A flexible high-throughput marker system to distinguish African rice (Oryza glaberrima) from Asia

The African rice Oryza glaberrima is an important reservoir of genes for abiotic stress tolerance. To discover such tolerance genes and to exploit them in rice improvement, a flexible, high-throughput marker system is needed. Single nucleotide polymorphism (SNP) sites, where the genome sequence of two or more individuals differs by a single base, are increasingly becoming the marker of choice. Although the number of discovered SNPs has increased significantly over the past few years, most of these efforts have focused on variations within the Asian rice Oryza sativa.The aim of the present study was to detect a set of SNPs that differentiate between O. sativa and O. glaberrima, and to use a representative subset to develop a high-throughput PCR-based genotyping panel.

A genome-wide 44,000 SNP genotyping array identified a set of 9523 SNPs polymorphic between O. glaberrima and O. sativa subspecies indica, and 7444 SNPs between O. glaberrimaand O. sativa subspecies japonica （Figure 1A）. From the above set, a subset of 1540 SNPs was selected in collaboration with partners within the Generation Challenge Program (GCP) for conversion into PCR-based markers, using the KASP (competitive-allele PCR) technology. A final set of 2015 SNPs were successfully converted to KASP markers, which are evenly distributed in the genome, with the exception of small gaps in chromosomes 4 and 10 (Figure 1B). The panel was validated in the ‘New Rice for Africa’ (NERICA) parents. Of the 2015 markers tested, 745 markers were polymorphs between CG14 and WAB56-104 (upland NERICA parents) and 752 between TOG5681 and IR64 (lowland NERICA parents) (Figure 2). Several subsets of these markers have been used successfully to map O. glaberrima introgressions in NERICA rice varieties and interspecific breeding lines.

This new genotyping panel is a cost-effective, gel-free genotyping platform that allows maximum flexibility for ‘pick-and-choose’ markers according to individual breeder’s needs. Presently, it is fully outsourced to service companies that can perform all steps, from DNA extraction to genotyping, which would extend the capacity of low-resource laboratories to perform molecular breeding using local rice varieties. In addition, the information for each SNP is publicly available allowing the rice breeding community to complement the set with their own subset of markers. JIRCAS is expanding its collaborative rice breeding network with applications ranging from parental surveys, development of QTL mapping populations, and marker-assisted introgressions of major stress tolerance genes like OsPSTOL1.

(M. Wissuwa, J. Pariasca-Tanaka, M. Lorieux [CIAT], C. He [GCP], S. McCouch [Cornell University], MJ. Thomson [IRRI])

Fig. 1. Flow chart indicating the selection of polymorphic SNPs between O. glaberrima vs O. sativa ssp japonica and indica for conversion into PCR-based markers (A). Distribution of SNP markers along the rice genome. Color represents the number of markers per 1 Mb (B).

Fig. 2. Distribution of polymorphic SNP markers for crosses of O. glaberrima vs O. sativa. There are 745 and 751 polymorphic markers for upland and lowland NERICA varieties, respectively.

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Manual of soil fertility improvement technologies in lowland rice ecologies of Ghana (PDF A4:535KB A3: 134KB)

The impact of fertilizer application on crop production in Sub-Saharan Africa (SSA) is considered enormous as the region is very low in soil fertility. However, access to chemical fertilizers is difficult especially for small-scale SSA farmers who do not have sufficient financial resources in a market-oriented economy. This crucial issue underscores the urgent need for the farmers to increase agricultural productivity, which can be achieved through inexpensive and cost-effective techniques of improving soil fertility in rural areas.

With financial support from the Ministry of Agriculture, Forestry and Fisheries (MAFF) of Japan, JIRCAS carried out a study on technology development for improved soil fertility using indigenous resources that are accessible and acceptable to local farmers. The study, with rice being the target crop, is aimed at contributing to the goal of the Coalition for African Rice Development (CARD) to double rice production in SSA by 2018. Ghana was selected as the country of implementation because it has two major rice ecologies (rainfed lowland and irrigated lowland) and has good research counterpart institutions.

