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There is an increased use of Glass houses and poly houses in commercial agriculture. The glass houses and poly houses provide a controlled environment for plants throughout the year. Some of the aspects of related to the advantages of Glass houses and poly houses are highlighted in the following text:
9.1. Glass houses
Glass houses are also referred as greenhouses. The glass prevents harmful ultraviolet radiations. The glass is transparent to solar radiations of wavelengths up to 300 nm and does not allow long-wave radiations to pass through it (Fig.9.1). Therefore, the Glass houses maintain higher temperature and high relative humidity during daytime as well as nighttime and offer the following advantages:
9.1.1. Controlled Environment: Glass houses facilitate regulation of temperature,
humidity, and light intensity, creating optimum environment for growing various plant species. This is especially beneficial for tropical and sub-tropical plants that require specific conditions to grow and survive.
9.1.2. Protection from Pests and Diseases: The enclosed glass house protects
plants from pests and diseases. The glass house also protects the plants from harsh weather conditions thereby minimizing risk of infestations and environmental stresses. Fig. 9.1: Microclimate management in Glass house
9.1.3. Extended Growing Season: By maintaining stable climate, glass houses
enable cultivation of plants that may not survive outdoors in certain climates thereby extending the growing season for sensitive species.
9.1.4. Research and Conservation: Botanical gardens often use glass houses for
research purposes, studying plant growth, genetics and breeding. The glass houses will also serve as a means for conserving rare or endangered plant species by providing stable environment for propagation. The advantage of glass houses is that the structure has long life span.
9.2. Poly houses
The poly houses are constructed using polythene material. The poly houses protect the plants from wind, cold weather, hail storms, extreme temperatures, insects and pests. The polythene house farming is a popular greenhouse technology due to its low cost of construction and maintenance. Generally, heat accumulation (70 to 75 per cent of solar energy) takes place inside the polyhouse. Solar radiation is allowed to pass through the polythene material and the long wave radiation cannot escape through polythene. The benefits of poly houses are:

There is growing demand for increasing fruit production as fruits are considered to be healthy, nutritious and easy to digest. Fruits are natural foods and have export potential as well as provide opportunities for increasing employment by establishing fruit processing industries. Some of the fruits can be grown around the year where as some fruits are of seasonal in nature. Usually, the fruit cultivation is undertaken by establishing orchards. In case of orchards, wrong decisions in planting may result in huge loss and therefore right method of planting is the key factor for establishing orchards.
The fruit crops are of three types depending on the adoptability to the climate of the region and are grouped as
• tropical fruits
• sub-tropical fruits
• temperate fruits
The microclimate of the orchards depends upon
• height of the plants/trees
• horizontal spread
• canopy architecture
• spacing/plant density
• age of plantation
• seasonal weather
15.1. Tropical Fruits
The tropical fruits require higher temperature throughout the year. The crops do not require low temperature for breaking dormancy and for flowering. The plants are ever green and grow throughout the year. There plants are well adopted to regions where the minimum temperatures are more than 10°C and very sensitive to frost. There are grown in tropical regions between 23°N to 23°S latitudes. The optimum maximum temperature for growth and development ranges from 30 to 37°C.
15.2. Sub-Tropical Fruits
The sub-tropical fruits perform better between temperate and tropical climates as the plant requires both high and low temperatures. Some of the fruit crops are green and some of those are deciduous. The temperate fruit crops are very sensitive to frost. The sub-tropical fruit plants break dormancy of flower buds

Microclimate under irrigated conditions and dryland conditions can differ significantly due to variations in water availability, which influences several environmental parameters such as temperature, humidity, soil moisture, and vegetation cover. The crops are grown both under irrigated and dryland / rainfed situations. The major difference between irrigated and dryland conditions is availability of water. In irrigated areas, the crops are regularly provided with water through irrigation at regular intervals. Under dryland situations, the water availability to the crops depends upon the rainfall and/or stored soil moisture. Under irrigated situations, there are two different possibilities as indicated below:
• vast stretch of irrigated areas
• isolated pockets of irrigated areas in predominantly dry areas. In dryland areas the following possibilities exist:
• humid and moist sub-humid areas where predominantly rice based cropping systems are adopted during rainy season
• per-humid areas where plantation crops and rice grown during rainy season.
• dry sub-humid areas with rice based cropping systems in low lands and finger millet, maize based cropping systems in upland areas
• semi-arid regions where kharif crops are grown during rainy season.
• rabi-crops grown under conserved moisture conditions during post rainy season.
• arid regions where pearl millet based cropping system are practiced during rainy season.
• hill agriculture
The microclimatic conditions are likely to vary between irrigated and rainfed conditions due to different agro-ecological settings. The comparative analyses of microclimatic variation under both conditions are given below:

