eChapters

Climatic conditions prevalent in rainfed areas

Weather, which is part of climate, plays an important role in crop planning in dry farming area. Out of the several elements of weather, rainfall has key position in success of dry farming. In dryland areas, South West Monsoon brings the bulk of rainfall. The South West Monsoon is followed by North East Monsoon which supplements to South West Monsoon are the main source of rainfall. There are four types of rainfall characterized by the nature in different parts of India. Generally, the rainfall is scanty, erratic and ill distributed.

1. Rainfall

The monsoon period is not one of continuous rains in any part of the country. Meghalaya that is uncommon in the behavior of monsoon in the country. There are at least four variations in rainfall.

1.The commencement of rains may be quite early or considerable delayed according to the dates of monsoon for central Maharashtra zone is 10th June but is started as early as 28th May 1925 and its onset was delayed upto 26th June 1954 according with the date of onset of monsoon in Rajasthan is between June 21 to 30 but is started as late as up to end of July 1987 to 1992.

2.There may be prolonged breaks in rainfall. These breaks in monsoon rains can be different duration. The breaks of 5-7 days may not be all serious concern but breaks of longer duration of 2-3 weeks created the situation of plant water stress leading to reduction in agricultural production. Another important point is the physiological properties of soil and available water holding capacity in the relation to the breaks and drought, some of the soils e.g. deep black soils have capacity to store more than 300 mm of water per meter depth where as the desert soil can ensure only 100 mm. The impact of drought is felt more quickly in the soil having less water holding capacity but in sols with high storage capacity 15 days dry break may not affect the crop where as the soils of less storage capacity show wilting symptoms in and dry break such breaks cannot be predicted for a given season in advance. The drought caused due to this break is therefore of different magnitude and severity.

Drought

There is no universally accepted definition of drought. Early workers defined drought as prolonged period without rainfall. Drought is a situation when the actual seasonal rainfall is deficient by more than twice the mean deviation. American Meteorological Society defined drought as a period of abnormally dry weather, sufficiently prolonged for lack of water to cause a severe hydrological imbalance in the area affected.

Prolonged deficiency of soil moisture adversely affected crop growth indicating incidence of agriculture drought. It is the result of imbalance between soil moisture and evapotranspiration needs of an area over a fairly long period as to cause damage to standing crops and to reduce the yields.

Natural resources conservation and their management hold key to sustainable agriculture and livestock production. It is all the more crucial for countries with predominant agrarian economies where development of sustainable agriculture is essential for overall growth, redressal of poverty and security. Conservation of both soil and rain water as very crucial and basic resources have been practiced since ancient times in India. However, there has been renewed emphasis on conservation and efficient utilization of these resources in the recent past. The fact that 70% of the arable area of India is rainfed with precarious supply of water and that rainfed agriculture supports 44% of India’ s human population and contributes 90 per cent of coarse cereals and pulses, 80 per cent of oilseeds and 65 per cent of cotton and growing realization that further gains i n productivity of crops and livestock will emanate from rainfed regions, leave no room for complacency in this regard.

Year after year, the fate of a vast ‘majority of Indian farmers hangs in balance, as success with rainfed agriculture continues to be a gamble. It is evident that crop yields in semi-arid areas depended more on rainfall distribution than on total rainfall and lack of serious efforts to create d water supply for crops through scientific management of rainwater is a factor favouring this avoidable uncertainty. In rainfed agriculture no other input can perhaps enhance the yield without effectively tackling of the rainfall aberration related sub-optimal moisture availability. Therefore a prerequisite for substantial improvement in the agriculture production in the semi-arid region is to manage runoff water and to use it either at the time of moisture stress even during the monsoon or in next season. It has been reported that only one supplementary irrigation at proper stage can double of Rabi crops. But supplemental water is a developed resource and is more expensive than the natural resources. Hence, it is all the more necessary to use this water judiciously and efficiently. Standardization of techniques by which as much of precipitation as possible can be conserved for crop use, either directly in the soil profile through infiltration or through runoff collection and recycling is an area of priority in research.

Soil and water conservation measures

Soil conservation is using and managing the land based on the capabilities of the land itself involving application of the best management practices leading to profitable crop production without land degradation.

Water erosion control

Water erosion occurs simultaneously in two steps : detachment of soil particles by falling raindrops and transportation of detached soil particles by flowing water. Therefore, water erosion can be minimized by preventing the detachment of soil particles and their transportation.

Crop plan and practices for rainfall scarcity prone areas

The appropriate crop plan and practices, which have so far been generated and recommended for achieving the objective of increased and stable crop production in dry land areas have been summarized in the following points:-

1.Proper and timely tillage

2.Early sowing

3.Choice of suitable crop/good plant material

4.Proper plant population

5.Cropping system

6.Fertilizer use

7.Timely weed control

8.Efficient rain water storage and its use

9.Alternate land use system

10.Planning for aberrant weather hazard

Watershed

A watershed is the area of land where all of the water that is under it or drains off of it goes into the same place. John Wesley Powell, scientist geographer, put it best when he said that a watershed is: “that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community.”

Watershed is defined as a hydro-geological unit of area from which the rainwater drains through a single outlet. Watershed development refers to the conservation, regeneration and judicious use of all the natural resources (like land, water, plants, animals) by human beings. Watershed Management brings about the best possible balance between natural resources on the one side and human beings on the other. Human beings and the ecology are interdependent. The changes in the environment directly affect the lives of the people depending on it. A degraded environment means a degraded quality of life of the people. This degradation can be tackled effectively through the holistic development of the watershed. A watershed provides a natural geo-hydrological unit for planning any developmental initiative. The approach would be treatment from “ridge to valley”.

A watershed, also called a drainage basin or catchment area, is defined as an area in which all water flowing into it goes to a common outlet. People and livestock are the integral part of watershed and their activities affect the productive status of watersheds and vice versa. From the hydrological point of view, the different phases of hydrological cycle in a watershed are dependent on the various natural features and human activities. Watershed is not simply the hydrological unit but also socio-political-ecological entity which plays crucial role in determining food, social, and economical security and provides life support services to rural people.

