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All life on planet Earth is carbon centered; hereditary characters are controlled by DNA and RNA, growth by proteins and activities by energy from carbohydrates and fats – all these are carbon compounds. Not only this, but the life also ends as carbon compounds CO₂ or CH₄, depending on aerobic or anaerobic decomposition. Incidentally soil fertility also depends very much on soil organic carbon (SOC). In ancient days, farmers used to apply manure to maintain soil fertility and even now, urea, the nitrogen fertilizer used in the largest amounts, is a carbon compound. All living forms on the Earth including all plant and animal species and their activities are a part of global carbon cycle. The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the earth.

INTRODUCTION

In biology, fertility is de?ned as capacity to produce off-springs; however, in Soil Science a ?ne difference is made between a fertile and a productive soil. Soil Productivity is the ability of a soil to produce a crop using the entire spectrum of its physical, chemical and biological attributes, while Soil Fertility refers to the capacity of a soil to supply all essential plant nutrients in the desired amounts. Thus, soil fertility management is basically the nutrient management. To put it in simple words, a productive soil is always fertile, while a fertile soil may not be productive for a variety of factors, such as lack of adequate moisture in drier regions or lack of adequate air due to water-logging for most upland crops. Of late, a term ‘ Soil Health’ has been introduced. Soil Health is an assemblage of chemical, physical and biological parameters that closely relate to native or acquired production capacity and sustenance of ecologically important regulatory role (Katyal et al., 2016). It is measured against prede?ned parameters of soil’s status of fertility, compact ability, erodibility and biology. This again tends to relate soil fertility to nutrient content, availability and management.

LAND VERSUS SOIL

Land is a part of Earth’s surface that is not covered by water. It is used for agriculture, building houses, of?ce buildings, schools, hospitals, roads, railroads and even water canals. Land is measured by area [length (l) × width (w)] and the units are square meters (m²), square centimeters (cm²) etc. On the other hand, soil is Earth’s crust, which could vary from a few centimeters to a few meters in thickness (depth), needs a measure of volume [length (l) × width (w) × depth (d)] and the units are cubic meters (m³), cubic centimeters (cm³) etc. Soil is thus a three-dimensional natural body on Earth’s surface that provides anchorage to growing plants/ trees and shelter to soil biota and is responsible for the storage of water and plant nutrients, which are essential for crop production. In addition, it helps in the biodegradation of soil pollutants and puri?cation of ground water, the major source of drinking water in the world. Soil feeds all living beings on Earth and its degradation is one of the reasons for inadequate human nutrition

11.1 Performance of Farm Irrigation Systems

The performance of farm irrigation systems is determined by the efficiency with which water is delivered to the field and utilized to the fullest amount possible with minimum losses due to seepage and percolation, runoff, evaporation and other operational losses. The efficiency of the irrigation system will increase if the conveyance losses, application losses and other losses are reduced to a great extent.

11.1.1 Overall Efficiency

The overall efficiency of a farm irrigation system is defined as the percent of water applied to the farm that is used for irrigation on the farm. Irrigation efficiency otherwise called as overall system efficiency is defined.

10.1 Application Efficiency and Irrigation Uniformity

All irrigation systems have some non-uniformity. This non-uniformity influences yields and irrigation efficiency especially application efficiency. If the net amount of water applied during irrigation is the same as that required to fill the soil water deficit, then because the distribution of water is never perfect, half of the field will receive too much water while the other half will receive too less water. In such a context, a farmer will try to apply more irrigation water to his field so that a larger fraction of the field has an adequate amount. This will tend to have higher percolation and runoff and thereby declining the application efficiency. An alternative to adding extra water is to improve the uniformity of water application. A major advantage when the uniformity is improved is that the amount of deficit in the area under irrigation is reduced and the potential for water logging and salinization is also reduced.

