Rice Yield Gaps Research Articles

Rice Yield Gap due to Iron Toxicity in West Africa

AbstractIron toxicity is a widespread nutrient disorder in lowland rice, notably in West Africa. It occurs in irrigated or rain‐fed rice crops when the soil contains excessive amounts of iron. Associated with leaf discoloration symptoms (bronzing), this excessive iron uptake causes poor growth and tillering and leads to severe yield reductions. Field experiments were carried out in West Africa from 1994 to 1998 at two sites with high iron toxicity and one non‐toxic site to assess the effects of iron toxicity on rice cropping and evaluate the tolerance of promising rice cultivars available in West Africa. To estimate yield losses caused by iron toxicity, the yield potential was simulated using the ORYZA‐S rice growth and yield model. Based on the potential yield, the yield loss in an iron‐toxic site is the combination of the yield gap caused by unknown site factors and the yield gap caused by iron toxicity. Compared to the referential yield obtained in a non‐iron‐toxic site, iron toxicity reduced rice yields by 16–78 % (mean 43 %). The extent of the yield loss depended on rice cultivar, iron toxicity intensity and crop management strategy (water control and mineral fertilisation). A strong correlation obtained between yield and the iron toxicity score, based on visual symptoms indicated an approx. 400 kg ha−1 yield loss for each visual score point increase. The high genetic variability in iron toxicity tolerance and close correlation between leaf symptom score and grain yield between rice genotypes provide a good basis for breeding varieties that can produce higher yields under iron‐toxic conditions.

An application of the DEA double bootstrap to examine sources of efficiency in Bangladesh rice farming

In this article we examine sources of technical efficiency for rice farming in Bangladesh. The motivation for the analysis is the need to close the rice yield gap to enable food security. We employ the DEA double bootstrap of Simar and Wilson (2007) to estimate and explain technical efficiency. This technique overcomes severe limitations inherent in using the two-stage DEA approach commonly employed in the efficiency literature. From a policy perspective our results show that potential efficiency gains to reduce the yield gap are greater than previously found. Statistically positive influences on technical efficiency are education, extension and credit, with age being a negative influence.

Extension service and rice yield gap in Nigeria, 1980-2002

Extension service and rice yield gap in Nigeria, 1980-2002

Rice yield gaps in irrigated systems along an agro‐ecological gradient in West Africa

AbstractIrrigated rice (Oryza sativa L.) in West Africa covers about 12 % of the regional rice‐growing area, and is produced all along the agro‐ecological gradient from the forest zone to the Sahara desert margins. Spatial and temporal variability of yield gaps (i.e., difference between actual and potential yield) were determined to set priorities for research and target technologies. On‐farm trials were conducted on 191 irrigated lowland fields in the humid forest, the savanna and the Sahel. Farmers' yields were compared with those of super‐imposed treatments of improved fertilization and weed management. Farmers' yields varied between 0.2 and 8.7 Mg ha‐1, with average yields of 3.4 Mg ha‐1 (Guinea savanna), 3.6 Mg ha‐1 (humid forest), 3.9 Mg ha‐1 (Sahel), and 5.1 Mg ha‐1 (Sudan savanna). Simulated potential yields increased from 7 Mg ha‐1 in the forest to about 10 Mg ha‐1 in the Sahel. Accordingly, yield gaps were large, ranging from 3.2 to 5.9 Mg ha‐1. Researcher weed control in the Sahel gave grain yield increases of about 1.0 Mg ha‐1. Improved weed and N fertilization management increased yields by 1 to 2 Mg ha‐1 in the forest and Guinea savanna sites. A share of 57‐80 % of the yield gap could not be accounted for. Improving weed control is likely to have the highest pay‐off in the Sahel while improved management of fertilizer N will be most beneficial in the forest and savanna environments.

Rice yield and productivity gaps in irrigated systems of the forest zone of Côte d'Ivoire

Much of the rapidly growing demand for rice in West Africa will be met from increased production in irrigated lowlands, which cover about 12% of the regional rice-growing area. A large potential for expansion of irrigated areas exists particularly in the inland valleys of the humid forest zone. Current production is characterized by large variability in productivity, management practices and production constraints. Quantifying the variability in rice yield and identifying the determining factors are prerequisites to the development of site-specific recommendations and to improved targeting of technologies. Diagnostic on-farm trials were conducted on 64 irrigated lowland fields in the humid forest zone of southern Côte d'Ivoire, in 1995–1996. This was a part of the regional gradient study of irrigated systems from the desert margin to the humid forest zone. Cropping calendars, field operations and input use were monitored. Weed biomass, rice N uptake, and grain yield were determined in farmers' fields as well as in super-imposed, researcher-managed subplots (clean weeding, no N control, and mineral fertilizer N application). Rice yield potential was simulated by using the Oryza-S crop growth model. Yield losses were attributed to management factors based on performance of rice in researcher-managed subplots (management-related yield gap) and by multiple regression with management options. Grain yields varied between 0.2 and 7.3 Mg ha −1 with mean yields of 3.2 in partially and 4.2 Mg ha −1 in fully irrigated systems, 44% and 57% of the potential yield of 7.3 Mg ha −1, respectively. Age of seedlings at transplanting, timeliness of operations and application of P fertilizer were correlated to yield and explained 60% of the observed variability. Grain yield was correlated with N uptake ( r 2 = 0.93 ***) but not with N application rate. Split application of mineral fertilizer N was associated with a 0.48 Mg ha −1 yield increase ( p = 0.002), regardless of the quantity applied. Additional weeding increased yield only in systems with imperfect irrigation. Weed biomass was reduced with improved water control and it increased with age of seedlings at transplanting, and was higher in direct-seeded than in transplanted rice. Echinochloa spp. were the most common weeds in fully irrigated systems and Panicum laxum was more common in the imperfectly irrigated fields. While improved water management was associated with substantial rice yield increases (1.16 Mg ha −1), the timeliness of transplanting, weeding and N fertilization appears to be the key to increased rice yields in the forest zone of West Africa.

Role of Higher Nitrogen Rate, Sulfur, and Zinc Application in Bridging the Yield Gap of Farmer's Boro Rice in Bangladesh

Role of Higher Nitrogen Rate, Sulfur, and Zinc Application in Bridging the Yield Gap of Farmer's Boro Rice in Bangladesh