Management of watershed in India

It involves management of water, land, energy and greenery, integrating all the relevant scientific approaches appropriate to socio-economic background for a pragmatic development of a watershed. In practice, it means allowing load free rainfall run off from the watershed. Clear outflow imply management of effective soil and water conservation and generating a lush green carpet in whole of the area. In other worlds, it is greening of a watershed through proper management of land, water and energy sources. The comprehensive development of watershed seems to make productive use of all its natural resources and also protect them is termed as watershed management.

The Banave terraces in Indonesia and those in Nepal, Mediterranean are examples of integration of human elements into a system of land management, which is an early achievement in watershed management. Watershed management is not merely anti-erosional and anti-run off approach but also a comprehensive integrated approach of land and water resources management. The approach is preventive, progressive, corrective as well as curative. Here wasted land resources could be fruit fully harvested into a productive face for rural development.

Integrated watershed management programme (IWMP)

The main objectives of the IWMP are to restore the ecological balance by harnessing, conserving and developing degraded natural resources such as soil, vegetative cover and water. The outcomes are prevention of soil run-off, regeneration of natural vegetation, rain water harvesting and recharging of the ground water table. This enables multi-cropping and the introduction of diverse agro-based activities, which help to provide sustainable livelihoods to the people residing in the watershed area. In addition, there is a Scheme of Technology Development, Extension and Training (TDET) is also being implemented to promote development of cost effective and proven technologies to support watershed management.

Till 1.4.2008, Department implemented 3 watershed programmes viz. Integrated Wastelands Development Programme, Drought Prone Areas Programme, Desert Development Programme. Since then, they have been brought under a comprehensive programme named Integrated Watershed Management Programme (IWMP) to be implemented under Common Guidelines on Watershed Development, 2008.

Exercise 1: Studies on climate classification

The Köppen climate classification is one of the most widely used climate classification systems. It was first published by the Russian climatologist Wladimir Köppen (1846-1940) in 1884, with several later modifications by Köppen, notably in 1918 and 1936.Later, the climatologist Rudolf Geiger introduced some changes to the classification system, which is thus sometimes called the Köppen–Geiger climate classification system.

Importance of Rainfed Farming

In India, rain dependent areas are vast and they have a great contribution to make in agricultural production, with just 1/40^th of the world land. India supports over half of its buffaloes and over one seventh of its cattle and goats that also share land utilization with humans and add to the national wealth. The second largest number (after Africa) of drought victims of the world live in India, out of 143 m ha cultivated land about 43 m ha are under irrigation and the rest of the area (about 70%) is rainfed but all is not too dry. About 90% of it located in the north-west part, out of which 60% is located in Rajasthan and sustains a human population of 20 million and a total livestock population of 23 million. The dry land areas contribute about 42% of food grains, almost all the coarse grains and about 75% of pulses and oil seeds of the total production of the country. About 2/3 of rice and rapeseed mustard and 1/3 of wheat are grown in rainfed areas. A large portion of industrially important crops such as cotton, groundnut and castor are cultivated under dry land conditions and has a great contribution to make to the production of food, fibre, fuel and furniture timber etc. Dry land agriculture may be classified into three groups on the basis of annual rainfall.

a) Dry farming : Cultivation of crops in areas where annual rainfall is less then 750 mm and crop failures due to prolonged dry spells during crop period are most common. Dry farming is practiced in arid regions with the help of moisture conservation practices. Alternate land use system is suggested in this region.

b) Dryland farming: Cultivation of crops in areas where annual rainfall is more than 750 mm but less than 1150 mm is called dryland farming. Dry spells may occur, but crop failures are less frequent. Higher evapotranspiration (ET) than the total precipitation is the main reason for moisture deficit in these areas. The soil and moisture conservation measures are the key for dryland farming practice in semi-arid regions. Drainage facility may be required especially in black soils.

The conservation of soil and water is very essential for sustainable production, environment preservation and balanced ecosystem. Fifty percent of total geographical area (329 m ha) of our country needs soil and water conservation measures. About 5334 million tonnes of soil is lost annually along with 10 million tonnes of fertilizer and other essential nutrients and organic carbon. Loss of nutrients is almost equal to their total production in India. In India about 70% of the cultivated area falls under the category of dryland conservation measures for soil and water and efficient utilization of these resources is needed in these areas. The fact that rainfed agriculture supports 44% of India’s human population and contributes 90 percent of coarse cereals and pulses, 80 percent of oil seeds and 65 percent of cotton and growing realization that further gains in productivity of crops and live stock will emanate from rainfed regions, leave no room for complacency in this regard.

In these areas, rainfall frequently occurs with high intensity that produces higher runoff due to non adoption of soil and water conservation (SWC) measures and poor permeability of the soil. As a result crop grown during rainy season often suffer from moisture stress due to inadequate moisture storage in the soil profile. Secondly soil erosion problems such as sheet, rill and even gully erosion are common in the region.

It has been reported that the black soils of peninsular region of India, under cultivated fallow gives runoff of about 23.4 percent of rainfall and results in a soil loss of 8.94 t ha^-1 at 1.0 percent slope (Verma et al., 1990). They further reported that the rate of siltation reduced by 83 percent within a span of five years due to adoption of agronomic measure of SWC. These studies clearly showed that soil erosion and runoff are the major factors causing land degradation in the region that needs appropriate SWC measures so that crop productivity could be maintained.

Soil and moisture conservation measures are a prerequisite for ensuring a good crop stand, growth and development of crop, and higher crop yields. These measures depend mainly on the land (topography and slope), soil type, rainfall pattern, and nature of the crop. The various management practices are:

Tillage

Off-season tillage is necessary to get a weed free seedbed having good tilth and better moisture conservation. Pre-monsoon showers should be utilized for deep ploughing (where necessary) and blade harrowing. This will enable sowing of large areas in limited time- a necessary in dryland areas. Higher yield advantage with deep ploughing (22 cm) has been obtained in case of sorghum, pearl millet, maize, and rice. In case of rice, use of mould board plough to a depth of 30 cm every year increased the rice yield at Ranchi. For small seed crops like finger millet, soil compaction below the seeding zone is absolutely necessary for getting good crop stand establishment and higher yields. Tillage requirement for pulse crops (cowpea, mungbean, black gram) varies with the type of soil on which they are grown. For loamy sand or sandy loam soils, one or two cross cultivation using a sweep harrow, will be enough to provide a good tilth.

