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Rice farming is the livelihood of millions of people in the World. It is the staple food and primary source of nutrition for about half of the world's population. Rice provides 60-70% of the total calorie requirements for more than 2 billion people in Asia through different rice-based food products. The crop is very important considering its economic, social and cultural significance in India and other Asian countries. Rice-based ecosystems and aquaculture are the lifeline of millions of people in India. Globally, rice is grown on about 165 million ha with an annual paddy production of about 787 million tonnes. There is wide variation in the production of paddy in different rice-growing regions of the world due to differential geographic location, genetic potential, weather elements, irrigation facilities and crop management systems. About 87% of the world’s area and 90% of the world’s paddy production occurred from Asia.

1.1. Introduction: India’s present population, growth rate & projections India is the second-most populous country in the world after China with its population of about 1.38 billion in the year 2020. The Population Division under the Department of Economic and Social Affairs, of the United Nations, has projected the country’s population to be growing to about 1.50 billion by the year 2030, and 1.64 billion by 2050, of course with its decreasing annual growth rate from 1.04 to 0.25% or so during the period of next thirty years (Fig. 1.1; UNDESA, 2019). The projection says the Indian population will exceed China by the year 2030 even with its decreasing rate i.e. India will be the most populous country by then. As agriculture and allied sectors are the backbone of this country and the largest livelihood source, it support this growing human and livestock population with diversified natural resources and varied agro-climatic conditions. However, the sustainability of agricultural production should be maintained in the face of perturbation and stress on the agro-ecosystem especially the degraded natural resource base and changing climate.

2.1. Introduction Water plays a pivotal role in this earth system. The withdrawal of water for irrigation is about 70% of the global freshwater. Water use efficiency is less than 50% in many countries. It has been forecasted by the Food and Agricultural Organization (FAO, 2015) that global water requirements will be increased by 50% by the year 2050 to meet the demands of agricultural water use. This is so because food demand will be higher for the growing human population. We have entered into an earth system where everything living has evolved and developed (Cosgrove and Loucks, 2015). There has been a new geological scenario, some say Anthropocene (Crutzen, 2002; Williams et al., 2011). Consequently, freshwater will increasingly be a scarce and the costliest resource in the future, which needs to be managed properly.

3.1. Introduction Rice is grown in varying geographical locations and climatic situations. Most of the rice area lies between the equator and 400 N latitude and between 700 and 1400 E longitude. It grows well from tropical to sub-tropical warm and temperate climatic regions up to 400 S and 500 N of the equator. However, the highest yields are obtained in the region between 300 and 450 N of the equator. The average yield generally increases as the countries are situated further away from the equator (Chatterjee and Maiti, 1985). In India, rice grows in regions from 80 N to 350 N latitudes under widely varying conditions of the land, rainfall, altitude and climatic conditions. It is grown at the sea level in river deltas as in parts of Kerala, as deepwater in states of West Bengal, Assam and Bihar; at high altitudes of 914 to 1524 m or even more as in Kashmir, and in the slopes of the Himalayas. A temperature range of 200 C to 37.70 C is required throughout the life period of rice crop.

4.1. Introduction Globally, rice is cultivated on about 165 million ha of land, which provides around 787 million tons of paddy annually (FAO, 2023). In Asia, 708 million tons of paddy is produced from nearly 143 million rice-cultivated areas. Rice crop is grown in a wide range of climates, varied soil types, and hydrological situations. Rice is the lone cereal crop that grows well in floods. The rice habitat can be divided into four groups based on the hydrology of the rice field: irrigated lowland rice (79~80 million ha), rainfed lowland rice (54~55 million ha), upland rice (14~15 million ha), and flood-prone rice (11~12 million ha) (Table 4.1) (Bouman et al., 2006).

5.1. Introduction Rice-fallows are a rainfed rice mono-crop production system, where only a single crop (rice) is grown and these lands remain without any crop for the rest of the period of the year (fallow). An estimate shows that rice-fallow areas extended over 22.3 M ha in South Asia, maximum in India ( 88.3%) followed by Bangladesh (8.7%), Nepal (1.4%), Sri Lanka (1.1%), Pakistan (0.5%), and Bhutan (0.02%) (Gumma et al., 2016). The eastern part of India accounts for ~ 84% (9.7 million ha) of the country’s total rice-fallow area (i.e. 11.7 million ha) (Ali et al., 2014; Singh et al., 2017), despite high rainfall during rainy / monsoon season. The reasons are that after the rainy season, irrigation facilities are lacking, very fast depletion of the soil residual moisture due to temperature rise, the poor economic condition of the farmers, and a lack of awareness or knowledge of available technologies. Additionally, delayed harvesting of long-duration rice (150-160 days) results in late sowing of winter crops, which, in turn, exacerbates the temperature and moisture stresses in winter crops (Kumar et al., 2018a; 2018b). Overall, the challenges of growing another crop in rice-fallow areas are the lack of irrigation facilities including declining groundwater levels, the dominance of the long-duration rice varieties cultivation, higher evaporative loss of the residual soil moisture, degradation of soil quality, and poor financial conditions of the farming community with diminishing profit. Recently, climate change with erratic rainfall and delayed monsoon arrival added more challenges for these areas in several places. Deficit soil moisture imposes stress on the crops and negatively affects the winter crops productivity in the rice-fallow system, and several times it results in complete crop failure (Singh et al., 2012; Ghosh et al., 2016).

