Forest-savannah Transition Zone Research Articles

Effect of anthropogenic activities on carbon stocks in protected areas within Ghana's forest-Savannah transition zone

Tropical forests play a significant role in climate change by sequestering atmospheric carbon dioxide. However, deforestation and forest degradation adversely affect these forests’ carbon stocks. Reports indicate that anthropogenic activities have led to forest degradation and deforestation in Boabeng Fiema Monkey Sanctuary (BFMS) and Kogyae Strict Nature Reserve (KSNR). This study assessed the effects of these activities on the carbon stocks of BFMS and KSNR. Using satellite imagery, field measurements and allometric models, carbon stocks of the study area were assessed from 1992 to 2023. The assessment revealed significant losses attributed to anthropogenic activities, such as hunting, farming and charcoal burning. BFMS experienced a total loss of 40,236 Mg C, while KSNR lost 272,109 Mg C. The closed forests had the highest carbon stock amongst the different vegetation types, with soil representing the most significant carbon pool in the protected areas, revealing the influence of vegetation structure on carbon sequestration and the need for soil conservation. The substantial carbon sequestration potential observed in the different vegetation types of the study area indicates that the Forest-Savannah Transition Zone is a prospective area for climate change mitigation aligning with the Sustainable Development Goals (Goals 13 and 15) and the National Climate Change Policy of Ghana. These findings provide valuable insights for carbon trading and biodiversity conservation, emphasizing the potential of nature-based solutions in addressing global climate challenges.

Maximizing Climate Solutions: Assessing Forest Plantation Productivity and Carbon Sequestration Potential of Tree Species

Climate change is projected to negatively impact forest ecosystems and related industries, emphasizing the urgency of effective mitigation strategies. Forests play a crucial role in climate change mitigation by sequestering carbon dioxide (CO2). Planting trees can contribute significantly, absorbing tonnes of CO2 annually and limiting climate change impacts. This process underscores the vital contribution of forests to mitigating climate change. The aim is to evaluate the role of forest plantation productivity in mitigating climate change and assess the carbon dioxide sequestration potential of some tree species. The carbon dioxide (CO2) sequestration potential of the tree plantations was highest in the moist semi-deciduous north-west (MSDNW) zone followed in a decreasing order by the dry semi-deciduous (DSD) and forest-savannah transition (FST) zones with the values being 23.02 ± 21.84 (SD), 11.16 ± 6.00 and 9.25 ± 5.25 Mg CO2eq ha-1 year-1, respectively. For the various tree species plantations, the CO2 sequestration potential exhibited by Cedrela odorata, mixed species and Tectona grandis stands was given as 36.93 ± 31.21 (SD), 19.06 ± 11.99 and 8.98 ± 4.67 Mg CO2eq ha-1 year-1, respectively. The comprehensive findings underscore the need for nuanced strategies in climate change policies and afforestation initiatives. Sustainable forest management, tailored afforestation practices are recommended to optimize forest plantation contributions to global climate goals.

Food-cash crop diversification and farm household welfare in the Forest-Savannah Transition Zone of Ghana

Food-cash crop diversification and farm household welfare in the Forest-Savannah Transition Zone of Ghana

Optimal Combination of Organic and Inorganic Fertilizers for Maize Yield in the Forest Savannah Transition Zone of Ghana

Optimal Combination of Organic and Inorganic Fertilizers for Maize Yield in the Forest Savannah Transition Zone of Ghana

Growth and Yield Response of Maize (Zea mays L.) to Integrated Nutrient Management of Biochar, Organic and Inorganic Fertilizers

