eChapters

Introduction

`The living and nonliving components of ecosystems, as well as the conditions and processes that occur within them, create services thus connecting ecosystems and human cultures. The preservation of Earth’s biological diversity and the protection of the benefits, or “ecosystem services,” those functioning ecosystems bring to humanity are two primary goals of environmental conservation. Agroforestry is increasingly viewed as providing ecological services, environmental advantages, and economic gains as part of a multifunctional working landscape. The multifunctional importance of agroecosystems was emphasized in both the Millennium Ecosystem Assessment (MES 2005) and the International Assessment of Agricultural Science and Technology for Development (2008).

Introduction

Climate change is threatening food security globally. Countries like India are more vulnerable in view of the tropical monsoon climate and poor coping capacity of the small and marginal farmers. Several agricultural practices like indiscriminate use of agro-chemicals and crop residue burning contribute to emission of greenhouse gasses leading to warming of the atmosphere. Sequestration of carbon both in the vegetation and soil is the most effective means of mitigating GHG emissions. There are several strategies of soil carbon sequestration which can be adopted at farm level. These include: conservation agriculture, biomass recycling, crop rotations and use of organic amendments. One of the recent developments is the conversion of crop residue biomass into biochar and using the char as a soil amendment rather than directly using the crop residues. Several studies show that biochar has a long life in soil and is more effective in sequestering carbon besides improving other soil properties like water holding capacity and nutrient availability. In Indian conditions, there is an immense scope for converting millions of tonnes of crop residues which are not used as fodder into biochar and use the same for enriching soil carbon.

The coastal salt affected soils are low in productivity due to various soil fertility constraints that affect the crop growth and yield. The high salt content &/or high pH cause changes in solubility, availability and efficiency of plant nutrients, besides deteriorating the physical condition of soil. The soil biology (microbial population and enzymatic activities) also severely affected in these salt affected soils. The bio-resources are known to improve soil physical, chemical & biological properties of the soil. The maximization of rice production and considerable improvement in quality and composition of rice in coastal salt affected soil with the use of bio-resources have been reported by several research workers.

Toxic elements like Cadmium (Cd), Fluoride (F), heavy metals, radioactive metals are associated with mainly rock phosphates, other organic wastes like sewage sludge and pollutants. Their chemistry is similar to plant nutrients and replace them in their physiology leading to reduced uptake of nutrients, productivity and contaminated food chain.

Rice farming under different subsystems of lowland ecology
1. Rainfed lowland with limited water at seeding and excess water at later growth stages: In rainfed lowland areas, the rice is direct seeded in dry soil in April-May before onset of monsoon (June) and seeds germinate with the showers received after sowing. Drought at the seedling stage kills seedlings and results in poor stand establishment. Furthermore, heavy rains in catchment areas of river basins result in water logging and flooding at late growth stages. The water hinders tillering and results in poor panicle number less than 200/m2 as against 350 /m2 of high yielding rice cultivars.
2. Rainfed lowlands with limited/excess water at transplanting and excess water at later stages: When on-set of the monsoon is delayed, transplanting delayed because the farmer has to wait for adequate rains for land preparation. Monsoon rain submerges the transplanted crop, resulting in poor stand. In some areas, the land gets inundated before transplanting and farmers generally transplant aged and tall seedlings to keep the plant parts above the water. Plant survival in deeper water depends on rise in water level and on the elongation ability and submergence tolerance of the plant. Varieties that elongate fast develop weak culms and may lodge when the water level recedes. In this situation tillering is poor and panicle per unit area are less.
3. Assured irrigated areas with excess water during crop growth due to poorly drained condition: Rice grown in the river deltaic areas of Krishna, Godavari and Indo-Gangetic rivers suffer from water stagnation even though some areas are having irrigation facilities. Heavy rains in the catchment cause flooding and stagnation in rice fields because of congested drainage or lack of drainage caused by topographically saucer-shaped land. These conditions develop during peak monsoon (July-September). The late planted crops, being at an early stage of growth, suffersfro water stagnation. In these areas, transplanting early in the season is necessary for plants to grow enough to escape submergence.

