Exploring opportunities for diversification of smallholders' rice-based farming systems in the Senegal River Valley

CONTEXT: Policy-based or technological interventions are more likely to be effective if aligned with farmers' objectives, constraints, and decision-making processes. OBJECTIVE: The objective of this study was to explore trade-offs and synergies of farming systems in response to innovative rice cultivation activities by understanding current farming systems, main drivers impacting farm management and farmers' perspectives on rice intensification. Understanding these interrelations is key in rice production areas, where smallholder farmers largely depend on growing rice to subsist. METHODS: A rapid system analysis was conducted interviewing 20 farmers in 4 villages along the Senegal River Valley (SRV) to obtain a general view on farm functioning and farmers' perspectives on farming systems. A detailed system analysis with four farmers was subsequently conducted to provide an insight into the underlying processes regulating farm management. A multi-objective optimization model was used to quantitatively evaluate and explore farm performances based on four selected indicators representing: rice production, household agricultural profit, household labour and farm nutrient balance. RESULTS AND CONCLUSIONS: The results of this study showed that government programmes and farmers' Unions were strongly influencing farmers' decision-making in agricultural production. Farmers also reported that although rice was still essential for their livelihoods, there were transitions towards less rice production in the wet season with short duration rice varieties and more vegetable production. Both farmers' interviews and the modelling results suggested that farmers would be unlikely to increase or even maintain the area of rice double cropping, which has been strongly promoted by the Senegalese government. Instead, farmers would rather keep investing in vegetable production. SIGNIFICANCE: This modelling study shows the consequences of policy-based and technological interventions for farming systems and may inform both policy makers and farmers in situations where objectives are strongly divergent. Hence, modelling outcomes may be used to inspire discussion and innovation in order to align the government priority of ensuring national food security and farmers' objectives and constraints in the SRV

Biochar improves fertility of a clay soil in the Brazilian Savannah: short term effects and impact on rice yield

The objective of this study was to report single season effects of wood biochar (char) application coupled with N fertilization on soil chemical properties, aerobic rice growth and grain yield in a clayey Rhodic Ferralsol in the Brazilian Savannah. Char application effected an increase in soil pH, K, Ca, Mg, CEC, Mn and nitrate while decreasing Al content and potential acidity of soils. No distinct effect of char application on grain yield of aerobic rice was observed. We believe that soil properties impacted by char application were inconsequential for rice yields because neither water, low pH, nor the availability of K or P were limiting factors for rice production. Rate of char above 16 Mg ha^(−1) reduced leaf area index and total shoot dry matter by 72 days after sowing. The number of panicles infected by rice blast decreased with increasing char rate. Increased dry matter beyond the remobilization capacity of the crop, and high number of panicles infected by rice blast were the likely cause of the lower grain yield observed when more than 60 kg N ha^(−1) was applied. The optimal rate of N was 46 kg ha^(−1) and resulted in a rice grain yield above 3 Mg ha^(−1)

Disponibilidade de nitrogênio, espaço poroso preenchido por água e fluxos de N 2 O-N após aplicação de biochar e fertilização nitrogenada

