Soil fertility management in irrigated rice systems in the Sahel and Savanna regions of West Africa: Part I. Agronomic analysis

Yield, input use, productivity and profitability of irrigated rice systems were analyzed based on surveys in Senegal (Thiagar and Guédé), Mali (Office du Niger) and Burkina Faso (Kou Valley). The objective was to determine agronomic factors contributing to farmers' fertilizer-use efficiency and productivity, given current farmer practices. (A second paper addresses profitability and risk issues). Grain yields were highly variable, within and across sites. Minimum grain yield was 0.2 t ha⁻¹ (Thiagar), maximum recorded grain yield was 8.7 t ha⁻¹ (Office du Niger). The yield gap between actual farmers' yield and simulated potential or maximum attainable farmers' yield ranged from 0.6 to 5.7 t ha⁻¹ (Kou), 1.8 to 8.2 t ha⁻¹ (Thiagar), 0.3 to 6.3 t ha⁻¹ (Office du Niger), 0.8 to 5.7 t ha⁻¹ (Guédé), indicating considerable scope for improved yield. Physiological nitrogen efficiency (δ grain yield/δ N uptake) was mostly between 40 and 80 kg grain kg⁻¹ plant N. Apparent recovery of fertilizer N was highly variable (average: 30–40% of applied N). Timing of N fertilizer application by farmers was extremely variable and often did not coincide with critical growth stages of the rice plant. Other agronomic constraints included: use of relatively old (>40 days) seedlings at transplanting (Kou, Office du Niger), P and/or K deficiency (Office du Niger), unreliable irrigation water supply (Kou, dry season), delayed start of the wet growing season resulting in yield losses of up to 20% due to cold-induced spikelet sterility (Kou, Guédé, Office du Niger), weed problems (Thiagar), and late harvesting (Thiagar). Discussions during meetings with farmers at the survey sites revealed that farmers lacked knowledge on (i) optimal timing, dosage and mode of fertilizer application, (ii) optimal sowing dates to avoid yield loss due to cold- or heat-induced sterility, and (iii) the importance of N as the main limiting factor to yield. Possibilities to achieve a sustainable increase in rice productivity and profitability in West African irrigation systems are discussed.     

Performance of diverse upland rice cultivars in low and high soil fertility conditions in West Africa

Traditional tropical japonica (Oryza sativa) and Oryza glaberrima cultivars are typically grown in low-input, subsistence production systems in the uplands of West Africa by resource-poor farmers. In these systems, low soil fertility (LF), which is generally associated with lower organic carbon content, and N and P availability, is one of the major constraints to rice productivity. Thus, cultivars adapted to LF are needed for the food security of farmers, who would otherwise be solely reliant on nutrient inputs to increase productivity. This study evaluated the performance of six diverse cultivars grown in LF and high soil fertility (HF) conditions with supplemental irrigation over two seasons. Average grain yield across all cultivars in LF was 54% of that in HF (156 vs. 340 g m⁻²). Three improved indica rice cultivars and CG 14 (O. glaberrima) out-yielded Morobérékan (traditional tropical japonica) and WAB450-IBP-38-HB (progeny from interspecific hybridization of tropical japonica and O. glaberrima) in LF (181 vs. 105 g m⁻² on average). The high grain yield in LF was the result of large spikelet number m⁻² due to superior tillering ability and high harvest index rather than biomass production. The high-yielding cultivars in LF consistently had lower leaf chlorophyll content and higher specific leaf area during the period from the early vegetative stage through the reproductive stage. Among them, two indica cultivars (B6144F-MR-6-0-0 and IR 55423-01) were also high yielding in HF. The use of improved indica cultivars adapted to LF, but also with input-responsiveness, appears to offer an attractive and economical approach to improving upland rice productivity and widening genetic diversity in this region.     

DIVECOSYS: Bringing together researchers to design ecologically-based pest management for small-scale farming systems in West Africa