Aims: Maize yield is largely influenced by integrated nutrient management of biochar, organic and inorganic fertilizers application. In view of this, field study to evaluate varying rates of chicken manure (CM), Gliricidia sepium biochar (GB) and NPK fertiliser on growth and yield of maize was carried out.
 Study Design: The study design was a 2 x 6 factorial arranged in Randomized Complete Block Design with three replications.
 Place and Duration of Study: The field study was carried out at Mampong- Ashanti in the Forest-Savannah transition zone of Ghana over 2 years in 2021 minor and 2022 major cropping seasons.
 Methodology: The study treatments were different rates of amendments using biochar, chicken manure and NPK (15-15-15) fertiliser; [10 t ha-1 CM, 300 kg ha-1 NPK, 2.5 t ha-1 GB, 150 kg ha-1 NPK + 1.25 t ha-1 GB, 1.25 t ha-1 GB + 5 t ha-1 CM and No fertiliser (Control)] which were applied to two maize varieties (Omankwa and Obatanpa). Physiological growth parameters (crop growth rate and relative growth rate) were determined. Vegetative growth parameter (leaf count) as well as yield and yield traits (number of lodged plants per plot, husked cob weight per plot, number of filled and unfilled cobs per plot and grain yield) were estimated.
 Results: The results revealed that the application of 10 t ha-1 chicken manure and 1.25 t ha-1 GB + 5 t ha-1 CM to Omankwa and Obatanpa maize outperformed in crop growth rate (RGR), relative growth rate (RGR) and leaf count compared to the unamended plots in both seasons. Omankwa had significantly higher filled cobs per plot than Obatanpa across seasons. The interaction of Omankwa and 10 t ha-1 CM and 1.25 t ha-1 GB + 5 t ha-1 CM gave higher number of filled cobs per plot than Obatanpa on same although not significantly different in both cropping seasons. The grain yield of maize was enhanced by soil amendments in the major and minor cropping seasons, especially with interaction of Obatanpa and 10 t ha-1 CM (7474.0 kg ha-1), (3473.4 kg ha-1) respectively. Obatanpa x 1.25 t ha-1 GB + 5 t ha-1 CM (6802.1 kg ha-1) interaction followed closely in grain yield in the major season.
 Conclusion: Both biochar, organic and inorganic fertilizers have varying effects on growth and yield of different maize varieties. For optimize maize grain yield, 10 t ha-1 CM or 1.25 t ha-1 GB + 5 t ha-1 CM application is recommended.

Cassava (Manihot esculenta) Yield, Nutrition, and Heavy Metal Bioaccumulation Responses to Circular Economy-Based Innovations in a Mining-Degraded Landscape

Mining operations in Ghana's Forest-Savannah Transition Zone have caused widespread land degradation, jeopardizing ecosystems, food security, and agroecological sustainability. In response, we conducted an experiment to evaluate the effects of biochar and poultry litter amendments on cassava (Manihot esculenta) growth, nutritional quality, and heavy metal accumulation at an illegal mining-degraded site in the Amansie Central District of Ashanti, Ghana. The experiment included five treatments: biochar (10 ton/ha), poultry manure (10 ton/ha), a biochar-poultry manure mix (1:1 ratio, 10 ton/ha each), and two control groups (degraded and forest sites). The combined biochar and poultry manure treatment yielded the highest cassava stover biomass (22.9 ton/ha) during the first year. Nutritional characteristics of cassava such as %carbohydrate, %protein and %total ash tubers were influenced by treatment amendments. Additionally, biochar and poultry manure reduced the accumulation of Arsenic (As) by 168.9% and Lead (Pb) by 149.8% in cassava compared with galamsey soil control. This study showcases a circular economy-based approach that employs locally available resources to restore mining-degraded landscapes and enhance regenerative agricultural practices, reducing waste, bioaccumulation of heavy metals and improving carbon sequestration. Promoting the use of biochar and poultry manure amendments for ecological restoration in mining-degraded areas can contribute to sustainable land use, food security, and livelihoods. Policymakers should consider these strategies to align with global and national development goals while improving food systems and ecosystem services. Future research should explore the long-term impacts of cassava cultivation on amended mining sites and assess the potential of these amendments for agroecological enhancement and heavy metal immobilization.

