a type of cropping now has been widely recognized to maintain balance between human needs and ecosystem system services. It is a type of cropping with more number of the crop species. Agricultural diversification can safe guard greater food and nutritional security, minimizing environmental degradation, lessening poverty, higher use efficiency of land resources, and also preventing the impact of degradation forces and helping in contesting desertification. Diversification of agriculture opens new vistas for additional environmentally safe, sustainable systems, enhanced livelihood options for farmers. Some of the crops which are presently considered as underutilized can become a potential tool and hence will ensure more ecologically sustainable agricultural production systems and provide newer livelihood options for small holder farmers. As a matter of the fact global food supply relies on 150 crop species. And the most gruesome challenge is that out of the 150 crops, there are only 12 crops which provide around 75% of the world's food demand. This indicates toward one of the most unsustainable land use types for food production practices in the world. The simple fact that three cereal crops like rice, wheat, and maize are the principal source of more than half of the global food energy and that too from a limited number of varieties of the three “mega‐crops” made the agriecosystems very unsustainable. These cereal crops are also very exhaustive in their demand for nutrients and water, which further complicates the problem of resource degradation.
2.3 Crop Diversification and Ecosystem Services
Generally, crop diversification is perceived as a change from the regional supremacy of one crop to regional production of number of the crops to meet ever increasing demand of cereals, pulses, vegetables, fruits, oilseeds, fibers, fodder, grasses, etc., of the human and livestock population. Crop diversification also guarantees higher profits for the growers. It also aims to improve soil health and to maintain dynamic equilibrium of the agroecosystem. Furthermore, in India crop diversification is generally viewed as a shift from traditionally grown less remunerative crops to more remunerative crops. In the present context, the unsustainability of the modern agricultural system, there lies high stack on crop diversification mainly due to disturbance in the ecosystem. The sustainability of agricultural production system can be achieved by maintaining ecosystem services, with the design of appropriate crop diversification plans specific to agro climatic conditions. From Figure 2.1, it can be well understood that among all the agricultural operations/practices, the crop diversification including the agricultural diversification has a greater role to play in maintaining the ecosystem services.
The agroecosystems provide ecosystem services through improved human interventions which have no or very little pressure on environmental resources, ensure recycling of waste products and support large biodiversity as maintained under natural, unmanaged ecosystems. The ecosystems are vital for survival of all living beings. The genetic diversity of crops and livestock, soil health maintenance, and the provision of water sources are some of the very important supporting ecosystem services. Whereas, the regulating services of the ecosystems are in the form of pollinators, which ensures better seed setting, and the presence of the natural enemies control the crop pest within agro‐ecosystems. Natural ecosystems also filter water and normalize its flow into agricultural systems. Therefore, crop diversification create favourable conditions for smooth functioning of the ecosystem services. This ultimately improves the overall health of the ecosystem which are essential for survival and well‐being of mankind. It also ensures enhanced floral and faunal diversity, better pollination, natural pest management, efficient nutrient cycling, soil fertility, and water regulation without compromising on crop yields. Sustainable agronomic management targets above and below ground biodiversity, ensures better pest management, improved water regulation, enhanced nutrient cycling, and improved soil health.
Figure 2.1 Crop diversification maintains many of the ecosystem services and hence also maintains the resilience in the production systems.
Figure 2.2 (a) Functional biodiversity delivering ecosystem services (e.g. pollination, natural biocontrol) in support of crop yields along a gradient of crop diversification and ecological infrastructure and (b) alternative options (efficiency, substitution, redesign) for farm management systems situated on a continuum from conventional agricultural intensification to ecological intensification.
(See insert for color representation of the figure.)
Even under stressed ecologies (poor soil fertility, dry land scenario, abiotic, and biotic stresses), the crop diversification and growing of large number of crops are widely recommended to reduce the risk factor of crop failures. For the majority of farmers in different parts of the country, the gains from application of scientific tools and technologies in agriculture are yet to be realized. On realization, it will help in greater expansion of crop diversification in many areas. It is hard fact that the productivity levels of many major crops in India do not match with the yields obtained in agriculturally advanced countries even under predominant rice–wheat system. On the other hand, as a result of growing few crops in large areas, many problems in the forms of increasing biotic and abiotic stresses are emerging. Therefore, diversification of predominant cropping system in India will bring the new dawn of prosperity and resilience in agricultural production system. Therefore, efficient and effective crop diversification is a crucial for the sustainability of Indian agriculture.
2.4 Reducing Emission of Greenhouse Gases
The good agronomic practices (GAPs), such as, conservation tillage, organic nutrient sources along with inorganic nutrient sources, weeds, insect pest, and disease management along with adequate irrigation water management in diversified production system can greatly reduce greenhouse gases in the atmosphere. The selection of climate smart crops which require comparatively lesser nutrient, water from production system and have lesser impact of biotic and abiotic stresses are the essential components of the crop diversification. In this category, oilseeds, pulses are good examples; for these crops, the GHC emission is also less. Conservation tillage and deficit irrigation can also substantially minimize CO2 and N2O emission. Appropriate use of the crop residue and complete banning of its burning reduces the generation of CO2, N2O, and CH4 to a significant extent. Crop diversification ensures greater functional biodiversity to cropping systems and it also regenerates biotic interactions underpinning yield‐supporting ecosystem services (Rathore and Shekhawat 2020). It embraces a variety of practices encompassing the management of crops, noncrop habitats, soil, and landscapes (Cardinale et al. 2012; Wagg et al. 2014; Renard and Tilman 2019; Tamburini et al. 2020).
2.5 Effect of Technology‐Induced Crop Diversification
The advancement in technological development especially development of high yielding and biotic, abiotic resistant varieties, of wide window of growing period, CA‐based systems, land configuration, and other improved agronomic management, along with increasing value addition and better postharvest handling are the encouraging forces for promotion of crop diversification in different parts of the country. Green revolution technologies intensified cropping system in irrigated areas in favor of rice and wheat and other crops got less acreage due to low productivity and less profitability. This enhanced total output of cereals tremendously but also created second generation problems like intensive use of chemical fertilizers, pesticides, etc., led to pollution of resource base, overexploitation of groundwater resulted in depletion of ground water, salinization. This made urgent call for crop diversification to achieve sustainable high levels of productivity
