Ship-based seabird and marine mammal survey pff Mauritania, 4 - 14 september 2015
Camphuysen, C.J. ; Spanje, T.M. van; Verdaat, J.P. - \ 2015
Den Burg [etc.] : NIOZ (Report / NIOZ etc. ) - 102
monitoring - fauna - marine ecology - mauritania - sea birds - marine mammals - adverse effects - oil and gas industry - monitoring - fauna - mariene ecologie - mauritanië - zeevogels - zeezoogdieren - nadelige gevolgen - olie- en gasindustrie
This report presents the first results obtained during the ship-based seabird and marine mammal surveys conducted between 4 and 14 September 2015 and must be seen as a preliminary analysis of the data and a further step in data collection. This cruise was part of the longer-term research project financed via the Programme “Biodiversity Gas and Oil” (BGO).
Notes and comments on the ex-post evaluation of the fisheries agreement EU Mauritania
Brunel, T.P.A. - \ 2011
IJmuiden : IMARES (Report / IMARES Wageningen UR C096/11) - 16
zeevisserij - visserijbeheer - visserijbeleid - evaluatie - internationale verdragen - europese unie - mauritanië - marine fisheries - fishery management - fishery policy - evaluation - international agreements - european union - mauritania
This report presents a summary of the content of the ex-post evaluation of the fishing agreement between the EU and Mauritania.
Desk study of the possible impact of fisheries and other human activities on the marine environment in Mauritania. An exploration
Wal, J.T. van der; Goudswaard, P.C. - \ 2008
Den Helder/Yerseke : IMARES (Report / Wageningen IMARES C100/08) - 42
visserij - menselijke activiteit - nadelige gevolgen - marien milieu - aquatische ecosystemen - oostelijke centrale grote oceaan - mauritanië - fisheries - human activity - adverse effects - marine environment - aquatic ecosystems - eastern central pacific - mauritania
Wageningen IMARES has been contracted by Dutch Ministry of Agriculture, Nature and Food Quality with funding from the “BO PPP”-programme to make an inventory of existing and expected future human activities in that part of the Eastern Atlantic Ocean that forms the Economic Exclusive zone of Mauritania with respect to their possible impact on the marine ecosystem. The inventory will mainly be focused on the different fisheries in the area, but will not be restricted to these. Based on this inventory of activities this report will consider data needed to properly assess the impacts on the ecosystem arising from these and the studies required to gather that data.
Travel report Mauritania bivalve Molluscs october 2008
Poelman, M. - \ 2008
Yerseke : IMARES (Rapport / Wageningen IMARES nr. C072/08) - 17
schaal- en schelpdierenvisserij - bivalvia - schaaldieren - mauritanië - voedselveiligheid - shellfish fisheries - bivalvia - shellfish - mauritania - food safety
During the last four years Mauritania has been working on the completion of a Food Safety Program of Bivalve Mollusks, in order to obtain an export approval by the Europe Union. During the preparations for an inspection by the FVO (Food and Veterinary Office) no fisheries or production activities for Bivalve Mollusks occurred in Mauritania. The aim of the mission was to perform a pre-assessment on the status of the Bivalve Food Safety program in Mauritania. The pre-inspection was carried out in order to prepare Mauritania for the upcoming Food and Veterinary Office (FVO) inspection, planned for the second semester of 2008 or the beginning of 2009.
Pre-inspection Mauritania Bivalve Mollusks Food Safety April 20-24th 2008
Poelman, M. - \ 2008
Yerseke : IMARES (Rapport / Wageningen IMARES nr. C049/08) - 17
mollusca - food safety - food inspection - inspection - mauritania - mollusca - voedselveiligheid - voedselinspectie - inspectie - mauritanië
Mauritania is working on the completion of a Food Safety Program for Bivalve Mollusks, in order to be obtain an export approval by the Europe Union for the last 4 years (and before). For the second semester 2008 the FVO has programmed a veterinary inspection for the on bivalve mollusks. In order to prepare themselves for the veterinary inspection the competent authority of Mauritania (ONISPA) has requested Wageningen IMARES for a pre-inspection of the Mauritanian system. The pre-inspection was performed during the period of 20-24 April in Mauritania (Nouakchott and Nouadhibou).