Farm typology and structure of farmer decision making: The case of the production basin of the forest-savannah transition zone, Centre Cameroon Region

Despite having a similar environment, not all of the farmers in a given region have the same history. They don't always share the same traits, and they don't always have the same access to land or diverse natural environment resources. This study aims to describe how agricultural production is organized in the Mbangassina-Ntui-Batchenga-Obala areas to improve food security, where agriculture is the primary economic activity. On 180 farms, mixed data were gathered, and a factorial analysis of the mixed data, along with a hierarchical ascending classification, allowed for the differentiation of 4 groups of farms. Farms in Type 1 (44.44%) have an average size of 2.51 ha, are predominately run by men, primarily employ family labor, and have the highest proportion of farmers. The majority of Type 3 farms (34.44%), which have an average area of 6.62 ha, are run by men and mostly employ family labor. The producers in this group are vulnerable to climate change and lack adaptation plans. Finally, 4 types of farms, which have an average size of 10.9 ha and are operated by both men and women utilizing family labor, account for 5.56% of all farms. All of these farmers are creating adaptation strategies as they recognize the effects of climate change. Through a correct understanding of the reasons that underpin the diversity of farms, this classification serves as a basis for the design of appropriate public policies. Taking into account this diversity of agricultural situations in the northern part of the Centre Cameroon Region is essential for the success of research and rural development operations. In addition, it would allow a more relevant use of typologies of knowledge on farms as a tool for sustainable development and decision support.

Soil suitability assessment for sustainable intensification of maize production in the humid Savannah of Ghana

In sub-Saharan Africa (SSA), food security is a significant challenge due to unreliable rainfall and depleting soil fertility. Most of the soil resource in the sub-region which constitutes majority of the fields of smallholder farmers is degraded. Hence, there is a need to identify suitable soils for sustainable intensification. The objectives of this study were to: (i) evaluate the suitability and fertility constraints of soils and (ii) discuss the influence of soil properties on maize production in the Nkoranza (north and south) district. A total of sixty (60) soil samples were sampled from smallholder farms under careful consideration of topography and the spatial pattern of land use systems. The evaluation of soil suitability was carried out using climate (temperature and rainfall) and physico-chemical characteristics of soils for maize (Zea mays) production. The results indicated that soil texture varied from sandy loam to sandy clay loam. Soil organic carbon concentration (SOC) ranged between 0.55 and 2.02%. Total nitrogen (TN) and SOC were low in all soil types except in the Bediesi series (Haplic Luvisol). Base cations (Ca2+, Mg2+, Na+, and K+) were low and varied between soil types. Although climatic factors and physical properties were highly suitable (S1), more than half of the pedons were moderately suitable (S2). The soils functioned at a moderate capacity for maize production. The major limitations identified were sub-optimal and related to soil fertility (CEC). Pearson correlation revealed a relationship between parametric actual index (PAI) and parametric potential index (PPI; r = 0.940, p < 0.003) and between soil resilience index (SRI; r = 0.768, p < 0.037) and the relationship between these variables is a perfect correlation. Soil management is required to increase maize yield in the study area. Soil erosion prevention measures such as cover crops, mulching, organic manure (poultry), and mineral fertilizer application are recommended to improve soil fertility in the Nkoranza (north and south) district. This study can inform policies and interventions geared toward sustainable agricultural intensification. Land and soil are heterogeneous and any decision on intensification in this study accounted for the prevailing local conditions of the study area. Therefore, indexing soil suitability using climate (rainfall and temperature), physical land characteristics (topography, drainage) and chemical properties (pH, SOM, SOC, TN, Av. P, Av. K, etc.) of soil resources for sustainable intensification of maize is proposed for smallholder farming communities of Nkoranza (north and south) districts in the Forest-Savannah Transition Zone of Ghana.

Vulnerability of family farming systems to climate change: The case of the forest-savannah transition zone, Centre Region of Cameroon

