Bio

Biodata

Dr. Richard N. Onwonga is a Kenyan citizen and holds: a PhD in Natural resource Management (Doctor rerum naturalium technicarum/Dr. nat. techn) from the University of Natural Resources and Applied Life Sciences (BOKU), Vienna; M.Sc. in Soil Science and B.Sc. in Agriculture Education & Extension from Egerton University.

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Publications


2013

Ndukhu, OH; Onwonga, RN; WRG; KJHHG;.  2013.  Crop performance and soil nutrient dynamics under different cropping systems and organic inputs in central Kenya.. Abstract

documents' citation: Ndukhu, O. H., Onwonga, R. N., Wahome, R. G., Kironchi, G., & Jensen, H. H. Crop performance and soil nutrient dynamics under different cropping systems and organic inputs in central Kenya.

2012

Abdul, K, Chemining’wa GN, Onwonga RN.  2012.  Relationships between Agronomic Practices, Soil Chemical Characteristics and Striga Reproduction in Dryland Areas of Tanzania.. Journal of Agricultural Science and Technology . A 2 (2012) :1134-1141.kudra_et_al_relationships_between_agronomic_practices_soil.pdf

2011

2010

Onwonga, RN, Mbuvi JP, Kironchi G, Githinji M.  2010.  Modelling the potential impact of climate change on sorghum and cowpea production in semi-arid areas of Kenya using the agricultural production systems simulator (APSIM. Abstract

Managing crop production risks associated with inter-annual climate variability and climate change has received insignificant attention in the semi-arid areas of Kenya. Against this backdrop, the potential impact of climate change on sorghum (Sorghum bicolor) and cowpea (Vigna unguiculata) production in the semi-arid areas of Kenya will be assessed using the Agricultural Production System Simulator (APSIM). The study will employ participatory tools in the use of APSIM model to identify risks and cropping system improvement options and designing cropping strategies for field experimentation. The field experiments will be conducted in Makueni district of Eastern Province, Kenya. Initially, a farmers’ workshop will be held to gather information on farmers’ experience with recent climatic changes and possible causes, effect on current farming systems, coping and adaption strategies to current management practices. Farm households’ perceptions of risks, options to reduce climatic risks, specific vulnerabilities of the current cropping systems and coping strategies will be documented using semi-structured interviews during farm surveys. This is in addition to establishing the socio-economic and agricultural systems setting of the smallholder farmers. Potential technologies to address the anticipated negative impacts of climate change in respect of cowpea (legume) and sorghum (cereal) cropping system will jointly be identified with the farmers and a subset of tactical adaptation options identified. The options will initially be tested on-station in the first year and on farm in the second year. The on station experiments will be conducted for two (four seasons) years to model sorghum and cowpea growth and soil-water, soil organic carbon and nitrogen dynamics in a legume-cereal cropping system. The APSIM model will be validated to simulate both the legume and cereal components of the cropping system. The integrity of the simulated system will be evaluated by comparing the simulated performance of the crops with actual experimental crop data and by exploring Managing crop production risks associated with inter-annual climate variability and climate change has received insignificant attention in the semi-arid areas of Kenya. Against this backdrop, the potential impact of climate change on sorghum (Sorghum bicolor ) and cowpea ( Vigna unguiculata ) production in the semi-arid areas of Kenya will be assessed using the Agricultural Production System Simulator (APSIM). The study will employ participatory tools in the use of APSIM model to identify risks and cropping system improvement options and designing cropping strategies for field experimentation. The field experiments will be conducted in Makueni district of Eastern Province, Kenya. Initially, a farmers’ workshop will be held to gather information on farmers’ experience with recent climatic changes and possible causes, effect on current farming systems, coping and adaption strategies to current management practices. Farm households’ perceptions of risks, options to reduce climatic risks, specific vulnerabilities of the current cropping systems and coping strategies will be documented using semi-structured interviews during farm surveys. This is in addition to establishing the socio-economic and agricultural systems setting of the smallholder farmers. Potential technologies to address the anticipated negative impacts of climate change in respect of cowpea (legume) and sorghum (cereal) cropping system will jointly be identified with the farmers and a subset of tactical adaptation options identified. The options will initially be tested on-station in the first year and on farm in the second year. The on station experiments will be conducted for two (four seasons) years to model sorghum and cowpea growth and soil-water, soil organic carbon and nitrogen dynamics in a legume-cereal cropping system. The APSIM model will be validated to simulate both the legume and cereal components of the cropping system. The integrity of the simulated system will be evaluated by comparing the simulated performance of the crops with actual experimental crop data and by exploring Managing crop production risks associated with inter-annual climate variability and climate change has received insignificant attention in the semi-arid areas of Kenya. Against this backdrop, the potential impact of climate change on sorghum (Sorghum bicolor ) and cowpea ( Vigna unguiculata ) production in the semi-arid areas of Kenya will be assessed using the Agricultural Production System Simulator (APSIM). The study will employ participatory tools in the use of APSIM model to identify risks and cropping system improvement options and designing cropping strategies for field experimentation. The field experiments will be conducted in Makueni district of Eastern Province, Kenya. Initially, a farmers’ workshop will be held to gather information on farmers’ experience with recent climatic changes and possible causes, effect on current farming systems, coping and adaption strategies to current management practices. Farm households’ perceptions of risks, options to reduce climatic risks, specific vulnerabilities of the current cropping systems and coping strategies will be documented using semi-structured interviews during farm surveys. This is in addition to establishing the socio-economic and agricultural systems setting of the smallholder farmers. Potential technologies to address the anticipated negative impacts of climate change in respect of cowpea (legume) and sorghum (cereal) cropping system will jointly be identified with the farmers and a subset of tactical adaptation options identified. The options will initially be tested on-station in the first year and on farm in the second year. The on station experiments will be conducted for two (four seasons) years to model sorghum and cowpea growth and soil-water, soil organic carbon and nitrogen dynamics in a legume-cereal cropping system. The APSIM model will be validated to simulate both the legume and cereal components of the cropping system. The integrity of the simulated system will be evaluated by comparing the simulated performance of the crops with actual experimental crop data and by exploring water use, denitrification and leaching. It is envisioned that the APSIM model will allow for quick exploration of production outcomes of a range of management alternatives under a range of climatic scenarios (realized or predicted), and for a range of soil conditions. This is in addition to provision of valuable information for evaluating a wide range of cropping system options