9.1 Introduction

After knowing when to irrigate and how much to irrigate, next important thing is how to irrigate the crop field. Methods of irrigation plays a very crucial role in deciding how to irrigate the crop fields since all the crops do not require same methods of irrigation. Depending on the sources of water available for irrigation, type of crop to be irrigated, quantity and quality of water to be applied and other economic considerations, methods of irrigation will vary. Irrigation water may be applied to the crops by flooding it on the field surfaces as surface irrigation, by applying it beneath the soil surface as sub irrigation, by spraying it under pressure as sprinkler or overhead irrigation or by applying it in drops around the root zone of the crop as trickle irrigation. The commonly used methods of irrigation are described in schematic diagram as follows

8.1 Introduction

For maximization of yield of crops, it is essential to provide irrigation to crops. When either the natural sources like rainfall, dew, snowfall and other forms of precipitation or when the capillary rise of groundwater is not sufficient to meet the crop water demand, then there is need to supply irrigation. This irrigation water is a precious resource and need to be used cautiously. There are three important things need to be understood for optimum utilization of irrigation water with basic purpose to maximize the yield and returns. 

7.1 Introduction

The entire amount of water that is diverted at the canal head regulator does not reach at the field for use of irrigation. Major amount of it is lost on way during its movement in the canal systems. During the passage of water from main canal to outlet at the head of the water course, water may be lost either by evaporation from the surface or by seepage through the peripheries of the channel. These losses are sometimes very high, and may go up to 50 % of the total water diverted into the main canal. Evaporation losses are low and may go to a maximum of about 7 percent of total losses. The major loss of water in the conveyance system is the seepage loss. Seepage loss depends on the channel geometry and evaporation loss is proportional to the area of free surface. In determining the designed channel capacity, a provision of these water losses must be made. The provision for the water lost in the watercourses and in the field however, already made in the outlet discharge factor, and hence no extra provision is made on that account. However, excluding the above two losses, there is operational loss which when added to the evaporation and seepage losses, the total losses goes up the maximum 50 percent level. The operational loss includes spillage, over-toping, leakage through rodent holes, dead storage, initial infiltration and evapotranspiration from the vegetation along the watercourse. Evaporation and seepage losses of the canals are discussed below.

6.1 Introduction

In order to increase the production and productivity of crops, provision of irrigation system is highly essential. A project that makes use of weir or a barrage for providing irrigation to fields is called as direct irrigation system. On the other hand, a storage irrigation system makes use of storage reservoir by construction of dams. In order to provide irrigation by both the schemes, it is necessary to have a network of canal systems. A canal is an artificial channel, generally trapezoidal in shape constructed on the ground to carry water to the fields. The canal systems that provide water to the fields include main canals, branch canals, distributaries, minors and watercourses. It is imperative to design the canal systems properly for a certain realistic value of peak discharge that must pass through them so as to provide sufficient irrigation to the command areas. The flow irrigation that provides irrigation water to the fields may be of two types i.e. Inundation irrigation and Perennial irrigation.

5.1 Soil

Soil and water are the two most important natural resources required for crop production. Without soil, no crop can be produced even if there is availability of plenty of water. It is vital not only for agriculture but also very vital for sustenance of life. No building can stand on any place without soil. Soil gives foundation support for any building. The term ‘soil ’is defined in various ways depending on the general professional field in which it is used. However to an agriculturist, soil is the substance existing on the earth surface, which grows and develops plant life. It contains all vital elements including its inherent fertility contents that support the growth of plants. For an engineer, soil is the unaggregated deposits of mineral and organic particles covering major part on the earth crust. It includes widely different materials like boulders, sand, gravel, clays and silts. Soil is produced by the weathering of solid rocks. The formation of soil is due to geologic cycle continuously taking place on surface of the earth. The geologic cycle comprises weathering or denudation, transportation, deposition and upheaval, again followed by the above mentioned processes. Weathering may be natural or artificial. In natural weathering, physical processes like temperature changes, flow of water, ice, wind and rain play the role. In artificial weathering animals especially human beings interference causes soil erosion and formation. It is obvious that it takes hundreds of years to form one inch of soil.

4.1 Introduction

A reservoir that collects and harvests in-situ rainfall as well as runoff from the catchment area can be used for many purposes: the most important of which is the supply of water to crops as supplemental irrigation. The water of the reservoir can be used for domestic and industrial uses. It is also a good source for recreational use. Total water demand of the reservoir including irrigation to different crops in different seasons, domestic and other non-agricultural uses are to be assessed. While estimating the crop water requirement and irrigation requirement, various crops to be grown in the service area of the reservoir, their water requirements, crop duration, extent of coverage and water management practices followed are to be taken into consideration. Multiplying the irrigation requirement with crop coverage area, volumetric irrigation water requirement of crop can be found out. Summation of irrigation requirement of all crops grown in service area of the reservoir gives total irrigation demand of the reservoir.

