Agro-ecological Zones Of Cameroon Research Articles

Agro-ecological Differentials in Soybean Crop Evapotranspiration and Implications for Adaptation to Climate Change

This study estimated soybean crop evapotranspiration from weather data using the cropwat model. The effects of reference evapotranspiration, crop coefficients, and yield response factor were quantified for three different agroecological zones in Cameroon. The evapotranspiration of soybean was observed to be 281.03 mm in the farming district of Ambam, 387.7 mm in Bamenda and 605.3 mm in Garoua, indicating pronounced differences in the agro-ecologies. Across the three regions studied, rainfall pattern determines soil water reserves and crop water uptake. In the farming zones of Bamenda and Ambam, water requirement for soybean are met by the rainfall. In the northern region of the country, irrigation needs are high. As a consequence, actual crop evapotranspiration is greatest in the hot dry zone of Garoua and lowest in the cool humid region of Bamenda. From this study it could be concluded that coping with climatic variations and future climate change will require complementary irrigation as well as improved crop management practices.Keywords: soybean, climate variation, crop water requirements, Cameroon

Pseudomonads and symbiotic micro-organisms as biocontrol agents against fungal disease caused by Pythium aphanidermatum

Experiments were undertaken to assess the antagonistic aptitude of Pseudomonas spp. alone or associated with mycorrhizal fungi on Pythium aphanidermaturm, the causal agent of seedlings damping-off and stem rot of cowpea (Vigna unguiculata L. Walp). Evaluation was made using selected strains of pseudomonad (Pseudomonas fluorescens, P. putida and Pseudomonas sp.) isolated from V. unguiculata andSolanum tuberosum rhizospheric soils collected in three agroecological zones of Cameroon. Cultures were conducted on agar plates and in liquid media to evaluate the antagonistic capacity of those strains against Pythium aphanidermaturm and to evaluate their biocontrol activity in protecting cowpea plants. The results showed a direct inhibition of the pathogenic fungus by these bacteria. P. fluorescens used alone against Pythium aphanidermaturm, provided a reduction of the disease index from 3.44 to 1.06. When the arbuscular mycorrhizal fungi Glomus deserticola is associated to P. fluorescens, the disease index dropped to 0.13, confirming the synergistic effect of those beneficial micro-organisms. Key words: antagonism, beneficial micro-organisms, biological control, Glomus deserticola, Pseudomonas spp., Pythium aphanidermaturm.

Pseudomonads and symbiotic micro-organisms as biocontrol agents against fungal disease caused by

Experiments were undertaken to assess the antagonistic aptitude of Pseudomonas spp. alone or associated with mycorrhizal fungi on Pythium aphanidermaturm, the causal agent of seedlings dampingoff and stem rot of cowpea (Vigna unguiculata L. Walp). Evaluation was made using selected strains of pseudomonad (Pseudomonas fluorescens, P. putida and Pseudomonas sp.) isolated from V. unguiculata and Solanum tuberosum rhizospheric soils collected in three agroecological zones of Cameroon. Cultures were conducted on agar plates and in liquid media to evaluate the antagonistic capacity of those strains against Pythium aphanidermaturm and to evaluate their biocontrol activity in protecting cowpea plants. The results showed a direct inhibition of the pathogenic fungus by these bacteria. P. fluorescens used alone against Pythium aphanidermaturm, provided a reduction of the disease index from 3.44 to 1.06. When the arbuscular mycorrhizal fungi Glomus deserticola is associated to P. fluorescens, the disease index dropped to 0.13, confirming the synergistic effect of those beneficial micro-organisms.