Family farms are especially vulnerable to the negative effects of climatic variations and changes. In this regard, this paper assessed the factors that influence family farmers' vulnerability to climate variability and change in the transition zone between forest and savannah in the northern part of the Centre Region of Cameroon. The study did this by combining primary data (gathered from a survey of 180 smallholder farmers) with secondary data (information on temperature and rainfall). Field observations were also conducted on these family farms in Mbangassina, Ntui, Batchenga, and Obala from January to March 2020, March to May 2021, and July to September 2021. We used statistical tools for both descriptive, multivariate and inferential analyzes. Small farmers have faced the highest temperatures and heat waves. Everybody living in this community is exposed to the same temperatures and heat waves. Maybe smallholder farmers are susceptible or vulnerable to these heat waves and high temperatures. Extreme droughts, which are becoming more often, and diminishing rainfall totals were assumed to be the key contributors to climate sensitivity. According to the findings, family farms in Obala are just marginally vulnerable to climatic variability and change (1.1 vulnerability score), whereas those in Batchenga, Ntui, and Mbangassina have considerable vulnerability indices (2.16, 2.17, and 2.99 vulnerability scores respectively). A significant noncausal correlation exists between vulnerability and four and five continuous and discontinuous explanatory factors, respectively. The binomial logistic regression model demonstrates statistically significant inverse causal links between five of the six explanatory factors and the sensitivity of family farmers to climate change. According to the model, useful agricultural area (β = −0.348, p < 0.0001), soil fertility (β = −0.568, p < 0.05), Dioscorea spp. (β = −0.926, p < 0.05), precipitation during these 10 to 30 years (β = −0. 582, p < 0.05), and annual income (β = −0.002, p < 0.01) all contributed to lessening smallholder farmers' vulnerability to unfavorable climate variability and change. The drought variable has a significant positive causal relationship. This leads to the conclusion that these six explanatory variables largely impact smallholder farmers' vulnerability to climate fluctuation and change. According to the study's conclusions, family farmers should be given more financial help and reliable climatic information to reduce their vulnerability to climate fluctuation and change.

Spatial variability of the occurrence of lesions on cattle carcasses in association with pre-slaughter factors in the forest–savannah transition zone

Spatial variability of the occurrence of lesions on cattle carcasses in association with pre-slaughter factors in the forest–savannah transition zone

Duration of Cultivation Has Varied Impacts on Soil Charge Properties in Different Agro-Ecological Zones of Ghana

Agricultural expansion into natural habitats causes soil fertility decline after a period of cultivation. This study investigated changes in soil exchange properties in different farm types at Dompem and Adansam in the Forest and Forest–Savannah transition zones of Ghana as influenced by the duration of cultivation. Sixty farms were selected for soil sampling through a reconnaissance survey. The soils were subjected to physicochemical analysis. The results showed that the Dompem soils were loamic, had more amorphous Fe and Al oxides, were strongly acidic and had low contents of exchangeable acidity, a low sum of exchangeable bases (SEB), low effective cation exchangeable capacities (ECECs) and low available P. Conversely, the Adansam soils were arenic, slightly acidic and had relatively higher SEBs and ECECs. Interestingly, soil organic carbon (SOC) in the Dompem soils declined by &gt;10% in relation to the duration of cultivation and showed rapid reductions within three years. Correspondingly, soil bulk density, CEC and SEB declined. In Adansam soils, only δpH declined in relation to the duration of cultivation. Soil organic carbon accounted for &gt;50% of the ECEC and 49% of the SEB in Dompem soils but 36% of δpH in the Adansam soils. In conclusion, agricultural expansion, manifested in the duration of cultivation, mainly influenced soil charge properties through SOC decline.

Cashew expansion holds potential for carbon stocks enhancement in the forest-savannah transitional zone of Ghana

Despite the scientific contributions of earlier studies to the understanding of shifts in land-use to cashew in the forest-savannah transition zone, some questions remain unanswered: (1) what is the extent of landscape-level conversions associated with cashew? (2) could the expansion of cashew in the forest-savannah transitional zone potentially serve as a carbon mitigation strategy relative to other land uses at the landscape level? and (3) how does the land use dynamics associated with cashew development hold implications for Ghana’s climate change mitigation strategies? The Wenchi Municipality was used as a case study. Landsat images for 2000, 2015 and 2020 were classified to produce land cover maps using the random forest algorithm to overall accuracies of 72.6 %, 86.9 % and 91.2 %, respectively. The InVEST software was used to estimate the carbon sequestered by each land cover class in the landscape. Finally, 150 cashew farmers, four focus group discussions and key experts were interviewed. The results show that cashew plantations had increased in the Municipality by 31103.05 ha between 2000 and 2020. The shift in land use towards cashew increased the Above Ground Carbon from 599956.73 tons to 1039402.32 tons between 2000 and 2020, representing 696219.15 tons (883.5 %) increase in the Municipality. According to the farmers, the shift in land use to cashew was mainly due to the available ready market and relative higher income. This suggests that, there is great potential for mitigating climate change in the forest-savannah transitional zone using cashew. Hence, Ghana needs to explore the gains associated with cashew plantations, particularly as it transforms low-income crops with challenging post-harvest and marketing constraints into relatively lucrative income generation cashew, which has major implications for improvements in livelihood and co-benefits for carbon stocks enhancement. Ultimately, as Ghana rolls out its Nationally Determined Contributions implementation among other forestry sector climate change mitigation interventions, it is important to consider the role of cashew as a major contributor to carbon stocks enhancement within the Forest–Savannah transitional zone. This study provides major decision support for formulating policies, interventions, and measures to promote climate change and livelihood improvement opportunities while rolling out safeguard measures to prevent further conversion of relatively high carbon stocks landscapes, such as the savannah woodlands within the forest-savannah transitional zone.

