| dc.contributor.author | Winnie, N. |
| dc.date.accessioned | 2023-02-28T09:20:27Z |
| dc.date.available | 2023-02-28T09:20:27Z |
| dc.date.issued | 2022-10 |
| dc.identifier.citation | Winnie, N. (2022). Assessing nitrogen flows and greenhouse gas emissions in low input cropping systems of Lake Victoria Basin. Nairobi, Nairobi, Kenya: Kenyatta University, (199 p.). |
| dc.identifier.uri | https://hdl.handle.net/20.500.12478/8068 |
| dc.description.abstract | Too little nitrogen (N) is a threat to cropping systems and soil fertility in sub-Saharan Africa (SSA). Nitrogen budgets (NB) and nitrogen use efficiency (NUE) are critical tools for assessing N dynamics in agriculture and have received little or no attention in the region. The study aimed to assess key N performance indicators at field and farm level based on N use scenarios and help to inform policy on formulating relevant decision and practices to enhance N management for improved crop productivity and environmental sustainability. To achieve this, data were collected from farmers’ fields and clustered into two categories, farmers applying and farmers not applying N fertilizers. Collected data on yield and N fertilizer were used to make projections on the changes of NUE based on scientific and policy recommendations for Sub-Saharan Africa for 2020 (base year), 2025, 2030, and 2050. Scenarios of N use were simulated under field conditions for maize crop in two catchments of the Lake Victoria basin. The scenarios included Business as Usual (BAU, 0 kg N ha-1), 25 % of the Abuja declaration (ADS 12.5 kg N ha-1), 50% of the Abuja declaration (ADS 25 kg N ha-1), and Abuja declaration-Abuja scenario (ADS, 50 kg N ha-1). A laboratory incubation experiment to assess the effects of two N use scenarios (12.5 and 50 kg N ha-1) and liming practices (CaCO3) on three acidic soils types from Lake Victoria basin on greenhouses gases was conducted. Data were analyzed using R programming language version 4.1.0. The results revealed negative N balances in different fields and farms. Similarly, at the farm gate, a deficit of -78.37 kg N ha -1 was observed; an indicator of soil N mining. Significant differences in maize grain yield for both fertilized and unfertilized farms were realized with very low yields of 2.4 t ha-1 (fertilized) and 1.4 tha-1 (unfertilized). The graphical representation of NUE of both maize and rice showed that most farmers were in the zone of soil N mining. Projected results showed that most maize farmers within Lake Victoria region will continue to experience NUE values >90%, low N inputs <50 kg N ha-1) and less than 5 t ha-1 maize crop yield over the years. For rice farmers, Nyando and Nzoia catchments had surpassed the set target of both yield (6 t ha-1) and N input (50 kg N ha-1). The results revealed that increasing N input levels significantly influenced the growth and yield of maize crops. N deficits were observed in all the N use scenarios with a range of -66.6 to -125.7 kg N ha-1 in Nyando and -62.5 to -105.4 kg N ha-1 in Rangwe catchments with 50 % ADS scenario having the highest deficits. The partial N balance observed at Nyando (1.56 - 3.11) and Rangwe (1.10- 4.64) were higher than the optimal values, a sign of insufficient N inputs and possible risk of soil N depletion in all the scenarios. The values of δ13C of CO2 showed that the source of CO2 from soils was negligible and the largest contributor was from application of CaCO3 followed by N fertilization in Ferralsol 1 and 2 while no visible differences observed in the Vertisol. N2O-N fluxes were highly influenced by N fertilization and CaCO3 in Ferralsol 1 and 2 which was 13 (81.73 mg m-2) and 4 (38.80 mg m-2) times higher when compared to unfertilized and unlimed control. The study concludes that Lake Victoria basin faces an extreme depletion of available N resources, the recommended nutrient level; at 50 kg N ha-1 is not sufficient to correct the negative balances, while managing acidity and soil fertility will lead to higher GHG fluxes but increase N availability. |
| dc.description.sponsorship | International Institute of Tropical Agriculture |
| dc.format.extent | 199 p. |
| dc.language.iso | en |
| dc.publisher | Kenyatta University |