Natural resources conservation and their management hold key to sustainable agriculture and livestock production. It is all the more crucial for countries with predominant agrarian economies where development of sustainable agriculture is essential for overall growth, redressal of poverty and security. Conservation of both soil and rain water as very crucial and basic resources have been practiced since ancient times in India. However, there has been renewed emphasis on conservation and efficient utilization of these resources in the recent past. The fact that 70% of the arable area of India is rainfed with precarious supply of water and that rainfed agriculture supports 44% of India’s human population and contributes 90 per cent of coarse cereals and pulses, 80 per cent of oilseeds and 65 per cent of cotton and growing realization that further gains in productivity of crops and livestock will emanate from rainfed regions, leave no room for complacency in this regard.

Year after year, the fate of a vast majority of Indian farmers hangs in balance, as success with rainfed agriculture continues to be a gamble. It is evident that crop yields in semi-arid areas depended more on rainfall distribution than on total rainfall and lack of serious efforts to create the water supply for crops through scientific management of rainwater is a factor favoring this avoidable uncertainty. In rainfed agriculture no other input can perhaps enhance the yield without effectively tackling of the rainfall aberration related sub-optimal moisture availability. Therefore a prerequisite for substantial improvement in the agriculture production in the semi-arid region is to manage runoff water and to use it either at the time of moisture stress even during the monsoon or in next season. It has been reported that only one supplementary irrigation at proper stage can double of rabi crops. But supplemental water is a developed resource and is more expensive than the natural resources. Hence, it is all the more necessary to use this water judiciously and efficiently. Standardization of techniques by which as much of precipitation as possible can be conserved for crop use, either directly in the soil profile through infiltration or through runoff collection and recycling is an area of priority in research.

Intercropping is growing two or more crops simultaneously on the same piece of land with a definite row pattern. The crops may or may not be sown or harvested at one time.

Advantages of intercropping

Intercropping provides yield advantages as compared to sole cropping. These are not by means of costly input but by the simple expedient of growing crops together.

1.It provides greater surety and stability of higher yield over different seasons.

2.It economizes the space and time of cultivating two or more component crops of comparable agronomic practices grown separately.

3.It helps to restore soil fertility when legumes are included as component crop.

4.It utilizes a greater total volume of both below and above ground environment.

5.It helps to avoid intra-crop competition and thus a higher number of crop plants can be grown per unit area.

6.It helps in better use of growth resources.

7.It also helps in better control of weeds pests and diseases.

8.It also controls erosion through providing continuous leaf cover over the ground surface.

9.It is the small farmers of limited means who is most likely to benefit.

Watershed management

Watershed is defined as a geohydrological unit draining to a common point by a system of drains. All lands on earth are part of one watershed or other. Watershed is thus the land and water area, which contributes runoff to a common point.

A watershed is an area of land and water bounded by a drainage divide within which the surface runoff collects and flows out of the watershed through a single outlet into a lager river or lake.

Low rainfall or failure of monsoon rains is a recurring feature in India. This has been responsible for drought and famines. The word drought, generally, denotes scarcity of water in a region. Though, aridity and drought are due to insufficient water, aridity is a permanent climatic feature and is the culmination of a number of long term process. However, drought is a temporary condition that occurs for a short period due to deficient precipitation for vegetation, river flow, water supply and human consumption. Drought is due to anomaly in atmospheric circulation.

Land capability classification

Introduction: The United States Department of Agriculture (USDA) land classification system is interpretative, using the USDA soil survey map as a basis and classifying the individual soil map units in groups that have similar management requirements. At the highest of categorization, eight soil classes are distinguished, namely, arable lands (I to IV) and non arable lands (V to VIII).

Origin of land capability classification (1933) : The Georgia Piedmont Land Capability Classification (LCC): First U.S. effort to systematically determine the best use of lands by classifying and mapping erosion rates and potential in relation to both physical characteristics and agricultural capacity.

Definition: Land capability classification is a system of grouping soils primarily on the basis of their capability to produce common cultivated crops and pasture plants without deteriorating environment over a long period of time.

Classes: Land capability classification is subdivided into capability class and capability subclass nationally. Some states also use a capability unit.

The capability classification provides three major categories of soil groupings: (1) Capability unit, (2) capability subclass, and (3) capability class.

Tillage

The mechanical manipulation of soil with tools and implements for obtaining conditions ideal for seed germination, seedling establishment and growth of crops is known as tillage. Tillage may be described as the practice of modifying the state of the soil in order to provide conditions favourable to crop growth.

Definition

Soil erosion is the process of detachment of soil particles from the top soil and transportation of the detached soil particles by wind and / or water. The agents causing erosion are wind and water. The detaching agents are falling raindrop, channel flow and wind. The transporting agents are flowing water, rain splash and wind.

Erosion is the process by which soil and rock are removed from the Earth’s surface by exogenic processes such as wind or water flow, and then transported and deposited in other locations.

While erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. Excessive erosion causes problems such as desertification, decreases in agricultural productivity due to land degradation, sedimentation of waterways, and ecological collapse due to loss of the nutrient rich upper soil layers. Water and wind erosion are now the two primary causes of land degradation; combined, they are responsible for 84% of degraded acreage, making excessive erosion one of the most significant global environmental problems.

Industrial agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion. However, there are many prevention and remediation practices that can curtail or limit erosion of denuded soils.

Drainage - definition

Agricultural drainage is the artificial removal and safe disposal of excess water either from the land surface or soil profile, more specifically, the removal and safe disposal of excess gravitational water from the crop root zone to create favourable conditions for crop growth to enhance agricultural production.

Benefits of drainage

a)It provides better soil environment for plant growth by creating favourable soil aeration conditions.

b)It improves the soil structure and in turn increases the soil infiltration.

c)High infiltration capacity reduces soil erosion.

d)It hastens the warming of the soils and maintains desirable soil temperature, which accelerates plant growth and bacterial activity.

e)It promotes increased leaching of salts and prevents accumulation of salts in the crop root zone.

f)In well drained soils, less time and less labour are required for tillage operations.

