eChapters

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

Plants are considered as immobile organisms with poor sensitivity and limited ability to respond. Within the plant kingdom, Mimosa pudica (also called the sensitive plant), Drosera (sundews), Dionea muscipula (flytraps) and tendrils of climbing plants which showed rapid and purposeful movements were considered as exceptions. These sensitive plants attracted attention of outstanding pioneer researchers like Pfeffer (1845-1920), Burdon-Sanderson (1828-1905), Darwin (1809-1882), Haberlandt (1854-1945) and Bose (1858-1937). Stahlberg, 2006 reported the presence of various mechanoreceptors in such species which could trigger action potentials (APs) which activated these sudden movements.

The first extracellular recording of a plant action potential (AP) development was initiated by Charles Darwin; later, the animal physiologist Burdon-Sanderson in 1873 performed similar studies on leaves of the Venus flytrap (Dionea muscipula Ellis). Haberlandt (1884) demonstrated that phloem strands were the actual paths for excitation by destroying the external, non-woody part of vascular bundles. This notion was confirmed in Mimosa and other plant species by a number of recent studies. Houwink (1935) carried out experiments with two species of Vitis (grape) and obtained electrical fluctuations which was similar and comparable with the action potentials he obtained with Mimosa. In 1907, Bose, used a D’arsonval galvanometer to demonstrate propagating electrical effects in different genera of plants such as Ficus, Artocarpus, Cucurbita, Corchorus, “fern” etc. APs have their largest amplitude in phloem sieve cells and cells adjacent to this area (Sibaoka, 1969). Other studies found that AP-like signals are propagated with equal rate and amplitude throughout the cells of vascular bundles.

Introduction

Plant architecture is defined as a three-dimensional organization of plant body in terms of its size, shape position of leaves, flower organs and branching pattern. Earlier this was the only criterion for systematic and taxonomic classification of plant species and the best means of identifying them (Stecconi, 2006). Study of plant architecture emerged as a new scientific discipline some 30 years ago. The subject derives its base from earlier works on plant morphology (Halle and Oldeman, 1970) but currently it is integrated with several disciplines of plant sciences ecology and engineering. Modification in plant architecture causes alteration in primary and secondary growth. This occurs due to differences in phyllotactic arrangement, branching pattern and floral differentiation. Plant architecture can be modulated by various parameters like climate, agronomic practices and human interventions. Manipulation of plant architecture is a major area in plant science which is currently adopted for productivity improvement by breeders, agronomists, horticulturists and landscape managers. However, the basis for such manipulation lies in the knowledge of the basic architecture of plants and its significance.

Introduction

Clean and renewable energy is a basic requirement for developmental activities. Global energy crisis is caused by increasing world population, escalating demand due to urbanisation, and continued dependence on fossil-based fuels. Non-renewable energy sources like coal, natural gas oil contribute 79 per cent of world electricity generation; only 21 per cent comes from renewable energy sources. Promoting the use of existing renewable energy sources and identifying new environment-friendly technology is gaining importance. Switching to renewable energy sources like wind energy, ocean energy and solar energy is gaining a lot of importance. These green technologies emit less greenhouse gases into the atmosphere and hence are pollution free and immensely available. Recently, investigators have identified plants as weak energy sources. Plants are versatile organisms capable of communicating with each other with a number of signaling mechanisms. It was observed that plants generate electronic signals inside their system. The concept of utilising electronic signals for studying various physiological plant processes was first put forth by Sir Acharya J. C. Bose, an eminent biophysicist, botanist, archaeologist and polymath from India (Fromm and Lautner, 2007). His ideologies and concepts of movements of plants laid the foundation for modern electrophysiology-a branch of physiology that deals with electrical phenomena associated with metabolic functions. Attempts have been made to harvest electricity from free electrons available in plant leaves produced during photosynthesis and from rhizosphere of plants formed as a result of bacterial activity. Currently, a lot of attention is being given to improvise and develop this technology. To proceed forward in this direction, it is very critical to understand the mechanism of electrical signaling in plants.

Introduction

Earth’s magnetic field (MF) is a natural component of environment and is an inescapable factor for all living organisms including plants. Earth has an inner core made of molten iron which rotates at a fairly high speed creating a magnetic field just like a dynamo. This Geo Magnetic Field (GMF) extends from the earth’s interior into outer space. It interacts with the solar wind, which is actually a stream of charged particles emanating from the sun. As earth is engulfed in a GMF, all living organisms, both plants, animals and all biological processes are under its influence. However, local differences in strength and direction of the geomagnetic field have been detected. The vertical component of GMF is maximum at the magnetic poles, which is around 67 μT, and the horizontal component is zero there. Conversely, at the magnetic equator the vertical component is zero and the horizontal component is maximum, about 33 μT (Kobayashi et al., 2004).