The objective of this work was to investigate the impact of the application of wood biochar, combined with N fertilizations, on N2O-N fluxes, nitrogen availability, and water-filled pore space (WFPS) of a clayey Oxisol under rice (wet season) and common bean (dry season) succession. Manual static chambers were usedto quantify N2O-N fluxes from soil immediately after a single application of wood biochar (32 Mg ha-1) andafter four crop seasons with N applications (90 kg ha-1 N). Soil ammonium (N-NH4 +) and nitrate (N-NO3-) availability, as well as WFPS, was measured together with N2O-N fluxes. There was no interaction between biochar and N fertilization regarding N2O-N fluxes in any of the four seasons monitored, although these fluxes were clearly enhanced by N applications. At 1.5 and 2.5 years after biochar application, the WFPS decreased. In addition, in the seasons characterized by low WFPS, N2O-N fluxes and soil N-NO3- and N-NH4+ availability were enhanced after N applications. Long-term experiments in the field are important to quantify the impacts of biochar on N2O-N fluxes and to determine the dynamics of these fluxes on soil-related variables.O objetivo deste trabalho foi investigar o impacto da aplicação de biochar de madeira, combinada com fertilizações itrogenadas, nos fluxos de N2O-N, na disponibilidade de nitrogênio e no espaço poroso preenchido por água (EPPA), em um Latossolo argiloso sob sucessão com arroz (época chuvosa) e feijão (época seca). Câmaras estáticas manuais foram utilizadas para quantificar os fluxos de N2O-N no solo logo após uma única aplicação de biochar (32 Mg ha-1) e após quatro épocas de cultivo com aplicações de N (90 kg ha-1 de N). A disponibilidade de amônio (N-NH4+) e de nitrato (N-NO3-) no solo, bem como o EPPA, foi medida juntamente com os fluxos de N2O-N. Não houve interação entre biochar e fertilização nitrogenada quanto aos fluxos de N2O-N, em nenhuma das quatro épocas monitoradas, apesar de esses fluxos terem aumentado com as aplicações de N. Aos 1,5 e 2,5 anos após a aplicação do biochar, o EPPA diminuiu. Além disso, nas épocas caracterizadas por reduzido EPPA, os fluxos de N2O-N e a disponibilidade de N-NO3- e N-NH4 + no solo aumentaram após as aplicações de N.Experimentos em campo de longa duração são importantes para quantificar o impacto do uso de biochar sobre os fluxos de N2O-N e para determinar a dinâmica desses fluxos sobre as variáveis relacionadas ao solo

Acknowledgements

For four years I have been working with pleasure on this thesis and it is now a pleasure to thank all those who contributed to its completion. First of all, I would like to thank my supervisors. Arnold, Sytze and Alfred, most of all I should thank you three for all your efforts in learning me to write a scientific article. Arnold, you were stimulating throughout the project, provided a great network when looking for casestudies and showed great engagement in the testing phase of the questionnaire for chapter 7. Sytze, you were the best reviewer I could have wished for. At the start of the PhD, I would get upset by your reviews on draft documents, only later to learn that your remarks were always to the point and always led to significant improvement. Alfred, your enthusiasm throughout, but especially on chapter 5, was much appreciated. Both Sytze’s and your statistical support were of the ideal combination of scientific soundness and pragmatism. The anonymous reviews on submitted articles were always to the point, they always showed great understanding of the topics addressed and always led to improvement of the submitted work. So thanks to you, anonymous reviewers. I hop

Abiotic stress maps for rice (STRASA): Maps (kmz) for Africa with probability of presence of a saline/sodic soil overlaid with crop maps to identify areas with lots of salinity/sodicity AND lots of rice

This dataset is produced for the STRASA project in which breeders are developing varieties tolerant to salinity/sodicity. The intended use is that tolerant varieties can be sent to places with high risk of salinity/sodicity. This "salinity/sodicity" map was combined with three crop maps (GAEZv3, MIRCA2000,SPAM2005) to identify countries and hotspots, that is sites with lots of rice and lots of salinity

Daily weather data for Tillaberi (Niger) from 1950 to 1984

Daily weather data owned or distributed by AfricaRice and available on http://eservices.africarice.org/weatherdata/index.php </a

Daily weather data for Tandjile East (Chad) in 2013

Daily weather data owned or distributed by AfricaRice and available on http://www.mlaxmel.com/weatherdata/query.php </a

Daily weather data for Tormabum (Sierra Leone) from 2014 to 2016

Daily weather data owned or distributed by AfricaRice and available on http://www.mlaxmel.com/weatherdata/query.php </a

Daily weather data for Kilombero-Ifakara (Tanzania) from 2014 to 2018

Daily weather data owned or distributed by AfricaRice and available on http://www.mlaxmel.com/weatherdata/query.php </a