4.2 Water and Irrigation Demand of Crops

Of the various demand of water from the reservoir, irrigation demand of crops grown in the command area of the reservoir is very important. Most of the crop water demand is met from rainfall. However, when the rainfall is deficient to meet the crop water demand, then the deficit is met from the stored water of the reservoir in the form of irrigation, more commonly called as supplemental irrigation. The irrigation to the crops is required mostly to meet the evapotranspiration requirement of the crop. Before discussing the water and irrigation demand/requirement of crops, it is essential to know some commonly used terms frequently used.

3.1 Introduction

Irrigation water that is supplied to crop fields is defined by a term commonly called as discharge which is also called as rate of flow. Discharge is defined as the volume of water flowing through a cross section in a unit time. It can be expressed as cubic metre per second (cumec), cubic feet per second (cusec), litre per sec (lps) etc. one cumec is equivalent to 35.5 cusecs or 1000 lps. The measurement of discharge is very important in everyday life starting from deciding the amount of irrigation to be supplied to a crop at a particular growth stage, or amount of water supply for domestic and industrial uses, for flood control and power generation etc. It plays a vital role in water resources planning.

3.2 Methods of Discharge Measurement

The various methods of discharge measurement can be broadly classified into the following types: (i) volume method of discharge measurement (ii) flow measuring structures such as orifices, mouthpieces, flumes and weirs.

2.1 Introduction

Rain and snow are the two chief sources of water of the earth. In-situ conservation of rainwater helps the plants to meet some of their consumptive uses directly. Not all the amount of rainwater that falls at a point is conserved by the soil reservoir to support the plant growth. Some part of it flows over the soil surface as surface runoff and some seeps down as infiltration and finally adds to the underground reservoir. Therefore, rain or snow, which is not used directly by the plants, becomes a potential source of either surface or ground water for irrigation. In areas with extreme low temperature, snow contributes major source of water supply wherever, in humid and sub humid regions, rain is the principal source. Precipitation, rain or snow, is the first stage of the continual cycle of water in its round from atmosphere to the earth and return by evaporation from water bodies, snow surfaces and land surfaces. The continual cycle of distribution of water is governed by the process called as hydrologic cycle. Thus, precipitation or atmospheric water is the first form of water above the earth’s surface, the second form being the surface water on earth and the third form is the subsurface water or underground water. The study of occurrence, distribution and circulation of precipitation through the unending hydrologic cycle forms the basic part of study of hydrology. As mentioned above, the part of precipitation that is not used by the plants in-situ flows over the soil surface as runoff and contributes to either surface or ground water supply.

Engineering hydrology is the science that deals with the estimation of runoff and its transmission from one place to the other, besides dealing with the properties of water in nature. For, an engineer, surface and groundwater are the two most important components to deal with. But due to lack of data of stream flow, it is usually necessary to study precipitation, evaporation and percolation to indirectly determine the availability of surface and groundwater. For planning and management of water resources systems, an engineer has to estimate (i) water resources potential of a basin, (ii) dependable yield for irrigation and hydel power generation and industrial water demand (iii) probability of occurrence of floods with their magnitude, (iv) sediment yield and transportation (v) hydrometeorology (vi) new sources of water for irrigation (vii) stream flow forecasting by use of precipitation data (viii) water control, navigation, control of soil erosion and control of pollution of water bodies and (ix) operation and maintenance of river valley projects. For estimation of the above mentioned parameters, it is important to understand the hydrologic cycle properly.

1.1 Importance of Water for Agriculture

All animals and plants require water for their survival. Animals cannot prepare their own food. They depend on plants for their food. Plants need water for preparation food by the process of photosynthesis. Majority of this water requirement of the crops is met from different forms of precipitation. However, when the water requirement is not fully met from precipitation, then growth of the crops is affected. Water requirement of crops depend on many factors. It depends on the type of crops, irrigation schedules practiced, soil texture, position of groundwater table below effective root zone of the crop and management practice followed in crop cultivation. The dry land crops need less water compared to rice which is a water loving crop. The perennial crops like sugarcane, banana etc. need more water than other crops like cereals, pulses, oilseeds etc. Water requirement of crops is partly met by the upward flux of groundwater. The capillary rise of shallow water table in the form of upward flux helps in meeting the water requirement of crops to some extent. The upward flux depends on the type of the soil, effective root zone depth of the crop, depth of water table below effective root zone depth of the crop and potential gradient of soil moisture suction. If the soil is heavy like clay, effective root zone depth of the crop is more (deep rooted crop) and position of ground water table is near to ground level (shallow water table), then the upward flux is more.