Pelagic Project Mauritania 2005-2006
Heessen, H.J.L. ; Tjoe-Awie, P.J. ; Haan, D. de; Ybema, M.S. - \ 2007
IJmuiden : IMARES (Report / Wageningen IMARES C018/07) - 29
pelagische visserij - mauritanië - beoordeling - sardinella - bijvangst - pelagic fishery - mauritania - assessment - sardinella - bycatch
The Pelagic Project Mauritania 2005-2006 was the continuation of two earlier, but similar, projects for the years 1998-2001 and 2002-2004. The project was carried out in cooperation between IMARES and IMROP and had as most important objectives to further the assessment of small pelagic species, mainly Sardinella, in Mauritanian waters, and the collection of by-catch data by the crews of Dutch freezer trawlers fishing in these waters. The project was commissioned by the Association of Dutch Pelagic Shipowners (RVZ). As far as the assessment of small pelagics is concerned, the scientific observer programme was continued and towards the end of the project period the responsibility for this programme was handed over to IMROP scientists. In the course of the project two acoustic surveys were partly funded by the project, as well as a meeting of the FAO working group on the assessment of small pelagics in Northwest Africa. During 2006, by-catch data were collected by four different vessels for 1072 hauls. In 343 hauls an excluder was used, a proto-type of which was developed during the preceding contract. By-catch rates observed in 2006 were rather low, especially when compared with records from scientific observers for the years 2001-2004. A positive effect of the excluder on the amount of by-catches could not be shown, possibly because part of the by-catches was released while the net was still in the water, and therefore not recorded. The efficiency of the excluder for small cetaceans remains as yet to be proven.
Water sampling at the Berge Helene FPSO at Chinguetti field in Mauritania using passive samplers
Korytar, P. ; Galien, W. van der - \ 2007
IJmuiden : IMARES (Report / Wageningen IMARES C009/07) - 19
water - bemonsteren - waterorganismen - ecotoxicologie - waterkwaliteit - marien milieu - mauritanië - water - sampling - aquatic organisms - ecotoxicology - water quality - marine environment - mauritania
Three rounds of water sampling were performed at the Berge Helene FPSO at the Chinguetti field in Mauritania using passive samplers attached to the FPSO to determine the levels of contamination that could potentially accumulate in organisms. Two rounds were carried out prior to the commencement of oil production (pre-PFW) and one following the start of produced formation water discharge (post-PFW). Although water was sampled at 3-m and 10-m depths, bioaccumulation data were possible to report only for 3-m depth due to the repeatable loss of samplers deployed at 10-m depth. The reason for these losses remains un-known. Retrieved passive samplers from each round were analysed for total bioaccumulative (petroleum) hydrocarbons, 9 phenols, benzene, toluene, ethylbenzene, xylene and 16 EPA polycyclic aromatic hydrocarbons. The accumulated amounts of chemicals during the two pre-PFW samplings were very similar and both of them can be considered to be representative for the pre-PFW phase. Surprisingly, the accumulated amount of chemicals during the post-PFW sampling round (i.e. after and during regular PFW discharges) was lower than in the pre-PFW sampling round. The most probable explanation is that drilling activities have stronger impact than the regular PFW discharges, but the possibility that the results were influenced by a variation in meteorological and hydrological conditions, such as ,e.g., direction and strength of the currents, could not be fully rejected. The biomimetic nature of the Empore® disk extraction was used to estimate total body residues of chemicals in biota. These values were compared with critical body residues for three toxicological effects to evaluate baseline toxicity of the environment under the FPSO. Results showed that the total body residue levels in the aquatic environment under the FPSO are below the no-effect level for sub-lethal fish toxicity. However, in all measurements the levels exceed safe level for effects on ecosystem (HC5): in pre-PFW sampling significantly, while in post-PFW only slightly. As these levels were observed directly at the source of possible contamination, the effects on the environment are likely to be substantially lower at increased distance from the FPSO.
