Keywords

4.1 Small-Farmers, Large-Field Model, Contract Farming, and One-Must-Do, Five-Reductions

4.1.1 Small Farmers, Large Field (SFLF)

The “Small-Farmers, Large-Field” model originated in a “Single-Variety Field” initiated by the Department of Agriculture and Rural Development in Can Tho, Vietnam, in 2004, to apply and promote good rice cultivation practices. The “Single-Variety Field” model was piloted with a field size of 50–100 ha, and best practices for seed rate, fertilizer use, and pest management were applied under the descriptor “Three Reductions, Three Gains” (3R3G). Another key feature was the use of certified rice seeds. The scaling out of 3R3G and hence SFLF began to be implemented during Phase 3 of the Irrigated Rice Research Consortium (IRRC) via the integration of technical agricultural knowledge and social science approaches relating to the use of mass media (Heong et al. 2010). In 2009, during the last phase of the IRRC, best practices to reduce water use and postharvest losses were added to 3R3G. The new package was promoted as 1-Must-Do (certified seed) and 5-Reductions (reduce seed rates, fertilizer use, pesticide use, water use, and postharvest losses) (1M5R) and launched in An Giang province in the MRD.

The advantages of the SFLF program, such as land consolidation, uniform varieties, best rice-management farming practices, and synchronized crop calendar and management, resulted in cost reductions and yield increases for smallholder farmers (Rosellon 2015; Thang et al. 2017; Flor et al. 2021). On the other hand, it also encouraged enterprises to sign farming contracts with farmer groups in SFLF rather than individual farmers (Ba et al. 2019). The SFLF has been successfully adapted in other countries, such as India (Mohanty et al. 2018). SFLF covers two major farming practices that are “contract farming” created in 2002 (PM 2002) and “One-Must-Do, Five-Reductions” (1M5R) (Prime Ministerial Policy for Mekong Delta region of Vietnam 62/2013/QD-TTg, 25 October 2013; Flor et al. 2021).

4.1.2 Contract Farming

Vietnam’s government enacted a decision to promote contract farming in 2002 (PM 2002). The decision consists of articles encouraging enterprises of all sectors to engage in contract farming, associating agricultural production with processing and consumption, ultimately promoting sustainable development. The decision gave details of the contract form, encouragement policies, and responsibilities of the involved entities, and support from the government institutes. Contract farming was adopted in 63,000 ha in the MRD by 2020 (Flor et al. 2021). A typical contract farming model between enterprises and farmers is shown in Fig. 4.1 (Nguyen et al. 2020c).

Fig. 4.1
A model of common rice-contract farming includes farmers who buy rice grains from rice mills or exporters, eventually contributing to high-value makers, slash S R P. The exporters provide technical support and agronomic inputs to the farmers.

A common rice-contract farming model that integrated the Small Farmers, Large Field Model (SFLF) in the Mekong River Delta

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4.1.3 One-Must-Do, Five-Reductions (1M5R)

As described above, 1M5R was leveraged from a previous good-practice package named “Three Reductions, Three Gains” (3R3G). In 2002, a pilot field was established in Can Tho province that encouraged farmers to work in groups and practice integrated pest management (IPM), reduce excessive use of agrochemicals, including seed rate and fertilizer and pesticide uses (3R) associated with increased rice yield, lower production cost, and higher income (3G) (Huan et al. 2005). In 2007, seed rate and seed quality were recognized as the key elements of 3R3G. During Phases 1 and 2 of CORIGAP, 1M5R, as a foundation for SFLF, was promoted in six provinces in the MRD. The 1M5R model became the main foundation of the SFLF development (MARD 2014; PM 2013). The 1M5R approach was ratified by the Ministry of Agriculture and Rural Development in 2013. Farmer groups had to demonstrate they were following 1M5R best practices to receive support under the Vietnam Sustainable Agricultural Transformation Project (VnSAT), a World Bank-funded initiative implemented in the MRD from 2017 to 2021 (see Flor et al. 2021) for details.

1M5R includes the following major criteria:

One-Must-Do: certified seeds:

The seeds are certified by MARD based on:

  • Cleanliness: ~99%;

  • Impurity from different varieties: ~0.3%;

  • Weed seeds: no more than 10 weed seeds kg−1 seeds;

  • Germination: ~80%;

  • Moisture content on a wet basis: ~13.5%.

Due to the challenges of the availability of certified seeds, 1M5R accepts two levels of certified seeds as follows:

  • Certified seed–level 1: certified by MARD, usually produced and supplied by the seed companies;

  • Certified seed–level 2: The seeds were produced from registered or certified seeds and satisfied all the criteria of cleanliness, purity, limited weed seeds, germination rate, and moisture content. All these criteria are verified by a standard seed-testing agency (eligibility certified by MARD). This type of seed is usually produced and supplied by farmer organizations, i.e., farmer groups and cooperatives.

Five-Reductions: seed rate, fertilizer use, pesticide use, water use, and postharvest losses (Fig. 4.2).