Crop pests are a major constraint to the intensification of agricultural production in the tropics, with novel issues related to global change (climate, land use, biological invasions, etc.), food security and preservation of natural resources and biodiversity. A research, extension and education network called DIVECOSYS (Diversity of cropping systems and ecologically-based pest management in West Africa) was launched in 2010 to synergize applied research actions in response to growing concerns on the vulnerability of agricultural systems to pest management in West Africa. This scientific network brings together research and academic institutions, with expertise spanning a multidisciplinary perspective from biology and ecology to remote sensing, agronomy and integrated pest management. Its main scientific objective is to explore the potential of biodiversity and ecological processes such as pest regulation, enabling novel ecologically-based models for productive systems, reduction of pesticide use, and adaptation or resilience of farming systems in the face of environmental disruptions. From Northern Senegal to Southern Benin, the research group explores a wide range of ecoregions and socio-ecological contexts, including stakeholders and their objectives, land use and agricultural practices, and management of biodiversity for enhancing biological control. Main challenges to be turned into opportunities include (i) encouraging collaborations amongst researchers from different scientific fields, (ii) fostering interactive research and synergies among research institutions and among countries, and (iii) developing an ecological engineering approach for the design of sustainable agricultural systems for smallholder farmers.     

High-yield irrigated maize in the Western U.S. Corn Belt: II. Irrigation management and crop water productivity

Appropriate benchmarks for water productivity (WP), defined here as the amount of grain yield produced per unit of water supply, are needed to help identify and diagnose inefficiencies in crop production and water management in irrigated systems. Such analysis is lacking for maize in the Western U.S. Corn Belt where irrigated production represents 58% of total maize output. The objective of this paper was to quantify WP and identify opportunities to increase it in irrigated maize systems of central Nebraska. In the present study, a benchmark for maize WP was (i) developed from relationships between simulated yield and seasonal water supply (stored soil water and sowing-to-maturity rainfall plus irrigation) documented in a previous study; (ii) validated against actual data from crops grown with good management over a wide range of environments and water supply regimes (n = 123); and (iii) used to evaluate WP of farmer's fields in central Nebraska using a 3-y database (2005–2007) that included field-specific values for yield and applied irrigation (n = 777). The database was also used to quantify applied irrigation, irrigation water-use efficiency (IWUE; amount of yield produced per unit of applied irrigation), and the impact of agronomic practices on both parameters. Opportunities to improve irrigation management were evaluated using a maize simulation model in combination with actual weather records and detailed data on soil properties and crop management collected from a subset of fields (n = 123). The linear function derived from the relationship between simulated grain yield and seasonal water supply, namely the mean WP function (slope = 19.3 kg ha⁻¹ mm⁻¹; x-intercept = 100 mm), proved to be a robust benchmark for maize WP when compared with actual yield and water supply data. Average farmer's WP in central Nebraska was ∼73% of the WP derived from the slope of the mean WP function. A substantial number of fields (55% of total) had water supply in excess of that required to achieve yield potential (900 mm). Pivot irrigation (instead of surface irrigation) and conservation tillage in fields under soybean–maize rotation had the greatest IWUE and yield. Applied irrigation was 41 and 20% less under pivot and conservation tillage than under surface irrigation and conventional tillage, respectively. Simulation analysis showed that up to 32% of the annual water volume allocated to irrigated maize in the region could be saved with little yield penalty, by switching current surface systems to pivot, improving irrigation schedules to be more synchronous with crop water requirements and, as a fine-tune option, adopting limited irrigation.     

Soil fertility and establishment potential of inoculated cyanobacteria in rice crop grown under non-flooded conditions

An investigation was undertaken using a combination of microbiological and DNA-based approaches to evaluate combinations of two/three/four cyanobacterial strains (BF1 Anabaena torulosa; BF2, Nostoc carneum; BF3, Nostoc piscinale; BF4, Anabaena doliolum), using a novel vermicompost-based carrier, for their promise as inoculants in rice crop. The crop was maintained under 60% WHC through intermittent irrigation. Selected combinations (BF1 + 2 + 3; BF1 + 2 + 4; BF1 + 3 + 4) showed a consistent trend regarding their superiority over other treatments in terms of plant growth promotion and soil microbiological parameters. Microscopic examination of soil enrichment cultures raised from the treatments revealed their comparative abundance over native flora. A significant enhancement in terms of soil microbial biomass carbon and humus content was also recorded in these treatments. The soil enzymatic profile of the inoculated treatments involving FDA, dehydrogenase, acid phosphates, alkaline phosphatase, aryl esterase and β-glucosidase also revealed the promise of the inoculated strains. 16SrDNA sequencing, followed by BLAST analyses provided valuable information regarding the establishment of Anabaena strains. RFLP analyses of the 16SrDNA sequences of soil DNA and phylogenetic analyses vis a vis sequences of the inoculated cyanobacterial strains revealed the promise of treatments ?BF1 + 2 + 3, BF1 + 2 + 4 and BF1 + 3 + 4. Panicle weight (yield attribute) was statistically at par with the fertilizer controls 1/2N + PK and significantly higher than 1/3N + PK. To our knowledge, this represents a first report on evaluating the establishment of cyanobacterial inoculants in rice crop grown under non-flooded conditions (or intermittent irrigation) using a combination of agronomic, microbiological and soil DNA related attributes.     