Irrigation Efficiency
Irrigation water is an expansive input and has to be used very efficiently. The main losses that occur during irrigation of fields as conveyance, run off, seepage and deep percolation; Irrigation efficiency can be increased by reducing these losses. Uneven spreading and inadequate filling of root zone are the other causes for low irrigation efficiency. Irrigation efficiency at the field level can be increased by selecting suitable method of irrigation, adequate land preparation and engaging an efficient irrigator. At the project level, it can be increased by proper conveyance and distribution system. Irrigation efficiency is the ratio usually expressed as percent of the volume of irrigation water transpired by plants, plus that evaporate from the soil, plus that necessary to regulate the salt concentration in the soil solution and that used by plants in building plant tissue to total volume of water diverted, stored or pumped for irrigation.
Wt+Ws-RsEi=×100Wi
Where,
Ei = Irrigation efficiency (percent)
Wt = the volume of irrigation water / unit area of land transpired by plants, evaporation from the soil during the crop period.
Ws = the volume of irrigation water per unit area of land to regulate the salt Content of soil solution.

Abstract

The groundwater targeting in hard rock aquifer systems is complex, because of the heterogeneity of the aquifer systems. The ground water mobility and stability in such aquifer systems varies because of the lithology, folded structures, fracture density, geomorphology, slope etc., These occur in various permutations and combinations and control the overall water holding and conducting capacity in different parts of the aquifer systems. Hence, one needs to analyse all the data so as to understand and bring out precise spatial models on the groundwater probability in hard rock aquifer systems. In the present study, the authors have carried out GIS based appraisals to understand the relation between the lithology and groundwater movement in hard rock aquifer systems of parts of Central Tamil Nadu covering 1300 sq.km. In the said study, GIS images were generated on the maxima zones of various aquifer parameters such as water level, width of aquifer depletion, transmissivity, permeability, specific capacity, storage co-efficient, optimum yield and recovery rate. These were overlaid with the lithology GIS image. Such an analysis has shown that, in general, the fissile hornblende biotite gneiss appears to have some control over the groundwater systems.

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.

About 60 per cent of total arable land (142 million ha) in India is rain-fed, characterized by low productivity, low income, low employment with high incidence of poverty and a bulk of fragile and marginal land. Watershed development program is, therefore, considered as an effective tool for addressing many of these problems and recognized as a potential engine for agricultural growth and development in fragile and marginal rain-fed areas. The Government of India has accorded high priority to the holistic and sustainable development of rain-fed areas through the integrated watershed development program since the 7th Five Year Plan (1985-90) and since then a number of watershed programs have been specifically launched in the rain-fed areas with the sole objective to improve the livelihood of poor rural households in a sustainable manner.

Moisture deficit causing shortfalls in crop production is the characteristic feature of dryland agriculture. Other adverse factors viz., decline in soil fertility together with play of biotic stresses add to the complexities of dryland crop production. Added to the proven agronomic management to combat the problem of drought in dryland agriculture, there is the need to tailoring of suitable crop varieties which can yield reasonably well under conditions of moisture deficit (Varshney et al., 2021). In this context, the appropriate developmental rhythm along with the combination of the constellation of characters of the crop plant matching with the rainfall and the soil moisture availability patterns of the zone are the important considerations together with stability of yield (Hanson and Nelsen, 1980). This task being a complex one, the problem should be approached through multidisciplinary strategy that should buffer the genetic and breeding efforts.

