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Abstract The productivity of smallholder farming systems is held back by poor soil fertility, low input levels and erratic rainfall distribution in the sorghum-based cropping systems of the Sudano-Sahelian zone of West Africa. We assessed the sensitivity of current agricultural practices to climate change and to improved management practices: (i) increased fertilizer application combined with increased plant populations and (ii) use of improved sorghum varieties. We applied the Decision Support Systems for Agro-Technological Transfer (DSSAT) Cropping Systems Model, and the Agricultural Production Systems sIMulator (APSIM), for a multiple-farm assessment (i.e. diverse types of management and soils) in Koutiala (Mali) and Navrongo (Ghana), which are representative sites for West African sorghum production systems. Baseline climate data from observed weather (1980–2009) and future climates from five Global Circulation Models (GCMs: 2040–2069) in two Representative Concentration Pathways (RCP 4.5 and 8.5) were used as inputs for crop models. In Navrongo, under current management, sorghum yields either decreased or increased compared to the baseline, depending on the crop models and the GCMs; changes in management options induced a yield increase of up to 256%. The addition of genetic improvement resulted in further yield increases (24%). In Koutiala, sorghum yield changes for future climates ranged from −38 to +8% assuming current management. Shifting to an improved cultivar had a marginal effect on grain yields, while increased fertilizer rates resulted in grain yield increases ranging of 20% and 153% for DSSAT and APSIM, respectively, assuming the current climate. We conclude that in the Sudano-Sahelian zone of West Africa sorghum, as it is cultivated today, appears moderately vulnerable to climate change, while doubling fertilizer inputs with an adjusted planting density, in the current climate, would more than double yields. However, by exploring farm diversity we established that, under certain conditions, the effect of the future climate might be as important as the effect of management changes in the current climate, hinting at the importance of locally-relevant management practices.

Ants are a very diverse taxonomic group. They display remarkable social organization that has enabled them to be ubiquitous throughout the world. They make up approximately 10% of the world’s animal biomass. Ants provide ecosystem services in agrosystems by playing a major role in plant pollination, soil bioturbation, bioindication, and the regulation of crop-damaging insects. Over recent decades, there have been numerous studies in ant ecology and the focus on tree cropping systems has given added importance to ant ecology knowledge. The only missing point in this knowledge is the reasons underlying difference between the positive and negative effects of ants in tree cropping systems. This review article provides an overview of knowledge of the roles played by ants in orchards as functional elements, and on the potential of Oecophylla weaver ants as biological control agents. It also shows the potential and relevance of using ants as an agro-ecological diagnosis tool in orchards. Lastly, it demonstrates the potential elements which may determine the divergent negative and positive of their effects on cropping systems.

Rainfall uncertainty and nutrient deficiency affect sorghum production in Sahel. This study aimed at (i) determining the responses (varieties*water*nitrogen) of various West-African sorghum (Sorghum bicolor L. Moench) varieties to the application of fertilizer (NPK and urea) at selected growing stages according to water regime (irrigated or not, different rainfall patterns) and (ii) simulating them to define alternative fertilization strategies. This chapter proposes alternative fertilization strategies in line with rainfall patterns. Split plot experiments with four replications were carried out in two locations (Senegal), with four improved sorghum varieties (Fadda, IS15401, Soumba and 621B). Treatments were T1, no fertilizer; T2 = 150 kg/ha of NPK (15-15-15) at emergence +50 kg/ha of urea (46%) at tillering +50 Kg/ha of urea at stem extension; T3 = half rate of T2 applied at the same stages; T4 = 150 kg/ha of NPK + 50 kg/ha of urea at stem extension +50 kg/ha of urea at heading, and T5 = half rate of T4 applied at the same stages. Plant height, leaf number, grain yield, and biomass were signifi-cantly affected by the timing and rate of fertilizers. Grain yield were affected by water*nitrogen and nitrogen*variety interactions. It varied from 2111 to 261 kg/ha at “Nioro du Rip” and from 1670 to 267 kg/ha at “Sinthiou Malème”. CERES-Sorghum model overestimated late fertilizer grain yields. To achieve acceptable grain yield, fertilizers application should be managed regarding weather.