IMARES' capacity building activities with Institut Mauritanien des Recherches Oceanographiques et de Peche (IMROP) within the Woodside Chinguetti PFW Baseline project
Korytar, P. ; Zeeberg, J.J. ; Galien, W. van der - \ 2007
IJmuiden : IMARES (Report / Wageningen IMARES C010/07) - 21
visserij - mariene gebieden - visbestand - onderzoeksinstituten - mauritanië - nederland - fisheries - marine areas - fishery resources - research institutes - mauritania - netherlands
An Environmental Impact Statement (EIS) prepared by Woodside (Perth, Australia) for the Chinguetti Development Project in Mauritania identified potential environmental effects from routine Produced Formation Water (PFW) discharges on the marine environment. Adverse effects on the industrial fisheries of Mauritania in particular, were identified as one of the key environmental risks represented by the project. Woodside therefore made a commitment to monitor PFW discharges and as a first step biological and water sampling was prepared prior to, and following first oil production from the Chinguetti Project. Woodside, recognizing the importance of involvement of Mauritanian institutions in monitoring studies, requested that the project be undertaken in association with National Mauritanian Institute for Oceanographic and Fisheries Research (IMROP), which is the Mauritanian body responsible for protection of the sea. In addition, part of the project is dedicated to improvement of IMROP’s capacity to perform sampling and to analyze the water and biological samples, so that over time all required activities could be performed by IMROP. The project is being undertaken by the Marine Resources Assessment Group (MRAG) of United Kingdom and the Institute for Marine Resources and Ecosystem Studies (IMARES) of the Netherlands. The capacity building activities are being shared by both partners and coordinated by MRAG. This document provides a final report on the capacity building activities performed by IMARES within the Woodside Chinguetti PFW Baseline project. The report covers the list of all activities performed, the discussion and evaluation of the current capacity of IMROP and suggestions/recommendations for further activities.
Levels of contaminants in Sardinella aurita caught at Mauritanian coast prior to and following produced formation water discharges from Berge Helene FPSO at Chinguetti field
Korytar, P. ; Galien, W. van der - \ 2007
IJmuiden : IMARES (Report / Wageningen IMARES C005/07) - 41
sardinella - vis vangen - mauritanië - bemonsteren - besmetting - aquatische toxicologie - bioaccumulatie - sardinella - fishing - mauritania - sampling - contamination - aquatic toxicology - bioaccumulation
Two sampling rounds of Sardinella aurita were conducted in the waters off the coast of Mauritania to evaluate levels of contamination prior to the commencement of oil production and following the start of produced formation water discharge.
Toxicity testing of produced formation water (PFW) from Chinguetti FPSO in Mauritania
Korytar, P. ; Foekema, E.M. ; Slijkerman, D.M.E. ; Kaag, K. ; Galien, W. van der - \ 2006
IJmuiden : IMARES (Report / IMARES C090/06) - 9
toxiciteit - mauritanië - oestrogene eigenschappen - waterorganismen - ecotoxicologie - toxicity - mauritania - oestrogenic properties - aquatic organisms - ecotoxicology
An ecotoxicological study of produced formation water (PFW) from the Berge Helene FPSO at the Chinguetti oil field, operated by Woodside in Mauritania was performed. The study was requested by MRAG Ltd as a part of Woodside’s Environmental Monitoring Plan.
Assessment demersal fish stocks Mauritania
Corten, A.A.H.M. ; Goudswaard, P.C. ; Heessen, H.J.L. - \ 2006
IJmuiden : IMARES (Report / IMARES C066/06) - 52
visstand - visbestand - demersale visserij - demersale vissen - mauritanië - fish stocks - fishery resources - demersal fisheries - demersal fishes - mauritania
The RIVO project "Assessment of demersal fish stocks in Mauritania" was commissioned by the Ministry of Foreign Affairs of The Netherlands to produce information on the state of the demersal fish stocks (species that live near the bottom) in Mauritania, in particular octopus and shrimps. These stocks are fished by fleets from the EU, working under the fishery agreement between the EU and Mauritania. Although there are no Dutch vessels targeting demersal fish in Mauritania, the government of The Netherlands is co-responsible for the fisheries agreement with Mauritania, and thereby for a rational and sustainable exploitation of the demersal resources.