Effect of water management on dry seeded and puddled transplanted rice. Part 1: Crop performance

An alarming rate of ground water depletion and increasing labour scarcity are major threats to future rice production in north west India. Management strategies that reduce the irrigation amount and labour requirement while maintaining or increasing yield are urgently needed. Dry seeded rice (DSR) has been proposed as one means of achieving these objectives, but little is known about optimal water management for DSR. Therefore a field study was conducted on a clay loam soil in Punjab, India, during 2008 and 2009, to investigate the effects of irrigation management on the performance of puddled transplanted rice (PTR) and dry seeded rice. Irrigation scheduling treatments were based on soil water tension (SWT) ranging from ponding/saturation (daily irrigation) to alternate wetting and drying (AWD) with irrigation thresholds of 20, 40 and 70 kPa at 18–20 cm soil depth. Rainfall was above average and well distributed in 2008 (822 mm), and average and less well distributed in 2009 (663 mm).     

Plant characteristics associated with weed competitiveness of rice under upland and lowland conditions in West Africa

Weeds are a major constraint to rice (Oryza spp.) production in West Africa. Superior weed competitive rice genotypes may reduce weed pressure and improve rice productivity. Two upland and two lowland experiments were conducted in southern Benin to examine genotypic variations in weed-suppressive ability and grain yield under weedy conditions, and to identify plant characteristics that could be used as selection criteria for improved weed competitiveness. A total of 19 genotypes, including Oryza sativa and Oryza glaberrima genotypes and interspecific hybrids developed from crossing O. sativa and O. glaberrima, were grown under weed-free and weedy conditions in an upland with supplemental irrigation and in a flooded lowland. In weedy plots, hand weeding was done once or not at all. Mean relative yield loss across all genotypes due to weed competition ranged from almost 0% to 61%. Large genotypic variations in weed biomass and grain yield under weedy conditions were found. Visual growth vigor at 42 and 63 days after sowing (DAS) under weed-free conditions significantly correlated with weed biomass at maturity in both upland and lowland experiments (R² = 0.26–0.48). Where weed pressure was low to moderate, with mean relative yield loss less than 23%, the multiple regression models using grain yield and plant height at maturity or only grain yield measured under weed-free conditions as independent variables could explain 66–88% of the genotypic variation in grain yield under weedy conditions. At higher weed pressure (mean relative yield loss: 61%), as observed in one of the upland experiments, biomass accumulation of rice at 42 days after sowing was associated with higher grain yield under weedy conditions. Biomass accumulation also significantly correlated with visual growth vigor at the same sampling dates. Therefore, we conclude that grain yield, plant height at maturity and visual growth vigor at 42–63 DAS under weed-free conditions appear to be useful selection criteria for developing superior weed competitive rice genotypes.     

Arsenic in irrigated water,soil, and rice: perspective of the cropping seasons

Arsenic contamination of shallow groundwater and related health problems are threats for the millions in endemic regions of West Bengal. Contamination of rice grain creates the food chain pathway of mineral arsenic besides drinking water contamination. Present study concentrated on association of arsenic concentration in irrigated water, paddy field soil and rice with the cropping seasons. Irrigated ground water arsenic concentration decreased significantly (p = 0.007) from summer (median 0.42 mg l^?1) to winter (median 0.35 mg l^?1). Carried over effect created significant decrease (p = 0.03) of paddy field soil arsenic concentration from summer (median 8.35 mg kg^?1) to winter (median 6.17 mg kg^?1). Seasonal variation was observed in rice straw (p = 0.03) but not in husk (p = 0.91). Arsenic concentration decreased significantly (p = 0.05) in the rice grains collected in winter season (median 0.23 mg kg^?1) than the samples collected in the summer season (median 0.30 mg kg^?1). In conclusion, seasonal effects need to be considered in case of human health risk assessment from arsenic consumption.     

