Climate Smart Agriculture Sourcebook

Climate-smart crop production

Production and Resources

Climate-smart crop production systems in practice

This chapter identifies four major production systems that require distinct sets of management practices. They are: annual crop systems (Chapter B1-3.1); horticultural systems, orchards and plantations (Chapter B1-3.2); integrated production systems (Chapter B1-3.3); natural and anthropogenic grasslands (Chapter B1-3.4). The management practices identified for each production system are relevant for both climate change adaptation and mitigation.

B1-3.1 Annual crop systems

Many annual crop production systems are net emitters of carbon to the atmosphere due to the accelerated mineralization of soil organic carbon and soil erosion, inefficient nitrogen management and the heavy use of fossil fuels. 

Climate-smart management measures should be oriented towards increasing soil carbon stocks that improve soil and water productivity and reduce the release of greenhouse gases. Due to its specific agronomic management practices and its importance for global food security, paddy rice is addressed in a separate sub-chapter. For all other annual crop systems, the climate-smart intensification of the production can be achieved through the management practices described in Chapter B1-2 and in Box B1.3, as well as through the integration of perennial species on farms. The use of perennial species as a climate-smart agricultural practice does not require a complete conversion from annual to perennial crop production systems, and particularly not to landscapes dominated by perennial crops. It involves progressively integrating, as is locally appropriate, perennial species on farms (e.g. multifunctional edible living fences that can be used for feed or food, or windbreaks) and/or in the crop system, as appropriate). There are many possible variations in the progression towards perennial crop systems that span from relatively simple intercropping systems to fully integrated production systems, which are considered in module B5, (e.g. multistoreyed systems with shade crops growing below a productive canopy), to orchard and plantation crops, which are addressed in this module in Chapter B1-3.2

Perennial plantsxviii are those that complete their life cycle in more than two growing seasons. Compared to annual cropsxiv, perennial crops require less labour to maintain, and do not need to be replanted on a seasonal base. However, they usually require more up-front investments and costs, and the benefits in terms of climate change mitigation can take a considerable amount of time to materialize. 

Perennial woody crops are especially important in climate-smart crop production because, in addition to food, they also provide fuel (e.g. fuelwood from coppiced nitrogen-fixing tree species), timber, materials for construction and craft making, fibers, herbicides and medicines. Introducing perennial woody food crops on the farm and/or in the crop system delivers several co-benefits for climate change adaptation and mitigation. These co-benefits, which are felt both on the farm and throughout the agricultural landscape, include the diversification of production and consequent risks; an increase in the number of harvests per season; extra sources of biomass; enhanced soil fertility; the prevention and reduction of soil erosion; the restoration of degraded land as some species are adapted to shade conditions or land ill suited for annual crops; the stabilization of slopes; and carbon sequestration. For example, crop systems in which Cajanus cajan (pigeon pea) is grown as a perennial crop with soybean and maize have a smothering effect on weeds and provide two harvests per season: pigeon pea and soybean; and maize and pigeon pea. Instead of growing maize alone, or maize in rotation with soybean, the pigeon pea is grown with soybean. Once these legumes are harvested, the pigeon pea is allowed to regrow; then maize is planted into the pigeon pea. 

Herbaceous perennial crops have longer growing seasons and more extensive root systems than annual crops. Because of this, they are better able to compete against weeds, capture nutrients, access soil moisture and build up soil organic matter. As they do not have to be replanted each year, farmers save time, labour, money on fuel, and can also reduce their greenhouse gas emissions. Annual crop production systems offer more flexibility to shift to locally adapted crops each year. However, this potential adaptation advantage is only realized when seeding operations can be done in a timely manner. 

Some perennial herbaceous crops (e.g. alfalfa) are widely used by farmers for animal feed. Efforts to develop perennial herbaceous staple crops have been made in different countries (e.g. perennial wheat in Australia and perennial rice in China). However, despite the great promise of perennial herbaceous grain staples as a strategy for addressing food security, climate change adaptation and mitigation and environmental conservation, none of these crops has received the same amount of attention by breeders as annual staples. As discussed in Chapter B1-4.1, more research is needed to develop new crop species capable of replacing annuals and scale up this technology (Batello et al., 2013). The cultivars available are generally not very productive, but because perennial grains regrow after seed harvest, livestock can be integrated into the system. Thanks to their deep rooting system they stabilize the soil and can be used in more marginal lands to increase the diversity on the farm. This leads to more diversified production and makes the farming system more flexible.