As one of the products of the study, a technical handbook, titled “Manual of soil fertility improvement technologies in lowland rice ecologies of Ghana,” was published. Written in English, this manual would greatly benefit extension workers and assist them in disseminating the technologies to rice farmers. A summary of the manual’s features is listed below.

1. The manual describes the application of indigenous organic matter as well as their composting and charring technologies, the application of phosphate rocks from neighboring Burkina Faso and its solubilizing technologies, and the enhancement of early rice growth using a minimum quantity of chemical fertilizer (Table 1).
2. The technologies mentioned in the manual were developed in consideration of available materials in each rice ecology and corresponding region. The technologies were evaluated for effectiveness and affordability to the rural communities in on-farm participatory studies.
3. Government officers as well as counterpart researchers in Ghana were actively involved in the editorial process, enhancing their sense of ownership of the manual and technologies. The foreword was written by the deputy minister of the Food and Agriculture (MoFA), Ghana.
4. This manual is compact enough to be carried around. It is printed on A5 size paper and contains only 44 pages, with visually descriptive text and plenty of visuals (photographs and illustrations).
5. The technologies adopted in the manual may be extended to other SSA countries having the same rice ecologies.

(Satoshi Tobita, Satoshi Nakamura, Monrawee Fukuda, Fujio Nagumo)

Table 1.Technology options adopted in the soil fertility manual

Fig. 1. Charring of saw dust (Kumasi City)

Fig. 2. Demonstration in an on-farm field (at Ziong Village, a suburb of Tamale City)

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Sorgoleone release determines the hydrophobic-BNI capacity in sorghum root systems (PDF A4:128K

Nitrification and denitrification are the two most important processes that contribute to greenhouse gas emissions and the inefficient use of nitrogen. Suppressing soil nitrification through the release of nitrification inhibitors from roots is a plant function, termed ‘Biological Nitrification Inhibition (BNI)’. Sorghum releases two categories of nitrification inhibitors from roots: hydrophilic BNIs and hydrophobic BNIs. Our earlier published work on sorghum mostly focused on characterizing hydrophilic BNI release. Here we report the characterization of hydrophobic-BNI release in sorghum. The functional role and contribution of sorgoleone release to hydrophobic-BNI function and the existence of genotypic variability for sorgoleone release is the focus of this investigation. Three sorghum genotypes (Hybridsorgo, IS 41245 and GDLP 35-5-5-3) were evaluated for their capacity to release sorgoleone in hydroponic, in soil culture, and under field environments. Sorgoleone released from roots is measured using a high performance liquid chromatograph (HPLC) and BNI activity is determined using a luminescent recombinant Nitrosomonas europaea assay.

Sorgoleone was found to be the dominant and major component of hydrophobic-BNI activity released from sorghum roots, and there were significant genotypic differences for sorgoleone release (Fig. 1). Sorgoleone release and BNI-activity release in sorghum roots are closely associated, i.e., 1 μg of sorgoleone released is equivalent to 1 ATU activity in the bioassay (Fig. 2). Sorgoleone genotypes release varying quantities of sorgoleone. GDLP 34-5-5-3 and Hybridsorgo have higher capacity for both sorgoleone release and BNI activity than IS41245. In soil culture, GDLP 34-5-5-3 released significantly higher quantities of sorgoleone into the rhizosphere, had higher BNI activity, and suppressed soil nitrification better than IS41245 (Fig. 3). Purified sorgoleone inhibited Nitrosomonas activity in the bioassay; when amended to soil, sorgoleone suppressed nitrification, improved NH₄⁺ availability, and reduced NO₃^- formation in soils during a 60-day incubation study (Fig. 4). These results demonstrate genetic differences for sorgoleone release and its functional link to hydrophobic-BNI release and BNI capacity in sorghum.

Sorgoleone release contributes significantly to BNI capacity in sorghum. The significant genetic differences for sorgoleone release from sorghum roots suggest that there is potential for genetic improvement to improve sorgoleone release and BNI capacity in sorghum. Higher BNI capacity is critical to the development of low-nitrifying sorghum production systems and the results presented here suggest the feasibility of this approach.