Due to rainfall or application of irrigation water, some amount of water is recharged to soil reservoir. This recharged water is stored in the soil as soil moisture content. The stored moisture or called as water in the soil reservoir helps in supporting water requirement of crops also. The heavy soil like clay has more moisture retention capacity than the light soils like sandy soil. The residual soil moisture held in clay soil is released slowly and supports more soil moisture to the crops for a longer period than the sandy soil which has less soil moisture retention capacity. After meeting the water requirement of crops from all sources including different forms of precipitation, ground water contribution by capillary rise and residual soil moisture, if there is any shortage of water, then this shortage should be met from other sources which are called as irrigation. It is to be noted that irrigation is not the natural phenomenon of supply of water; rather it is the artificial means of supply of water to the crops. Irrigation may, therefore, be defined as the science of artificial application of water to the crop in accordance with the crop requirement for better nourishment of the crops.

Introduction

The resource conservation technologies (RCTs) is primarily focussed on resource savings through minimal tillage, ensuring soil nutrients and moisture conservation through crop residues and growth of cover crops, and adoption of spatial and temporal crop sequencing. These practices have long been practised by the farmers in the Indo Gangetic Plains (IGP) but it got eroded in recent times due to various geo-socio economic- political reasons. This region (10.5 million ha) comprises of Punjab, Haryana, Uttar Pradesh, Himachal Pradesh, Bihar and West Bengal and have major share in production of rice and wheat due to adoption of green revolution technologies followed by area expansion. It has been reported that rice-wheat system has strained the natural resources of this region (Swarup and Singh, 1989; Kumar and Yadav, 1993; Lal et al., 2004). In present scenario there is little scope to meet future target by earlier approaches like area expansion and intensive use of natural resources. Therefore, RCTs can be regarded as energy, water and labour efficient system to sustain soil health and production environment and produce more at less cost (Jat et al., 2012; Gathala et al., 2011b).

Major emphasis is given upon the RCTs components like zero/reduced tillage, direct seeded rice, crop residue management and crop diversification. However, other RCTs like site specific nutrient management, leaf colour chart, laser land leveller, nutrient use efficient genotypes, integrated crop and pest management provide options to the farmers as per their resource endowment.

Introduction

Persistent income from agriculture is most important for sustaining the farming sector. Conservation agriculture (CA) is a resource-saving agricultural production system that aims to achieve production intensification and high yields while enhancing the natural resource base through compliance with three interrelated principles, along with other good production practices of plant nutrition and pest management (Abrol and Sangar, 2006). Conservation agriculture is largely promoted as one of the few win–win technologies affordable to farmers, in the sense that potentially it improves farmers’ yields (in the long term) at the same time conserving the environment. CA is described by FAO (http://www.fao.org.ag/ca) as a concept for resource saving agricultural crop production which is based on enhancing the natural and biological processes above and below the ground. As per FAO definition CA is to a.) Achieve acceptable profits, b.) High and sustained production levels, and c.) Conserve the environment. It aims at reversing the process of degradation inherent to the conventional agricultural practices like intensive agriculture, burning/removal of crop residues. Shifting from tillage-based agriculture to no-tillage CA systems removes unsustainable elements in the current tillage based systems and replaces them with CA elements that make the production systems profitable and ecologically sustainable. Conservation agriculture offers an opportunity for arresting and reversing the downward spiral of resource degradation, decreasing cultivation costs and making agriculture more resource – use-efficient, competitive and sustainable.

Introduction

Precise and continuous measurement the greenhouse gases (GHGs) fluxes/ emissions in agricultural systems are required for accounting and budgeting of carbon. Further, the long-term measurements of GHGs fluxes are equally important as precise measurement. Therefore, high frequency and long-term measurement of GHGs across the cropping systems are essential for chalking out the GHGs emissions mitigation strategies. Various technologies with definite working principles are used for estimation of GHGs emissions in agriculture.