Fig. 4.2
An infographic chart lists the criteria and their respective requirements. The criteria are seed rate, nitrogen, insecticides, fungicides, water management, and harvesting.

Requirements of 1M5R

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  1. 1.

    Seed rate: not higher than 100 kg ha−1. This is dependent on crop establishment (CE) methods. In current practices in the MRD, transplanting uses <60 kg while broadcast seeding, which is a common practice in the MRD (applied across more than 60% of the rice production area) uses >150 kg ha−1. To be realistic and to encourage farmers to meet this criterion, the 1M5R was updated in 2020 to set the acceptable seed rate at 120 kg ha−1 (Flor et al. 2021).

  2. 2.

    Fertilizer use is set for Nitrogen (N), at not higher than 100 kg ha−1.

  3. 3.

    Pesticide use is set for insecticides and fungicides based on the maximum applications per season (1 and 2, respectively) and the period when to apply pesticides. The latter includes no application of insecticide within 40 days after sowing and no application of fungicide after flowering of the rice crop.

  4. 4.

    Water use: the best practice is alternate wetting and drying (AWD)—see Lampayan et al. (2015) for details. However, to be realistic for MRD conditions, this criterion required at least one or two drainages mid-season (re-irrigating before the subsoil water level reaches 15 cm) during the wet and dry seasons, respectively.

  5. 5.

    Postharvest losses: The focus is on optimal harvesting using combine harvesters and the timing of the rice harvest.

There are various solutions to support 1M5R, such as mechanization, precision farming, digital agriculture, etc. Most of these approaches are described in the following sections.

4.1.3.1 Benefits of 1M5R

The benefits and adoption of 1M5R have been captured in CORIGAP studies. Applying 1M5R in the MRD can improve farmers’ benefits by increasing net income by 19% while cutting costs by 23% (Chi et al. 2013; Stuart et al. 2018). An impressive number of smallholder farmers have shifted from conventional to 1M5R practices covering at least 113,870 ha (Flor et al. 2021). Reduction of postharvest losses by using combine harvesters was the most adopted practice (>99% of farmers), followed by reducing seed rate (85.6%), with reducing water use being the least adopted of the technologies (45.4%) (Connor et al. 2021).

Approximately 37% of farmers, from a cross-section of farmers interviewed in An Giang and Can Tho provinces in the MRD, adopted all six requirements, which doubled from 16% reported in 2011 (Connor et al. 2021). This successful adoption and qualification of 1M5R were significantly supported by AWD and mechanization. With the application of 1M5R and mechanized transplanting, farmers can reduce inputs while having no reduction in yield and profit increased by 7–20% or 600–1,000 USD ha−1 season−1 more than other farmers (Nguyen et al. 2020c). Despite the clear benefits of adopting 1M5R, some farmers are still reluctant to adopt some practices for various reasons, including lack of technical equipment, e.g., seeding machines and laser land leveling machines, lack of access to certified seed, concerns over possible pest outbreaks or extreme weather events, and lack of access to a reliable source of irrigation water or drainage (Tuan et al. 2021).

4.2 Ecologically-Based Pest Management

Chapter 3 introduced and explained the ecological dimension of the CORIGAP project concentrating on faunal biodiversity in rice-dominated wetlands. While CORIGAP predominately focused on introducing best management practices in the form of mechanization and improved agronomic methods, in the last phase of CORIGAP, the project also designed pathways for an agroecological transition toward sustainable food systems. Food-system sustainability is a complex issue, combining sustainable production and consumption with agroecological practices being one avenue to improve food system sustainability in low- and middle-income countries (Ng’endo and Connor 2022). In this section, we will provide an overview of progress during CORIGAP of two sustainable pest management approaches: ecological engineering (EE) to manage insect pests and ecologically-based rodent management (EBRM) to manage mice and rats. The two approaches urgently require greater attention in intensive rice-growing systems (Sattler et al. 2021; Singleton et al. 2021).

4.2.1 Ecological Engineering

Ecological engineering is defined as the design of sustainable ecosystems, in this case, sustainable rice agroecosystems that integrate human society, i.e., rice farmers with their natural environment, to benefit both (Mitsch 2012). In the context of pest management in rice ecosystems, one of the avenues for ecological engineering is to increase landscape and habitat diversity to support natural pest regulation and lessen the need for pesticide inputs (Gurr et al. 2017; Sattler et al. 2021). Over the last decades, rice production in Southeast Asia has intensified drastically, as has agrochemical inputs, especially fertilizers, and pesticides (Sattler et al. 2018). The overuse of pesticides has been associated with biodiversity loss in rice-growing areas (Peng et al. 2009). Therefore, a variety of approaches have been designed to counteract farmers’ overuse of pesticides to enhance beneficial arthropod populations in rice fields. EE by which farmers plant additional flowering plants in rice bunds, i.e., small dikes surrounding rice fields to keep the water level in the field, has been shown to be a promising method. Sattler et al. (2021) found that withholding pesticide use did not decrease yields in either EE treatment or control plots. However, parasitoid abundance was higher in both treatments during the wet season. The authors concluded that pesticide use is likely the main driver causing low arthropod abundance. The study used an experimental design consisting of a multi-method approach based on feedback from farmers on the preferred types of plants that they either cultivate or collect for consumption. In order to be suitable for inclusion in the EE experiment, these plants had to meet several criteria, such as that the plants could grow on rice bunds, had flowers that could potentially provide additional food sources for insect species (flowering plants), and have a growth duration that was shorter or equal to that of the rice crop (annual plants). The experiment used a treatment–control design described in detail by Sattler et al. (2021). This case study will focus on a side experiment during the 2019 wet season from July to October in a lowland rice ecosystem in Prey Veng province. The aim of this case study was to identify which insect species were present the rice bunds that are the focus of EE habitat modification and which four functional groups they belonged to, i.e., detritivore, parasitoid, pollinator, and predator.