(T. Tesfamariam, H. Yoshinaga, S. P. Deshpande. [International Crops Research Institute for Semi-Arid Tropics (ICRISAT)], P. Srinivasa Rao [ICRISAT], K. L. Sahrawat [ICRISAT], Y. Ando, K. Nakahara, C.T. Hash [ICRISAT], G. V. Subbarao)

Fig. 1. Chemical structural formula of sorgoleone

Fig. 2. The relationship between total sorgoleone concentration (μg) and BNI activity (ATU) in root–DCM wash of three sorghum genotypes

Fig. 3. Nitrification rate at 30-day incubation period along with NH4+ inoculation of rhizosphere soil collected from two sorghum genotypes (IS1245 and GDLP 34-5-5-3) grown up to heading stage in potted soil. Control pots were included with bare soil without plants but handled the same way like pots with plants. As positive control, soils taken from control treatments were also incubated with DCD addition at 25 ppm (a known synthetic inhibitor) as a reference.

Fig. 4. Concentration of inorganic N (NO3− and NH4+) in soil samples incubated after adding different concentrations of sorgoleone (0, 10, 20, 30, 40, and 100 μg g−1 soil) for 60 days

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Extraction of gully erosion-affected areas by image analysis of high spatial resolution satellite da

Gully erosion is a natural phenomenon that occurs during and after severe rainfall leading to the loss of topsoil, the formation of ditch-like features on sloping areas, and the deterioration of productive agricultural lands. Over the past decade, gully erosion has developed significantly on hilly areas along Cagayan River in the northern part of Luzon Island in the Philippines. Photo 1 shows the natural landscape at the site on November 23, 2010. In order to grasp the actual condition and spatial distribution of gullies in this area, the author attempted to develop a method to extract gully information using high spatial resolution satellite data.

Gully-eroded areas are presented as dark linear features on satellite images on the condition that the spatial resolution of satellite data is small enough. According to the survey report by the Philippine Bureau of Soil and Water Management (BSWM), the average gully top width was about 2 meters, which was considerably larger compared with the 0.5 meter spatial resolution of the WorldView panchromatic data adopted in this study. After performing median filtering to reduce local noise, the Sobel filter was applied to enhance the edge features of the images. Enhanced linear parts were contaminated with gully and non-gully objects, and the following processes were undertaken to extract only the gully-affected areas: First, the topographic factors were considered by enhancing the image contrast of the pixels oriented orthogonally to the slope orientation. Second, texture parameters (window size: 21 by 21 pixels) were calculated and non-gully objects were discriminated after setting an appropriate threshold. This method was effective in masking out non-gully parts such as roads, houses, piles of crop residue, irregular ground conditions on arable land, and so on. Third, forest areas (another mask data) were estimated from multi-temporal ALOS/AVNIR2 data, which has a 10-m spatial resolution. Figure 1 shows extracted gully-affected areas overlaid on WorldView imagery for a part of the study site. To verify the results, the author compared it with the gullies surveyed by the BSWM. Figure 2 shows the heads and ends of the surveyed gullies. Because the survey data indicated only the location of gullies including branches and did not indicate continuous features, the agreement between extracted and surveyed gullies was ranked into 4 levels by manual interpretation and then assigned quantitative values. Table 1 shows the average ratio of properly extracted gullies weighted by length and it concludes that 63.4 percent of gullies were properly extracted.

The method mentioned above can be applied to any region in the world if high spatial resolution satellite data (taken in the period when ground is barely covered) can be obtained. This can realize rapid mapping of gully erosion-affected areas seamlessly over wide areas and without conducting field surveys. It is also advantageous that the output data are readily available in georeferenced digital format and are of homogeneous quality, thus facilitating spatial analysis operations for the characterization of existing gullies. Adjustment of parameters, however, may be necessary to discriminate gully and non-gully features in accordance with image conditions. 