Impact of rainfall variability and land-use changes on river discharge in Sanaga catchment (forest–savannah transition zone in Central Africa)

Abstract Climate change/variability and land-use changes are the main forcings of river discharges variability. However, an understanding of their simultaneous impacts on river discharges remains limited in some parts of the world like in Central Africa. To shed light on this issue, the objective of this article was to investigate the effects of rainfall variability and land-use changes on river discharges in the Sanaga watershed (at Song Mbengue and Nachtigal gauging stations) and some of its sub-watersheds (Mbakaou, Lom Pangar, Magba and Bamendjing) over the 5 or 7 recent decades (depending on the data availability). To achieve this goal, hydrometeorological data of the Sanaga watershed and sub-watersheds were analyzed using the Pettitt and Mann-Kendall tests. Likewise, land-use changes in the watershed and sub-watersheds were also analyzed using supervised classifications of Landsat satellite images of the watersheds at two periods (1984 and 2020). The results show that annual rainfall decreased throughout the Sanaga watershed. This decrease is only statistically significant for the Sanaga watershed at Nachtigal (−5%), for which the study focused on relatively longer hydropluviometric series, including the 1950 and 1960s (wet decades). However, although the rainfall decreased in this watershed, the flows increased insignificantly according to the tests used in most cases. The 2010s seems particularly concerned by this increase, including in the Sanaga watershed at Nachtigal, where the general trend is downward. The flows increase in the Sanaga watershed would be the consequence of the increase in impervious areas in the latter (between +181.3 and +1,300% for built and roads and between +4.1 and +11.9% for bare soils), which would compensate for the drop in precipitation by increasing runoff. These results could be used for long-term planning of water demand and use in this watershed, as well as for improving future simulations of flows.

Pigeonpea (Cajanus cajan) and white yam (Dioscorea rotundata) cropping system: Improved resource use and productivity in Ghana

Yam production along the West African yam belt is challenged with deteriorating soil fertility and unavailability of stakes, resulting in decreased yam productivity, and farmers' livelihood. This study evaluated resource use and yam productivity in pigeonpea-yam cropping systems in Ghana's forest and forest-savannah transition zones from 2017 through 2019 cropping seasons. Pigeonpea was established either in an alley or as a border during the 2017 cropping season, while yam was cultivated in 2018 and 2019. A split-plot design of cropping system (yam planted in alleys of pigeonpea—PA; yam planted with pigeonpea as a border—PB and sole yam) as main-plot treatments and chemical fertilizer (0–0–0; 23–23–30; 45–45–60 N-P2O5-K2O kg ha−1) as subplot treatments were used for the study. Productivity data on pigeonpea and yam were collected. The results revealed significantly higher leafy biomass and correspondent higher N content and N due to fixation in PA fields than PB fields in both locations and seasons. The presence of the pigeonpea and its biomass resulted in a significant suppression of ridge erosion and weeds, while soil moisture and nutrients improved, resulting in increased yam tuber productivity than in sole yam production. Further, planting yam with pigeonpea and half (23–23–30 N-P2O5-K2O kg ha−1) the recommended fertilizer rate significantly improved tuber yield and productivity than planting sole yam with full recommended fertilizer level in both locations and seasons. Promoting and adopting the pigeonpea-yam cropping system could sustain soil fertility, provide readily available stakes to address the constraint of deforestation and land degradation associated with yam production.