The experiment used sponge gourd (Luffa aegyptiaca MILL.) and chili (Capsicum annuum L.), which were the preferred plants by the interviewed farmers in addition to mung bean (Vigna radiata (L.) R. WILCZEK) and sesame plants (Sesamum indicum L.) that have been shown to have positive effects on insect natural enemies (Gurr et al. 2016; Horgan et al. 2019). The EE fields, which had additional crop plants on bunds, were not treated with pesticides and were compared to fields where farmers usual practice (FP) were applied. In the FP fields, rice crops were treated with pesticides and had no vegetables growing on their bunds. Other growing practices, such as fertilization, rice cultivar, and water management were the same in both fields. Three rice fields were selected, each serving as a replicate for each treatment. Fields were located at least 100 m away from one another to account for a buffer zone. The bund plants were planted after the rice crop had been established to ensure growth duration was parallel for the rice and vegetable crops. The two vegetable crops were planted alternately on each side of the bund (as shown in Fig. 4.3). In total, there were six sampling sites, of which three sites were for EE, and another three sites were for FP.

Fig. 4.3
2 layouts. First. A rectangle labeled ecological engineering field is in the center. The 4 rectangles on each side are labeled plants and have 2 dots representing blue and yellow pan traps on opposite sides. Second. Identical diagram. The rectangle in the center is labeled farmers practice field.

Layout for one replicate of the ecological engineering (EE) experiment. Pan traps were placed at sampling points on the bunds both in EE and farmer practice (FP) fields

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To investigate insects visiting the selected plants in the rice bunds, pan traps were used in the color of the selected plant flowers. The bunds around the EE and FP fields were used as transects for placing the pan traps. Three pan traps were placed on each bund of a field. No traps were placed on the corners because this would conflate data as there were different vegetable crops on each side of the fields (Fig. 4.3). This meant a total of 40 sampling points covering all EE and FP sites. To capture the insects in the pan traps, the trap contained a mixture of 150 ml of water, detergent, and fungicides. Sampling was conducted starting at the flowering stage of the vegetable crop. The pan traps were left in the field for 48 h. Insects collected were stored in vials containing 80% ethanol. The collected insects were identified to the family level and assigned to their functional group. Functional groups were compared between EE and FP fields applying linear models.

In total, 3,252 specimens were collected in the pan traps. Some 2,033 specimens were collected in pan traps next to FP rice fields, and 1,219 specimens were collected in the pan traps next to EE fields. Samples were dominated by the detritivore dipteran family Phoridae and the predatory dipteran family Dolichopodidae. When comparing the functional groups between ecologically engineered and farmers’ fields, we found significantly higher detritivores in FP than in EE treatments. No differences were found between the two treatments for the abundance of predators, parasitoids, and pollinators (Fig. 4.4). Noticeable was that some taxa such as the detritivore fly Phoridae, parasitoid fly Pipunculidae, the parasitoid wasp Scelionidae, and the predatory fly Dolichopodidae were twice as abundant in pan traps located on the bunds of the FP fields (as compared to those retrieved from the EE fields).

Fig. 4.4
2 scattered box plots of log individuals ranging from 0 to 4 versus treatment of F P and E E respectively. The maximum number of log individuals is approximately 4 for F P in detritivores. The maximum number of log individuals is approximately 3.7 for F P in predators.

Functional groups collected in pan traps next to farmers’ rice fields (FP) and ecologically engineered rice fields (EE)

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Results from the EE experiment showed no differences in the abundance of natural enemies and pollinators between farmers’ practice (FP) and EE field. A number of possible explanations arise: insects may be attracted by the pan trap color regardless of whether vegetable crops were on the bunds; the experiment might have been too short for vegetation growing on rice bunds to provide maximum advantage for beneficial insects; and finally, the landscape structure might be too homogenous to generate significant differences at field level (Gurr et al. 2012). This could also explain why single taxa occurred in higher numbers next to FP fields compared to pan traps next to EE fields. Furthermore, the experiment might have been too short for vegetation growing on rice bunds to provide a maximum advantage for beneficial insects. Results of an experiment using string beans on rice bunds also showed a similar trend of no difference in natural enemies on the bunds sampled of EE fields versus control (Horgan et al. 2017).