Turbulent flows of the fluid metallic inner core of earth mainly contribute to GMF and the effect of external MFs located in the ionosphere and the magnetosphere is very meagre (Qamili et al., 2013). As GMF extends beyond the earth’s surface it is this force along with magnetosphere that protects the earth and its biosphere, from the solar wind by deflecting most of its charged particles (Occhipinti et al., 2014).

Introduction

The ultimate aim of agricultural research or any other related activity is to increase yield. Yield improvement could be obtained mainly through the enhancement of photosynthetic efficiency. Photosynthesis is a process in which plants convert light energy to chemical energy. Sun is the ultimate source of energy for photosynthesis. However only half of the total solar radiation (51%) reaches the earth’s surface of these only 1.2% reaches the plant canopy. Solar spectrum contains an array of other radiations which can be harmful for plant and human life. With increasing global climatic change amount of harmful radiation reaching the earth’s surface has increased and this is found to influence plant productivity. Under this scenario, protected cultivation is gaining popularity in many countries as it helps to reduce harmful effects of undesirable radiation, to allow cultivation of crops irrespective of seasons and also expand cultivation to non-traditional areas by artificially manipulating crop environment. In this context, spectral manipulation for crop production has emerged as an important area in crop production system

Introduction

Plants possess complex, systematic and specific mechanisms to cope up with abiotic as well as biotic stresses in the existing environment. ‘Do plants respond to sound ? How can plants perceive sound without a hearing organ?’- are interesting queries among the scientific community. Responses of plants to different factors such as temperature, moisture, light, wind, pests and microbes are well understood. However, information on the effects of audible sound frequencies on plants are still lacking. Recent evidences suggest that audible sound stimulation can contribute to better plant growth and improved quality of plant produce. It also represents a new trigger for plant protection. Sound is an acoustic energy in the form of a mechanical wave which transmits through gases, liquids and solids. Acoustic spectrum consists of three regions, infra sound (less than 20 Hz), audible region (20-20,000 Hz) and ultrasound (greater than 20,000 Hz). Infra sound and ultrasound are used in clinical diagnosis and therapeutics.

Research on plant responses towards different stimuli started during 1880s by Charles Darwin. In 1848, Dr. Gustav Theodor Fechner, a German experimental psychologist, suggested that plants are capable of feeling emotions and that one could promote healthy growth of plants with talk, attention, attitude and affection. Later, J. C. Bose (1926), famous Indian botanist and physicist, made several studies on the effect of sound vibrations on plants. According to him, a plant treated with care and affection gives out a different vibration than a plant subjected to torture. In addition, Bose found that plants grew more quickly in pleasant music and more slowly in loud noise or harsh sounds. He also noticed that plants can “feel pain and understand affection” based on variation of cell membrane potential under different sound frequencies. Retallack (1973) also described several experiments involving plants and music.

Introduction

Plasticity is a unique attribute by which the otherwise sessile plant species are capable of adjusting to environmental vagaries by changing their phenotypic and morphological characters. Any plant population will be able to survive only if it can respond to an extremely variable environment by becoming more plastic and more genetically variable. To achieve this, plants should be able to suitably change their morphology anatomy and physiology or any one of these parameters based on environmental changes so as to improve their adaptability and survival in the altered environment. When such changes are genetically heritable, then they lead to species evolution.

Plasticity helps plants to adapt to new environmental conditions, after migration to new geographical areas, by genetic assimilation of traits that can help to improve their performance under a new set of conditions. Understanding plasticity is important for predicting and managing the effect of climate change on native species as well as crop plants. Response of plants to modified environmental conditions is critical for their persistence.

Phenotypic plasticity has been defined as the ability of an individual genotype to produce different phenotypes when exposed to different environmental conditions (Pigliucci et al., 2006). This includes the ability of a plant to modify its development in response to environmental cues and also its ability to bring about changes in its metabolism which increases the chances of survival of an organism under a specific condition.

The biofertilizer technology has paved way for the manufacturers and entrepreuners to establish a biofertilizer production unit due to an increasing demand and awareness among farmers. Biofertilizer production units have already been started with most of them in the southern states of India. The biofertilizers can be produced using different kinds of carrier materials (peat, coal, lignite, clays, inorganic soil), organic materials (composts, soybean meal, wheat bran, sawdust, etc.), or inert materials (e.g., vermiculite, perlite, kaolin, bentonite, silicates). Natural carriers like peat, plant waste materials, composts, sawdust, sludge lignite, clays, coal, vermiculite, perlite and bentonite and mixture of organic and inorganic materials may also be used.