Both dryland crops and irrigated crops experience an assortment of ecological or environmental stresses which include abiotic viz., drought, water logging, salinity, extremes of temperature, changes in atmospheric gases and biotic viz., insects, birds, other pests, weeds, pathogens. Dryland crops are more vulnerable to stress in the present context of changing climatic scenarios. The ability to tolerate or adapt effectively by challenging these stresses is a very complicated phenomenon would be due to various plant interactions occurred in the specific environment. Both biotic and abiotic stresses occur at various stages of plant growth and development and frequently more than one stress concomitantly affects the crop. It is difficult to distinguish effects of these stress factors on the performance of crop plants with respect to yield and quality of harvested products. This is of special significance of maximizing productivity of dryland crops in changing climate scenarios, with complex consequences for ecologically and environmentally sound Indian agriculture. In order to successfully meet this challenge, one should understand the various aspects of stresses in view of the current development and to promote a competitive dryland production system.

In dryland areas, moisture conservation accounts prime most important concept for maximizing productivity of dryland crops. Varied topographic and agro- climatic conditions ranging from arid to semi-arid climates with high evaporation because of varied temperature regimes permit the cultivation of drought resistance crops. Reducing the cost of cultivation without compromising the socio-economic status of farmers is prime importance. Conservation of moisture by reducing the weed menace is great task performed by the dryland farmers. Under such situations, effective utilization of dryland tools and implements used are of a primitive nature throughout the dryland farmers for higher factor productivity. Traditional farm tools and implements for self-sustenance have been adapted through experience over generations to meet emerging socio- economic and farming challenges.

Relatively small yields consequently larger areas must be farmed for a given return and the successful exploration of dryfarming requires the adoption of methods. The methods which enable farmers to do the maximum effective work with the smallest expenditure of energy. The type of soils and topographic conditions largely influence the type, size and shape of particular tillage tools/ implements among the dryland farmers. The following is a list of local tools/ implements found in the various dryland regions.

Understanding the principles involved in plant growth and development is prime important for managing agronomic practices for higher productivity of dryland crops sustainably. Systematic study of plant growth based on the variability and interpreting plant development based on biometric methods is called as growth analysis. Plant data in turn biometric data is collected from the field and analysed over the period to know the growth condition of the plants. Based on biometric data, agronomic practices like application of fertilizers, irrigation and weed management practices were employed. Several growth indices are devised for identifying environmental or genetic factors as sources of variation in plants. Both whole plant and their component organs (leaf) are basis for calculating growth indices.

The most common parameters used in growth analysis are leaf area index, crop growth rate, relative growth rate, net assimilation rate and leaf area duration.

For the preparation of this book, the authors have drawn heavily from the following sources.

Aamodt,O.S and Johnston W.A. 1936. Can.J.Res.14: 122-152.

Adams, J. E. 1962. Agron. J. 54: 257-261.

Barrs, H.D. and Weatherley, P.E. 1962. Australian Journal of Biological Sciences, 15:413-428.

Blackman, V.H. 1919. Annals of Botany, 33:353-360.

Chen, D; Sarid, A. and Katchalski, E.1968.Proc. Nat.Acad.Sci;US. 61: 1378-83.

De, G.C. 1989. Fundamentals of Agronomy. Oxford and 1 BH pulishing Co. Pvt. Ltd. New Delhi.

El Sharkawy, M. Loomsi, R.S. and Williams, W.A. 1968. J. Applied Ecol.5:241-51.

Exercise No. 1. Rainfall analysis and interpretation

Procedure: Collect the rainfall data from the Department of Agrometeorology and interprete it zonewise and district wise for various districts of Haryana. Correlate it with last year’s rainfall.

Introduction

In order to keep pace with the development there is rise in energy use but it has adverse effects on climate due to greenhouse gas emissions from burning of fast depleting fossil fuels. In this context, we need to harness and use more and more renewable forms of energy, especially solar energy that is plentiful on most part of India. Also, at several locations harnessing wind power and utilizing biomass could be effective alternatives. Solar based devices may also work in an integrated manner with small wind turbines as hybrid devices. At present, about 20% of the country’s installed electricity generation capacity is contributed by renewable sources e.g. wind, solar, bioenergy, hydro etc., which is about 71.325 Giga Watt (GW) as on 30^th June, 2018. In agricultural sector, energy is directly used for pumping irrigation water, operating different mechanized farm implements/tools and processing of foods. Share of agricultural sector in total energy consumption is about 7-8% and further increase in energy use from its present value of 1.6 kW ha^-1 to 2.5 kW ha^-1 is expected to meet the production target of next 20 years.

Introduction

The development of any region is reflected in its quantum of energy consumption. With a view to keeping the pace we have to grow our energy resources at a rate that commensurate to sustainable development. There is already shortage of electricity, reflected in power cuts notwithstanding enhancement of electricity production of several folds in the country. The problem is more severe in context with rural areas in India where some 70% of population live and have agriculture as the main occupation. Although statistically few thousand villages are yet to be electrified, the availability of regular supply in far off places has been a problem and the farmers are unable to derive benefits of electricity. The fast depleting kerosene is used for lighting and diesel oil for running agricultural machinery including pumps. In addition people burn firewood, agricultural waste and cow dung cake for cooking food causing irreparable damage to the ecosystem. According to Lester Brown there will be plenty of food to eat but no fuel to cook. The burning of cow dung deprives farmers the use of potential source of organic manure. Further, due to shortage of energy resources, farmers are unable to process the agricultural products to enable them to accrue more benefits. The situation is still worse in arid region where bio mass is scarce and there is no hydro electricity. In addition, farmers are unable to generate additional income due to lack of energy resources to run appropriate device in cottage industries. In this context, solar energy utilization has a tremendous potential for providing needful energy to the farmers for domestic, agricultural and allied applications leading to a sustainable development.

Introduction

In Indian Thar desert regions, excessive heat is the major problem that causes human and animal thermal discomfort. Space cooling is, therefore, the most desirable factor for the inhabitants. Various examples of dwellings responsive to climatic constraints are found in vernacular architecture throughout the world. Compact cellular layout with minimum external surface exposure to the sun, whitewashed surfaces to reduce absorptivity, blind external facades, courtyards, vegetation to provide humidity and shade, and heavy buildings constructed from high thermal capacity materials are common passive features in most of the arid regions. Wind towers for cooling ventilation are well known in Iranian and Middle East architecture, which along with cooling of the air by earth and water evaporation keep the building comfortable in hot periods. Building underground to take advantage of the large thermal storage capacity of the earth is also used in Tunisia and central Turkey.