Greenhouse Gases Estimation Techniques

Two basic principles are followed to estimate greenhouse gases in agriculture. One is the collection of GHGs from the field and subsequent analysis of the concentration of gases through gas chromatography (GC). Another principle is based on sensors measurement with the help of infrared gas analyze (IRGA). The two techniques used for the measurement are (i) ‘closed chamber method’ (manual/automatic), and (ii) ‘sensor-based method’. Generally, the GHGs fluxes in agricultural crop field are estimated by ‘closed chamber method’ for methane (CH₄) and nitrous oxide (N₂O). And for carbon dioxide (CO₂) measurement either soil respiratory chamber or canopy chamber is used that measures CO₂ with the help of infrared gas analyzer (IRGA).

Introduction

Intensive soil tillage, burning of crop residues and over use of fertilizer and irrigation water under current agricultural practices has accelerated the pace of degradation in Indian agriculture. Intensive soil tillage increases soil erosion and nutrient runoff into nearby waterways. Crop residue burning resulting in loss of plant nutrients and release of greenhouse gases (GHGs) in the atmosphere. Imbalanced use of chemical fertilizer leads to soil compaction, slows down the fertilizer utilization rate and contaminates the local environment. Increasing demand of irrigation water causes water shortage and harms the environment in several ways including increased salinity, nutrient pollution, and the degradation of flood plains and wetlands. In the face of these management and environmental challenges, there is a need to formulate such agricultural practices which improve the productivity of natural resources as well as of external inputs and help to prevent soil degradation. Conservation agriculture (CA) practices such as reduced tillage, residue retention and proper crop rotations offer such solutions. CA also helps in making agricultural systems more resilient to climate change and safeguard ecosystem services.

Introduction

Conservation of biodiversity and mitigation of global warming are two major environmental challenges today. In the context of climate change and the global carbon cycle, the relationship between plant biodiversity and soil organic carbon (SOC) sequestration has become a subject of considerable scientific interest. The Earth’s terrestrial vegetation plays a pivotal role in the global carbon cycle. Not only are tremendous amounts of carbon stored in the terrestrial vegetation, but large amounts are also actively exchanged between vegetation and the atmosphere. Anthropogenic perturbations exacerbate the emission of CO₂ from soil caused by decomposition of soil organic matter (SOM) or soil respiration (Schlesinger, 2000). The emissions are accentuated by agricultural activities including tropical deforestation and biomass burning, plowing, drainage of wetlands and low-input farming or shifting cultivation. In addition to its impact on decomposition of SOM, macroclimate has a large impact on a fraction of the SOC pool which is active. Conversion of natural to agricultural ecosystems increases maximum soil temperature and decreases soil moisture storage in the root zone, especially in drained agricultural soils (Lal, 1996). Thus, land use history has a strong impact on the SOC pool (Pulleman et al., 2000). The dynamic relationship between plant biodiversity and SOC depicts that any land use practices that increase vegetative cover, or reduce its removal, could have an influence on the global carbon budget by increasing the terrestrial carbon sink.

Introduction

The inevitability of detrimental effects of climate change is looming large not only on the sustenance of agriculture, but also on the survival and progress of mankind. Estimates by the Organization for Economic Cooperation and Development (OECD) reveal that the atmospheric concentration of GHG would exceed 680 parts per million (ppm) CO₂-equivalents by 2050, which is about 50% higher than baseline year 2010 (OECD, 2012). Additionally, global temperature is predicted to increase by 2°C within this period, resulting in meansea level rise and erraticweather conditions. Consequently, the catastrophic effects on food consumption pattern by the end of 2050 will create malnutrition in at least 290 million people. Agricultural crops provide 63% of the human protein, and additionally supply almost 100% protein to the livestock, which are the second major sources of protein in human diet. Altogether, the detrimental effect of climate change on agriculture would make about 300 million additional people malnourished. Add to that a 2.7 billion increase in human population by 2050, coupled with shortage of water availability that would affect 3.9 billion people by 2050, and one can easily perceive the grim scenario for our kind in not so distant future.