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

Citation
M. Becker et De. Johnson, Rice yield and productivity gaps in irrigated systems of the forest zone of Cote d'Ivoire, FIELD CR RE, 60(3), 1999, pp. 201-208
Citations number
18
Categorie Soggetti
Agriculture/Agronomy
Journal title
FIELD CROPS RESEARCH
ISSN journal
03784290 → ACNP
Volume
60
Issue
3
Year of publication
1999
Pages
201 - 208
Database
ISI
SICI code
0378-4290(199902)60:3<201:RYAPGI>2.0.ZU;2-D
Abstract
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 r egional rice-growing area. A large potential for expansion of irrigated are as exists particularly in the inland valleys of the humid forest zone. Curr ent production is characterized by large variability in productivity, manag ement 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 lowl and fields in the humid forest zone of southern Cote 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 opera tions and input use were monitored. Weed biomass, rice N uptake, and grain yield were determined in farmers' fields as well as in super-imposed, resea rcher-managed subplots (clean weeding, no N control, and mineral fertilizer N application). Rice yield potential was simulated by using the Oryza-S cr op growth model. Yield losses were attributed to management factors based o n performance of rice in researcher-managed subplots (management-related yi eld gap) and by multiple regression with management options. Grain yields v aried between 0.2 and 7.3 Mg ha(-1) with mean yields of 3.2 in partially an d 4.2 Mg ha(-1) in fully irrigated systems, 44% and 57% of the potential yi eld of 7.3 Mg ha(-1) respectively. Age of seedlings at transplanting, timel iness of operations and application of P fertilizer were correlated to yiel d 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 appl ication of mineral fertilizer N was associated with a 0.48 Mg ha(-1) yield increase (p = 0.002), regardless of the quantity applied. Additional weedin g increased yield only in systems with imperfect irrigation. Weed biomass w as reduced with improved water control and it increased with age of seedlin gs at transplanting, and was higher in direct-seeded than in transplanted r ice. Echinochloa spp. were the most common weeds in fully irrigated systems and Panicum laxum was more common in the imperfectly irrigated fields. Whi le improved water management was associated with substantial rice yield inc reases (1.16 Mg ha(-1)), the timeliness of transplanting, weeding and N fer tilization appears to be the key to increased rice yields in the forest zon e of West Africa. (C) 1999 Elsevier Science B.V. All rights reserved.