Modifying microclimates in agriculture involves altering the local climate conditions surrounding crops or plants to create a more favorable environment for growth. This can be achieved through various techniques when the crops are subjected to weather related stresses.
14.1. To Mitigate Moisture Stress during Droughts
When the crops are under moisture stress, the principles involved are conservation of soil moisture and reduce the evapotranspiration from crops. The moisture conservation can be achieved by suppressing soil evaporation using mulches (Fig. 14.1). The evapotranspiration can be reduced using anti transpirants. These are chemicals sprayed on crops. Some antitranspirents close the stomata of the leaves to reduce evapotranspiration. Some chemicals increase the reflectance of radiation from the crops, thereby reducing heat load on crops. When crops are grown under irrigation in isolated patches, micro shelter belts can be provided across the predominant wind direction to reduce the increased evapotranspiration from advection. Advection is phenomena of horizontal transport of heat due to strong hot and dry winds.

Modifying microclimates in agriculture involves altering the local climate conditions surrounding crops or plants to create a more favorable environment for growth. This can be achieved through various techniques when the crops are subjected to weather related stresses.
14.1. To Mitigate Moisture Stress during Droughts
When the crops are under moisture stress, the principles involved are conservation of soil moisture and reduce the evapotranspiration from crops. The moisture conservation can be achieved by suppressing soil evaporation using mulches (Fig. 14.1). The evapotranspiration can be reduced using antitranspirants. Some antitranspirents close the stomata of the leaves to reduce evapotranspiration. Some anti-transpirants increase the reflectance of radiation from the crops, thereby reducing heat load on crops. When crops are grown under irrigation in isolated patches, micro shelter belts can be provided across the predominant wind direction to reduce the increased evapotranspiration from advection. Advection is phenomena of horizontal transport of heat due to strong hot and dry winds.

The science dealing with the measurement of size of any microscopically visible microorganism is known as micrometry which is based on the principle of physics. Before measuring a cell, the diameter of the microscopic field must be established by means of optic devices, namely an ocular micrometer and a stage micrometer.

a)Ocular micrometer : It is a circular disc that is placed in the eyepiece. The disc is graduated in to several small divisions marked from 0 to 100.It is placed inside the eyepiece of the microscope. The distance varies according to the objective of the microscope which can be easily determined by using a stage micrometer.

b)Stage micrometer : It is a glass slide graduated in 1 mm. Again 1mm is divided into 10 large divisions and 100 small divisions (10 x 10 = 100 divisions). These divisions are equally placed therefore 1 small division is equal to 0.01 mm or 10 μm.

Micronutrients are those elements essential for green plants but required in very small quantity for their growth and development. There are altogether eight micronutrient elements in soil consisting of iron, manganese, zinc, copper, boron, molybdenum and chlorine with the recent addition of nickel. These together with large number of other elements usually present in plants with small concentrations are formed as trace elements. Another element, cobalt is known to be required for microorganisms concerned mainly with nitrogen fixation in legumes affects indirectly the growth of many higher plants, thus, may be considered to be included in the list of essential micronutrient element. Similarly, Vanadium and sodium although present as beneficiary elements for plant growth may also have the possibilities to be enlisted into this group of elements.

Abstract

Micronutrient (vitamin and mineral) deficiencies affect more than 2 billion people worldwide and are especially prevalent in developing countries including India. Conditions due to vitamin mineral deficiencies account for 7.3 percent of the global disease burden.Iron deficiency (anemia), vitamin A and iodine deficiency disorders continue to be a grim public health problem. Thus, elimination of vitamin and mineral deficiencies is essential to improve the overall health of the masses as well as to sustain economic growth and national development. Food fortification is an effective intervention to deliver vitamin and mineral rich foods to large populations. In addition to the prevention of vitamin and mineral deficiencies, food fortification is an effective measure to raise vitamin and mineral levels by moving the population towards consuming recommended dietary allowances for most micronutrients-making it a long–term and a sustainable strategy. India is the largest producer of milk in the world with 146.3 million tonnes and the consumption rate of milk and milk products by all age groups of people are high.Therefore, fortification of milk with mineral and vitamins could be a safe and effective strategy to fight these micronutrient deficiencies.