(S. Uchida)

Photo 1. Gully erosion appears at the study site near Ilagan City, Isabela Province,
Philippines (taken on November 23, 2010)

Fig. 1. Image overlay showing the gully erosion-affected
areas (in red) extracted from satellite imagery

Fig. 2. Location map of gullies surveyed by BSWM (Green rectangle indicates spatial range shown in Fig. 1)

Table 1. Agreement (Ratio of extraction) between the extracted gully erosion features and the surveyed gullies (data by BSWM)

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Improvement of land use efficiency and drought resistance with a maize-soybean intercropping system in Northern Mozambique

Subsistence maize production is the first priority for smallholder farmers in Northern Mozambique; however, soybean has been attracting increased attention as a new cash crop in recent years. Our study, therefore, examined the simultaneous growth of maize and soybean in an intercropping system. Intercropping systems are considered particularly suitable in areas with unreliable rainfall and little external inputs as it diversify environmental risks and increase resource-use efficiency among the component crops. However, there is little empirical data available in the region on maize-soybean intercropping.

The performance of the intercropping system was assessed with respect to the land equivalent ratio (LER) using different fertilizer management practices in three agricultural environments, from a hot and semi-arid climate to a cool and humid climate, in Northern Mozambique. LER is calculated as the sum of the relative yields of maize and soybean in the intercropping plots with respect to the monocropping plots. It is generally accepted that LER values above 1 indicate that an intercropping system offers superior land-use efficiency over a monocropping system. 

Locally recommended cultivars of maize (cv. Matuba; early maturity) and soybean (TGX-1937-1F; intermediate maturity) were grown at planting densities of 6.25 hills m^-2 (80 × 20 cm) and 12.5 hills m^-2 (40 × 20 cm), respectively, in the monocropping system. In the intercropping system, a maize row was replaced by three soybean rows every other two rows, which correspond to the planting densities of maize and soybean at two thirds (=0.67) and a half (=0.50) of those in the monocropping system, respectively (2Maize:3Soybean strip allocation). Three weeks after sowing, urea was side-dressed along the maize rows for both monocropping and intercropping systems at three different rates (0, 30, and 60 kg N ha^-1). No additional fertilizer was applied to any soybean rows.

The experimental results are summarized as follows:

• Maize-soybean intercropping demonstrated consistent advantage in productivity over monocropping, with LER values above 1 irrespective of N application rates to maize or experimental sites. LER values were particularly high in Nampula where a long dry spell occurred during the seed-filling stage of soybean (Table 1). 
• The high LER values were partly attributed to more vigorous maize growth in intercropping than in monocropping, providing relative yields of 75-86% with two thirds of planting densities across fertilizer treatment and experimental sites (Table 1). 
• When exposed to a dry spell, intercropped soybean (shaded by maize canopy) showed an apparent benefit in drought avoidance, as reflected by the slow depletion of soil water potential and the retention of the aboveground biomass relative to the monocropped soybean (Fig. 1). 
• Under moist field conditions in Gurue and Lichinga, the LER values tended be smaller with increasing N application rates to maize because maize plants became more competitive and depressed the intercropped soybean yields to greater degrees.

Based on these results, it is concluded that maize-soybean intercropping can be recommended, allowing the introduction of soybean while ensuring subsistence maize production particularly in the low-N-input and drought-prone environment that prevails in the rainfed-upland areas of Northern Mozambique.

  

*The study was financed by the JICA Project for Improving Research and Technology Transfer Capacity for Nacala Corridor Agriculture Development (Year 2011-2016).

(Y. Tsujimoto, S. Tobita, T. Oya, O. Ito [United Nations University], J. A. Pedro [National Agricultural Research Institute of Mozambique, IIAM], G. Boina [IIAM], M.V. Murracama [IIAM], C.E. Cuambe [IIAM], C. Martinho [IIAM])

Table1.Maize and soybean yields in the monocropping system, relative grain yields of maize and soybean in the inter cropping system,and LER values at different N application rates in three sites

Fig.1.Changes in soil water potential beneath the soybean canopy at 20cm deep (above figure) and in aboveground soybean biomass (below figure) in Nampula.

Fig.2.Comparison of soybean growth after a long dry spell in Nampula.
Monocropped soybean was more severely affected by drought stress with substantial leaf abscission.

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Long–term global outlook of crop yields under climate change (PDF A4:310KB A3:253KB)

A long–term outlook of crop yield is necessary for an economic evaluation of climate change on food supply and demand. If the temperature is lower than the optimum level, the crop yield will increase with rising temperature. Conversely, if the temperature exceeds the optimum level, the crop yield will decrease with rising temperature. The yield function, which considers the inverse U–shaped relationship between temperature and yield, is required for long–term outlook under climate change.