Discards in the Mauritanian shrimp fisheries : an evaluation of lost value
Goudswaard, P.C. ; Meissa, B.O. - \ 2006
IJmuiden : IMARES (Report / IMARES C067/06) - 31
garnalen - visserijbeheer - visserijbeleid - mauritanië - bijvangst - discards - visserijbiologie - shrimps - fishery management - fishery policy - mauritania - bycatch - discards - fishery biology
The discards of the shrimp fishery in Mauritania are calculated on basis of direct observations on board of commercial vessels from 2004-2006. Data were collected from 175 hauls in 12 trips. The fisheries for the three different shrimp fisheries take place at different depths and so have a different by-catch and discard composition. The percentage of discards varies from 80.7 to 86.4% in weight which corresponds to a volume of 31 516 tons of fish discarded annually. Commercial species constitute 58.8% of the discards in the gamba fishery and 73.8% in the langostino fishery. In particular the hake and round fish stocks experience a fishery mortality as discards, which is high compared to the mortality induced by the specialized fleets
Evaluatie demersale visbestanden Mauritanie Jaarverslag 2004
Corten, A.A.H.M. ; Goudswaard, P.C. ; Heessen, H.J.L. - \ 2005
IJmuiden : RIVO (Rapport / Nederlands Instituut voor Visserij Onderzoek (RIVO) C045/05) - 17
demersale vissen - visbestand - schaal- en schelpdierenvisserij - garnalen - mauritanië - demersal fishes - fishery resources - shellfish fisheries - shrimps - mauritania
De werkzaamheden binnen het project werden in 2004 grotendeels volgens de bestaande planning uitgevoerd. Veel tijd werd gestoken in de analyse van al bestaande gegevens in de data base van het IMROP. Hoewel deze data base een aantal belangrijke tekortkomingen kent, kon op basis van de beschikbare informatie toch een redelijk beeld gevormd worden van de garnalenvisserij. De gegevens werden ook gebruikt tijdens twee workshops op het IMROP waarbij de toestand van de garnalenvisserij in Mauritanië werd geëvalueerd. Het bleek dat de garnalen in de ondiepe zone dicht onder de kust (langostino’s) al overbevist waren, terwijl dat voor de garnalen in de diepere zone (gamba’s) nog niet aantoonbaar was. Merkwaardig genoeg had de toename van de visserij inspanning op garnaal in eerste instantie niet geleid tot afname van de garnalenstand. Dit verschijnsel werd toegeschreven aan het wegvangen van de natuurlijke vijanden van de garnaal (grote vissen), waardoor er meer jonge garnalen volwassen konden worden. De gevolgen van de garnalenvisserij op andere visbestanden werden nog niet bekeken. Verwacht mag worden dat dit effect sterk negatief zal zijn.
The use of satellite imagery in sardinella and sardine fisheries in the Mauritanian EEZ - Annual Report 2003
Zeeberg, J.J. - \ 2004
IJmuiden : RIVO (RIVO report C028/04) - 20
visserij - vismethoden - remote sensing - sardines - sardinella - satellietbeelden - bijvangst - mauritanië - fisheries - fishing methods - remote sensing - sardines - sardinella - satellite imagery - bycatch - mauritania
Remote sensing research missions on board Dutch freezer trawlers in the Mauritanian EEZ in 2003 have focused on the relationship between water temperature, trawling tactics, and by-catch. During the research missions, which last 8-12 days each, satellite images of sea surface temperature (SST) are received by the trawler on a daily basis and tows are planned on the basis of oceanographic information to limit search time and minimize by-catch of non-target species.