Micronutrients are required in small quantities but are essential for normal plant growth and crop productivity. Their availability in irrigated soils can vary considerably because of changes in soil pH, moisture conditions, organic matter, texture and interactions with other nutrients. This chapter introduces the concepts of micronutrient deficiency and toxicity and discusses critical limits used for evaluating micronutrient status. Particular emphasis is placed on boron and zinc. Boron content, deficiency in Indian soils, availability and leaching are examined, together with the influence of soil texture, pH and moisture. Boron indicator plants, correction of deficiency, sources, crop response and frequency of application are also discussed. Interactions between boron and other nutrients receive attention. The chapter then considers zinc content and zinc deficiency in soils and examines the influence of pH, phosphate level, organic matter and adsorption by clay minerals on zinc availability. Methods, timing and rates of zinc application and crop responses are presented to support effective micronutrient management.

ZINC (Zn)

Chandler et al., (1932) deduced the requirement of zinc by plants while working solution for little leaf or “rosette” on peach. Zinc plays significant role in assimilation of NO₃ and for synthesis of tryptophan. Involved in biosynthesis of indole acetic acid which is responsible for f lowering and fruiting, it is an activator of several enzymes (triphosphate dehydrogenase and tryptophan synthetase), involved in photosynthesis and nitrogen metabolism.

Deficiency results in poor growth of the terminal bud. Decrease in stem length resulting in resetting and whorling of leaves. Zinc deficiency disorder in rice is called khaira. Common when zinc availability is < 0.7 ppm. White bud in maize and malformation of fruits, reduction in water uptake. Interveinal chlorosis often with necrosis and pigmentation and reduced leaf size in broad leaved crops known as little leaf and malformation of leaves.

The crops which are known to respond for zinc application are maize, rice, soyabean, castor, onion, barley, wheat, potato, sorghum and cotton

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.

18.1. Determination of Available Micronutrient Cations (Zn, Cu, Fe and Mn) in Soil

The available micronutrient cations (Zn, Cu, Fe and Mn) can be estimated in a single extraction with diethylene triamine pentaacetic acid (DTPA) as proposed by Lindsay and Norvell (1978). DTPA has the excellent property to combine with free metal ions in the solution forming soluble complexes. The stability constants of metal-DTPA complexes make DTPA as a most suitable extractant for simultaneous complex formation with Zn, Cu, Fe and Mn. In calcareous soil DTPA extractant may result overestimation due to excess dissolution of CaCO_3, thus releases occluded micronutrient cations which are not plant available. To avoid this excessive dissolution of CaCO₃, DTPA is buffered at pH 7.3 using triethanol amine (TEA). At this pH major part (3/4^th) of TEA is present as HTEA⁺ (protonation) and exchanges for Ca and Mg ion from the soil exchange site. This increases concentration of Ca and Mg in the solution phase and suppresses dissolution of CaCO₃. The DTPA has the capacity to complex each of the micronutrient cations 10 times of its atomic weight and it ranges from 550 to 650 ppm depending on the micronutrient cation.

The amount of cation in the extract is determined on an atomic absorption spectrophotometer (AAS). The experimental condition such as shaking time, DTPA concentration, pH and temperature during shaking influence the amount of Zn, Cu, Fe and Mn extracted. Increase in shaking time and temperature markedly influence the extractability of these cations.

25.1 Determination of Available Micronutrient cations (Zn, Cu, Fe and Mn) in Soil

The available micronutrient cations (Zn, Cu, Fe and Mn) can be estimated in a single extraction with diethylene triamine pentaacetic acid (DTPA) as proposed by Lindsay and Norvell (1978). DTPA has the excellent property to combine with free metal ions in the solution forming soluble complexes. The stability constants of metal-DTPA complexes make DTPA as a most suitable extractant for simultaneous complex formation with Zn, Cu, Fe and Mn. In calcareous soil DTPAextractant may result overestimation due to excess dissolution of CaCO₃, causingrelease of occluded micronutrient cations which are not plant available. To avoid this excessive dissolution of CaCO₃, DTPA is buffered at pH 7.3 using triethanol amine (TEA). At this pH major part (3/4^th) of TEA is present as HTEA⁺ (protonation) and exchanges for Ca and Mg ion from the soil exchange site. This increases concentration of Ca and Mg in the solution phase and suppresses dissolution of CaCO₃. The DTPA has the capacity to form complex with each of the micronutrient cations 10 times of its atomic weight and it ranges from 550 to 650 ppm depending on the micronutrient cation.