10.1 Introduction

Rainwater is the main source of water for agriculture but its current use efficiency for the crop production is low ranging between 30-45%. The rising demand for water for non-agricultural uses is proportionately decreasing its share for agricultural uses. Efficient methods of water harvesting in the farm reservoirs including farm ponds and its management for subsequent uses in agriculture with improved water use technologies are vital for increasing the productivity and reducing poverty in rainfed ecosystems. It is not to be forgotten that the harvested water in the pond is a very valuable commodity. It may be used for industrial use or for irrigation in agriculture. The harvested water is also a good source to meet the water demand of domestic animals and for human beings (Fig. 10.1). The stored water of the pond can be used for fish farming, tree plantation, intensive irrigation to small area and extensive supplemental irrigation to rainfed crops. Stored water in a pond is developed resource and is, therefore, more expensive than the natural resource. Hence, there is a need to utilize it judiciously and efficiently.

Introduction

One of the most common concerns in irrigated agriculture is regarding water quality or salinity. Out of the ground water surveyed in different Indian States, as much as 84% is rated either saline or alkaline (Minhas 1996). Salinity management is very important for using saline water in irrigation safely. This requires an understanding of how salts affect soil as well as plants, of how hydrogeologic processes affect salt accumulation, and also of how cropping and irrigation activities affect soil and water salinity.

The objectives of management practices for getting optimal crop production with saline irrigation water include the prevention of salt build-up in soil which limit the productivity of soils and the control of salt balances in the soil-water system, as well as minimising the damaging effects of salinity on crop growth (Meiri and Plaut 1985). Amongst the various soil, water, and crop management options available, there is usually no single way to achieve safe use of saline water in irrigation but many different approaches and practices can be combined into satisfactory irrigation systems using saline water. The appropriate combination depends upon edaphic, hydrogeologic, climatic factors as well as social and economic condition of the farmer. Several practices interact with each other, and should be considered in an integrated manner, along with climatic and human factors. Because of the climate, the basic principles of saline water management need some adaptation, e.g. providing for a leaching requirement is not appropriate when the growing season for post-monsoon winter crops starts with a surface-leached soil profile, because it would increase the salt load. High salinities during the initial stages of growth are particularly harmful. Recommendations for effective management of irrigation water salinity depend upon local soil properties, climate, and water quality; options of crops and rotations; and irrigation and farm management capabilities

11.1. Determination of Electrical Conductivity of Soil Solution

The conductivity or more precisely the specific conductance of a soil at a given soil-water ratio is the reciprocal of the specific resistance offered by the solution at 25ºC between the electrodes of 1 sq cm cross section kept 1 cm apart. Thus, the electrical conductivity of any solution depends on the amount of soluble salt present in it. Knowledge on the extent of salinity is important for management of saline soil including the choice of the crop suitable for that soil. Soluble salt content in saturation extract is more reliable index of salinity level than in soil: water ratio of 1: 2 or 1: 2.5 because it simulates the extent of salinity experienced by crop in field moisture condition.

Salinity class of soil is based on the electrical conductivity (EC) of saturation extract at 25ºC. However, EC of water extract from 1:2 soil-water suspension can be transformed into the EC of saturation extract following the formula (except for soil containing gypsum).

Pure water is a poor conductor of electricity. Water may carry electricity fairly well when it contains electrolytes such as Acids, bases and salts. Electrolytes in the solution dissociates with cations and anions and pass on electrical conductivity. Hence, more electrolytes concentration in water, more its electrical conductance. The following ions are crucial for adding conductivity to water.
i) Cations: Mg 2+,Ca2+, Na+ and K+
ii) Anions: Cl-, S4
-, CO3
-, HCO3
-and NO3
-
In the International System of units (SI) the reciprocal of ohm is the Siemens (S) and conductivity is reported as millisiemens per meter (mS/m). 1 mS/m = 10 µS/cm = 10 µmhos/cm and 1 µS/cm = 1 µmhos/cm Principle
The quantity and kind of ions present in a solution affect conductivity, which is a numerical representation of a water sample’s capacity to conduct electricity. Since the majority of dissolved inorganic compounds in water are ionised, they add to conductance. The definition of conductance G is the reciprocal of resistance R.