Cash crops and food security: evidence from smallholder cocoa and cashew farmers in Ghana

BackgroundFood security is a major development concern worldwide. The use of arable lands to grow cash crops raises additional concerns, yet empirical evidence on the relationship between cash cropping and food security remains inconclusive. Using survey data from 408 randomly sampled households, this paper assesses the income and food security implications of reviving cocoa farming in the Forest-Savannah Transition Zone of Ghana. In addition, the paper examines the influence of socioeconomic factors and diversification into cashew on the food security of cocoa households. Data was collected from 12 rural communities, where food crop production was the main source of livelihood. A causal-comparative design was used. Food security was measured using the USDA Food Security Core Module.ResultsContrary to the literature that cash crops undermine food security, findings indicate a positive relationship between cocoa farming, household crop income and food security, highlighting complementarities between cocoa, food crop and cashew production. Although income from cocoa alone was not sufficient enough to guarantee food security, it enhanced the financial ability of farmers to diversify into cashew and expand food crop production. This minimised market dependency for food staples, enhanced annual crop income, and ensured a continuous flow of income. Overall, the food security advantage of cocoa farming was predicted by diversification into cashew, displacement of food crops using cocoa, socioeconomic factors, such as land ownership, livestock ownership, and formal education; and marginally by total annual crop income.ConclusionsIncome from cocoa alone is not high enough and widely distributed to guarantee food security. Reinvesting the returns from cocoa in cashew and food crops seems to be a more reliable pathway to enhancing food security than merely depending on the income to buy food. A semi-subsistence system that ensures optimum combination of cash and food crops is, therefore, recommended, but this may require sufficient access to land.

Determinants of crop choice decisions under risk: A case study on the revival of cocoa farming in the Forest-Savannah transition zone of Ghana

The revival of cocoa farming in the Forest-Savannah Transition Zone (FSTZ) of Ghana despite high production risk raises questions on the factors underlying it, and whether the renewed interest in cocoa can be sustained. This paper examines the reasons that underlie households’ decision to farm cocoa or otherwise in the FSTZ, and how risk perceptions, demographic factors and livelihood assets predict such crop choice decisions. Methods of data collection include household surveys and key informant interviews. Four hundred and eight household heads and 32 key informants were interviewed in 12 farming communities. Findings indicate divergent crop choice decisions on cocoa among farming households. While market security generally created a strong incentive for cocoa farming, some households exhibited risk aversion by avoiding or abandoning cocoa farming. The decision to farm cocoa was negatively predicted by perceptions of drought and lack of money as the most severe risk factors of cocoa farming, the sex of the household head (being a female) and lack of land ownership and social network with cocoa farmers. Currently, it appears the renewed interest in cocoa farming can be sustained, especially considering market uncertainties for alternative crops (cashew and food crops). This may, however, not be the case in the long term. More households are likely to avoid or abandon cocoa farming if climate and food security risks should worsen as projected, and more so if the cashew market is stabilised by government. Cocoa investment programmes in the FSTZ aiming at long-term sustainability ought to target households that are more likely to farm cocoa under high production risk. Such programmes may also attract new farmers and sustain their interest in cocoa farming by enhancing their access to land, capital, and irrigation facilities (for managing drought). At the moment, crop diversification (towards cashew and food crops) rather than crop switching is needed to manage the climate, market and food security risks confronting farmers. Overall, the paper contributes to a better understanding of the determinants of farmers’ crop choice decisions on cocoa in the context of multiple risks.

High Prevalence of Asymptomatic Plasmodium Falciparum Malaria in Makenene, a Locality in the Forest-Savannah Transition Zone, Centre Region of Cameroon

High Prevalence of Asymptomatic Plasmodium Falciparum Malaria in Makenene, a Locality in the Forest-Savannah Transition Zone, Centre Region of Cameroon

High prevalence of asymptomatic Plasmodium falciparum malaria in Makenene, a locality in the forest-savannah transition zone, Centre Region of Cameroon

