3.5.1. Stress-tolerant/resistant varieties

The prevailing practice of cultivating local or high-yielding varieties leaves farmers susceptible to climate change shocks, often leading to poor productivity or even complete failure during extreme climatic events. Various national and international research institutes have developed stress-tolerant varieties for South Asian countries (see list in Table 4), which need to be validated and extended to vulnerable regions, enabling farmers to achieve reasonably good yields in the face of climate-induced stresses.

3.5.2. Grafting plants to build stress tolerance

Climate change has exacerbated abiotic stresses in vegetable production, posing threats from flooding, drought, and extreme temperatures. Vegetable grafting has emerged as an eco-friendly, expedient, and efficient technique for producing climate-resilient plants that can withstand these abiotic pressures (Singh, Sethi, Kaushik, & Fulford, 2020).

3.5.3. Climate-resilient cultivation practices

Replacing existing crops with new climate-resilient alternatives is an emerging strategy for combating climate change. For example, in wind-prone areas of India, some farmers grow millets (e.g., pearl millet) and sorghum. They also integrate leguminous crops to enhance soil nitrogen and preserve fallow land (Satapathy, Porsche, Kunkel, Manasfi, & Kalisch, 2011). Shifting the timelines for wheat sowing and rice transplantation to 15 days earlier than conventional practices could mitigate yield losses by more than 4% (Jat et al., 2014).

3.5.4. Soil health management

The vitality of soil health in evolving environments is paramount to crop production. Notably, soil health extends beyond agriculture, with its status as an indicator of human well-being (Lal, 2022). Strategies to enhance soil health include building soil carbon, controlling soil losses due to erosion, and increasing soil water-holding capacity. Embracing practices like conservation agriculture or zero tillage, soil mulching, crop rotations involving legumes, soil microbiome management, soil nutrient management, soil-borne pest and disease management, soil moisture management, agroforestry, and integrated farming systems are pivotal in enhancing soil health and building crop resilience to climate change.

An Australian study reported that annual wheat production could increase by 1.1 to 1.2 billion AUD by improving soil conditions (Linehan, Thorpe, Andrews, & Beaini, 2012). As the largest carbon pool on Earth, soil plays a crucial role in global carbon and nutrient cycling. Enhancing soil carbon storage and sequestration is essential for improving soil quality, fortifying plant nutrition reservoirs, and increasing crop productivity amidst ongoing and upcoming climate change impacts. Furthermore, soil carbon sequestration can help mitigate adverse climatic effects, including increased surface and soil temperatures, elevated CO₂ levels, and fluctuating precipitation patterns.

The most effective strategy for accumulating and sequestering soil organic carbon lies in prudent management practices that stimulate soil carbon inputs (e.g., plant residues) rather than outputs (e.g., decomposition and leaching). Achieving a balanced and integrated use of fertilisers (organic and inorganic) presents an alternative approach to enhancing soil carbon sequestration, preserving plant nutrients, and increasing productivity.

Below are some instrumental farming practices for managing soil health.

Conservation agriculture: Significance of zero tillage

Zero tillage is becoming a cornerstone of conservation agriculture and climate-smart farming (Figure 2). Two main principles underpin zero tillage:

1. Minimum soil disturbance
2. Stubble retention in fields

Zero tillage offers numerous advantages, such as:

• Enhanced soil structure
• Improved nutrient recycling
• Increased crop yields
• Time-saving attributes
• Feasibility for early sowing
• Reduced soil erosion
• Reduced pollution arising from stubble burning or soil erosion
• Improved soil water-holding capacity
• Provision for grazing, if required

Data from long-term (25 years) zero-tillage experiments conducted in Australia, Mexico, Brazil, Spain, the UK, and the USA have revealed incremental yield with zero tillage over time. In Western Australia, the adoption rate of zero tillage among farmers stands at a remarkable 100% (Ward & Siddique, 2015). In India, farmers often burn crop residues for disease and weed control. However, zero-tillage systems are promoted to minimise stubble burning, and farmers can hire zero-tillage seeders for sowing. Various zero-tillage seeders are available across different countries. Recently, the Indian Agriculture Research Institute developed technology involving a consortium of microorganisms for in-situ stubble decomposition (Maheshwari, Mahapatra, Bharti, & Singh, 2020).

