Biological and Physical Constraints on Maize Production in the Humid Forest and Western Highlands of Cameroon

The aim was to identify biological and physical factors responsible for reducing maize yield in Cameroon. Two surveys were conducted in 137 fields in two agroecological zones in 1995–1997. In the Humid Forest (HF), Bipolaris maydis, Stenocarpella macrospora, Puccinia polysora, Rhizoctonia solani and soil fertility were factors that reduced maize production in 1995 and 1996. In the Western Highlands (WHL), Cercospora zeae-maydis, and the interaction between soil fertility and maize variety were the most important constraints to maize production in 1996. In 1997, C. zeae-maydis, S. macrospora, physiological spot and stem borer damage (Busseola fusca) were negatively related to ear weight. The combination of these biological factors (diseases and insects), and the physical parameter of soil fertility were responsible for reducing maize yield in these selected benchmarks of Cameroon. Maximum potential yield reductions were estimated at 68% due to B. maydis and 46% due to S. macrospora, respectively, in the HF in 1995. In 1996, maximum potential yield reductions in the HF were estimated at 34%, 41% and 30% due to S. macrospora, P. polysora and R. solani, respectively. In the WHL, C. zeae-maydis had the potential to cause a yield reduction of 79% in 1996. In the WHL in 1997, the interaction between C. zeae-maydis and B. fusca, stem diseases and the physiological spot caused potential reductions of 52%, 34% and 39%, respectively.     

Integrated Pest Management in Cocoa Agroforests in Southern Cameroon: Constraints and Overview

Imports of pesticides have long been subsidised for use in the cocoa agroforests of the humid forest zone of southern Cameroon. With the liberalisation of the cocoa and pesticides sectors and the devaluation of the local currency (CFA franc), farmers are facing fluctuations in the price paid for cocoa and the high cost of farm inputs. Without the support of the extension services, they themselves have developed traditional integrated control methods based on the use of plant extracts mixed with conventional pesticides. From a survey of 300 cocoa farmers, the study assesses the farmers' command of these methods, the pests controlled, the problems encountered and the institutional constraints in the definition and dissemination of integrated control methods. The study concludes with recommendations for research and development towards the better definition and dissemination of integrated control methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Biomass and Phosphorus Uptake Responses of Maize to Phosphorus Application in Three Acid Soils from Southern Cameroon

Abstract

A phosphorus (P) greenhouse experiment was carried out with maize (Zea Mays L.) using surface horizons of three contrasted acid soils from southern Cameroon. The objectives were (i) to assess causal factors of maize differential growth and P uptake and (ii) to explore plant–soil interactions in acid soils under increasing P supply. Shoot and root dry‐matter yield and P uptake were significantly influenced by soil type and P rate (P<0.000), but the interaction was not significant. Soil properties that significantly (P<0.05) influenced maize growth variables were available P, soil pH, exchangeable bases [calcium (Ca), magnesium (Mg)], and exchangeable aluminium (Al). Data ordination through principal‐component analysis highlighted a four‐component model that accounted for 88.1% of total system variance (TSV) and summarized plant reaction in acid soil condition. The first component, associated with 36.1% of TSV, pointed at increasing root–shoot ratio with increasing soil acidity and exchangeable Al. The second component (24.6% of TSV) highlighted soil labile P pool increase as a function of P rate. The third and fourth components reflected nitrogen (N) accumulation in soils and soil texture variability, respectively.     

Complete Larval Development of the Fresh Water Prawn Macrobrachium vollenhovenii in Cameroon