Annual forage legumes in dryland agricultural systems of the West Asia and North Africa Regions: research achievements and future perspective

Forage legumes are vitally important to animal production in the dryland farming systems of the Mediterranean region. Of the diverse forage‐legume species adapted to the Mediterranean climate, vetches, (Vicia spp.), chicklings (Lathyrus spp.), annual medics (Medicago spp), clovers (Trifolium spp.) and species of the Lupinus, Lotus, Onobrychis, Hedysarum and Ornithopus genera are considered to be the most agronomically important and economically valuable species for the region. Adoption of perennial self‐regenerating medic (Medicago spp.) has been limited because of technical difficulties, but annual vetch (Vicia spp.) has the greatest potential as a viable animal‐feed source and a rotation crop with cereals. Some forage legumes survive harsh conditions by their unique underground growth habit, for example, V. amphicarpa and Lathyrus ciliolatus. Efforts to improve forage legumes have been based on both management/cultural factors and breeding. Research based on several long‐term barley‐ and wheat‐based rotation trials has demonstrated the viability of forage legumes, especially vetch, in the region's improved farming system. An additional benefit to such legumes is the enhancement of soil quality, that is, soil fertility, soil organic matter and soil physical properties. Thus, the development of forage legumes is essential to agricultural sustainability in the Mediterranean region and in other dryland cereal‐growing areas of the world where grazing livestock is a dominant enterprise. To build upon the considerable research conducted on forages, intensified efforts are needed to develop locally adapted forage cultivars, to provide economic assessment of forages in cropping systems and to promote technology transfer at the farm and community level.     

Productivity and residual effects of legumes in rice-based cropping systems in a warm-temperate environment: II. Residual effects on rice

Field experiments were conducted over the period 1994–1996 to investigate the residual effect on rice of a wide range of temperate legume species, grown during the preceding winter season in a warm-temperate environment in Nepal. The incorporation of large quantities of above- and below-ground legume biomass (roots and foliage) resulted in substantial residual effects on the subsequent upland rice crop. The effects on rice yield in terms of percent increase over the control were more pronounced at a site of comparatively lower inherent soil fertility where grain yields of rice grown after high yielding legume crops such as bitter lupin (Lupinus mutabilis) and Persian clover (Trifolium resupinatum) were almost twice as high (up to 7.6 t DM ha⁻¹) than those of the control treatment (rice after wheat). In contrast, the residual effects of below-ground biomass (roots, nodules) on the following rice crop were not very pronounced and resulted in similar residual effects as rice, after fallow. Although up to 480 kg ha⁻¹ of legume foliage N had been applied to rice, only a small proportion of the legume N (up to 70 kg N ha⁻¹) was recovered by the following rice crop. Total rice dry matter yields were highly correlated with the amount of legume N applied, yet other factors such as residue quality and residue management practices appeared to also affect the magnitude of the residual effects. Future work should aim at investigating the effect of residue quality as affected by legume species and residue management practice on decomposition and N mineralisation processes in rice soils.     

Effect of interrow spacing and weeding frequency on the performance of selected rice cultivars on hydromorphic soils of West Africa

Field experiments were conducted on hydromorphic soils at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria to determine the effects of crop-management practices on rice yield. The performances of three rice cultivars at different crop densities and weeding regimes were investigated. Weed weight decreased significantly as the interrow spacing was decreased from 45 cm to 15 cm. Tillering and the number of rice panicles also decreased with reduction in interrow spacing. When rice was kept weed free, there was no significant difference in yield between rice planted at 15, 30 and 45 cm interrow spacing. However, when the crop was weeded once only at 30 d.a.s., yield was significantly reduced at the widest spacing. Yield reduction caused by weed competition at the wide interrow spacing was more pronounced in the semi-dwarf cultivar than in the taller cultivars. All cultivars competed better with weeds when grown at 15 and 30 cm interrow spacing than at the wider spacing used by most peasant rice farmers in West Africa.     

Texture determinants of cooked,parboiled rice. II: Physicochemical properties and leaching behaviour of rice

This paper reports the pasting, gelatinisation and leaching behaviour of 11 cultivars of rice, the starch structural properties of which were determined in the preceding paper. The results show that the contents of leached amylose in the cooking water, as determined by both size exclusion–high performance liquid chromatography (SE–HPLC) and iodine colorimetry, were correlated positively with the texture of cooked rices, which possessed total amylose contents in the range 18·4–29·5%. The amount of leached amylose depended on the total amylose content of the rice. A similar correlation between the conventional «setback» value, measured using the Viscoamylograph, and the texture of cooked rice may be a result of the leached starch content. The gelatinisation temperatures of rice starches determined by differential scanning calorimetry (DSC) were not correlated with the texture of cooked rice, but were significantly related to the crystallinity of the rice starch. The longest chain population (92–98 DP_n), which had been detected previously in the hard rice samples, was not found in their corresponding leached starches. This observation may well support the suggestion in the preceding paper that the longest amylopectin chains could interact with other components in rice, the resultant complexes being retained in the cooked grain and inhibiting softening.     