Nevertheless, the connected study by Sattler et al. (2021) showed that EE did not reduce rice yields despite withholding pesticides. Indeed, the study indicated that the absence of pesticide use on EE fields contributed to increased abundance of parasitoid fauna compared to conventional practice at least in wet season. These results indicate that omitting pesticides does not negatively influence rice yields and that applying EE farmers have a better cost–benefit ratio. Farmers save costs for pesticide and labor use. Furthermore, farmers can either earn additional income from crop plants on the bunds or use them for their own household consumption and are able to diversify their food intake. Applying EE is a useful method to reduce pesticide applications without reducing rice yields. Cultivating a variety of other crop plants on the otherwise barren bunds will increase floral biodiversity and may reduce negative impacts on faunal biodiversity. However, it must be noted that using color pan traps alone to assess arthropod biodiversity may not be sufficient and other methods, such as net swee** or blow-vac suction, should also be used.

4.2.2 Ecologically-Based Rodent Management

The concept of EBRM was developed in the late 1990s (Singleton 1997; Singleton et al. 1999) primarily from research on the management of house mice, Mus domesticus, in Australian wheat fields and rice field rats, Rattus argentiventer, in lowland irrigated rice in Indonesia and Vietnam (Singleton et al. 2007). EBRM was subsequently adopted as a national policy for the management of rats in rice crops in Vietnam in 1999 and Indonesia in 2002. In Myanmar, activities on rodent population ecology and management under CORIGAP led to adopting EBRM as a national policy in 2015–2016.

During the CORIGAP project, the international profile of EBRM was raised internationally via multiple conference presentations, peer-reviewed publications, and media coverage. The adoption of EBRM is currently documented to be the main approach for managing rodent problems in agricultural systems in 37 countries (G.R. Singleton, unpublished data, Table 4.1). Some of the key research activities on EBRM under CORIGAP include:

Table 4.1 Adoption of ecologically-based rodent management (EBRM) globally as of January 2023
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  • research on postharvest losses in grain stores in Myanmar (Htwe et al. 2017) and Sri Lanka (Htwe et al. 2021);

  • a detailed replicated experimental study on rodent-weed interactions and their associated impacts on rice crops (Htwe et al. 2019);

  • the interactions between habitat use of rodents and the use of AWD of lowland irrigated rice crops (Lorica et al. 2020);

  • the effectiveness of the contraceptive hormones quinestrol and levonorgestrel, on the fertility of the rice field rat (R. argentiventer) in Indonesia (Stuart et al. 2022); and

  • the effectiveness of community-based management of rodents in lowland irrigated rice in Cambodia (dominant rodents were R. argentiventer and the R. rattus complex of species) (Stuart et al. 2020).

A major review of the progress of EBRM in Asia covers the key findings from these studies (Singleton et al. 2021).

An additional major impact of EBRM has been reported in the tidal rice systems of South Sumatra. Rodent and weed pests restricted rice to be planted on only 30 ha in the dry season of 2012. In 2013, a successful demonstration of EBRM and weed management was established for the dry-season crop (Sudarmaji, pers. comm.). In 2014, 300 ha of dry-season rice was grown successfully. This led to strong financial support from the provincial government for establishing EBRM, particularly using a trap-barrier system (see Singleton et al. 2003). In 2015, there were 17,000 ha of dry-season rice grown, increasing to 93,500 ha in 2016 (Budi Raharjo pers. comm.; Singleton and Quilloy 2017).

The progress of EBRM internationally since 2010 has been impressive. Research supported by CORIGAP has been a key driver of the increased adoption and parallel activities across several projects in southern and eastern Africa (see Swanepoel et al. 2017). Together, these studies in Asia and Africa have led to a marked reduction in the use of rodenticides and an increase in yields and profit for smallholder farmers (Singleton et al. 2021; Makundi and Massawe 2011).

Further progress is required because rodents remain a major economic burden on smallholder farmers (John 2014). Some of the key challenges ahead include the following.

  • There remains a paucity of knowledge on the biology of most species of rodents in develo** countries.

  • Long-term data must be collected, especially in upland rice-based systems where sporadic population outbreaks occur. Such data are required to develop forecasts of what are often massive rodent outbreaks that have major food security impacts at a local level (Singleton et al. 2010).

  • Better estimates of losses caused by rodents in fields and in grain stores to enable rigorous economic analyses of the cost and benefit of EBRM (see Ngoc et al. 2016).

  • In Southeast Asia, the mean rice holding of a family is 1–1.5 ha. Rodents do not respect the borders of fields. Hence, community action is the key to effective management. More sociological studies are required to recommend the most effective approach to coordinate community action given the specific context of cultural and farming systems.

  • Quantitative data are urgently needed on the likely effects of climate change on rodent pest populations.

  • Very little is known about the impact of rodent-borne diseases that affect humans in an agricultural context. We require quantitative data on the effects of rodent diseases on the rural livelihoods of smallholder farming communities.