The African River prawn Macrobrachium vollenhovenii is the largest of the local Palaemonidae prawns along the Cameroonian coast and an important target species for fisheries and aquaculture. A preliminary study on larviculture of this species was carried out at the IRAD-AQUASOL hatchery in Kribi, Cameroon. Berried females M. vollenhovenii were obtained from the Lobe and Lokoundje Rivers in the Southern Region, typical Lower Guinea rainforest streams. The larval rearing system consisted of a single recirculation system of four 65 L cylindrical plastic containers connected to a submerged biological filter container (65 L). Experiments were conducted three times in the same condition, with two batches of larvae reared separately in duplicate per experiment, at a density of 40/L, temperature 26°C, and salinity 16%. Larvae were fed from 1 day after hatching until metamorphosis to postlarvae (PL) with newly hatched Artemia nauplii, three times daily at the rate of 5 nauplii per mL water. The number of newly hatched larvae per female body weight unit was not affected by the female size and ranged between 531 to 1349 larvae g^?1. The six batches succeeded from hatching to metamorphosis, and the 11 distinct larval stages described for M. rosenbergii were found. Larvae in all the batches developed more or less at the same pace up to stage V. However, a clear difference in the timing of appearance of the developmental stages was observed between batches and individuals of the same batch during the subsequent stages. The transition from stage V to stage VI and from stage IX to stage X was longer than the passage to other stages and seems to be the critical rearing period of M. vollenhovenii. From day 20 onward to sampling, the larval stage index (LSI) showed that larval development of the batch 1 was significantly faster than for all other batches. The time for first appearance of postlarvae was variable between batches (41–74 days), and batch 1 larvae passed through metamorphosis within a shorter span of time (41 days). Survival up to postlarvae was variable among batches, ranging between 3%–9%, and was better in batch 1 (9.31 ± 1.09). The general poor performance in terms of survival and metamorphosis rates of larvae seems to be related to the wild condition of broodstock. To improve performance of larvae, domestication of stock may be necessary. This result is the first recorded success in larviculture of M. vollenhovenii in Cameroon.     

An AHP Assessment Of Barriers in Adopting Sustainable Forest Management Practices in The Context Of Carbon Emission Reductions in Cameroon

ABSTRACT

As the role of forests in climate change mitigation is explicitly recognized in the Paris Agreement, the need to enhance the adoption of Sustainable Forest Management (SFM) practices is crucial. Therefore, this paper aims at identifying and evaluating barriers in adopting SFM practices in the context of forest carbon emission reductions. A total of 15 barriers in adopting SFM practices are listed through literature and expert inputs. Using Cameroon as a case study, the listed barriers are then evaluated by experts to determine their relative importance using the Analytical Hierarchy Process (AHP) method. According to our findings, the ‘Regulatory and Legislative frameworks’ barrier category was attributed to the highest importance among other categories, in adopting SFM practices in the forestry sector. ‘Inadequate political will and incentive to enforce regulations’ appears to be the major obstacle in adopting SFM practices in Cameroon. As carbon emission reduction initiatives are being developed, there is need to move from broad to concrete suggestions that will overcome these barriers. However, proper diagnosis is necessary in order to target barriers with the right incentives and enabling conditions that will support carbon programs and projects to deliver effective emission reductions.     

Mapping landscapes: Integrating GIS and social science methods to model human-nature relationships in Southern Cameroon

Participatory mapping and GIS are both necessary to model the interactions between humans and their environment. A case study from the forest margin in the Congo Basin demonstrates how data from participatory community mapping and other social science methods can be prepared for quantitative modelling. This approach bridged the gap between spatial modelling data and social decision-making in space by elaborating a geographically consistent social representation of the landscape and giving a geographical base to the connection between land use, its cultural representation, and its social management. This was achieved through an iterative process of GIS cartography, using feedback from village informants and field checking, to transpose the spatial references from participatory mapping sketches into reliable geographic locations. As well as demonstrating the utility of such data for modelling, this work clarified the distribution of land rights among the six main owner-clans spread through the eight hamlets in the watershed. The ‘basin’ of spatial resources and its relation to the rules of land use and natural resource management were defined for each clan. Land-use systems at the forest-agriculture interface in the study area proved to be complex, strongly driven by social rules and influenced by history and settlement strategies. These social and historical aspects established the framework within which communities make current decisions and interventions. The authors thank the people of Akok for their collaboration and hospitality. Village technician Michel Engueng and village contact Adolphe Ze facilitated and assisted this work. Our thanks also to Julie Mbazo’o and Remy Assoumou, both members of the ‘social side’ working group of the FLORES modelling team. Christopher Legg’s contribution to the discussion of this work through his constant reviewing of the CamFlores model is gratefully recognized. Finally, thanks to the whole CIFOR-ACM team for numerous scientific and methodological inputs. The Italian Foreign Ministry funded the work of Valentina Robiglio (APO-GIS specialist) through an APO contract with IITA. The European Union (Tropical Forestry budget line DG VIII) contributed to the CIFOR’s research program on the ‘Adaptive Collaborative Management of Forests’ (ACM) in Africa, and to the Alternative to Slash and Burn (ASB) program in Cameroon on ‘Environmental Services and Rural Livelihoods’ through the World Agroforestry Centre.     