Variability and estimating in fruiting of shea tree (Vitellaria paradoxa C.F. Gaertn) associated to climatic conditions in West Africa: implications for sustainable management and development

ABSTRACT

Shea tree (Vitellaria paradoxa) is one of the main native oil plants with high economic value in Africa. Its fruits are used for food, medicinal, cultural and exportation purposes. However, the lack of efficient tools to assess annual fruit production of the species limits the sustainable management of its resources. Therefore, production statistics are useful to organize the activities of the shea sector. This study aimed to (i) assess the interannual variation in fruit production along a climatic gradient in Burkina Faso, (ii) examine fruit production patterns according to climatic zones and tree size, (iii) assess the contribution of high-yielding trees in the annual potential production and (iv) develop allometric equations for estimating fruit yields of the species. The yield of 212 trees distributed across three climatic zones was monitored over four successive years. Within each climatic zone, fruit production was significantly different among years. Fruit production was positively and significantly correlated with tree size. The interannual variation in fruit production at tree individual level was higher in drier climatic conditions. The mean interindividual synchrony was less than 50% in each zone, suggesting a large range in fruit production patterns of the species. Annually, more than 55% of the total fruit production was supported by high-yielding trees. The best regression models for estimating fruit yields had R ² values of 69–73% with prediction errors ranging from ?7% to 4%. Our findings are useful tools for the planning of rational exploitation of shea tree’s resources and its sustainable management.     

Intensifying groundnut production in the Sudan savanna zone of Nigeria: including groundnut in the irrigated cropping systems

Inadequate and erratic rainfall pattern and extreme temperature variations induced by climate change being experienced in Sudan savanna areas have compromised the cropping systems of these areas. A change in the cropping patterns is required to maintain and improve upon crop output levels. The pod yield ha(-1) and other growth and yield components of three varieties of groundnut grown under irrigated conditions were measured in a field experiment conducted at the Irrigation Research Station of the Institute for Agricultural Research, Zaria, from 2003 to 2006 dry seasons. Treatments consisted of three plant populations (50,000, 100,000 and 200,000 plants ha(-1)), three varieties (Samnut 23, Samnut 21 and Samnut 11) and three basin sizes (3 x 3, 3 x 4 and 3 x 5 m) arranged in a split plot design with population and variety as main plot and basin size as sub plot. Treatments were randomly assigned and replicated three times. Plant populations significantly affected plant height and canopy spread but had no effect on number of branches plant. Plants grew significantly taller at 200,000 plants ha(-1) while plant canopy spread was significantly widest at 50,000 plants ha(-1). Samnut 23 grew significantly taller than Samnut 21 and 11 although they exhibited wider canopies. Pod yield ha(-1) and 100 seed weight were significantly highest at 200,000 plants ha(-1). Samnut 23 produced the significantly highest pod yield ha(-1) and number of pods plant(-1). Samnut 11 produced significantly highest 100 seed weight. Samnut 23 planted at 200,000 plants ha(-1) in 3 x 4 m basins is most promising for irrigated groundnut cultivation in the Sudan savanna of Nigeria.     

Economic assessment of water-saving irrigation management techniques and continuous flooded irrigation in different rice production systems

Paddy and Water Environment - Globally, increasing water scarcity and higher production costs are the challenges in the cultivation of conventional transplanted rice (TPR). Under such conditions,...     

Comparison of high-yield rice in tropical and subtropical environments: II. Nitrogen accumulation and utilization efficiency

Nitrogen requirements to achieve rice grain yields higher than 13 t ha⁻¹ and the associated internal N-utilization efficiency (NUE) have not been documented. The objective of this study was to compare N accumulation and NUE of irrigated rice in tropical and subtropical environments at yield-potential levels in both climates. Field experiments were conducted in 1995 and 1996 at the International Rice Research Institute, Philippines (IRRI, tropical site), and at Taoyuan Township, Yunnan, China (subtropical site). Three to five high-yielding rice cultivars were grown under optimum crop management. Plants were sampled at key growth stages to determine tissue N concentration, plant N accumulation, N harvest index (NHI), N translocation ratio and NUE. Plant N accumulation at maturity was 19 to 30% greater at Yunnan than at IRRI. Most of this difference resulted from greater N accumulation and N uptake rate during the vegetative period at Yunnan than at IRRI. During reproductive and grain-filling periods, N accumulation and N uptake rate were similar or higher at IRRI than at Yunnan. Grain N concentration at maturity was lower and N translocation ratio from straw to grains during grain filling was higher at Yunnan than at IRRI, and these traits contributed to larger NHI and NUE at Yunnan than at IRRI. Cultivars that produced grain yields over 13 t ha⁻¹ at Yunnan required the accumulation of about 250 kg N ha⁻¹ within the crop and had a NUE of 59 to 64 kg grain per kg plant N.     