Rice systems

More than 90 percent of the world’s rice is produced in flooded fields. Grown in continuously flooded paddies, rice receives two to three times more water than other irrigated cereals, even though they have a similar transpiration rate. As a result, to produce 1 kg of paddy rice, often as much as 2 500 litres of water is used, which translates to a water productivity of 0.4 kg per cubic metre (Bouman et al., 2007). Flooded rice fields are one of the main sources of methane emissions. Rice paddies emit methane totalling approximately 625 million tonnes of carbon dioxide equivalent annually (FAO, 2016b). In continuously submerged fields, drainage at the end of the growing season releases the methane formed by the anaerobic decomposition of the organic matter (Chapter B1-1.3). Nitrogen is also released, mainly through ammonia volatilization (Xu et al. 2012).

Farmers have a number of options for saving water in irrigated paddy/lowland rice production. These options include no-tillage in combination with mulching to provide soil cover; raised beds; land levelling; alternate wetting and drying irrigation; and aerobic rice (Bouman et al., 2007; Thakur et al., 2011).

The aerobic rice production system uses especially developed aerobic rice varieties that are grown in well drained, non-puddled (dryland preparation) and non-saturated soils. Because aerobic rice needs less water at the field level than conventional lowland rice, the system is targeted at relatively water-short irrigated or rainfed lowland environments. Irrigation can be applied through flash flooding, furrow irrigation (with the rice growing on raised beds) or sprinklers. Weed control is particularly important in this system, as the number of weed species is higher and their growth is faster. Soil-borne pests and diseases, such as nematodes, root aphids, and fungi are more common in aerobic rice than in flooded rice, especially in the tropics. For this reason, it is recommended to grow aerobic rice in rotation with suitable upland crops. Site-specific nutrient management can be used to determine the optimal management of fertilizers. With appropriate management, aerobic rice production systems aim for yields of at least 4 to 6 tonnes per hectare. See the International Rice Research Institute's web page on aerobic rice for more information.

Non-continuous water regimes, like alternate wetting and drying, reduce water demand and allow water to be allocated for other uses. This is particularly beneficial in major irrigated rice areas where the water supply is forecast to be insufficient to meet demand. This technique also reduces fuel for pumping water, which reduces farmers’ expenses. Intermittent water applications also temporarily remove the anaerobic conditions. This results in a significant reduction (above 16 percent) of overall methane emissions during the growing season compared with continuous flooding. It should be noted however that nitrous oxide emissions may increase. The recurring shift between aerobic and anaerobic conditions enhances nitrification, and if the nitrates are not taken up by the plants, nitrogen may be released into the atmosphere through denitrification (the biological reduction of nitrates to nitrogen gas by bacteria (Chapter B1-1.3). In alternate the alternate wetting and drying technique, irrigation water is applied when the rice plant becomes established. The fields are kept flooded and the soils are saturated for two weeks to discourage the growth of weeds. The flooding is then interrupted, and the fields are allowed to dry out until the water level falls to 15 cm below the soil surface. During flowering, a layer of water 3 to 5 cm deep is maintained. During grain filling, the alternate flooding and drying scheme is repeated until two to three weeks before harvest. Alternate wetting and drying can be applied with different rice production methods. It can be used instead of continuous flooding as well as under System of Rice Intensification (Box B1.4)

Box B1.4  System of Rice Intensification

The System of Rice Intensification uses alternate wetting and drying in combination with land levelling. In this system, rice seedlings are transplanted at shallower depths with a wider spacing (25 x 25 cm) between plants than in flooded systems. This allows for tillers to emerge and develop easily and quickly and to develop healthy, large and deep root systems that are better able to resist drought, waterlogging and rainfall variability, all of which are potential impacts of climate change. 