The Government of India is also encouraging a low cost technology by providing a subsidy to establish a biofertilizer production unit . The major equipment’s and other materials required for a biofertilizer production unit with the capacity of 150 metric tonnes/annum are given below

There are many manufacturers of biofertilizers in both government and private sectors. Only some of them have been listed here for the information

The soil fertility is depleting in the current scenario of gap between nutrient removal from soil and supplies. Moreover, increase in the fertilizer prices has become unaffordable to small and marginal farmers. There is also a growing concern about the environmental hazards and its threat to sustainable crop production. Indiscriminate use of synthetic fertilizers for intensive crop production has resulted in large quantity of nutrient (particularly P) accumulation in soils which has resulted in generating a dead soil. In this context, the long term use of biofertilizers are considered to be economical, eco-friendly, more efficient, productive and accessible to marginal and small farmers over chemical fertilizers (Subba Rao, 2001). Biofertilizers mainly consists of specific living cells which supplies nutrients to plants through their root system. Microbes in these fertilizers provide nutrients to the plants by nitrogen fixation, phosphate solubilization, phosphate mobilization, and promotion of beneficial rhizobacteria (Bhat et al., 2010). Biofertilizer application improves the supply of nutrients, organic carbon, accumulation of soil enzymes, productivity, soil fertility index, economy of farmers, and maintenance of sustainability in natural soil ecosystem and horticultural crops. The production of efficient and sustainable biofertilizers for crop plants needs to be undertaken to make the biofertilizers popular and efficient. The important and specific research in future may be focused on the following aspects.

Microbes present in the biofertilizer formulations help in microbial processes in the soil which augment the availability of nutrients to be taken up by plants. They are of different types based on their nature and function such as nitrogen fixing, phosphate solubilizing, phosphate mobilizing or biofertilizers for micronutrients. Plants use different strategies for growth promotion at different stages of plant growth and development. Biofertilizers are mass multiplied cultures of specific beneficial microbial strains which improves the fertility of soil and productivity. The nutrients are added through natural processes of nitrogen fixation, solubilization of phosphorus and synthesis of growth promoting substances to stimulate the plant growth. The main sources of biofertilizers are bacteria, fungi and cyanobacteria.

11.1. Bio-enrichment of chemical fertilizers- A new approach

Yield response of different host plant depends on the mineral fertilizer and its fertilizer use efficiency. Generally, such fertilizers are low in efficiency due to environmental and soil factors. A large portion of synthetic fertilizers are lost due to fixation, leaching, run-off, erosion, volatilization, denitrification and precipitation without reaching plants. Hence, there is an economic loss and water and environmental pollution.

Microbial inoculants applied to the soil enhances the uptake of nutrient by plants and increase the efficiency of synthetic or organic fertilizers. In this context, it is possible to impregnate mineral fertilizers with specific microbial strain. A new approach is to incorporate the microbes or microbial compositions into fertilizer compositions.

It has been well established that the biofertilizers are beneficial to plants and are cost-effective inputs for sustainable production system. However, there are some constraints with respect to its production, which are presented below:

10.1 Production constraints

10.1.1 Raw material

Eventhough there are large number of biofertilizer formulations, only few are considered as good carrier materials for biofertilizers such as peat and lignite. Moreover, its availability in India is limited and the quality is lacking for these carrier materials. Hence, a cost effective and locally available material with increased shelf-life is the need of the hour.

10.1.2 Specificity and availability of strains

As the microbial strains used as biofertilizers are specific to soil and agro-ecological conditions, availability of specific strains for the specific host and soil edaphic factors are inadequate.

Quality Control is very important in biofertilizer production, which determines the efficiency of microbial strains. Generally, the quality control based on BIS are voluntary in nature. However, some of the biofertilizers are brought under the ambit of Fertilizer Control Order 1985 (FCO) during 2006 (Yadav and Chandra, 2014). At present, biofertilizers are under the FCO with specific quality standards. Biofertilizer production and its sales can be regulated and is a mandatory requirement for registration of manufacturing unit with the State Fertilizer Controller (who is generally the Commissioner or Director of Agriculture Department) under the statutory provision of FCO. Moreover, some officers of the Agriculture Department have been declared as Fertilizer Inspectors at the district level, who are authorized to inspect production and storage facilities and draw samples for quality analysis. National Centre of Organic Farming (NCOF), Ghaziabad under the Govt. of India and its six Regional Centre’s located at Bhubaneswar, Bangalore, Jabalpur, Nagpur, Hissar and Imphal have been declared as testing laboratories. Under the provisions of the FCO act, State Governments can also develop their own quality control laboratories and notify them under the FCO (1985). Peat, lignite, peat soil, humus, wood charcoal or similar material favouring the growth of microbial strain could also be used. The FCO specifications for different biofertilizers are presented below:

Biofertilizer is already proven to be beneficial for agricultural and horticultural crops. The most important pre-requisite for the success of biofertilizer application is the presence of high population of viable cells which will show the desired effect on plants. Biotic interactions along with competition from native microflora is a major challenge to an applied strains of biofertilizers. The formulation is an important parameter for biofertilizer production containing efficient microbial strain with suitable carrier material and additives. The microbial strain needs suitable protective environment to increase their efficiency at the target site and also make it user-friendly. Performance of biofertilizers under field condition is the major requirement for inoculants. Inadequate formulations and poor inoculant quality are the major hurdles for the successful use of biofertilizers.

Formulation of biofertilizers has to be consistant during production, distribution, storage and transport to the farmer/end users. The shelf-life of inoculated microbial fertilizer depends on the formulation with suitable carrier material. If local production and distribution of an efficient native biofertilizer formulations are developed, the present problems in the field performance of biofertilizers could be significantly solved. Specific formulations of native strains for use in saline soils, acid soils, drought, high temperature and eroded soils requires specific formulations. Therefore,use of native strains of biofertilizer formulations which are tolerant to the abiotic stress is an important approach. The formulations of biofertilizers are challenging and limited success has been observed in the commercialization of new biofertilizers. Hence, the search for new formulations has been a continuous approach. However, the choice of the formulation depends on the application method, available equipment, farmer’s convenience, plant inherent characteristics and developmental stage, cost, mode of action and colonization pathway of the inoculated strain. Conventionally, solid based formulations are used, which have problems of low viability during storage and application.

Biofertilizers can directly or indirectly influence the growth of plant. The direct influence can be through production of phytohormones or making the nutrients available to plants. The indirect effect can be through management of plant pathogens through biological control. Therefore, the purposeful introduction of biofertilizer inoculants to plant microbiome represents an environmentally sound option that holds a prominent position in order to reduce the dependency on agrochemicals (Adesemoye and Kloepper, 2009; Abhilash et al., 2016; Aloo, et al., 2019).

Microbes in soil can rarely exists as single cells and survive near the plant root canopy or in bulk soils or endophytes or even on plant surfaces (Lorito, 2006). The soil microflora occurs as complex members of microbiota (Hacquard, 2015). Microbial consortia (MC) are unique mixture of organisms which respond to the environment stress and adapt to stresses due to internal beneficial interactions among the microbial community. Ecosystem’s physiological functions by microflora is carried out by more than one microbial species with the functional diversity and succession among different microbial components. The microbial balance among the different microflora of a MC will consist of a continuous shift between actively growing cells and non-dividing cells of the microbial consortia. It has been reported that different microbial populations “talk” to each other by “quorum sensing” mechanism in a given environment by exchanging specific chemical signals (Thompson, 2015). Natural microbial consortia holds many specific properties like stability, functional diversity and perform complex functions. The natural consortia have generated an interest in manpulating synthetic consortia for the benefit of application (Minty, et al., 2013).

Fruits, vegetables, ornamentals, plantation crops and spices, medicinal and aromatic plants, tubers, are the major horticultural crops contributing to the economic growth in India. Even though the horticultural sector is growing fast, with India being the second largest producer of fruits and vegetables in the world, the productivity and quality have to be improved in order to meet the demand of increasing population. Under these circumstances, ecofriendly techniques needs to be adopted which could ensure food security and sustainable production. Indiscriminate application of agrochemicals and chemical fertilizers in horticultural crops and their residues could harm the human health, soil and environment. Horticultural crops need an ecofriendly technique, as most of the horticultural products are directly consumed. Hence, there should not be any residues of agrochemicals in food products. In the current context, use of ecofriendly, cost effective and organic-based inputs like biofertilizers can maintain health of the soil and good quality in horticultural crops. The application of biofertilizers offers an attractive and sustainable means of improving the quality of food products. Biofertilizers like Azotobacter, Azospirillum and AMF and PGPRs not only supplies the required nutrients to plants, but improves the fruit quality and quantity (Pathak et al., 2017).