Incidental catches of pelagic megafauna by the Dutch pelagic fleet in the Mauritanian Exclusive Economic Zone during the years 1999 - 2003
Hofstede, R. ter; Zeeberg, J.J. ; Haan, D. de; Couperus, A.S. ; Mantingh, I.T. - \ 2004
IJmuiden : RIVO (RIVO report C032/04) - 20
pelagische visserij - visserij - vangstsamenstelling - bijvangst - cetacea - haaien - raja - xiphias gladius - maanvissen - cheloniidae - mauritanië - pelagic fishery - fisheries - catch composition - bycatch - cetacea - sharks - raja - xiphias gladius - sunfishes - cheloniidae - mauritania
This report presents all registered catches of pelagic megafauna by the Dutch pelagic fleet in the Mauritanian Exclusive Economic Zone during the years 1999-2003. ‘By-catches’ incidentally include large species, notably cetaceans, sea turtles, sharks, rays, and some large pelagic fish such as swordfish and ocean sunfish. All observations were made in the framework of different projects of the Netherlands Institute for Fisheries Research (RIVO B.V.) in the area, financed by the Dutch Ministry of Agriculture, Nature Management, and Fisheries (LNV) and partly by the Redersvereniging voor Zeevisserij, part of the Pelagic Freezer-Trawler Association (PFA): “Assessment of Sardinella and other small pelagics in West Africa” (313-1230001), “Application of remote sensing data to analyse the distribution and recruitment of sardinella” (313-1230002), and “Preventing by-catches of protected or endangered species in the pelagic trawl fishery in West Africa” (313-1230003). The sampling procedures of incidentally caught pelagic megafauna on board of Dutch pelagic freezer-trawlers in Mauritania throughout the period 1999-2003 are evaluated in this report. The collected raw data on this by-catch of large species is whenever possible validated with an observation factor, shortcomings are discussed, and recommendations for improvements are given. This report presents raw data and explicitly avoids extrapolations up to mission or even fleet level.
Assessment of Sardinella and other Small Pelagics in West Africa
Corten, A.A.H.M. - \ 2004
IJmuiden : RIVO (RIVO report C042/04) - 18
pelagische visserij - visbestand - visstand - duurzaamheid (sustainability) - ultrasoon sporen - akoestisch sporen - mauritanië - pelagic fishery - fishery resources - fish stocks - sustainability - ultrasonic tracking - acoustic tracking - mauritania
The year 2003 was the sixth year of the cooperation between RIVO and the Mauritanian fisheries research institute IMROP (Institut Mauritanien des Recherches Océanographiques et de Pêche). It was also the second year of the current contract between RIVO and the Dutch Ministry of Agriculture, Nature and Food Quality. The cooperation between the Dutch and Mauritanian institutes is aimed at the transfer of technology and experience in the field of pelagic stock assessment. By increasing Mauritania’s capacity for pelagic stock assessment, prospects are improved for a sustainable management of pelagic resources in the area.
Catch composition of the Dutch pelagic fleet in the Mauritanian Exclusive Economic Zone during the year 2003: results of the scientific observer program
Hofstede, R. ter - \ 2004
IJmuiden : RIVO (Report / RIVO-Netherlands Institute for Fisheries Research C054/04) - 58
pelagische visserij - sardinella - sardines - sardina pilchardus - makrelen - scomber scombrus - visserij - discards - bijvangst - vangstsamenstelling - mauritanië - pelagic fishery - sardinella - sardines - sardina pilchardus - mackerels - scomber scombrus - fisheries - discards - bycatch - catch composition - mauritania
This report describes the total catches of the Dutch pelagic fleet in the Mauritanian Exclusive Economic Zone during the year 2003. Data have been obtained by the 'Scientific Observer Program', which monitors the catch (both landings and discards) of the Dutch fishery for small pelagics in Mauritania. The Dutch pelagic fleet in Mauritania focuses mainly on the group of sardinella (Sardinella aurita and Sardinella maderensis). Additional target species are pilchard (Sardina pilchardus) and chub mackerel (Scomber japonicus). The landings by weight in 2003 consisted for 95% of these 4 species, S. aurita being the dominant species (58% of the landings). In the year 2003, 91.6% of the estimated total catch by weight has been landed and 8.4% was discarded, which is reasonably comparable to previous years (1999-2002). The total estimated catch of the Dutch fleet has remained about the same, approximately 170 thousand tons per year. The dominance of S. aurita in the total estimated catch has gradually diminished throughout the years 1999-2003. Pilchard (S. pilchardus) and chub mackerel (S. japonicus) gradually replaced the round sardinella in the catches of the Dutch fleet since 1999. As in previous years, the catch of round sardinella mainly took place during the summer from June to September and the pilchard S. pilchardus appeared to be the dominant species in wintertime. The number of observer days has reduced slightly throughout the period 1999-2003. Nevertheless, the sampling method, both for small pelagic species and by-catch of pelagic megafauna, has improved in quality and quantity, which resulted in high quality data. The extension of the observers’ dataset in 2003 with a fifth year in a row enlarged the possibilities to use this database for detailed research on the biology and ecology of small pelagic species in the Mauritanian Exclusive Economic Zone, which is therefore highly recommended to be performed in the near future.