This system improves yields higher than those obtained in flooded systems. The rice also matures earlier, and the land becomes available sooner for the timely planting of the next crop or for the intensification of the crop rotation. Some examples are available from the FAO Save and Grow Farming Systems Fact Sheet. However, the System of Rice Intensification is more labour-intensive than flooded systems. Its success depends on the farming system’s specific characteristics and whether the increased labour required has a positive or negative effect on the local economy. The economic effects will be determined by whether the increased demand for labor generates employment for otherwise idle family labour during the dry season, or whether it translates into production costs that are too high to be sustained. Labour requirements could be lowered with technical innovations, such as seedling trays that simplify seedling preparation and transplanting, or replacing transplanting altogether with direct seeding (FAO, 2016a). 

Strengthening farmers' decision-making skills through activities in which they can learn from experience and providing platforms for collaboration between farmers and researchers can help ensure that crop management practices are adapted to farmers' needs. A study carried out in the Senegal River Valley assessed the agronomic and socio-economic viability of various management practices, including the System of Rice Intensification, the farmers' current practices, and adapted practices. The adapted farmer practices, which were a combination of improved practices designed by farmers and researchers to better respond to local conditions and needs, obtained the largest yield, reduced the labour needed for weeding, lowered the need to apply herbicides, and minimized the risk of production losses in the field (Krupnik et al,. 2012). 

The training modules available on Youtube on the System of Rice Intensification in Burundi developed by IFAD and Cornell University provide a useful knowledge-sharing tool: Seed germination and nursery preparation; Field preparation and transplanting; Weeding and water management.

Source: Authors

B1-3.2 Horticultural systems, orchards and plantations

Horticulture production systems involve the growing of fruits, vegetables, root and tuber crops, condiments and mushrooms. 

Orchards and plantations are agricultural systems that are productive for many years and can provide multiple harvests. 

Horticulture species are particularly rich in diversity. They offer a vast range of cultivars that can naturally perform well in many locations and accommodate changing climate variables. Along with the proper irrigation and drainage management, the initial selection of a site that best meets the crops agro-ecological requirements is of utmost importance in all climate-smart horticultural systems (Table B1.1). 

The FAO HORTIVAR database provides a useful reference for field performances of all crop species and varieties under the prevailing climatic conditions in a given location during the crop cycle. The information on cultivars, their preferred planting and harvesting times and location is georeferenced, and can be linked to specific climatic parameters. This information can be extrapolated for use in areas where climate change is expected to create similar climatic conditions.

Protected cultivation

Protected cultivation, which embraces a broad range of practices, 'protect' the plants against external factors. These practices are meant to ensure consistent productivity under various and variable, sometimes unpredictable, climate variables. Protected cultivation can involve very simple practices, such as the use of soil mulch or floating mulch, as well as highly sophisticated vertical farming systems (Table B1.1). These technologies require different levels of investment and costs and cannot be equally applied to all crops. The level of technology will largely depend on the commercial value of the crop and the target market.

The major greenhouse gas emitted from greenhouse production is carbon dioxide, which is released by the burning of coal, natural gas and oil for heating and by the generation of electricity for cooling and artificial lighting. Indirect sources of greenhouse gases include the production of the greenhouse materials, such as disposable polyethylene.

Greenhouse gas emissions can be reduced by increasing productivity per unit of water, fertilizer and energy. In horticultural systems for vegetable crops, conservation agriculture, in combination with drip irrigation, has the potential to increase yields, reduce water evaporation from the soil and decrease labour. Energy savings can be achieved by ensuring greenhouse production is carried out on sites that have been selected based on careful assessments, and adopting the suitable greenhouse design and covering material. Fortunately, a major proportion of greenhouses have passive climate control systems based on ventilation and shading, and do not have heating or cooling systems, which are major sources of energy consumption and greenhouse gas emissions. Energy use can be monitored by the following values and ratios: kg per square metre of floor area (crop productivity); millijoules per square metre of floor area; millijoules per kg of product; carbon dioxide emissions per kg of product; and water (in quantity and value) used for irrigation per kg of product.