Malaria transmission and prevalence is still not well documented across Cameroon particularly in medium-sized cities or localities representing high transit zone. Different risk factors could be associated with persistence malaria transmission such as population movement from high to low transmission settings. A cross-sectional community-based study was carried out to determine malaria prevalence and risk factors in Makenene, a small city in a forest-savannah which is a crossroads between different parts of the country where travellers usually stop-over day and night to rest. Using malaria diagnostic test (mRDTs from SD-BIOLINE) and microscopy (thin and thick blood smears), 406 participants from 237 households were tested for malaria infection. The prevalence of malaria was high irrespective of the detection method: mRDT (41.87%) or microscopy (38.42%). At household level, 46.41% of households had at least one case of malaria with an average of 1.41 infected individuals per household. Parasite density was also high with the majority of infected individuals (64.74%) bearing more than 500 parasites/μl. Only Plasmodium falciparum was found. The chances of being infected with malaria parasites was almost the same for all participants irrespective of the sleeping behavior, bednet usage, house type and environmental factors. The study supports high malaria transmission in the locality and the need for additional studies on vectors bionomics and transmission patterns.

Sustaining maize yields and soil carbon following land clearing in the forest–savannah transition zone of West Africa: Results from a 20-year experiment

Sustainable alternatives to slash-and-burn shifting cultivation in the (sub)humid tropics rely on the use of external nutrient inputs to address soil fertility decline. The use of organic inputs is widely accepted as a practice to improve soil fertility, in particular soil organic carbon (SOC). On the other hand, its combined use with mineral fertilizer has the potential to maintain or increase crop productivity through positive interactive effects between both resources. Few studies have investigated these effects in the long term. Therefore, the objective of this study was to investigate whether maize productivity and soil SOC can be sustained under permanent cropping with sole and combined use of compost and mineral nitrogen (N) fertilizer. Here, we report results from a long-term experiment carried out in Gagnoa, Ivory Coast, from 1971 to 1990. The experiment followed a randomized block design comprising eight replicates of 12 treatments. The two studied factors were compost (0 or 10 t DM ha−1 yr−1) and mineral N (0, 40, 80, 120, 160 or 200 kg N ha−1 yr−1) additions. Average maize grain yields of the first cropping cycles were significantly lower without compost (5.05 ± 1.57 t ha−1) than with compost addition (6.07 ± 1.31 t ha−1). The annual yield variability as shown by the standard deviation of the mean was reduced by 20% with compost addition. Without compost, 53% of the initial SOC stock in the 0–20 cm soil layer was lost, resulting in a SOC loss rate of − 0.62 t C ha−1 yr−1 compared to 21% with compost (−0.27 t C ha−1 yr−1). Compost addition therefore reduced SOC loss with an apparent SOC storage rate of 0.35 t C ha−1 yr−1. The conversion rate of organic carbon (OC) inputs to SOC was about 12%. The Introductory Carbon Balance Model (ICBM) reproduced well SOC dynamics, especially without compost. Without mineral N and without compost, maize grain yield decreased with decreasing SOC concentration until the introduction of leguminous crops in the second cropping cycle. We conclude that combined application of compost with mineral N fertilizers was effective at maintaining maize productivity but inadequate to prevent the decline of SOC stocks, despite large additions. Leguminous crops in the rotation were key for maize productivity, but probably due to effects non-related to supplementary N supply.

Socio-economic assessment of different cocoa agroforestry systems in the forest-Savannah transition zone in central Côte d’Ivoire

ABSTRACT Cocoa production in Côte d’Ivoire is generally based on “full sun” crops. However, the presence of traditional agroforestry systems based on cocoa (AFSc) has been highlighted in several regions including the Centre and Centre-West. This study aimed to provide information on the financial profitability and the potential economic value of simple, mixed and complex AFSc types identified in central Côte d’Ivoire. A socio-economic survey and direct observations carried out among farmers with these AFSc types, revealed an annual average cocoa production of 207.7 kgha−1 (i.e. US$323.9). This income does not vary significantly from one type to another. Fruit species associated with cocoa trees yield an average of US$32.39 ha-1yr-1. This fruit contribution is more important in simple AFSc than in the two other types. Considering the profitability of cocoa trees and associated species, no system is more profitable than the other. However, the potential economic value of the stored carbon and the other benefits that the complex AFSc type provides to farmers make this type more efficient and sustainable than the two others considering ecosystem services. We therefore recommend that payment for ecosystems services be considered if one would like to promote complex cocoa agroforestry systems in the study areas.