becoming increasingly important for understanding of nearly every aspect of biochemistry. These macromolecules p ass on information for cellular growth and reproduction. All the genetic information in the cells is called the genome. Every time a cell divides, the information is copied and passed on to the new cells.