Onwonga, RN, Gachene CKK;, Baaru MW;.  2010.  Assessment of changes in natural resources: a participatory approach. AbstractWebsite

This study analyzed changes in natural resources in Machakos District of Kenya using participatory approaches. The results show that natural resources have decreased since the ranch became a settlement scheme. Natural forests decreased, vast land was cleared, rivers dried-up while soil erosion, drought, temperatures and land degradation increased. Land productivity declined and most farmers abandoned the traditional crops for modern high value crops. However, farmers adopted various coping strategies. Drought resistant crops, early maturing crops and water harvesting were some of the strategies adopted by farmers. The results also show that resource base management at the community level was still a challenge and a lot of investment needed to be made in this area. As part of the study, farmers knowledge of changes in natural resource use was assessed in a resettlement area. Over a period of about 50 years, significant land degradation has occurred as a result of increased population pressure, poor natural resource management and climate change effects. This was reflected in poor/low land productivity and reduced availability of water. Farmers responded by moving away from growing indigenous crops to growing short-duration crop

Eyvazi, J, Irannejad H, Kianmehr MH, Esmaeili M, Akbari QA, Onwonga RN.  2010.  The effect of Pellet fertilizer application on Wheat Yield and its Components. International Research Journal of Plant Science. 1(6):163-171.eyvazi_et_al2010_the_effect_of_pellet_fertilizer_application_on_wheat_yield.pdf

2009

2008

Onwonga, RN, Freyer B, Lelei JJ.  2008.  Traditional soil fertility management strategies: Do they conform to recommendations in organic farming? A case study of the smallholder farmers of the Central Rift Valley Province of Kenya Abstract

The low input nature of organic farming (OF) is often likened to the traditional soil fertility management practices (TSFMP) of smallholder farming systems in developing countries. There are however no concrete studies to support this assertion. The present study aims at comparing the TSFM practices with recommendations in OF specifically recycling of organic wastes of crop and animal origin and maintenance of long-term fertility of the soil. These were monitored through resource flow mapping and calculation of nitrogen balances, at crop production level, using NUTMON toolbox. The study was conducted in Gilgil, Lare and Molo divisions of the Rift Valley Province of Kenya. Crop residues and manure were the principal organic resources recycled within the smallholder farming systems. The calculated N balances were negative; -70.9, -80.2 and -99.8 kg/ha/year for Gilgil, Lare and Molo, respectively. The organic resources recycled within the farm were therefore insufficient to sustain soil fertility. This is contrary to recommendations in OF, in which the long-term soil fertility should be maintained and/or enhanced. There were however opportunities; composting, biomass transfer and improved use of external and internal farm boundaries, enhanced livestock manure handling and integration of agroforestry trees, for improving the TSFMP to expectations of OF

Onwonga, RN, Lelei JJ, Freyer B, Friedel JK, Mwonga SM, Wandhawa P.  2008.  Low Cost Technologies for Enhancing N and P Availability and Maize (Zea mays L.) Performance on Acid Soils. World Journal of Agricultural Sciences. 4(s):862-873.onwonga_et_al_2008_low_cost_technologies_for_enhancing_n_and_p_availability_2.pdf

2006

Lelei, JJ, Onwonga RN, Mochoge BO.  2006.  Interactive Effects of Lime, Manure, Urea and TSP on Maize (Zea Mays L.) Yield and Nutrient Uptake in an Acid Mollic Andosol of Molo, Kenya. Egerton Journal of Science and Technology. 6 (2):http://journal.egerton.ac.ke/index.php/ejt/article/view/16.

2000

Lelei, JJ, Mochoge BO, Onwonga RN.  2000.  Effect of lime, urea and triple super phosphate on nitrogen and phosphorus mineralisation in an acid soil during incubation. African Crop Science Journal. 8(3):327-336).

1999

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