Introduction

The age-old necessities of life are food, clothing and shelter. The 20^th century had dramatized a fourth-energy. Energy starvation of the technological complex that maintains modern society may soon be as crucial a problem as feeding the hungry. Indeed, energy starvation could well precipitate more wide spread food starvation. Solutions for the energy crisis are strongly dependent on the technology of how energy is produced and used. To make a physical change in the world it is necessary to use four resources: energy, matter, space and time. How well a task has been performed can be measured in terms of amount of fuel consumed, the mass of material used, the space occupied, the hours of labour to accomplish it, and the ingenuity with which these resources are utilized. Squandering of irreplaceable energy resources, waste of materials, or large expenditure of space and time cannot be tolerated if the necessities of life are to be provided for all. Energy is intricately linked to development of a country. Growing demand on account of industrialization, urbanization, transportation and also increase consumption in rural areas is putting added pressure on energy supply network. Electricity generation has been increased from 1,400 MW in the year 1947 to 303,118 MW up to August 31, 2016 in India but still there is 10-15% shortage of power in peak hours and all villages are not electrified. Even many electrified villages receive 6 to 8 hours of electricity per day in India. To overcome this shortage there is a need to utilise new and renewable sources of energy. Fortunately, India is blessed with abundant solar energy. The arid parts of India receives much more radiation as compared to the rest of country i.e. maximum solar radiation i.e. 7600-8000 MJm^-2 (2111-2222 kWhm^-2) per annum, followed by semi-arid parts, 7200-7600 MJm^-2 (2000-2111 kWhm^-2), per annum and least on hilly areas where solar radiation is still appreciable i.e. 6000 MJm^-2 (1667 kWhm^-2) per annum (IMD 1985). In this chapter review of different solar thermal technologies in Indian perspective has been carried out.

For electromagnetic radiation, there are four “laws” that describe the type and amount of energy being emitted by an object. In the following sections, these four laws of radiation e.g. Planck’s law, Wien’s displacement law, Steffan-Boltzman law and Kirchhoff’s law are described briefly.

Planck’s Law

Planck’s law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. The spectral radiance of a body, B_í, describes the amount of energy it gives off as radiation of different frequencies. It is measured in terms of the power emitted per unit area of the body, per unit solid angle that the radiation is measured over, per unit frequency. Planck showed that the spectral radiance of a body at absolute temperature T is given by

Introduction

Cooking accounts for a major share of energy consumption in developing countries. Fifty per cent of the total energy consumed in India is for cooking (Fritz 1981). Most of the cooking energy requirement is met by non-commercial fuels such as firewood (75%), agricultural waste and cow dung cake (25%) in rural areas. The fuel wood requirement is 0.4 tons per person per year in India. In rural areas firewood crisis is far graver than that caused by a rise in oil prices. Marginal villagers have to forage 8 to 10 hours a day in search of firewood as compared to 1 to 2 hours ten years ago. One third of India’s fertilizer consumption can be met if cow dung is not burnt for cooking and instead is used as manure. The cutting of firewood causes deforestation that leads to desertification. Fortunately, India is blessed with abundant solar radiation (IMD, 1985). The arid parts of India receive maximum radiation i.e. 7600-8000 MJ m^-2 per annum, followed by semi-arid parts, 7200-7600 MJm^-2, per annum and least on hilly areas where solar radiation is still appreciable i.e. 6000 MJm^-2 per annum. Therefore, solar cookers seem to be a good substitute for cooking with firewood.

Principle of cooking

The different methods of cooking of food are boiling, frying, roasting, and baking. For boiling of rice, lentils etc. the temperature of food being cooked is about 100° C while for other methods, high temperatures are required. Heat is supplied at the bottom of the vessel for frying and boiling purposes in conventional cooking. Roasting and baking is generally performed on open fire or in ovens, wherein food is surrounded by hot surfaces and heat is transferred to the food by radiation and convection.

Introduction

Flat plate collector is the heart of a solar heat collection system designed for delivery of heated fluid in the low to medium temperature range (5o70oC above ambient temperature) for applications, such as water heating, space heating, drying and similar industrial applications. The flat plate collectors absorb both beam and diffuse radiation. The absorbed radiation is converted into heat which is transferred to water or air flowing through the collector tubes or duct, respectively. Such collectors do not require tracking of the sun and little maintenance is required.

The conventional flat plate solar air heater, shown in Fig. 7.1, consists of a flat blackened absorber plate, a transparent cover (such as a glass cover) at the top and insulation at the bottom and on the sides. The air to be heated flows through the rectangular duct below the absorber plate. The glass cover transmits a major part of solar radiation incident upon it to the absorber plate where it is converted into heat. The glass is, however, opaque to longwavelength radiation and thus it does not allow the infrared radiation from the heated absorber plate to escape.

Karwa et al. (2002) have presented the following deductions of heat collection rate and pumping power equations for the flat plate solar air heater.

Introduction

We are blessed with solar energy in abundance at no cost. The solar radiation incident on the surface of the earth can be conveniently utilized for the benefit of human society. Solar energy can be used as thermal energy for water heating, cooking, drying, distillation, space heating, cooling and power generation or it can be converted to electricity through photovoltaic cells, commonly known as solar cells. One of the popular devices that harness the solar energy is solar hot water system (SHWS). Flat plate collectors are used for low temperature applications (below 100^oC) while concentrators are preferred for higher temperatures. The most efficient application of flat plate collector is for getting hot water. Hot water in winter is an essential requirement for domestic uses such as bathing, cleaning of utensils and washing of clothes. In rural areas hot water is also required for softening of animal feed. Generally it is obtained by using firewood and cow dung cake in rural areas or using kerosene, liquid petroleum gas, coal or electricity in urban areas. Therefore, the use of solar water heaters will conserve lot of commercial and non-commercial fuels which are being wasted in merely getting hot water. A solar water heating system (SWHS) is made of several important elements: one or more solar collectors, a pump, a heat exchanger, a storage tank (or multiple tanks) and a back-up storage tank. The Solar heating system can be classified as passive or active. For water heating purposes, the general practice is to use flat plate solar energy collectors (FPC). The evacuated tube collectors (ETC) and evacuated tube heat pipe collectors (ETHP) are more efficient, though, the initial cost is comparatively higher. There are three type of water heaters extensively studied by various workers viz. natural circulation, collector-cum-storage and forced circulation in all over the world.