Intercropping and relay cropping

Intercropping, the practice of cultivating multiple crops simultaneously in a field (Figure 3), offers resource optimisation and enhanced land productivity, increasing system productivity. For example, system productivity increased by 19% under soybean and pigeon pea (4:2 ratio), 25% under pearl millet and pigeon pea (3:3), 25% under Bt cotton and green gram (1:1), 14% under Bt cotton and black gram (1:1), and 24% under Bt cotton and pigeon pea (5:1) (Prasad et al., 2014). As another climate-resilient crop diversification, tree-based farming systems also benefit farmers due to the high value of horticultural products.

3.5.5. Direct-seeded rice

Direct-seeded rice (DSR) technology conserves water resources by up to 50% as it does not require flooding, with pregerminated rice seeds sown in puddled soil. This technique also reduces the carbon footprint of rice by reducing methane emissions. Irrigation is applied during crucial crop growth stages, such as crop emergence (first 7–15 days after sowing). DSR requires efficient weed management to prevent yield losses.

3.5.6. Leaf-colour-based nitrogen application

IRRI developed a leaf colour chart (LLC) for nitrogen application in rice (Figure 4; MSME MART, n.d.). Reports indicate nitrogen savings of up to 40% (Satpute, Surje, & Maity, 2014).

3.5.7. Water management

Water availability is a critical determinant of crop yield, with efficient water use particularly important in changing environments. For example, the water use efficiency of wheat is impacted by delayed sowing, weed proliferation, waterlogging, and nematode infection (Figure 5; French & Shultz, 1984 cited in Sadras 2020).

Integrated water management, encompassing various water-saving practices and technologies, can save between 22% and 84% of water. Practices such as the system of rice intensification (SRI), DSR, relay cropping, use of waste and marginal water, laser levelling, mulching, and conservation agriculture have demonstrated water savings ranging from 22% to 43% in various crops (Jat et al., 2014). Adopting micro-irrigation systems, such as drip and sprinkler, can yield additional savings of up to 84% (Kumar, 2016).

Several water management practices conducive to adapting rice cultivation to climate change have been identified (Aryal et al., 2020):

1. Alternate wetting and drying enhances water use efficiency by 30%.
2. DSR improves water use efficiency and water stress resilience.
3. Micro-irrigation system (sprinkler and drip) saves up to 90% water.
4. Laser land levelling contributes up to 30% water savings.

Floating bed cultivation

Floating bed cultivation is particularly advantageous for areas prone to extended periods of submersion (UN Climate Technology Centre and Network [UNCTCN], n.d.), as observed widely in Bangladesh. The floating beds are constructed from various substrates, such as crop residues, water hyacinth, and straw, secured with ropes atop a bamboo base (Figure 6). After harvest, the floating beds can be composted and reintroduced into the same field as a nutrient source.

Relay cropping

Relay cropping is a multiple cropping system where a subsequent crop is sown into a standing crop before it is harvested. This method addresses challenges related to resource utilisation, sowing time, fertiliser application, and soil degradation (Figure 7). Relay cropping is a sophisticated toolkit for enhancing soil quality, increasing net returns, increasing the land equivalent ratio, and managing weed and pest infestations.

For instance, corn (grown for seed) and soybean are suitable for relay cropping as seed corn is harvested in mid-September, leaving moderate residues. Annual winter crops, such as winter wheat, could be added to the seed corn–soybean rotation to use solar energy and heat device accessible during corn harvest in September and soybean planting in May. However, winter wheat is not harvested till mid-July, much later than the prime time for soybean planting. Relay cropping in Nebraska requires middle-pivot irrigation, glyphosate-tolerant soybean, and a method of seeding soybeans into wheat at heading (approximately 30 days before wheat harvest).

The advantages of relay cropping include:

1. Decreased nitrate leaching
2. Increased carbon sequestration
3. Increased farmer income

Some examples:

1. For small grain crops as the first planting and legumes as the second, legumes can be seeded into small grain crops well before it is harvested.
2. For rice as the first planting and legumes as the second, seeding of the legume crop can be done by aerial broadcast before harvesting of rice crop so as legume crop is established and utilises residual mixture to germinate and establish before the rice crop is harvested.
3. For maize, sorghum, or millet as the first planting and soybean or legumes as the second, the second crop can be banded between rows of the first crop well before its harvesting.