Farmers' perceptions of cassava pests and indigenous control methods in Cameroon

A survey of farmers' views on cassava pests was conducted in 61 locations in four cassava-producing agro-ecological zones in Cameroon. Farmers in all zones considered vertebrates, grasshoppers and cassava root rot as their most important pest and disease constraints. Weeds, although cited in all zones, received relatively low ratings. Damage caused by the cassava green mite (CGM) [Mononychellus tanajoa Bondar (Acari: Tetranychidae)], was recognized but its cause was unknown. The cassava root scale [(Stictococcus vayssierei Richard (Homoptera: Stictococcidae)] was important only in the semi-humid forest zone. Farmers control pests using cultural methods including trapping, scaring, poisoning and burning for vertebrates, hand picking for grasshoppers, and burning, hand weeding and long fallows for weeds. In most cases, root rot occurred after cassava reached maturity, and farmers recognized the importance of timely harvesting to control crop losses. Cassava diseases such as cassava mosaic disease (CMD), cassava anthracnose disease (CAD), and cassava bacterial blight (CBB), although recognized, were not considered as serious constraints. However, entomologists and the other researchers found CGM to be the most important arthropod pest overall, causing serious damage to cassava. Damage due to vertebrates was also found but not to the extent that farmers reported. It was apparent that farmers considered highly visible pests such as vertebrates and grasshoppers more important than less visible ones such as CGM. The need to educate farmers about small arthropod pests and their damage/importance was clear. Therefore IPM programmes aimed at cassava pests should involve consideration both of the importance farmers attach to each pest and of the education farmers receive concerning the prevailing pest situation.

Physico-chemical properties of the African pear and Black olive from different agro-ecological zones of Cameroon

Introduction. Dacryodes edulis and Canarium schweinfurthii are two tropical multi-purpose trees in Cameroon which produce fruits (African pear and Black olive, respec- tively) for human consumption, which are marketed more and more on the national and international markets. This study aimed at characterising these two fruits starting from their physical and chemical properties. Materials and methods. Fruits were collected during the harvest peak in three agro-ecological zones of Cameroon. The physical properties measured were the weight, the length, the fruit circumference and the pulp thickness, while the chemi- cal analyses included the moisture and protein, lipid and ash contents. Results. The fruits from the humid forest were largest (96 g), whereas the smallest came from the grassland (54 g). The highest pulp per fruit content (69% for the African pear and 57% for Black olive) was observed in fruits harvested in the humid forest zone. The strongest correlation (r = 0.25) between the fruit weight and that of pulp was observed for Black olive produced in the humid forest zone. The crude protein rate was highest (8%) in fruits from the humid forest, whereas that of the lipids (42%) prevailed in the semi-forest zone. Conclusion. The humid forest zone offers the best agro-ecological conditions for commercial production of the fruits of D. edulis and C schweinfurthii. These two fruits contain proteins and lipids in significant quantities and can, consequently, be used as alternative sources for these nutritive elements. Cameroon / multiple-use trees / Dacryodes edulis / Canarium schweinfurthii / fruits / proximate composition

Fusarium pallidoroseum in maize samples of three agro-ecological zones of Cameroon

Investigations were conducted to determine the presence of mycotoxigenic fungi in maize samples from Cameroon. The deep freezing blotter method, and the medium DG-18, with and without 1% sodium hypochlorite surface sterilization pre-treatment, were used. The plated grains were incubated for 7 days under a cycle of 12 h (NUV) daylight and 12 h darkness. Fusarium pallidoroseum was found infecting 1–2% of the tested grains. Eleven samples out of 65 tested were found infected, 2 samples from the locality of Melong in the humid forest agro-ecological zone with monomodal rainfall, 1 from Foumbot and 2 from Bamenda in the highlands agro-ecological zone, and 6 from Yaounde, in the humid forest with bimodal rainfall agro-ecological zone. An infection rate of 2% of the grains was found on blotter paper while only 1% was recorded on the reduced water activity medium DG-18, with or without surface sterilization. F. pallidoroseum is reported here for the first time from maize samples of Cameroon. This underlines the need for detailed research on toxigenic fungi and the improvement of common storage practices to avoid mycotoxin contamination and the resulting human and animal health problems.

Variations in the yielding ability of sweet potato clones in grassland and forest ecologies in Cameroon

Twenty sweet potato genotypes were evaluated for four years in seven locations representing three agro-ecological zones in Cameroon, to study their performance across environments, to identify cultivars suitable for the different zones and to study their reaction to weevils and viruses in target sites. The best storage root yields (13.3 t ha−1) were in the humid forest region and the lowest (7.4 t ha−1) in the grassland region. Storage root counts were about the same in the humid forest and in the grassland regions. Root yields were not affected by weevil attack, but virus severity was associated with storage root yield depression. Shukla’s stability method was less conservative than the Eberhart-Russell method of assessing stability. The genotype grouping technique of Francis and Kannenberg was considered easier to use in grouping clones into classes of desirability and stability. The study suggests that it may not be necessary to select separately for different agro-ecological zones because high yieldin...