Introduction

Solar refrigeration technology engages a system where solar power is used for cooling purposes. It offers a wide variety of cooling techniques powered by solar collector-based thermally driven cycles and photovoltaic (PV)-based electrical cooling systems. Cooling can be achieved through four basic methods: solar PV cooling, solar thermal cooling, solar thermo-electrical cooling and solar thermo-mechanical cooling. The first is a PV-based solar energy system, where solar energy is converted into electrical energy and used for refrigeration much like conventional methods. The second method utilizes a solar thermal refrigeration system, where a solar collector directly heats the refrigerant through collector tubes instead of using solar electric power. The third one produce cool by thermoelectric processes. The fourth method converts the thermal energy to mechanical energy, which is utilized to produce the refrigeration effect.

The performance of solar refrigeration systems is determined based on energy indicators of these systems. The COP (coefficient of performance) can be calculated as follows:

Introduction

Solar air heating is the conversion of solar radiation to thermal heat. The thermal heat is absorbed and carried by air which is delivered to a living or working space. The transparent property of air means that it does not directly absorb effective amounts of solar radiation, so an intermediate process is required to make this energy transfer possible and deliver the heated air into a living space (Fig.10.1). The technologies designed to facilitate this process are known as solar air heaters. Solar air heating technologies use only free, renewable and clean energy and can help defray the rising cost of conventional energy.

Introduction

The sun is an abundant source of solar energy (average value on horizontal surface 6 kW m^-2 day^-1), which is freely available. This huge source of energy is non-polluting and inexhaustible in nature. It has the potential of supplementing the conventional energy sources to a great extent. There is acute shortage of conventional energy sources, which affects the overall development. Work on the utilization of such a huge, non-polluting and everlasting energy source has been carried out at CAZRI, Jodhpur for various domestic, industrial and agricultural applications in order to supplement the energy demand. This includes the development of a lot of solar thermal devices, such as, solar still, solar dryer, solar cooker, animal feed solar cooker, solar candle device and cool chamber. The details of some of these devices are given as following.

Introduction

A solar collector, the special energy exchanger, converts solar irradiation energy either to the thermal energy of the working fluid in solar thermal applications, or to the electric energy directly in Photovoltaic (PV) applications. For solar thermal applications, solar irradiation is absorbed by a solar collector as heat which is then transferred to its working fluid (air, water or oil). The heat carried by the working fluid can be used to either provide domestic hot water/heating, or to charge a thermal energy storage tank from which the heat can be drawn for use later (at night or cloudy days). Solar collectors are usually classified into two categories according to concentration ratios: non-concentrating collectors and concentrating collectors. A non-concentrating collector has the same intercepting area as its absorbing area, whilst a sun-tracking concentrating solar collector usually has concave reflecting surfaces to intercept and focus the solar irradiation to a much smaller receiving area, resulting in an increased heat flux so that the thermodynamic cycle can achieve higher Carnot efficiency when working under higher temperatures.

Introduction

Water is the primary source of life for mankind and one of the most basic necessities for crop production. The demand for water to irrigate the crops is increasing. For sustainable production from agricultural farms, irrigating the crops at right stages is highly important. Even in rainfed situation, lifesaving irrigation during long dry spell has also been found beneficial for crop survival and to obtain the targeted yield. Considering the depletion of groundwater below the critical zone in most part of the country, energy intensive pumping for irrigation is not a viable option. Therefore utilization of available runoff water through surface storage systems followed by pumping may be a potential solution to achieve the set goal of ‘crop per drop’ mission. In this connection, micro-irrigation system including drippers and sprinklers is of great importance. However, ensured power supply is essential to operate the micro-irrigation system even in remote areas. Reliable solar photovoltaic (PV) pumps are now emerging in the market and are rapidly becoming more attractive than the traditional power sources. These technologies, powered by renewable energy sources, are especially useful in remote locations where a steady fuel supply or electricity supply is problematic. About 16 million electric pumps and 7 million diesel pumps are in operations in the country for irrigation purpose; however they are highly energy intensive. Moreover, diesel operated and electrified pumps directly or indirectly emit large amount of CO₂ gas in atmosphere and hence are not environment friendly. To meet the energy demand for irrigation, solar PV pumps have been introduced under the off-grid power generation category of National Solar Mission (NSM) with a target of 1000 MW by the end of phase II (2013-2017). The target has been revised in 2015 to a total grid connected solar power generation of 1,00,000 MW comprising 40,000 MW roof top generation and 60,000 MW grid connected solar power plants (Resolution of MNRE, Govt of India, No. 30/80/2014-15/ NSM dated 1^st July 2015).

PV clad structures and hybrid devices for rural and agricultural applications have been developed after considering different design aspects, climatic parameters, solar radiation availability on different planes, heat transfer coefficients, performance of PV in arid region and inter phasing of different components while keeping in view, practicality, application and ease of operation. Performance of the developed systems was studied, mathematical model developed and energy savings worked out for techno-economic considerations. The chronology and details of the developed PV structures and hybrid devices are as follows:

Green structure for environmental control

First of all a Quonset type environment control structure having a length of 5.3 m and width 4 m was fabricated with angle iron and iron rods and it was covered by agro-net (75%) having surface area of about 55 m². The structure having a volume of 33 m³ was fixed with long side along east west direction and had provisions for incorporation of misting unit on west side and a door on east.

Introduction

Agriculture has been the back bone of Indian economy and culture and it will be continued to remain as such for a long time in future. Parallel to this, energy security of a country is also very important and efforts have been given on renewable energy utilization since the fossil fuel based energy is depleting at a very fast rate. In agricultural fields, considerable amount of energy is used to do different field activities e.g. ploughing, irrigation through pumps, intercultural operations, spraying of agricultural chemicals for plant protection, harvesting, post-harvest processing etc. Therefore, there is also need to replace the conventional energy source with renewable sources to operate above mentioned agricultural activities.

