Limited food availability

While food security is a major worldwide issue, it is a much more serious problem in Low-Income (LI) and Lower Middle-Income (LMI) countries. Currently, sub-Saharan Africa is the sub-continent with the highest proportion of undernourished people, the largest gap between current and potential yields, and between cereal consumption and production. Looking to the future, population growth and climate change may worsen the situation, particularly in Africa. African countries are still facing rapid population growth with uncertain prospects about the ability of their agriculture to meet growing food demand. In addition, without sufficient adaptation measures, climate change will negatively impact food production in most African regions

Climate smart agriculture from field to farm scale: a model based approach for Southern Africa. [P40]

Southern Africa (SA) is expected to be particularly impacted by climate change projecting a 40% decrease in rainfall in critical areas over the next 70 years and maize productivity falling by up to 30% by 2030. The high variability in agro-climatic conditions, farming systems and rural livelihoods in SA represents a challenge in the generation of locally adapted climate-smart cropping systems. To explore and test adaptation strategies to climate change at the farm level, and to assess the role of alternative maize-based cropping systems, an interdisciplinary approach was developed that consists of loose coupling of cropping systems and farm household models. Using data from long-term agronomic field trials, the crop growth model APSIM was calibrated to simulate a wide range of maize-based cropping systems for different agro-ecologies and climate change scenarios. At the farm household level, the efficient frontier analysis was used to identify efficient farming systems which minimize their inputs utilization and negative externalities (erosion and greenhouse gases) and at the same time maximize their production. Our approach takes advantage of the prediction potential of field-scale models to generate thousands of simulated maize based cropping systems, and an optimization method to benchmark farm-level performance and eco-efficiency. Compared to common linear programming methods (e.g. profit maximization), we simulate more sophisticated farmer's strategies (e.g. trade-offs between market sales and food self-sufficiency, between use of crop residues for soil fertility and animal feed) based on data from a 500 farm household survey recently conducted in SA. This framework, taking into account long term cropping systems effects and efficiency frontier analysis at the farm scale, allows identifying practices and pathways for climate smart agriculture in this vulnerable region. (Texte intégral

Labour burden not crop productivity increased under no-till planting basins on smallholder farms in Murehwa, Zimbabwe

No-till planting basins are promoted using seed and fertiliser inputs as incentives for their widespread uptake in Zimbabwe. Notill planting basins are planting holes measuring 15 cm width x 15 cm length x 18-20 depth, spaced 60 cm within the row and 75- 90 cm between rows leaving up to 90% of the soil surface undisturbed. They are intended to conserve moisture and improve the targeting of nutrient application. We evaluated the effect of planting basins on crop yield and labour requirement in an on-farm experiment over two seasons in Murehwa district, Zimbabwe. The experiment was established in clay and sandy soils, in two fields types; degraded and better managed fields in 2009/2010 and 2010/2011 seasons. Two tillage treatments i.e mouldboard ploughing and no-till planting basins were tested. Tillage plots measured 1080 m2 (18 m x 60 m) and labour hours were derived by direct measurement in these plots. Due to grazing in the dry season, soil surface cover by crop residues in the experimental fields was less than 10% in both seasons. Previous field management, nutrient management in the experiment and season had a significant effect on crop yields (p <0.001); there was no significant effect of tillage. The largest maize grain yield of 5.6 t ha-1 was obtained with a combination of 3 t of manure and 60 kg N ha-1 under conventional tillage the equivalent treatment under planting basins yielded 4.6 t ha-1 in the 2009-2010 season. Rainfall was poorly distributed in 2010-2011 season and the same treatment gave the largest grain yield of 1.6 t ha-1 under conventional tillage and 1.2 t ha-1 under no-till planting basins. Land preparation under conventional tillage required 6 man days ha-1 while making planting basins required 27 man days' ha-1 for the clay soils and 15 man days ha-1 for the sand soils. Weeding in planting basins required 40% more labour compared with conventional tillage (12 man days ha-1) due to greater weed densities associated with no-tillage. Planting basins did not enhance moisture conservation in a the 2010-2011 season when rainfall was poorly distributed. The increased labour requirement suggests it is unlikely that farmers will abandon the plough in favour of the hand hoe especially if they own cattle. Planting basins are easier to make in sandy soils and require less labour than in clay soils. Conversely, they are easier to maintain in clay soils than in sandy soils. Although planting basins were practiced by about 98% of farmers, the maximum land size allocated to planting basins was only 0.2 ha per farm, 10% of the landholding at most. Given that planting basins increase the labour burden but not crop yield, widespread adoption by smallholder farmers seems unlikely. (Texte integral

Effect of tillage practices on the soil carbon dioxide flux during fall and spring seasons in a Mediterranean Vertisol

In this study, we assessed the effect of conventional tillage (CT), reduced (RT) and no tillage (NT) practices on the soil CO2 flux of a Mediterranean Vertisol in semi-arid Morocco. The measurements focused on the short term (0 to 96 h) soil CO2 fluxes measured directly after tillage during the fall and spring period. Soil temperature, moisture and soil strength were measured congruently to study their effect on the soil CO2 flux magnitude. Immediately after fall tillage, the CT showed the highest CO2 flux (4.9 g m-2 h-1); RT exhibited an intermediate value (2.1 g m-2 h-1) whereas the lowest flux (0.7 g m-2 h-1) was reported under NT. After spring tillage, similar but smaller impacts of the tillage practices on soil CO2 flux were reported with fluxes ranging from 1.8 g CO2 m-2 h-1 (CT) to less than 0.1 g CO2 m-2 h-1 (NT). Soil strength was significantly correlated with soil CO2 emission; whereas surface soil temperature and moisture were low correlated to the soil CO2 flux. The intensity of rainfall events before fall and spring tillage practices could explain the seasonal CO2 flux trends. The findings promote conservation tillage and more specifically no tillage practices to reduce CO2 losses within these Mediterranean agroecosystems. (Résumé d'auteur

The conundrum of conservation agriculture and livelihoods in Southern Africa

Low crop productivity, food insecurity, hunger and malnutrition; inadequate farming knowledge and skills, implements and inputs are characteristic of smallholder agriculture in Southern Africa. Many researchers argue that conservation agriculture can guarantee higher crop productivity, food security, improved livelihoods and environmental protection, better than the unsustainable traditional systems of slash and burn practices. In this paper, we present the results of a meta-analysis of over 40 academic publications to review conservation agriculture’s role in influencing desired livelihood outcomes in Southern Africa. We conclude that the effectiveness of conservation agriculture towards better livelihood outcomes in Southern Africa remains debatable, especially when supportive government policies are lacking

Combining ecosystem modelling and remote-sensing to establish the spatial and temporal dynamics of the carbon budget of fast-growing tropical Eucalyptus plantations

In the aim of estimating regional-scale carbon budgets of Eucalyptus plantations, the G'Day ecosystem model was combined with remotely-sensed estimates of the daily fraction of absorbed photosynthetically active radiation (fAPAR). (Résumé d'auteur