The purpose of this research is to analyze the effects of climate change on major crop yields using yield trend functions, incorporating parameters of yield for climate variables obtained from a crop model. The scenarios used in this research are those of the Representative Concentration Pathway (RCP) in the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). There are four scenarios, i.e., RCP8.5, RCP6.0, RCP4.5, and RCP2.6, in descending order according to CO₂ concentration.

The parameters and functions for 46 crops of the crop model used for analyzing the Global Agro Ecological Zone of the FAO are presented in the report of the International Institute for Applied Systems Analysis (IIASA). The relationship between temperature and yield as indicated in Figure 1 is obtained from the parameters and the functions of the biomass production and photosynthetic rate of the model. These functions are smoothed using cubic spline interpolation.

The target crops are rice, wheat, maize, and soybeans, covering 126 countries or regions, the same number as when the world food model was developed. Data on crop yields were obtained from the FAO (data from 1961 to 2007).

Logistic functions or linear functions with logarithmic time trends are estimated for each crop yield for each country as yield trend functions. Climate parameters of the crop model are incorporated into the trend function.

Climate data in this research are those of the Model of Interdisciplinary Research on Climate (MIROC5), which is a Global Circulation Model (GCM), and these are aggregated for large countries such as China based on the crop cultivation map of the United States Department of Agriculture (USDA).

Figure 2 depicts wheat yields in India and China. The baseline scenario assumes unchanged temperature, solar radiation, and rainfall values during simulation (period 2008-2050). Wheat yield in India is decreased by climate change under the RCP8.5 scenario. Climate change simulation results in China, on the other hand, show substantial fluctuation because the slope of the yield to temperature as indicated in Figure 1 (ii) is steeper than those of other crops.

Figure 3 presents differences in wheat yields between baseline and RCP6.0 scenario during the periods 2021–2030 and 2041–2050. These figures suggest that wheat yields in southern Asian and sub–Saharan African countries will decrease under the RCP6.0 scenario.

(J. Furuya, S. Kobayashi, Y. Yamamoto, M. Nishimori [NIAES])

Fig 1.Relationship between potential yield and temperature

Fig. 2. Trends in crop yield

Fig. 3. Effects of climate change on wheat yield: differences between baseline and RCP6.0

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Heat tolerance and flower opening time of popular rice varieties in the tropics (PDF A4:97KB A3: 50KB)

Rice spikelets are most susceptible to heat stress at flowering, inducing spikelet sterility. Moreover, rice varieties face a higher risk of exposure to heat stress because of progressive global warming. Hence, improving heat tolerance and shifting flower opening time (FOT) to the cooler early morning period are among the recommended strategies to mitigate damage by heat stress at flowering. In this study, the heat tolerance and FOT of 23 popular varieties in the tropics were investigated.

The spikelets of 23 popular varieties were exposed to heat stress at 38°C for 6 hours (0900h-1500h) at flowering. It was found that there is a wide genetic variation in heat tolerance (Table 1). Ciherang, a popular Indonesian variety, and Samba Mahsuri, a popular Indian variety, showed high heat tolerance comparable to that of N22, the heat tolerance check variety (Table 1). This result indicated that Ciherang and Samba Mahsuri are useful new genetic resources for heat tolerance at flowering. On the other hand, Fedearoz50, a popular variety in Latin America, showed moderate heat tolerance, whereas Sahel329 and Nerica L-19, popular varieties in West Africa, and KDML105, famous aromatic rice in Thailand, showed high heat susceptibility (low heat tolerance) similar to that of Morobrekan, the heat susceptibility check variety (Table 1). These results suggested that the heat resilience of Sahel329, Nerica L-19, and KDML105 must be improved. With regard to the FOT of the 23 popular varieties, no variety had early-morning flowering (EMF) trait when compared with near-isogenic line (NIL) for EMF trait (Fig. 1), clearly indicating transferring quantitative trait locus (QTL) for EMF to these popular varieties would be effective at increasing heat escape capability at flowering. Because NIL for EMF showed significant earlier FOT than glaberrima (which is known as an EMF variety to this day ), NIL for EMF is considered a novel breeding material for improving heat resilience to cope with future hotter climates.