6.1. Introduction The growing human population presents a number of issues, including food scarcity, malnutrition, inadequate natural resources (land and water) for agricultural production, and environmental deterioration (MacDonald, 2010). Today, viable intensification of agri-production systems can fulfill rising food, nutrition and environmental demands (Pretty and Bharucha, 2014). Production of rice (Oryza sativa L.), a vital element of food security, which feeds nearly half of the world's population, occupies 143 million hectares of land (FAOSTAT, 2023), and uses up to 90% of all irrigation water in Asia (Liu et al., 2018). For instance, it has been determined that systems for producing rice are one of the main industries that wastes water resources and greatly increases greenhouse gas emissions (FAO, 2013). Therefore, it is necessary to look for ways to manage the rice production system more effectively. In paddy rice systems, co cultivating aquatic animals (fish, shrimp, crab, shellfish, and ducks) and rice has been suggested as a way to reduce the risks of environmental pollution/ contamination linked with rice production while simultaneously optimizing the use of land and water resources to provide humans with both grains and meat (Hu et al., 2016; Ahmed and Garnett, 2011). Co-culture systems have drawn more interest recently due to their potential to reduce the stresses associated with environmental and food insecurity.

7.1. Introduction The integrated farming system (IFS) is becoming increasingly important for effective farm resource management in order to increase farm productivity, reduce environmental degradation, improve the quality of life for resource-poor farmers, and ensure sustainability. Integration happens when one production sub-system's outputs (typically by-products) are used as inputs in another within the farm unit (Radhammani et al., 2003; Lightfoot and Minnick, 1991). IFS are a mixed farming system made up of at least two distinct but logically linked components of crop and animal enterprises. The integrated farming system is effective in reducing risk, increasing productivity and revenues, and improving the use of organic waste and agricultural leftovers.

8.1. Biofloc aquaculture Among the innovations in the field of aquaculture, biofloc technology (BFT) has attracted great attention due to its ability to foster the goals of sustainable aquaculture (Khanjani et al., 2022a). If implemented correctly, BFT capitalizes on the existing organisms in water to significantly reduce water use and environmental impact and increase biosafety at farms (Avnimelech, 2012).  

9.1. Introduction Human dependence on natural processes for the goods and services provided by nature, especially food, fuel and fibre, has been a known fact. In recent times, the value of less tangible services, such as climate control, water f iltration, and soil fertility, as well as recreational and cultural services has been emphasized also. Ecosystem services underpin human existence, health, and prosperity. It has been beneficial to humans through the transformations of resources (or environmental assets, including land, water, vegetation, and the atmosphere) into a flow of essential goods and services like clean air, water, and food (Costanza et al., 1997). Ecosystem services are those functions of ecosystems- including agroecosystems that are useful to humans or supportive of human well-being (Kremen, 2005). Services provided by ecosystems receive little notice for their support to human civilization often leading to poor management of the ecosystems. Land use systems influence ecosystem functions, which determine the supply of ecosystem services. Land and water resources are under considerable pressure from the expansion of cultivated and residential lands. Diverse land use in agrarian landscapes not only fosters biodiversity, but also provides potential ecosystem services such as air cleaning by vegetation, natural water filtration by plant roots, natural pest suppression, soil conservation, nutrient retention, and crop pollination by insects, etc. Lowland floodplains or waterlogged land areas are generally more conscious of the benefits provided by ecosystem services. It is important to create awareness among the people on provisioning services provided by ecosystems, such as crops, biofuel, fresh water, natural medicine, wildlife, and several cultural services. Managing ecosystem services, which link human well-being to conservation outcomes, is essential for achieving the sustainable development goals (SDGs) of the United Nations (Zhang, 2017).

10.1. Introduction Irrigation facilities are created by the Government at huge cost for supplying water to the farmers for raising crops to increase agricultural production. The major and medium irrigation projects are planned, constructed, managed, operated and maintained by the Irrigation Departments, wherein certain procedures and rules are evolved and followed to the delivery schedule of canals, frequency of supply and distribution of water to the farmers, and closing of canals. The creation of such facilities resulted in ushering the green revolution in the sixties and seventies in the production of food grains and also employment generation in the country, thereby improving the socio-economic condition of Indian farmers. However, optimized management of irrigation water is the key to the sustainable development of agriculture and livestock. Since management of water for irrigation is highly location-specific, depending upon agro-ecological and socio-economic conditions, type of irrigation project and land use pattern, it differs from project to project and region to region in the country.

A  Abiotic stress 157, 346  Acid saline 90  Acid sulphate soils 69, 92 Aeration 78, 115, 139,  218, 295, 296,  297, 302, 306, 309, 310, 315  Aerobic rice 108, 114, 120, 123, 124, 125, 126, 127, 131, 133, 135, 136,  137  Aged seedlings 88, 91  Agrarian Landscape 323  Agricultural crisis 330 Agro-ecological conditions 8  Agro-ecosystem  1, 66, 231, 325, 326  Air-breathing fish 270, 297  Alternate wetting and drying 111, 120, 131, 132, 184  Aquaculture 200, 202, 204, 205, 211, 213, 214, 215, 216, 232, 240, 251, 252, 259, 260, 267, 268, 271, 272, 273, 274, 276, 277, 278, 279, 280,     281, 282, 283, 284, 285, 287, 288,  293, 294, 295, 297, 303, 304, 306, 312, 316, 320