The aim of this study was to assess the potential of commercial mycorrhizal inoculants and a rhizobial inoculant to improve soybean yield in Kenya. A promiscuous soybean variety was grown in a greenhouse pot study with two representative soils amended with either water-soluble mineral P or rock P to assess product performance. The performance of selected mycorrhizal inoculants combined with a rhizobial inoculant (Legumefix) was then assessed with farmer groups in three agroecological zones using a small-plot, randomized complete block design to assess soybean root colonization by mycorrhiza, nodulation, and plant biomass production in comparison to rhizobial inoculant alone or with water-soluble mineral P. Greenhouse results showed highly significant root colonization by commercial mycorrhizal inoculant alone (p < 0.001) and in interaction with soil type (p < 0.0001) and P source (p < 0.0001). However, no significant effect was shown in plant P uptake, biomass production, or leaf chlorophyll index. In field conditions, the effects of mycorrhizal and rhizobial inoculants in combination or alone were highly context-specific and may induce either a significant increase or decrease in root mycorrhizal colonization and nodule formation. Mycorrhizal and rhizobial inoculants in combination or alone had limited effect on plant P uptake, biomass production, leaf chlorophyll index, and grain yield. Though some mycorrhizal inoculants induced significant root colonization by mycorrhizal inoculants, this did not lead to higher soybean yield, even in soils with limited P content. Our results are further evidence that inoculant type, soil type, and P source are critical factors to evaluate commercial inoculants on a context-specific basis. However, our results highlight the need for the identification of additional targeting criteria, as inoculant type, soil type, and P source alone were not enough to be predictive of the response. Without the identification of predictive criteria for improved targeting, the economic use of such inoculants will remain elusive.

Dans cette étude, nous étudions les changements de température et les précipitations extrêmes en Afrique de l'Ouest et du Centre (ci-après, domaine WAF) en fonction de la température moyenne mondiale en mettant l'accent sur les implications du réchauffement climatique de 1,5 °C et 2 °C conformément à l'Accord de Paris. Nous avons appliqué une approche de mise à l'échelle pour capturer les changements dans les extrêmes climatiques avec l'augmentation de la température moyenne mondiale dans plusieurs sous-régions du domaine WAF : Sahel occidental, Sahel central, Sahel oriental, côte de Guinée et Afrique centrale, y compris le bassin du Congo. En este estudio, investigamos los cambios en la temperatura y las precipitaciones extremas en África occidental y central (en adelante, el dominio WAF) en función de la temperatura media global, centrándonos en las implicaciones del calentamiento global de 1,5 °C y 2 °C según el Acuerdo de París. Aplicamos un enfoque de escala para capturar los cambios en los extremos climáticos con el aumento de la temperatura media global en varias subregiones dentro del dominio WAF: Sahel Occidental, Sahel Central, Sahel Oriental, Costa de Guinea y África Central, incluida la Cuenca del Congo. في هذه الدراسة، نقوم بالتحقيق في التغيرات في درجات الحرارة وهطول الأمطار القصوى فوق غرب ووسط أفريقيا (فيما يلي، مجال غرب ووسط أفريقيا) كدالة لمتوسط درجة الحرارة العالمية مع التركيز على الآثار المترتبة على الاحترار العالمي من 1.5 درجة مئوية و 2 درجة مئوية وفقا لاتفاق باريس. طبقنا نهج التدرج لالتقاط التغيرات في الظواهر المناخية المتطرفة مع زيادة متوسط درجة الحرارة العالمية في العديد من المناطق دون الإقليمية داخل نطاق منطقة غرب أفريقيا: الساحل الغربي والساحل الأوسط والساحل الشرقي وساحل غينيا ووسط أفريقيا بما في ذلك حوض الكونغو. In this study, we investigate changes in temperature and precipitation extremes over West and Central Africa (hereafter, WAF domain) as a function of global mean temperature with a focus on the implications of global warming of 1.5 °C and 2 °C according the Paris Agreement. We applied a scaling approach to capture changes in climate extremes with increase in global mean temperature in several subregions within the WAF domain: Western Sahel, Central Sahel, Eastern Sahel, Guinea Coast and Central Africa including Congo Basin.

AbstractHorticulture production in Senegal is an important agricultural activity that is mainly located in the Niayes zone. However, the increasing use of fertilizers and pesticides to boost production in order to meet a growing demand has many implications for the environment. The recognition of the negative impact this system of production has on the health of the soil and farmers, but also on the atmosphere with the emission of GHGs, has increased in recent years and some leading NGOs have started promoting organic farming systems. Therefore, the rising level of environmental hazards from conventional farming system made it attractive to farmers in the Niayes to adopt sustainable agriculture practices based on organic farming.A whole farm model is used to study the economic and environmental performances of the organic farming system compared to the conventional farming system in the horticulture production in the Niayes region in Senegal. The gross margin is regarded as the economic indicator, while carbon emissions are regarded as environmental indicators. The results indicate that the organic farming system will be economically more attractive to farmers in the Niayes compared with the conventional farming system only when a premium price is applied to organic crops. Simulation results also reveal that there exist a “win-win” situation for conventional farmers when they go for organic farming for certain types of crops. However, environmental results based on carbon emissions reduction show that organic system is found to be more effective in mitigating climate change.Our study suggests that, through appropriate investment in agro-ecological research to improve organic management and the establishment of a local organic market for organic crops, organic farming can be a very competitive alternative to conventional farming, when it comes to healthy food production with less environmental impact in the horticultural sector. However, further studies are needed on components of sustainable intensification to see which system of production is more profitable for farmers of the Niayes region, but also beneficial for the environment, and at regional and even national levels.