Browsing by Author "Graef, F"

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Analysis of Intra and Interseasonal Rainfall Variability and Its Effects on Pearl Millet Yield in a Semiarid Agroclimate: Significance of Scattered Fields and Tied Ridges
(Water, 2019-03) Silungwe, F.R; Graef, F; Bellingrath-Kimura, S.D; Tumbo, S.D; Kahimba, F.C; Lana, M.A
Establishing food security in sub-Saharan African countries requires a comprehensive and high resolution understanding of the driving factors of crop production. Poor soil and adverse climate conditions are among the major drivers of poor regional crop production. Drought and rainfall variability challenges are not fully being addressed by rainfed producers in semiarid areas. In this study, we analysed the spatiotemporal rainfall variability (STRV) and its effects on pearl millet yield using two seasons of data collected from 38 rain gauge stations scattered randomly in farm plots within a 1500 ha area of semiarid central Tanzania. The STRV effects on pearl millet yield under flat and tied ridge management were analysed. Our results show that seasonal rainfall can vary significantly for neighboring fields at distances of less than 200 m, which impacts yield. The STRV for daily rainfall was found to be more critical than for total seasonal rainfall amounts. Scattering fields can help farmers avoid total harvest loss by obtaining at least some yield from the areas that received adequate rain. The use of tied ridges is recommended to conserve soil moisture and improve yields more than flat cultivation in semiarid areas.
Assessment of upgrading strategies to improve regional food systems in Tanzania: Food processing, waste management and bioenergy, and income generation
(SAGE, 2015) Graef, F; Schneider, I; Fasse, A; Germer, J.U; Gevorgyan, E; Haule, F; Hoffmann, H; Kahimba, F.C; Kashaga, L; Kashaga, L; Lambert, C; Lana, M; Mahoo, H.F; Makoko, B; Mbaga, S.H; Mmbughu, A; Mmbughu, S; Mrosso, L; Mutabazi, K.D; Mwinuka, L; Ngazi, H; Nkonya, E; Said, S; Schaffert, A; Schäfer, M.P; Schindler, J; Sieber, S; Swamila, M; Welp, H.M; William, L; Yustas, Y.M
Food security is one of the main goals of rural poor people. To enhance food security in this context, participatory action research can help to ensure sustained success while considering entire food value chains (FVC). This paper assesses the feasibility and potential success of upgrading strategies (UPS) as well as their assessment criteria as developed by German and Tanzanian agricultural scientists. The results form part of a larger participatory research project conducted in two climatically representative regions of Tanzania: semi-arid Dodoma and subhumid Morogoro. This paper presents the findings with respect to food processing, waste management and bioenergy, along with income generation and market participation. Assessments on other components of the FVC, including natural resource management, crop production and consumption, are reported by Graef et al (2015). The assessments for food processing revealed preferences for preservation techniques, oil extraction processes and food storage devices for the semi-arid region. In contrast, in the subhumid region, the experts favoured food storage devices and preservation techniques. Assessments of waste management and bioenergy UPS for both regions indicated the importance of animal feed from crop residues, crop residues as mulch and compost from food waste, although with somewhat different priorities. Assessments on income generation and markets in both regions revealed preferences for savings and credit cooperatives and communication techniques, but also indicated that warehouse receipt systems and guarantee systems had a high impact. Assessments differed between the two different climatic regions, and to some extent also between the nationality of experts and their gender. The authors therefore attach importance to integrating different South–North and female–male awareness in assessments among scientists. Moreover, local and/or regional stakeholders and experts should be involved in developing site-adapted UPS for enhancing FVCs.
Combined effects of biochar and fertilizer application on maize production in dependence on the cultivation method in a sub-humid climate
(Taylor and Francis, 2018) Graef, H; Kiobia, D; Saidia, P; Kahimba, F; Graef, F; Eichler-Lobermann, B
Low, erratic rainfall amounts and restricted accessibility of chemical fertilizer for rural farmers in developing countries may have negative effects on crop production. Agricultural methods like biochar applications, fertilizer microdosing and tied ridging can help to mitigate these constraints, but have rarely been studied in combination and under varying water availability. A field trial was conducted in split-plot design over two contrasting cropping seasons in 2016 and 2017 in Tanzania to study the effect of these agricultural methods on maize grain yield, biomass, leaf area index, plant height and soil moisture content. In both seasons each with contrasting irrigation frequencies, fertilizer microdosing increased the grain yield of maize. Biochar alone affected the yield only at high application rates (10 t/ha) and low irrigation frequency. However, when combined with fertilizer microdosing the yield effect of biochar was more pronounced. For example, combining 5 t/ha biochar with fertilizer microdosing under flat tillage increased yield by 170% compared to the control without biochar and fertilizers. Tied ridges increased soil moisture content and tended to increase maize yield compared to flat tillage, whereas biochar application resulted in significantly higher soil moisture contents. Fertilizer microdosing with biochar application can be recommended to improve maize yields mainly under flat tillage.