The amount of cation in the extract is determined on an atomic absorption spectrophotometer (AAS). The experimental condition such as shaking time, DTPA concentration, pH and temperature during shaking influence the amount of Zn, Cu, Fe and Mn extracted. Increase in shaking time and temperature markedly influence the extractability of these cations.

There are nine essential micronutrients, namely, iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), chlorine (Cl), vanadium (V) and nickel (Ni). Out of these, Fe, Mn, Zn, Cu and Ni (Dominic et al., 1978) are taken up by plants in their ionic form X²⁺, Mo as MoO^2-, chlorine as Cl^– form and boron as boric acid (H₃BO₃) or as its ionic form B (OH)₄ ^–. The absorption of vanadium by plants has received only limited attention (Lepp et al., 1983); it may be absorbed as cation V or vanadyl (VO²⁺) and anion vanadate (VO₄ ^3–). Bulk of the information is available on Fe, Mn, Zn and Cu, because of the acceptability of the single DTPA (Diethylene triamine pentaacetic acid)–CaCl₂ extraction test of Lindsay and Norvell (1978) for availability of all these four nutrients followed by their estimation on Atomic Absorption Spectrometer (AAS). Available B is estimated by hot 0.15 M CaCl₂ extraction method (Saha and Singh, 1997). Molybdenum data base is poor, because its determination is dif?cult and Mo de?ciency in crops has not been much noticed in India. Chloride is available in plenty in irrigation water and soil in India and has not received much attention in India.

Abstract

Impact of climate change and related stresses on plant productivity are being witnessed worldwide with developing countries being more vulnerable due to more dependency on agriculture. Microorganisms can play important role as economic and farmer’s friendly strategy to combat abiotic stress in agriculture. A wide range of microorganisms associate with plants, and many of them confer beneficial effects to their hosts through different mechanisms like production of growth promoting substances, nutrient acquisition, protection against plant pathogens etc. In the last few decades, role of microorganisms in imparting tolerance to plants against different abiotic stress has been reported in many crop plants. Under stresses conditions, plant-microbe interactions become more common towards coping with the stress. Selection and application of efficient abiotic stress tolerant microorganisms can be a fruitful strategy to alleviate negative effects of abiotic stresses in plants.

The adoption of modern agricultural technologies has culminated into serious problems of pesticide resistance in major pests, resurgence in minor pests, elimination of populations of natural parasites, predators and pollinators, environmental pollution, pesticide residues in food chain and health hazards. World Health Organization (WHO) estimates one million pesticides poisoning cases and 20,000 deaths every year globally. This is due to high pesticide residues in food chain including cereals, pulses, vegetables, fruits, milk and milk products (including mother’s milk), fishes, poultry, meat products and water. Twenty five per cent of Indian food products contain pesticide residues above tolerance level compared to only 1.2% globally.

Herbicides are the chemical substances used to kill weeds, i.e., unwanted plants that compete with crop plants for soil nutrients. Chemical herbicides are the most effective immediate solution to most weed problems. Use of chemicals, however, can be harmful to wildlife, to the environment and to humans. Chemicals are also expensive, and weeds develop resistance to the chemicals. For these reasons, there is now a move toward alternative methods of controlling the weeds. One of the most promising is biological weed control, which involves using one living organism to control the activities of another organism.

Emphasis of present day agriculture is to produce more with lesser land, water and man power. Apart from natural calamities like drought, flood etc., biotic stresses like pests, diseases and weeds also influence the crop productivity greatly. Sixty to eighty per cent of the total crop losses are attributed to the devastations caused by pests and diseases. Farmer’s income in recent years is decreasing gradually due to increased cost of inputs particularly in plant protection. The excessive dependence on chemical pesticides leads to the development of resistance in insect pests and pathogens, out breaks of secondary pests and pathogens / biotypes and occurrence of residues in food chain. To avoid this situation the concept of Integrated Pest Management (IPM)/ Integrated Disease Management (IDM) approach should be considered on top priority.

Sustainable agriculture or organic farming wherein biological inputs are maximum and chemical inputs are minimal, is drawing the attention of farmers across the world including India. For replacing chemical fertilizers, which supply plant nutrients by organic manure, the basic requirement is the availability of raw material i.e. the organic matter or biomass that can be decomposed to organic manure. The question that is often asked is what are the different sources of available biomass and how much of it is available? Different sources of biomass can be categorized as