(T. Ishimaru, K. Sasaki [Univ. of Tokyo], H. Hirabayashi [NARO], R.B. Gannaban [IRRI], W. Oane [IRRI], W. Shi [IRRI], S.V.K. Jagadish [IRRI])

Table 1.Heat tolerance of popular varieties

Humidity was maintained at 60-70%. Different alphabet in Tukey’s test indicates significant difference at 5% level. ¹Check variety for heat tolerance, ²Check variety for heat susceptibility. Data not shown for the rest of 16 varieties.

Fig. 1. Flower opening time of popular varieties, NIL for EMF (Nanjin11+qEMF3), and glaberrima (CG14). ◆ in each genotype indicates 50% FOT±SE of at least three replications. The left and right sides of the horizontal bars in each genotype indicate 10% FOT and 90% FOT, respectively. Different alphabets in left side of each genotype indicate the significance at 5% level by Tukey’s test.

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Development of a near-isogenic line with early-morning flowering trait in the genetic background of Indica-type variety in the tropics

Rice spikelets are most susceptible to heat stress at flowering. Air temperature at 35°C is the general threshold for heat-induced spikelet sterility (HISS) at flowering. Even a one-hour heat exposure to flowering spikelets can cause sterility. It is predicted that global warming will increase the risk of spikelet sterility in rice. Early-morning flowering (EMF) trait is considered effective in alleviating heat stress by shifting flower opening time (FOT) to earlier in the morning when it is cooler. In this study, we attempted to develop a near-isogenic line (NIL) with EMF trait in the genetic background of Indica-type variety, IR64.

Marker-assisted selection was employed to transfer the QTL for EMF (qEMF3) using the backcrossing approach. Eventually, the NIL with clear genetic background other than the QTL region was obtained (Fig. 1A). Under field condition, the developed NIL advanced peak (50%) FOT by 1.5-2.0h compared with the recurrent parent, IR64, both in the wet season and dry season (Fig. 1B). The NIL for EMF was further tested under elevated temperature regimes in environmentally controlled chambers. The times from dawn (zero hour) to 10% (T10), 50% (T50) and 90% (T90) FOT were calculated based on the R program. (T10, T50, and T90 means the starting, peak, and finishing FOT, respectively.) Under the given temperature regimes, T90 of NIL for EMF finished before the temperature reached 35°C, while T10 of IR64 started after the temperature exceeded 35°C (Fig. 2A). This result indicated that almost all flowered spikelets of NIL for EMF could escape from heat stress at flowering, but most of flowered spikelets of IR64 were exposed to heat stress. Spikelet sterility in IR64 and NIL for EMF was manually counted at maturity. The percentage of spikelet sterility was 55% in IR64 and 10% in NIL for EMF (Fig. 2B), indicating that NIL for EMF could significantly reduce heat-induced spikelet sterility at flowering. The NIL for EMF, therefore, is a novel breeding material that can be used for the development of heat-resilient rice to cope with future hotter climates.

(T. Ishimaru, K. Sasaki [Univ. of Tokyo], H. Hirabayashi [NARO], N. Kobayashi [NARO], M.S. Mendioro [University of the Philippines, Los Banos], E.V. Simon [IRRI], P.D. Lumanglas [IRRI], S.V.K. Jagadish [IRRI]

Fig. 1. Graphical genotype of IR64+qEMF3 (A) and 50% of flower opening time in IR64 and IR64+qEMF3 (B).

(A) Gray bar on the rice chromosome 3 is a locus of qEMF3. Other regions on chromosomes 1-12, indicated in white, refer to the IR64 genetic background. The horizontal lines on each chromosome refer to the positions of available SSR markers.

(B) Dawn was set as 0. Values indicate mean±SE of three or four replications. **Significant at 1% level by t-test. WS: wet season. DS: dry season.

Fig. 2. The changes in time of day of flowering under elevated temperature conditions (A) and percentage of spikelet sterility at maturity (B).