  • Finally, we need to provide more consideration on how rodent populations are likely to respond to changes in intensive production to meet increased food demands. Rodent experts need to be active in providing advice to policymakers on this issue.

4.3 Mechanization

Rice production in Asia and Africa has faced labor shortages and climate-change issues such as unanticipated droughts and floods that cause unstable yields and a high risk of crop losses. Low farming efficiencies (high energy and labor costs and agronomic input-use) are mainly caused by poor land consolidation, lack of precision land leveling, crop establishment, and crop care. Laser land leveling (LLL) and mechanized crop establishment help to significantly increase agronomic use efficiency.

4.3.1 Laser Land Leveling

Small-sized and uneven fields can cause poor management and low efficiency of agronomic inputs. Poor field leveling can cause difficulty in crop establishment (Fig. 4.5a), adverse water management (Fig. 4.5b), and crop lodging at maturity (Fig. 4.5c). Lodging of rice plants and non-uniform growth of the rice paddy at the maturity stage leads to high postharvest losses (Fig. 4.5d).

Fig. 4.5
4 photographs. First. A few farmers pick crops from a wet field. Second. A photo of a waterlogged field. Third. A field has slightly bent crops growing in it. Fourth. A photo of a crop harvester tractor that is harvesting the crop in a field.

a Difficulty in crop management, b Poor water management, c Crop lodging, and d High harvest and postharvest losses caused by crop lodging and poor water management

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LLL is used for precision land reformation in rice cultivation to optimize water and crop management. It increases yield and input-use efficiency of water, energy, and agronomic inputs. A laser-controlled leveling system is shown in Fig. 4.6a, b. Assisted by a laser controlling system, this technology can reduce the unevenness of the field surface to a 1–2 cm height difference, even in a large field of 3 ha. In this case, the field slope can be set to 0.02% for draining the field.

Fig. 4.6
a. A photo of a tractor with laser receiver and scraper labeled. There is a laser transmiter at its right. b. A photo of a laser land leveler and a tractor harvester in a soiled field. 3 illustrations labeled topographic survey, R C M, and optimized scheduling are indicated with arrows at b.

Laser land leveling system (a) and drone and digital tools supporting laser leveling (b)

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4.3.1.1 Benefits of LLL

Several studies reported this technology’s benefits (Nguyen et al. 2022a; Jat et al. 2015). This application can help to increase land use efficiency by 3–6% when consolidating several small fields into one large field, save irrigation water by 20–40%, increase fertilizer and pesticide-use efficiencies by 10–13%, and increase rice yield by 10–13%. The benefits of LLL are summarized in Table 4.2.

Table 4.2 Benefits of Laser Land Leveling (LLL); adapted from Nguyen et al. (2022a)
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LLL is applied to reform the field in dry-soil conditions. It is best practice to conduct laser leveling once every five years (Nguyen et al. 2022a). The benefits of LLL are affected by many factors, such as soil conditions, equipment quality, operation of the technology, etc. As presented in Nguyen et al. (2022a), LLL can increase energy efficiency by at least 27% and reduce carbon footprint by at least 14% in rice production. Furthermore, precision land leveling enables the consolidation of small fields into larger ones by reducing the slopes of land incline and unevenness. Well-leveled fields are critical for mechanized crop establishments such as mechanized transplanting and direct seeding, which can increase farming efficiency and reduce the rice carbon footprint (Nguyen et al. 2022b).

On the other hand, there are challenges in promoting LLL, such as high cost, lack of service availability, and lack of scale-appropriate technology adoption interventions. LLL can be more effective if integrated with other supporting technologies, such as drones for field topographic surveys (Anguiano-Morales et al. 2018) and optimized scheduling of service providers (IRRI 2020). The LLL technology was promoted in the MRD, Vietnam, and the central plains of Thailand during the CORIGAP project.

4.3.2 Mechanized Crop Establishment

Scale-appropriate and site-specific precision sowing options, including mechanized direct seeding and mechanized transplanting, can help increase seeding precision, vigor of seedlings, and yield. Compared with broadcast-seeding practices such as manual broadcast, blower, and drone seeding, these practices also reduce seed rate, fertilizer and pesticide use, water use, and carbon footprint.

4.3.2.1 Mechanized Transplanting

Transplanting rice is a process of planting young rice seedlings either manually or using a machine. Manual transplanting is a traditional practice requiring about 100–200 labor hours per ha (Quilty et al. 2014; Nguyen et al. 2019) and almost the same labor for producing seedlings. Moving from manual to mechanized transplanting has been happening in the MRD, particularly for seed production, due to its advantages of increased yield, reduced risks of pests and diseases, reduced postharvest losses, and better conditions for rogueing in seed production. Mechanized transplanting employs two separate operations: seedling production (Fig. 4.7a, b) and transplanting (Fig. 4.7c, d). The use of machines for both operations is discussed in a training manual developed during the CORIGAP project (Nguyen et al. 2020a, b).