Urban and peri-urban horticulture

The objective of urban and peri-urban horticulture is to improve the availability of fresh horticulture produce in cities and increase the access of urban populations to this nutritious food, while also creating jobs and improving livelihoods. As 'proximity' food production systems with short supply chain, urban and peri-urban horticulture can save energy and reduce greenhouse gas emissions by cutting down on transport, packaging and conservation. Urban and peri-urban horticulture has emerged as a preferred activity for small-scale producers, who can grow different horticulture specialty crops within and around cities. Crops are grown either in peri-urban greenbelts, plots within the cities, home gardens or microgardens.

Microgardens are container-based small-scale production units that can be used to cultivate a wide range of vegetables, roots, tubers and condiments in small spaces, such as patios, balconies and rooftops. They are adapted to densely populated urban environments, where space is limited and water scarce. Microgardens are a good example of producing more with less, delivering higher yields and greater diversity than larger-scale production per unit of surface area, water used and labour expended.  Not only do they require less space, water and labour, they also use less pesticides and mineral fertilizers and need less transport and packaging to reach consumers. They are also less affected by soil-borne diseases and produce less food waste.

Urban horticulture is gaining in popularity. It has been acknowledged as a development opportunity by the Milan Urban Food Policy Pact signed by the mayors from around the world in 2015. In 2014, the microgarden technology has been awarded the Dubai prize by UN-Habitat as the 'Best Practice' in the urban environment. The city of Barcelona has also nominated the technology as an environmentally friendly technology.

Orchards and plantations

The productivity of orchards and plantations is strongly determined by the species and cultivars that are grown. These can be identified by their 'set points', which correspond to values of the climate factors required for optimal growing, flowering and fruit development. These set points should be considered as the guiding values for site selection. Adaptation to local conditions can be enhanced by using grafting technology, whereby the rootstock can bring specific resistance to biotic and abiotic factors. The climate-smart management of orchards and plantations involves the efficient use of water and energy for husbandry operations, and the transportation and storage of produce. Climate-smart orchard and plantation crops, once established, require no-tillage and minimal fossil fuel inputs. On average, they can sequester more carbon in their biomass and in the soil than annual crop production systems. The amount sequestered depends on the climate, the species grown and their management. 

As well as producing nutritious food and sequestering carbon, orchards and plantations stabilize slopes and help build soils. There are many trees and palms worldwide that produce crops that are rich in carbohydrates (in starchy fruits, seeds, nuts, pods, tubers), provide fats (in fruits, seeds, nuts), and some proteins (in nuts, beans and leaves). Research is needed to fully exploit their potential in climate-smart agricultural development.

B1-3.3 Integrated production systems

Integrated production systems are dealt with in module B5.

B1-3.4 Natural and anthropogenic grasslands

Rangelands and grazing areas, used by pastoralist, cover 38 percent of the total agricultural land. Most of those areas are arid, semiarid lands or cold mountains areas where no crops can be grown sustainably. 

The world’s soils are considered to store the largest terrestrial pool of organic carbon (Amundson, 2001). Carbon stocks in the soil can be altered when changes are made in the way land is used. Changes in land use and management are considered particularly important components of any comprehensive strategy to reduce the concentration of greenhouse gases in the atmosphere (Thomson et al., 2010; Deng et al., 2013). The root systems of grasslands can sequester carbon and redistribute it to deeper soil layers (Nepstad et al., 1991). The carbon stored in a deeper soil profile is likely to be less susceptible to decomposition (Batjes and Sombroek, 1997).

There have been several scientific research studies to assess the role of management practices on soil carbon balance in various grassland ecosystems. However, grasslands ecosystems are very complex in both plant composition and soil types. Grasslands should be considered with a holistic approach looking to the complete ecosystem preserved by pastoral use of land. Those, together with wild species and livestock breeds, contribute to soil fertility and biodiversity. There is not a one-size-fits-all approach for grassland management. However, the role of grasslands in sequestering organic carbon can be improved by ensuring that grazing is kept to sustainable levels. Controlled grazing promotes growth of herbaceous species and reduces grassland degradation. As well as increasing soil carbon sequestration, improvement in the nutrient status of grassland soils can improve forage yield and quality. The introduction of deep-rooted grasses and legumes can also play an important role in improving soil carbon sequestration (Fisher et al., 1994; Batjes and Sombroek, 1997; Schuman et al., 2002; Schuch et al., 2013).