Pure water is a poor conductor of electricity. Water may carry electricity fairly well when it contains electrolytes such as Acids, bases and salts. Electrolytes in the solution dissociates with cations and anions and pass on electrical conductivity. Hence, more electrolytes concentration in water, more its electrical conductance. The following ions are crucial for adding conductivity to water.
i) Cations: Mg 2+,Ca2+, Na+ and K+
ii) Anions: Cl-, S4
-, CO3
-, HCO3
-and NO3
-
In the International System of units (SI) the reciprocal of ohm is the Siemens (S) and conductivity is reported as millisiemens per meter (mS/m). 1 mS/m = 10 µS/cm = 10 µmhos/cm and 1 µS/cm = 1 µmhos/cm Principle
The quantity and kind of ions present in a solution affect conductivity, which is a numerical representation of a water sample’s capacity to conduct electricity. Since the majority of dissolved inorganic compounds in water are ionised, they add to conductance. The definition of conductance G is the reciprocal of resistance R.

Principle

Different ions migrate at different speed dictated by their size and by the amount of charges they carry. As a result, different ions can be separated from each other by electrophoresis. The magnitude of the electric force F exerted on the charged particle when subjected to electrophoresis is product of the charge q of the particle and the electric field E generated between the two electrodes.

8.1 Design of Canal Embankments

 There are two aspects of canal embankment design.

 (i) The general requirement, such as free board, dowel, service/inspection road, drainage of banks etc. The aspect of free board is discussed in Para

8.2 to 8.3 and that of service/ inspection road in Para

 8.4 and drainage of banks in Para 8.5 in this chapter.

 (ii) Safe design of embankment i.e. Hydraulic and structural requirement.

It includes stability of inner and outer slopes, Structural safe design of inner cut slopes in deep cuttings in different types of soils/rocks of varying nature and ground water conditions. Stability of slopes may include drainage, so as to prevent rock falls/debris in canal. For outer slopes in embankment (filling sections) hydraulic gradient/pharetic line, toe drains etc, similar to the earthen dams, on different types of soil/rock foundation with respect to varying ground water level conditions are important.

The canal embankments in filling may even fail through its foundations by sloughing or liquefactions. All these aspects of canal embankments are discussed in this chapter in Para 8.4 to 8.9.

Microbes that live inside plant tissues without causing disease are termed as endophytes. Endophytes have been found in all parts of plant viz., seeds, roots, stems, leaves, fruits etc. Within these organs, there is evidence of endophytes living in apoplastic intercellular space within parenchyma tissues and xylem vessel apoplast. Endophytic bacteria have been isolated from both monocotyledonous and dicotyledonous plants, ranging from woody tree species to herbaceous crop plants. Further, a single plant may be a host for several different bacterial species. They are consistently present in the root, stem, leaf, fruit and tuber tissues of a wide range of agricultural, horticultural and forest species. All plants in nature harbor a diverse community of endophytic bacteria which can positively affect host plant growth.

The potential of endophytic bacteria to fix nitrogen, promote plant growth and suppress plant diseases has renewed interest in such associations. It is advantageous to have the endophytic plant growth promoting organisms safely inside the plant, which could supply substantial amounts of nitrogen and other nutrients, growth hormones and other beneficial effects to the crop plants without the interference of the rhizosphere soil environment. Furthermore, plant growth promotion is often greater when it is induced by endophytes rather than by rhizosphere bacteria.

Introduction

The basic needs of life are food, clothing and shelter. In the 21^st century a fourth need added to mankind is energy. According to the laws of physics, energy is defined as capacity to do work. Energy, economics and the environment are mutually dependent. Also, there is very close relationship between agriculture and energy. The level and pattern of energy use in agricultural production system depends on variety of agronomic and socio-economic factors. Energy use in agriculture encouraged maximization of yields from limited available arable land, minimization of labour intensive operations and improving standard of living. Efficient and effective energy use in agriculture is one of the conditions for sustainable agricultural production, since it provides financial savings.

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