Approximately, 35% of the crop production is damaged if pest and diseases are not controlled at right time. Uniform spraying of liquid formulations throughout the crop field is very important for effective control of pest and diseases. Using sprayer, liquid pesticide formulations are generally broken down to minute droplets of effective size for uniform distribution over a large surface area. Different types of sprayers are used in agricultural field based on different requirements.

Introduction

For optimum use of harvested rain water in surface reservoir like farm ponds or tankas, small sized solar PV pumping systems with 1 hp AC and DC motor were experimentally tested at research farms of ICAR-Central Arid Zone Research Institute, Jodhpur (Fig. 16.1). Total suction head in both pumps was about 5 m. Among two installed pumps, the system with AC pump consisted of 1400 Wp (200 Wp × 7) whereas the DC pump consisted of PV array of 920 Wp (230Wp × 4). Each PV panel of AC solar pump was connected in series, which was further connected with an inverter to generate AC output of about 220-240 volt and 4-4.2 ampere. In case of DC solar pump, panels are connected in parallel to generate DC output of 40-50 volt and 15-20 ampere.

Introduction

Agricultural produce are being sun dried since ages as the first step to preserve the product for future consumption. It is still practised being most inexpensive over mechanical and other advanced drying systems. The most prevailing disadvantage of open sun drying is the quality losses due to insect infestation, enzymatic reactions, microorganism growth, and mycotoxin development. On the other side, sun drying is also a highly labor intensive and time consuming process prone to theft and damage by birds. It also suffers with the lack of process control and treatment uniformity (Bansal and Garg 1987, Bansal, 1987).

To overcome these disadvantages several types of solar dryers have been developed over the years (Ekechukwu and Norton 1999). These dryer may be identified into three group namely active, passive and hybrid. As regards their structural arrangement three generic subclasses were also identified: direct-modes (the solar-energy collection unit is an integral part of the entire drying system), indirect-modes (the solar collector and the drying chamber are separate units) and mixed-modes solar dryers. Natural convection solar dryers have become more suitable for rural sector and remote areas, as they work on single energy option and do not require any other external energy source (Pangavhane et al. 2002).

Introduction

Cultivation of crops in greenhouse or protected structure has been increased tremendously in recent times and also has been spread from temperate regions to the warmer regions of tropics and subtropics. Plentiful technologies have been developed for heating the inside environment of greenhouse for optimum plant growth (Sethi et al. 2013). However, in hot arid areas, cultivation in greenhouse is very difficult as the temperature reaches to a very high level to sustain plant growth (Pek and Hayles 2004, Saran et al. 2010). Under such situation requirement for cooling the greenhouse microclimate environment is the necessity, but is very energy and water intensive. Hence, in such regions, reduction of air temperature inside the greenhouse or the regulation of temperature closer to the ambient temperature during summer is necessary for successful crop production. A typical diurnal variation of temperature and global solar radiation during late winter months inside a shade net structure has been plotted in Fig. 18.1. It has been found that global solar radiation has been decreased to almost 1/3 of the radiation received outside by using 75% shade net cover. The temperature inside structure during morning time has also been found higher than outside temperature and in summer such increase is expected to be much higher.

Therefore, cooling is considered as the basic necessity for greenhouse crop production in tropical and subtropical regions to overcome the problems of high temperatures during summer months. Development of suitable cooling system that provides congenial microclimate for crop growth is a difficult task as the design is closely related to the local environmental conditions. Different cooling techniques for greenhouse crop cultivation may be found in Kumar et al. (2009). Fan pad cooling system has been widely used for greenhouse cultivation however, requires large amount of water during evaporation based cooling. Since water resources are becoming scarce in future such fan-pad cooling system may not be viable in future specifically in hot arid region.

Life cycle cost analysis

Economics of solar energy devices can be calculated through life cycle cost (LCC) analysis. Total life cycle cost of a device is comprised of capital cost, maintenance cost, replacement costs for damagaed components and operational cost. Before adding these above costs, all future costs (C) are converted to present worth considering the relative rate of inflation (i) and discount rate (d).

Where, PW is the present worth of any future cost, i is the relative rate of inflation and d is the discount rate per year and n is the time period in years. Relative rate of inflation accounts for the escalted increase or decrease in prices of a commodity in comparison to general inflation rate. For any commodity, if the price escalation is expected as per the general inflation rate then relative rate of inflation is considered zero. In general case, relative rate of inflation is considered zero. Discount rate accounts the real value of money in future and in most of the economies of the world it is about 8-12%, and therefore 10% is considered in most analyis. The discount rate also refers to the interest rate used in discounted cash flow (DCF) analysis to determine the present value of future cash flows. The discount rate in DCF analysis takes into account not just the time value of money, but also the risk or uncertainty of future cash flows; the greater the uncertainty of future cash flows, the higher the discount rate. A discount rate of 10 % per year would mean that in real terms it makes no difference to a farmer whether he has ? 100 now or ? 110 in one year’s time. Conversely, a cost of ? 110 one year from now has a present worth of ? 100. For a future single cost in n^th year, the present worth of that cost is calculated using Eq (1). However, for future multiple payments, costs are to be converted to present worth for each year and then needs to be cumulated. For calculation of annualized life cycle cost (ALCC) of solar devices, annuity factor (AF) needs to be calculated for a period of life cycle of the device as follows:

Introduction

Solar energy could be converted to electricity both through thermal route and photovoltaic cells but the latter is more advantageous as it has no moving part, it doesn’t require water, a rare commodity specifically in arid regions. Moreover, the maintenance of PV systems is easy, it can be installed right at the place of utility, the system is modular and these are reliable having life more than twenty years and of course eco-friendly.