Evaluation of <Emphasis Type="Italic">sawah</Emphasis> rice management system in an inland valley in southeastern Nigeria. I: Soil chemical properties and rice yield

Failures in agricultural development in parts of West Africa may have been caused by the inability of the farmers to develop the abundant inland valleys for cultivation of such crops like rice, using appropriate water management systems. An inland valley in southeastern Nigeria was used to evaluate the influence of sawah and non-sawah water management using inorganic and organic soil amendments on the soil chemical properties and rice grain yield. Soil chemical properties tested were soil organic carbon, total nitrogen, pH, exchangeable K⁺, Ca²⁺ and Mg²⁺. Others were CEC, percent base saturation and exchangeable acidity while the grain yield of rice was also measured. The soils are loose, low in pH and poor in plant nutrient elements. In spite of that, the sawah-managed system was able to improve the pH of the soil by raising it slightly both in the first and second year of planting. Generally, essential plant nutrients such as exchangeable K⁺, Ca²⁺ and Mg²⁺, including fertility index like the CEC, were improved within sawah management within the period. Also, rice grain yield increased significantly (5.62 and 6.25 tons/ha in the first year and 5.32 and 6.53 tons/ha in the second year for non-sawah and sawah, respectively) with sawah system such that about 11 and 23% yield increases were obtained in sawah over the non-sawah in the two years, respectively. Although organic carbon can be used to explain the variation in total grain yield in the first year, it was the CEC that explained the total grain yield in the second year. The study revealed the superiority of sawah over non-sawah in the production of lowland rice in an inland valley in southeastern Nigeria.     

Investigating early vigour in upland rice (Oryza sativa L.): Part II. Identification of QTLs controlling early vigour under greenhouse and field conditions

Early vigour is an important characteristic for direct-seeded rice systems. The genetic control of early vigour was studied using a population of 129 backcross lines derived from a cross between Vandana, an improved indica, and Moroberekan, a traditional japonica. Screening was conducted under controlled conditions in greenhouse and field conditions, and indicators of early vigour, including shoot length, shoot biomass, leaf area, number of roots, root biomass, partitioning coefficients, and growth rates, were measured. Phenotypic correlations suggested that traits that were related and combined could be used to define early vigour. Broad-sense heritability ranged from moderate to high. Many regions were identified containing more than one QTL, suggesting that these traits were controlled by pleiotropic and/or closely linked QTLs. Many QTLs were specific to one environment but G × E interaction analysis showed that the main effects of the environment were large. Differences in temperature between experiments resulted in large differences in seedling age when expressed in thermal time. Different genes (QTLs) may be expected to control growth at different time intervals and thus may partly explain the limited agreement between experiments. However, several regions showed co-location of QTLs from more than one experiment. Comparisons with published studies revealed that these regions were previously identified in different genetic backgrounds and could potentially be used as introgression targets in a marker-assisted breeding program to improve germplasm for direct-seeded environments.     

Sawah Rice Eco-technology and Actualization of Green Revolution in West Africa： Experience from Nigeria and Ghana

The development and dissemination of sawah rice eco-technology in Nigeria and Ghana as prerequisites for the actualization of green revolution in West Africa were described. It showed that the neglect of the eco-technology and the overemphasis of the biotechnology have rendered the ineffective transferability of the green revolution process from Asia to Africa. The sawah eco-technology increases yield up to 5 t/hm² through bunding and the use of inlet and outlet connecting irrigation and drainage, which enhances effective water control and management, improves the efficiency of fertilizer, improves nitrogen fixation by soil microbes and algae, increases the use of wetlands, improves soil organic matter accumulation, suppresses weed growth, and enhances immune mechanism of rice through nutrient supply. The current experience has therefore established that the technology overcomes the constraints that have limited the realization of green revolution in West Africa.