| dc.subject | Greenhouse Gases |
| dc.subject | Cropping Systems |
| dc.subject | Soil Fertility |
| dc.subject | Crop Production |
| dc.title | Assessing nitrogen flows and greenhouse gas emissions in low input cropping systems of Lake Victoria Basin |
| dc.type | Thesis |
| cg.contributor.affiliation | Kenyatta University |
| cg.contributor.affiliation | International Institute of Tropical Agriculture |
| cg.coverage.region | Africa |
| cg.coverage.region | East Africa |
| cg.coverage.country | Kenya |
| cg.coverage.hub | Central Africa Hub |
| cg.identifier.bibtexciteid | WINNIE:2022c |
| cg.authorship.types | CGIAR and developing country institute |
| cg.iitasubject | Agronomy |
| cg.iitasubject | Crop Systems |
| cg.iitasubject | Farming Systems |
| cg.iitasubject | Food Security |
| cg.iitasubject | Plant Breeding |
| cg.iitasubject | Plant Production |
| cg.notes | IITA supervisor: Dr C. Masso |
| cg.publicationplace | Nairobi, Kenya |
| cg.accessibilitystatus | Limited Access |
| cg.reviewstatus | Internal Review |
| cg.usagerightslicense | Copyrighted; all rights reserved |
| cg.targetaudience | Scientists |
| cg.futureupdate.required | No |
| cg.contributor.acknowledgements | I first thank Almighty God for granting me good health, wisdom, knowledge, patience, and protection while pursuing my PhD studies.
I sincerely wish to register my heartfelt gratitude to my supervisors; Prof. Joseph Onyango Gweyi, Dr. Cargele Masso from the International Institute of Tropical Agriculture (IITA) and Prof. Benson Mochoge from the Department of Agricultural Science and Technology, Kenyatta University, for their inspiring guidance, scholarly comments, positive criticism, encouragement and constructive suggestions throughout the study. I also thank my advisors, Dr. Mekonnen Giweta, Dr. Generose Nziguheba from IITA, and Dr. James Mutegi from the African Plant Nutrition Institute (APNI), for their guidance and assistance during the research work. I thank them most sincerely for dedicating their time and effort to make me complete this course within the shortest time possible.
I acknowledge IITA for giving me a full scholarship to pursue my Ph.D. degree through the funding from Towards an International Nitrogen Management System (INMS) project. Many thanks to IITA administrative and finance staff for their help in facilitating and planning for field work. I am grateful to my fellow students and colleagues at IITA, Catherine, Esther, Celestine, Janet, Mike, Sam, Machango, Maryfaith, Effie, Calvince, Evans and Grace for their encouragement during PhD time.
I also wish to thank the Consultative Group on International Agricultural Research (CGIAR) Research Program on Climate Change, Agriculture and Food Security (CCAFS) and the Global Research Alliance on Agricultural Greenhouse Gases (GRA)
v
through their CLIFF-GRADS program for providing funding through the Government of New Zealand to support my experiment in greenhouses measurement.
Special thanks to the Institute of Bio and Geo-sciences (IBG-3) Forschungszentrum Julich, Germany, for hosting me to conduct my experiment in their labs. I greatly appreciate the outstanding mentorship I received from Prof. Dr. Roland Bol and Prof. Dr. Nicolas Brüggemann during my visit in Germany. I thank Dr. Rüdiger Reichel for his support in planning and carrying out the incubation experiment in Germany. I thank Holger Wissel, technical staff at IBG-3, for his help in-mass spectrometry analysis. Many thanks to Dr. Otávio dos Anjos Leal for his assitance in the lab work.
I thank Kenyatta University and the Department of Agricultural Science and Technology for the support and guidance during progress seminars. I am grateful to my fellow PhD student Michael Sakha for his support in planning laboratory work. I sincerely thank the Laboratory Technician Kallen Kaaria for supporting me during lab work and sacrificing her time, even on weekends. I also thank my friends Lilian Muriuki and Latara Nyambeya for their moral support and encouragement during my study.
In a special way, I thank my family; my late father Sebastian, my mother Jane Inoti, and my brothers Laban and Festus for moral support, love, prayers and patience during the study period. |