In photovoltaic cells, generally known as solar cells, charge carriers are generated by the incoming irradiance (energy greater than band gap) and these are separated and swept away by an internal electric field, which is created by either making metal semiconductors contact (Schottky barrier) or p-n junction or MIS (Metal Insulator Semiconductor) or SIS (Semiconductor Insulator Semiconductor) devices. The height of potential barrier at the junction determines the voltage and the flowing charge carriers contribute to the current when connected externally. The choice of material depends on its band gap, absorption coefficient, diffusion length, mobility of charge carriers, ease in contact formation, type of junction with thermal and electronic compatibility, availability of material, toxicity and several other fabricational opto-electronic and practical aspects. PV cells based on single crystal and polycrystalline silicon, amorphous silicon, CdS, CdTe, CuInGaSe, InP, GaAs etc. have been much studied. PV modules of efficiency above 16% on silicon and 10% on CdTe, CuInGaSe and 8-9 % on amorphous silicon are commercially available. Dye sensitized TiO₂ devices have also been receiving more attention with coloured panels for windows. Organic semiconductors are explored and more recently perovskite solar cell has been studied. Flexible solar cell panels based on thin film devices are in use. The applications have gone from solar lighting to operation of pumps, small and medium size equipment, stand alone and grid connected solar power plants, roof top and building integrated PV and now even energizing cars and aero planes. With technological advancement and enhanced production (233 GW in 2015) the cost of commercially available PV modules, which used to be high at one time has been brought down from 30 $/Wp in seventies to about $0.5/Wp at present.

Introduction

As the most of the conventional resources are depleting and can last only for about a few 30 to 50 years. Scientists worldwide are looking for alternative energy resources and they have come to an agreement that solar energy can provide much of our energy needs in the future. The major challenge before them is to store this energy. The radiation falling on the earth surface can be tapped and stored in no of ways. However, the most efficient way is done through the latent heat storage through PCM. The PCM has many added advantages i.e. high energy density, isothermal behavior, non-polluting and low cost. Nowadays, it gaining popularity worldwide and now seen as the most efficient way of thermal energy storage. There is a large number of PCM at use i.e. organic, inorganic, eutectic and salt hydrates. Their utilization depends on the user’s requirement technological constraints. They also serve the purpose of energy availability at night beside the uninterrupted supply during the day. They are seen as the materials for ensuring the environmental sustainability

Introduction

The thermal performance of a building refers to the process of modeling the energy transfer between a building and its surroundings. For a conditioned building, it estimates the heating and cooling load and hence, the sizing and selection of HVAC equipment can be correctly made. For a non-conditioned building, it calculates temperature variation inside the building over a specified time and helps one to estimate the duration of uncomfortable periods. These quantifications enable one to determine the effectiveness of the design of a building and help in evolving improved designs for realizing energy efficient buildings with comfortable indoor conditions. The lack of proper quantification is one of the reasons why passive solar architecture is not popular among architects. Clients would like to know how much energy might be saved, or the temperature reduced to justify any additional expense or design change. Architects too need to know the relative performance of buildings to choose a suitable alternative. Thus, knowledge of the methods of estimating the performance of buildings is essential to the design of passive solar buildings.

Introduction

Considering the accountable post-harvest losses which is approximately 30-35 percent, food processing becomes an extremely important sector for preventing the losses and feeding the growing population. The Indian food industry is poised for huge growth, as currently valued at US$ 1.3 billion with compound annual growth rate of 20 per cent per year, increasing its contribution to world food trade every year. In India, the food sector has emerged as a high-growth and high-profit sector due to its immense potential for value addition, particularly within the food processing industry. Increasing population of the country and high cost of fuels have also created a demand for new alternate sources of energies for post-harvest processing of foods. Solar food processing technologies may become a viable option that provides good quality foods at low or no additional fuel costs. The energy policy of the developing countries now focuses on the clean renewable energy to create a further reduction of the petroleum import and to alter the utilization of petroleum energy toward the utilization of solar energy. It is an interesting fact that most of the developing countries fall in the climatic zone where the insolation is considerably higher than the world average of 3.82 kWh m-2 (Majumdar 2015). The daily horizontal insolation of India is approximately 5.80 kWh m-2 (Visavale 2009, Visavale et al. 2011). Solar dyers are an alternative to traditional drying technique and a contribution towards the solution of the problems of the open sun drying from perspective of renewable and clean energy. The International Energy Agency (IEA) declared in its 2011 solar energy perspectives executive summary (SEP 2011): “Solar energy offers a clean, climate-friendly, very abundant and inexhaustible energy resource to mankind, relatively wellspread over the globe. Its availability is greater in warm and sunny countries that will experience most of the world’s population and economic growth over the next decades.

Trees are the largest plant components of gardens and landscapes. However much architectural features dwarf them, for human beings, they are the largest living entities in the environment. Profoundly influencing our habits, styles of habitation, culture and daily life, trees have been revered, sanctified and given symbolic importance and above all, depended upon as means of livelihood by entire communities through the ages. Through folklore, traditional knowledge and rituals, the usefulness of trees has been handed down from generation to generation-in societies all over the world. In India, cave paintings and carvings in addition to ancient literary works document the aesthetic and medicinal knowledge of our forefathers about trees found in the sub-continent.

Trees differ in stature, branching habit, girth of trunk and branches, canopy structure, outline and crown shape. The colour of the foliage, its texture, glaze, shape and size, foliage colour, floral features and season of flowering also differ among trees. These characteristics in addition to giving distinctiveness, also determine their ornamental use in gardens and landscapes. In tropical gardens evergreen dicotyledons and palms dominate among the trees, whereas in temperate situations evergreen conifers are selected over the deciduous dicots for tree planting. Palms among trees are universally grown as avenue trees or as clumps in areas where they can be easily grown while the other trees are grown as such or pruned and trained into various forms or as bonsai in gardens.

Shrubs are the most diverse groups of ornamentals grown in tropical gardens. In habit they are hardy perennials having low spreading woody branches. They vary widely in stature and include dwarf bushes to those attaining the stature of small trees.

IMPORTANCE AND USES OF SHRUBS

Shrubs are quick growing and many of them flower continuously in the humid tropics. Their variability in flower colours and foliage characteristics and their easiness in propagation by vegetative means make them garden favourites. The various uses to which shrubs are put to in gardens are detailed below: -

In A Shrubbery : Grouping of shrubs in a shrubbery is done to display the attractiveness of their flowers and foliage. In temperate situations shrubs grown in shrubberies include Rhododendron, Peony, Fuchsia, Buddleia, and Camellia while in the tropics and subtropics, the range of shrubs available for planting are very wide.

As Focal Point Plants : Shrubs that are ever flowering like Hamelia and Hibiscus or those that have spectacular flowers such as Mussaenda, Neerium and Ixora are grown as focal point plants in small gardens. They are also grouped for mass effect in large gardens.