Mission Report Mauritania: Consultancy on Implementation of a Shellfish Quality monitoring Programme
Poelman, M. - \ 2004
IJmuiden : RIVO (Internal report / RIVO 04.016) - 16
schaaldieren - schaal- en schelpdierenvisserij - kokkels - venus - venerupis - vistoxinen - toxinen - fytoplankton - metalen - polycyclische aromatische koolwaterstoffen - monitoring - kwaliteit - kwaliteitsnormen - europese unie - mauritanië - shellfish - shellfish fisheries - clams - venus - venerupis - fish toxins - toxins - phytoplankton - metals - polycyclic aromatic hydrocarbons - monitoring - quality - quality standards - european union - mauritania
Mauritania has several commercially interesting shellfish species, such as Venus verrucosa, Venus rosalina and Venerupis dura , in her coastal waters. In order to comply with the European standards and to export these shellfish to the European market a shellfish monitoring programme for parameters such as marine phycotoxins, toxic phytoplankton, metals, Polycyclic Aromatic Hydrocarbons (PAH), metals, physical parameters, and microbiology should be set up. Therefore a mission to Mauritania took place in order to evaluate the needs and make an inventory of the lacking items with respect to a monitoring programme. IMROP (Institut Mauritanien des Recherches Océanographiques et de Pêche), DVIS (Département de Valorisation et Inspection Sanitaire) was visited for these purposes. In order to set up an adequate monitoring system legislation should be written, a monitoring programme should be designed, an Internal Quality system should be set up, and various analyses should be implemented. The implementation of these requires the input of expert knowledge and training possibilities. The needs for a successful implementation of a monitoring programme are therefore depicted in the report.
Marine mammals and seabirds in Mauritanian waters : pilot study April 2004
Tulp, I.Y.M. ; Leopold, M.F. - \ 2004
onbekend : RIVO Biologie en Ecologie (Internal report / RIVO 04.020) - 42
zeezoogdieren - zeevogels - kustgebieden - mauritanië - inventarisaties - marine mammals - sea birds - coastal areas - mauritania - inventories
The upwelling zones in Mauritanian coastal waters provide food-rich conditions for fish. Fish-stocks are exploited by a large international fleet of freeze-trawlers. Trawlers, fish and fish predators therefore congregate in a relatively narrow strip where the upwelling takes place. As an unwanted side-effect large animals, such as cetaceans, sharks and rays are accidentally caught in the nets. To be able to estimate the effect of by-catches on local populations of these groups informationon densities and occurrence in relation to season and environmental variables is needed. In April 2004 the Netherlands Institute for Fisheries Research (RIVO) and Alterra conducted a pilot survey of marine mammals and seabirds in cooperation with the Mauritanian Institute for Oceanographic and Fisheries Research (IMROP). As sea mammals often interact and form multi- species feeding associations with seabirds, the census included both sea mammals and seabirds. The main aim of the project was to investigate the suitability of the combination of a survey of marine mammals and seabirds with an acoustic survey that is carried out twice per year to assess pelagic fish stocks. The ultimate goal is to set up a monitoring program with several surveys per year. If the combination with the acoustic survey is useful and successful, the monitoring program can be carried out at relatively low cost. Between 16 and 28 April 2004 two observers joined the acoustic survey on board the Al Awam, the research vessel of IMROP. A total of 28 transects positioned East-West at distances of 10 nm apart