Fig. 4.7
4 photographs. a. A photo exhibits rows of rectangular crop beds. b. A close-up of the crop. c. A photo focuses on 2 mechanical crop transplanters that are transplanting the crop in a field. d. A photo of 3 rows of young plants in a wet field.

Two major steps of mechanized transplanting—seedling production and transplanting. a Seedling growing, b Seedling ready for transplanting, c Mechanized transplanting, and d Transplanted seedlings

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The benefits of mechanized transplanting were captured via a case study in the MRD of Vietnam conducted under the CORIGAP project (Nguyen et al. 2022a). Compared to the broadcast-seeding method, mechanized transplanting has the following advantages:

  • Reduced seed rates (40–60%): A lower seed rate is achieved with transplanted rice as it can be properly controlled and managed during the raising of seedlings in the nursery and through the regular spacing of seedlings when transplanted.

  • Lower risk of seeds being eaten in the field by birds and rats.

  • Better weed control. Rice seedlings have a head start compared to the weeds in the field, so weeds will be a lesser problem. This is further supported by the proper leveling of the land. Weeds can easily be controlled with better water management when the field is well-leveled.

  • Allows deeper anchoring of roots into the soil, thus, lodging is less likely throughout the growth of the crop, and this leads to a postharvest loss reduction of about 5–10%.

  • Rogueing in seed production is easier in transplanted rice.

When labor is limited and expensive, using machines for transplanting is more advantageous. Around 20–30 persons are needed for the manual transplanting of rice to cover 1 ha day−1 compared to mechanical transplanting, which would only need two or three operators to accomplish transplanting 1–2 ha day−1. Advantages that can be derived from the use of a mechanical transplanter in establishing rice in the field are:

  • Efficient use of resources by saving labor costs;

  • Timely transplanting of seedlings at optimal age;

  • Reduced transplanting shock;

  • Ensured uniform spacing and optimum plant density (26–28 hills m−2);

  • Higher yield compared to the traditional method (e.g., manual broadcasting);

  • Lower drudgery and health risks for farm laborers; and

  • Improved employment and entrepreneurship opportunities for rural youth and women through custom service provision.

4.3.2.2 Mechanized Direct Seeding

Direct-seeded rice (DSR), especially wet seeding, is a common practice in Asian countries to respond to labor-, water-, and energy-intensive problems (Kumar and Ladha 2011). Of these, manual broadcast seeding and blower seeding are widely adopted (Nguyen et al. 2022b). These broadcast-seeding practices use a high seed rate, usually higher than 150 kg ha−1, due to its non-uniform seeding. Therefore, mechanized direct seeding (mDSR) for more precise seeding has been promoted to address the problems of broadcast seeding.

There are two main types of mDSR, including dry and wet seeding. Dry-mDSR is a mature technology recently adopted in several countries such as India, China, etc. (Kumar 2023). Responding to the demand and aligning with the development, mDSR has been introduced, tested, and promoted during the CORIGAP project in some SE Asian countries, including Cambodia, Sri Lanka, Thailand, the Philippines, and Vietnam (see Nguyen et al. 2022a). Some typical mDSR machines are shown in Fig. 4.8a, b.

Fig. 4.8
2 photographs. a. A photo presents moving sowing equipment in a soiled field. b. A photo exhibits young rice plantlets in a paddy field.

Mechanized dry seeding, a Mechanized dry seeding in India, b Rice seedlings at 15 days after mechanized dry-seeding

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On the other hand, the wet-mDSR is still at the adaptation stage, particularly for the high demand for wet irrigated rice in the MRD of Vietnam and Cambodia. The major challenges for this practice are that it requires a well-leveled field and land preparation and the risk of seeding losses caused by unpredicted rain. Some typical wet-mDSR machines tested in the MRD of Vietnam are in Fig. 4.9a–d.

Fig. 4.9
4 photographs. a. A photo of a moving line seeder in a wet field. b. A photo of a moving seeder in a wet, soiled field. c. and d. 2 photographs of young plants growing in 3 and 4 rows, respectively.

Typical wet-mDSR machines being tested in the MRD a Line seeder, b Hill seeder, c Seedlings at 20 days after line seeding d seedlings at 20 days after hill seeding

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A case study under CORIGAP and the OneCGIAR Excellence in Agronomy Initiative (Kumar 2023) demonstrated the benefits advantages of mechanized wet-direct seeding for rice production in the MRD of Vietnam over the broadcast-seeding method. Compared to the broadcast-seeding method, mechanized transplanting has the following advantages:

  • reduced seed rate by 2–3 times compared with broadcast seeding,

  • seeding costs amounting to 1/3–1/2 of mechanized transplanting,

  • reduced fertilizer use by 20–30% and reduced risk of pest and diseases,

  • no yield penalty,

  • reduced postharvest losses by decreasing risks of lodging and increasing grain quality and uniformity, and

  • Less water use than transplanting (for seedlings).

However, compared to mechanized transplanting, mechanized DSR still needs to use herbicides for weed management (before seeding). In contrast, weeds can be controlled by water management after sowing by using stagnant water.