3.5.8. Protected cultivation

Protected or greenhouse cultivation represents an advanced approach to growing crops in an optimal environment, shielded from abiotic (e.g., temperature, rain, wind, humidity) and biotic (plant pests and diseases) stressors. This method enables farmers to grow crops on demand, irrespective of the traditional growing seasons (Figures 8–11), resulting in higher yields using 90% less water and fewer nutrients.

Various types of structures are used in protected cultivation:

1. Climate-controlled greenhouses are sizeable structures incorporating transparent or translucent material, offering an ideal environment for crops to thrive under optimal conditions. Suitable for high-value crops such as vegetables and flowers.
2. Zero-energy, naturally ventilated greenhouses are simple yet effective blanketed structures with no heating or cooling devices. They rely on natural ventilation through pest-proof netting, mainly on the top and the sides. These medium-value greenhouses are supplemented with manually operated natural air flow devices. Suitable for growing cucumber, tomato, and capsicum for 8–9 months each year.
3. Shade net houses are used during critical summer months (May–September), reducing the sunlight intensity by 25–75% to decrease radiation and temperature to a certain threshold. Suited to areas where night temperatures do not drop below 15–18 °C and daytime temperatures are generally 28–30 °C.
4. Insect-proof net houses are reasonably priced, temporary or lasting structures clad with 40–50 µm mesh UV-stabilised insect-proof nylon or rust-proof metal net These structures prevent the access of dangerous insect-pest and vectors of illnesses, reducing the need for pesticides in fresh vegetable cultivation.
5. Walk-in tunnels are temporary constructs crafted from materials such as galvanized iron (GI) pipes, plastic pipes, or semi-spherical bent bamboo clad with UV-stabilised (150–200 µm) polyethylene. The central top is retained to 6–6.5 ft. and 4.0–4.5 ft wide. The tunnel length varies according to need. These tunnels are designed to be easily assembled and disassembled using nuts and bolts (no welding required). They can bear trellis loads of 15–25 kg/m².

3.5.9. Zero-energy cooling chambers

Zero-energy cooling chambers (ZECC) work on evaporative cooling principles, i.e., temperatures decrease due to liquid evaporation. Each chamber is an aboveground double-walled brick structure with a 7.5 cm wide cavity packed with river sand. The top of the structure is covered with gunny fabric filled with straw in a bamboo structure. The cool chamber is soaked with water initially and thereafter sprinkled with water in the morning and evening to preserve the specified temperature and humidity (Figures 12 and 13). These chambers can hold excessive humidity (95%) throughout the year and even reduce the chamber temperature during summer. ZECCs are best used for short-term produce storage and are particularly beneficial for marginal farmers needing short-term storage solutions (Kitinoja, Saran, Roy, & Kader, 2011; Mishra, Jha, & Ojha, 2020).

3.5.10. Broad bed and furrow

In the broad bed and furrow (BBF) system, a machine is used to create 90 cm wide beds and 45 cm wide furrows, maintaining a 30 cm row spacing (Figure 14). BBFs conserve rainwater in-situ in furrows, allowing for excess water drainage, proper aeration, and weed control.

3.5.11. Crop pest and disease management

Crop pest and disease management are critical as many pests and diseases have shifted their geographical boundaries due to the changes in temperature and humidity, creating favourable conditions for their migration. Crop pests and diseases are projected to extend to higher altitudes. Projected global yield losses for three staple grain crops (rice, wheat, and maize) due to insect pests are 10–25% per 1 °C increase in global mean surface warming, with such losses more acute in temperate regions (Deutsch et al., 2018). Governments in South Asian countries focus on integrated pest management strategies and farmer training to handle the growing emergence of pests and diseases. Insect and disease forecasting models have been developed for their timely management. Innovative techniques, such as pheromones, push–pull, microbial seed inoculants, and resistant varieties, also aid in pest and disease control.

3.5.12. Climate-smart future foods

Given the impact of climate change on traditional staple crops like wheat and rice, scientists have started advocating for the cultivation of climate-resilient local grains such as millets, which can withstand most abiotic stresses and are nutritionally dense (Reay, 2019). An FAO study identified numerous Future Smart Foods (FSF) for South and South-East Asia, prioritising 39 FSFs such as sorghum, pearl millet, elephant foot yam, roselle, drumstick, Amla, lentil, jackfruit, and fenugreek (Li & Siddique, 2018).