were sampled, at depths varying from 20 m to 500 m. All marine mammals and seabirds encountered were noted, using standard seabirds at sea counting methods. Besides assessing numbers, also behaviour was recorded, following the observation protocol for ship-based seabird surveys in Europe. Observations were carried out when the ship was steaming. During fishing operations (2-5 times per day) observations were interrupted.In this report a short overview of the results is presented. Cetaceans were only rarely encountered during the survey. In total, ten groups or singles were observed during 91.5 hours of counts. The sightings included two large whales (Fin Whale and Humpback Whale), three species of small whales (Killer Whale, Long- or Short-finned Pilot Whale and unidentified Beaked Whale) and two species of dolphin (Common and Bottlenose Dolphin). In total 51.838 seabirds and 314 species were recorded of which Common/Arctic Tern, Black Tern, Wilson’s Storm-petrel and Sabine’s gull were the most abundant species. The general pattern can be characterised by a clear near shore-offshore gradient, with peak densities of most species at the drop-off of the continental shelf. The majority of birds was associated with trawlers.
Explaining yield gaps on farmer-identified degraded and non-degraded soils in a Sahelian irrigated rice scheme
Asten, P.J.A. van; Wopereis, M.C.S. ; Haefele, S. ; Isselmou, M.O. ; Kropff, M.J. - \ 2003
Netherlands Journal of Agricultural Science 50 (2003)39541. - ISSN 0028-2928 - p. 277 - 296.
oryza sativa - gewasopbrengst - gewasproductie - gewasteelt - landbouwplantenteelt - kunstmeststoffen - bodemdegradatie - irrigatie - sahel - mauritanië - bodemchemie - oryza sativa - crop yield - crop production - crop management - crop husbandry - fertilizers - soil chemistry - soil degradation - irrigation - sahel - mauritania - boundary line approach - seeded flooded rice - west-africa - transformations - management - fertility - norms
The objective of this study was to identify to what extent rice productivity problems are caused by soil quality problems (soil alkalinity) and to what extent by sub-optimal crop management. The study area used is the Foum Gleita irrigation scheme, Mauritania
Farmers in the Foum Gleita irrigation scheme in southern central Mauritania experienced declining rice yields, and within a decade after its establishment 12% of the scheme's land had been abandoned. Actual rice yields (less than or equal to 4.0 t ha(-1)) are low in comparison with potential yield (ca. 8 t ha(-1)) and with yields elsewhere in the Sahel (4-6 t ha(-1)). Farmers related the productivity problems to salt efflorescences on the soil surface. Rice yields on the 'upper and middle slope' soils were lower (3.4 t ha(-1)) than the yields on soils further down the slope (> 4.2 t ha(-1)). Farmers classified the 'upper and middle slope' soils as degraded, but following the USDA classification the soils could not be classified saline or sodic. Low yields on the 'degraded' soils were related to co-limitation of nitrogen (N) and phosphorus (P), which was due to low soil N supply (ca. 18 kg ha(-1)), low soil P supply (ca. 8 kg ha(-1)), occasional low N fertilizer doses (35 kg N ha(-1)) in combination with low N fertilizer recovery efficiency (0.3 kg kg(-1)), or non-application of P fertilizer. On the 'non-degraded' soils, soil P supply (ca. 16 kg ha(-1)) was higher and N deficiency prevailed despite a higher soil N supply (ca. 32 kg ha(-1)) and a higher N fertilizer recovery efficiency (0.4 kg kg(-1)). Higher contents of carbonate salts in the 'degraded' soils increase soil pH (> 7.5) and are, therefore, likely to contribute to low soil P supply and low N fertilizer recovery efficiency.