4.4 Harvest and Postharvest Management

Poor harvest and postharvest management cause high postharvest losses. More than 10% of grain produced is lost physically, and poor practices can markedly reduce grain quality (Gummert et al. 2018). Of these processes, harvesting, and drying are the major causes of both physical and quality losses. Recent research conducted under CORIGAP indicated that 70% of farmers who grow a pulse crop after their wet-season rice crop practice manual harvesting and stacking of the unthreshed rice in piles (field stacking) in the Ayeyarwady Delta. This can cause up to 40% physical loss and 7% discoloration, representing major quantity and quality losses (Gummert et al. 2020). CORIGAP’s in-country collaboration with national partners and the private sector promoted the introduction of mechanical harvesting and/or mechanical threshing in the region to address this issue.

Sun drying losses average 2–5% and are mostly caused by improper handling and poor physical conditions for drying the rice (RKB 2013). In addition, both physical and quality losses can be severe due to delays in harvesting and poor logistics that delay drying, which are the major postharvest challenges in Vietnam. A delay in harvesting leads to over mature rice grains, which can cause shattering losses of more than 5%. Delays to wet paddy drying of more than 24 h can also lead to significant quality losses of up to 1% day−1 from discoloration, mold, and broken grains (RKB 2013). This section covers several mechanization and postharvest solutions tested and extended to local smallholder farmers to address the challenges and problems. The partnerships under the CORIGAP project between IRRI scientists and NARES country partners have produced major outcomes and benefits for postharvest management. In addition, LLL and mechanical transplanting have begun to gain favor in partner countries. Figure 4.10 shows a typical postharvest process and some solutions to support sustainable rice production. Optimized timing of harvesting and use of technology, plus improvements in paddy logistics, drying, storage, and milling management, significantly reduce postharvest losses and maintain grain quality.

Fig. 4.10
An illustrative linear arrow diagram. It lists the combine harvester, which is used for harvesting, flatbed dryer and solar bubble dryer, which are used for drying, hermetic storage on industrial and household scales for storage, and finally milling, which reaches the markets.

Postharvest solutions to support sustainable rice value chains

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4.4.1 Harvesting

Best practices for harvesting are mainly achieved through two criteria: optimal timing of harvest and best use of equipment available for harvesting the rice crop.

4.4.1.1 Timing of Harvesting

The timing of harvest is important to reduce losses in both quantity and quality. Grain losses in the field may occur from shattering, lodging, and pests such as birds, rodents, and insects. Premature or early harvesting will result in a higher percentage of unfilled or immature grains, which reduces the overall yield, increases grain breakage during milling, and has a negative effect on seed quality. Late harvesting will result in increased physical losses in the field due to shattering, lodging, and birds and may decrease quality through weathering in the field and grain breakages at the mill. The timing of harvesting can also affect the germination potential of rice seeds. There are several ways to determine whether the crop is ready for harvest (SRP 2020). These include:

  • Number of ripe grains per panicle: The crop should be cut when 80–85% of the grains are straw- or yellow-colored.

  • Grain moisture: The proper grain moisture content for harvesting depends mainly on varieties and climate. Usually, the ideal grain moisture for harvesting is between 22 and 24%.

  • Number of days after sowing: Generally, early duration varieties are ready for harvest 100–120 days after establishment, medium-duration varieties between 120 and 140 days after establishment, and long duration between 140 and 160 days. Transplanted crops will mature faster in the field than direct-seeded crops.

  • Number of days after panicle initiation and flowering: The time taken from panicle initiation to ripening is similar for most rice crops. The optimum time of harvest is 55–60 days after panicle initiation or 30 days after flowering.

  • Harvest management: The cutting time must be closely linked with threshing and drying capabilities. Threshing and drying should be done within 24 h of cutting. If cut panicles are left in stacks for more than 24 h, the grain will begin to heat up and discolor and increasing the risk of mold growth and losses to pests such as birds and rodents.

4.4.1.2 Technology Options

There are two practices commonly used for rice harvesting in South Asia (SA) and Southeast Asia (SEA): (1) manual cutting and mechanical threshing, and (2) combine harvesters. The first practice causes higher grain losses because of the delay in harvesting and transportation of rice plants between cutting and threshing. In some countries such as Myanmar, freshly cut rice plants are often stacked in the field to dry before threshing, which can cause up to 40% postharvest losses due to shattering, consumption by rodents, damage from insects and molds, and fissuring of grains and discoloration (Gummert et al. 2020). Hence, the second practice, combine harvesting, has been rapidly adopted in SA and SEA in response to the demand and avoiding the constraints of the first practice. A combine harvester allows for putting crop cutting, threshing, and cleaning in a one-pass operation (Figs. 4.11a, b). Grain is temporarily stored on board the combine before being discharged into a bulk wagon or into bags. Straw is discharged behind or to one side of the combine into a windrow. Some combines also have straw choppers and devices to spread the straw evenly. Proper use of combine harvesters can help to significantly reduce harvesting and postharvest losses by avoiding transportation losses between different stages of cutting and threshing and delay of harvesting.