Salt Stress Effects on Germination,Plant Growth and Accumulation of Metabolites in Five Leguminous Plants

The investigation was conducted to determine physiological criteria of early selection for salt tolerant leguminous plants. Plants were subjected to 5 levels of salt stress at the roots （0, 50, 100,150 and 200 mM NaCI）. Results showed that sodium chloride had an underrating effect on growth of stems and seed germination of the species studied. The germination rates of seeds of Glycine max and Phaseolus vulgaris （sensitive glyeophytes） were affected from 3 g/L of NaCl, with critical thresholds at 9 and 12 g/L respectively. In contrast, critical thresholds with Mucunapoggei （facultative halophyte）, Vigna unguiculata （moderately tolerant glycophyte） and P. adenanthus （natural halophyte） was found to be above 21 g/L. The reduction of stems growth rate were not significant in P. adenanthus whereas in M. poggei and V. unguiculata this inhibition was observed just when nutritive solutions were enriched with 200 mM. The lipid contents were reduced in all the species under salt stress, whereas proteins and proline contents in the leaves were substantially increased in tolerant species （M. poggei, P. adenanthus and V. unguiculata）. In contrast, proteins and leaf proline contents were negatively affected by salt concentration to G. max and P. vulgaris. Seed germination, proteins and proline could be used as physiological criteria of early selection for salt tolerant leguminous plants.     

Economic opportunity survey of small scale dairy farms of the north west province of Cameroon

An Economic Opportunity Survey was conducted on dairy farms in the North West Province of Cameroon. Results showed that median (range) number of cows in milk per farm was zero point six (0–4) and six (3–12) in the zero grazing and transhumance systems, respectively. Medians (range) of three (0–24) and four (3–10) litres of milk were sold per farm per day, corresponding to 30% and 60% of milk produced. 24% and 13% of total cattle per herd were milking cows in the zero grazing and transhumance systems respectively. Median milk production per cow on one day was two (0–25) and two (1–3) litres. Median calf production interval was 14.5 (12–25) and. 21.5 (14–29) months. More milk produced per day represented the best economic opportunity in both systems while reduced age at first calving and longer lactation length were the next in both. Wastage of milk through spoilage from poor hygiene and lack of cooling was a major problem. Holstein cows, which were in the zero grazing system, had unexpectedly short lactations. Constraints identified led to the setting up of interventions of training and advice for farmers and of better nutrition.     

Availability and plant uptake of nutrients following the application of paper pulp and lime to tropical acid soils

Availability and plant uptake of nutrients were evaluated in three tropical acid soils (Kandiudult) amended with paper pulp and lime under greenhouse conditions. Amendments were applied to attain target pH values of 5.5, 6.0, and 6.5. A control treatment (no paper pulp or lime added) was also included. Rye grass (Lolium perenne L.) as a test plant was grown for three successive cycles of 40 days each. Extractable nutrients and cumulative nutrient uptake were determined. The application of paper pulp or lime resulted in a significant increase in exchangeable Ca and K and a decrease in exchangeable Mg and extractable Fe, Mn, and Zn. Amendment of soils with paper pulp or lime increased plant uptake of Ca and Mg and decreased that of K, Mn, and Zn. Both amendments behaved similarly, but the effect of lime seemed generally greater than that of paper pulp. Paper pulp in tropical acid soils behaved as a liming agent rather than an organic amendment. Similar to lime, amendment of soils with paper pulp resulted in an increase in availability of Ca and Mg and in a decrease in availability of K, Mn, and Zn for plants. Soil extractions appeared to be appropriate for assessing the availability of Ca, Mn, and Zn. Soil pH and effective cation exchange capacity positively influenced the availability of Ca and negatively the availability of Mn and Zn. Thus, the precision of predicting nutrient availability in paper pulp amended tropical acid soils could be improved by including soil pH or effective cation exchange capacity in relevant regression equations.