(A) ◆ indicates 50% FOT±SE of three replications. The left and right sides of the horizontal bars indicate 10% FOT and 90% FOT, respectively. Horizontal broken line indicates the general threshold temperature (35°C) for HISS at flowering. (B) *Significant at 5% level by t-test.

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Sustainable use of biogas digester by applying unused biomass (PDF A4:214KB A3: 127KB)

A biogas digester (BD) is a simple and manageable farm equipment that collects biomass and produces gas through anaerobic respiration (Fig. 1). It was introduced as a Clean Development Mechanism (CDM) project in farming households in Vietnam’s Mekong Delta. Pig manure is the main feedstock for BD; however, biogas production will diminish if the number of pigs decreases due to sale of mature pigs, disease outbreaks, or lowered profitability. When biogas shortage is prolonged, households become more inclined to stop using BDs. On the other hand, there is plenty of unused biomass like the fast-growing water hyacinth in canal networks and ponds. With the appropriate technology, applying unused biomass as feedstock will make BD use sustainable.

Annual monitoring was conducted on 435 households from 1 June 2013 to 31 May 2014, and results showed that 44 households did not use biogas for more than one day during this period. Cited as the main reason (55%) for the non-use of BD was the absence of pigs due to stoppage of pig raising activities, pig disease, and sale of mature pigs to market (Fig. 2). Can Tho City, where the CDM project is being implemented, is located at the center of the Mekong Delta and surrounded by tributary streams and canal networks. Plenty of productive and unused biomass like water hyacinth grow in these waterways and ponds. If the unused biomass is applied as feedstock for BD in case of pig shortages, BD use will be stabilized. Experiments applying unused biomass to BD were conducted to examine biogas production from selected materials. The experiments consisted of 4 materials: (1) pig manure (control), (2) duckweed (Pistia stratiotes), (3) water hyacinth (Eichhornia crassipers), and (4) grass weed, including Oryza rufipogon Griff. The size of BD was the same as the one used by households. After cutting these materials to 20-30cm, 2.7kg (dry matter weight) of each material was filled to each experimental BD every day continuously for 30 days and the biogas produced from BDs was measured for 60 days from the start of the experiment. The experiments were replicated 3 times. Results of the experiments showed that biogas production from water hyacinth and from both duckweed and grass weed was 70% and 90%, respectively, compared to the control (Fig. 3). As a verification study, one household that installed a BD was asked to apply only duckweed to the BD as feedstock for a year from the beginning. Results of this study showed that biogas from duckweed could be used as cooking fuel continuously, that it substituted with 2.4t of fuel wood, and that it contributed to 1.8tCO₂/year of GHG emission reductions (Fig. 4).

In summary, this technology contributes to sustainable BD use by bridging the gap in BD feedstock when livestock manure is in short supply. One important thing to consider, however, is that farm households that apply unused biomass as feedstock for BDs must have easy and continuous access to the resource. Although the collection time for unused biomass is shorter compared with fuel wood, it is longer compared with livestock manure. Unused biomass, therefore, should be applied as supplemental feedstock only when livestock manure is insufficient.

 (T. Izumi, E. Matsubara)

Fig. 1. Plastic-type biogas digester system

Fig. 2. Reasons for non-use of biogas

Fig. 3. Biogas production by applying unused biomass

Fig. 4. Results of a verification study on a BD household applying only Pistia stratiotes.
Graph shows significant drop in fuel wood use and GHG emissions over a one-year period.

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[Environment and Natural Resource Management] Development of agricultural technologies based on sustainable management of environment and natural resources in developing regions

Fig. 1. Development of agricultural technologies based on sustainable management of natural resources and the environment in developing regions  A Third Medium-Term goal, "Development of agricultural technologies based on sustainable management of the environment and natural resources in developing regions" has been set as one of the research directions, towards which JIRCAS should endeavor. The following global environmental problems enumerated below have manifested themselves recently. Agricultural technology development based on sustainable resource management is required to maintain and expand the agricultural, forestry and fishery industries in developing countries which are susceptible to these types of problems. The Natural Resources and Environment Program will strive towards five projects to achieve this goal, as shown in Fig. 1.

For further details log on website :
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