Fig. 4.11
2 photographs. a. A photo of a moving combine harvester advancing towards a triangular area of crop in a field. b. A photo of a combine harvester in a soiled field.

Small and big scale combine harvester a Small and medium scale combine harvester, lower than 2 ha per hour, b Big scale combine harvester, higher than 2 ha per hour

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4.4.2 Drying and Storage

Grain is hygroscopic and the final moisture content depends on the relative humidity of the surrounding air. This means that when the grain is in contact with high-humidity air, moisture content increases. This is a major problem in tropical areas during the rainy season when the relative humidity may reach 95–100%. Grains and seeds stored in tropical climates face the problems of discoloration or yellowing, molds, insects, and germination and vigor losses (for seeds).

Drying is the process of reducing grain moisture content. Drying is the most critical operation after harvesting, and delays in drying or incomplete drying will reduce grain quality (quality loss) and quantity (physical loss). Drying and storage should be considered related processes and, in some instances, can be combined with in-store drying. Storage of high-moisture grain will reduce quality, irrespective of the storage facility.

Drying should begin as soon as possible after harvesting, as even short-term storage of high-moisture grain can cause quality deterioration. Ideally, drying should commence within 12–24 h after harvesting. For safe storage in a tropical country, paddy grains should be dried to reach a moisture content lower than 14%, while the moisture content of seeds should be lower than 12% (RKB 2013).

Here, we introduced several typical drying and storage technologies and good practices for paddy grains promoted by IRRI. Detailed information, such as the basics of drying, can be accessed at RKB (2013), and how to identify the best drying practices is presented in Nguyen et al. (2018).

4.4.2.1 Solar Bubble Dryer

The solar bubble dryer (SBD) (Fig. 4.12a), using only solar energy, was developed by IRRI, the University of Hohenheim, and GrainPro, Inc. This dryer has a capacity of 1-ton paddy grain with a drying time of about 16 h for the SEA climate. The SBD was further developed by IRRI for mushroom drying (Fig. 4.12b).

Fig. 4.12
4 photographs. a. A photo of a drying bin combined solar collector and a solar panel for charging battery. The inside view of the drying bin is also illustrated. b. A close-up of a drying bin with a combined solar collector and a spread of dry mushrooms on its top.

Types of dryers a Solar bubble dryer for paddy drying, b Solar bubble dryer for mushroom drying

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4.4.2.2 Flatbed Dryers

Figure 4.13a, b show two types of flatbed dryer widely used for paddy drying in SEA countries (Nguyen et al. 2018). Advantages of flatbed drying technology include low drying costs and suitability for both small and industrial scales. Drying costs, including machine depreciation, maintenance, labor, and energy, are about US$6–12 t−1 of paddy grain dried.

Fig. 4.13
2 photographs. a. A photo of a drying chamber with a blower and a furnace attached to it. b. A schematic diagram of a reversible air flatbed dryer. The labeled parts are the furnace, blower, electric motor, sidewall of the drying bin, sealing canvas for the air reverse phase, and paddy grains.

Flatbed dryer (a) and reversible air flatbed dryer (b)

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4.4.2.3 Two-Stage Drying on Industrial Scale

A two-stage drying system, including a fluidized-bed and recirculating columnar dryers (Fig. 4.14), is suitable for industrial scale because it allows high capacity and mechanized and automatic operations. Wet paddy grain is dried by fluidized-bed dryers at the first stage, usually to reduce grain moisture content (MC) to 2–4%. In the second stage, the grain is dried for storage to an MC of 14%. Typically, a two-stage drying system with a fluidized-bed and 10 recirculating columnar dryers has a capacity of 300 t working day−1 (about 8 h). Its drying cost in SEA is about US$5–10 t−1 of paddy grain dried.

Fig. 4.14
A photo of a fluidized bed dryer. The schematic diagram of the same filled with grain indicates the direction of air and tempering. On the right is a photo of the recirculating column dryer along with its schematic diagram. Some of the labels are bucket elevator, furnace, and paddy elevator.

Two-stage drying system at industrial scale

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4.4.2.4 Hermetically Sealed Storage

Sealed- or hermetic storage systems are very effective for controlling grain moisture content and insect activity for grain stored in tropical regions. By placing an airtight barrier between the grain and the outside atmosphere, the moisture content of the stored grain will remain the same as when the storage container was sealed. Respiration by the grain and insects reduces the oxygen level and increases CO2, which, in turn, kills the insects. Hermetic systems can increase head rice recovery by 10% and double the viability of seeds.

Sealed-storage containers come in many shapes and sizes (Fig. 4.15). They may range from small plastic containers to more complex and costly sealed plastic commercial storage units with 1 to 1,000-t capacity per unit. Hermetic “Super bags” with 50 kg capacity are also commercially available and widely used.

Fig. 4.15
2 photographs. First. A hand holds the mouth of a grain-filled sack bag. Second. A few people cover the huge hermetic bag.

Hermetic storage 50 kg bag (left) and industrial scale 300 t hermetic bag (right)

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