Crop Upgrading Strategies and Modelling for Rainfed Cereals in a Semi-Arid Climate—A Review
(Water, 2018-03) Silungwe, F.R; Graef, F; Bellingrath-Kimura, S.D; Tumbo, S.D; Kahimba, F.C; Lana, M.A
Spatiotemporal rainfall variability and low soil fertility are the primary crop production challenges facing poor farmers in semi-arid environments. However, there are few solutions for addressing these challenges. The literature provides several crop upgrading strategies (UPS) for improving crop yields, and biophysical models are used to simulate these strategies. However, the suitability of UPS is limited by systemization of their areas of application and the need to cope with the challenges faced by poor farmers. In this study, we reviewed 187 papers from peer-reviewed journals, conferences and reports that discuss UPS suitable for cereals and biophysical models used to assist in the selection of UPS in semi-arid areas. We found that four UPS were the most suitable, namely tied ridges, microdose fertilization, varying sowing dates, and field scattering. The DSSAT, APSIM and AquaCrop models adequately simulate these UPS. This work provides a systemization of crop UPS and models in semi-arid areas that can be applied by scientists and p
Effects of Nitrogen and Phosphorus Micro-Doses on Maize Growth and Yield in a Sub-Humid Tropical Climate
(2018) Saidia, P.S; Rweyemamu, C.L; Asch, F; Semoka, J.M.R; Kimaro, A.A; Germer, J; Graef, F; Lagweni, P; Kahimba, F; Chilagane, E.A
Inadequate knowledge on fertilizer usage and poor financial resources are among the reasons for low maize productivity under small-scale farming. Fertilizer micro-dosing may increase food production by using low rates which are affordable by most resource poor farmers and have a high investment return. A two-year field experiment was conducted on sandy loam and sandy clay soils being typical representatives of sub-humid tropical agroecological zones. A split-plot design involved di-ammonium phosphate (DAP), Minjingu mazao (MM) and triple super phosphate (TSP) as main plots and fertilizer micro-dose rates of 10 kg N and 5 kg P/ha, 20 kg N and 10 kg P/ha, 40 kg N and 20 kg P/ha, 60 kg N and 30 kg P/ha, recommended rate 80 kg N and 40 kg P ha-1 and control as sub-plots. Phosphate fertilizers that produced highest grain yield were MM (2317 kg/ha), followed by DAP (2173 kg/ha) and TSP (2115 kg/ha). Fertilizer micro dose rates (10 kg N and 5 kg P/ha; 20 kg N and 10 kg P/ha) increased the yield by 90.5 and 136.6% from 1012 kg/ha in control, respectively. Intermediate rates (40 kg N and 20 kg P/ha) and (60 kg N and 30 kg P/ha) produced average grain yields of 2629 and 2647 kg/ha while the recommended rate produced 2601 kg/ha. The highest grain yield was 3910 kg/ha from MM at 40 kg N and 20 kg P/ha. Considering the micro-dose options therefore, MM fertilizer and micro dose rates (10 kg N and 5 kg P/ha) and (20 kg N and 20 kg P/ha) are recommended in these agro-ecological zones.
The management strategies of pearl millet farmers to cope with seasonal rainfall variability in a semi-arid agroclimate
(Agronomy, 2019-07) Silungwe, F.R; Graef, F; Bellingrath-Kimura, S.D; Tumbo, S.D; Kahimba, F.C; Lana, M.A
Rainfed agriculture constitutes around 80% of the world’s agricultural land, achieving the lowest on-farm crop yields and greatest on-farm water losses. Much of this land is in developing countries, including sub-Saharan Africa (SSA), where hunger is chronic. The primary constraint of rainfed agriculture—frequently experienced in SSA—is water scarcity, heightened by the unpredictability of season onset, erratic rainfall, as well as the inability of farmers to provide adequate soil and crop management. Farmers react differently to constraints, making a variety of choices—including the timing of planting, type of land cultivation, fertilization, and scattered fields, among many others. Limited information is available on the combined effects of these strategies for improving crop yield and water use efficiency (WUE). An experiment was co-conducted with farmers over four consecutive rainy seasons (2014–2018) in Tanzania, to evaluate these strategies for single and joint effects in improving yield and WUE on rainfed pearl millet (Pennisetum glaucum (L.) R.Br.). The treatments used were flat cultivation both without and with microdosing, as well as tied ridging without and with microdose interaction, with different planting dates depending on farmers’ decisions. Results show that farmers react differently to the early, normal, or late onset of the rainy season, and cumulative rainfall during its onset, which affects their decisions regarding planting dates, yield, and WUE. Microdose fertilization increases both the yield and WUE of pearl millet significantly, with greater effects obtained using tied ridging compared to flat cultivation. For low-income smallholder farmers in a semi-arid agroclimate, using tied ridging with microdosing during early planting is an effective response to spatiotemporal rainfall variability and poor soils.
Modelling rainfed pearl millet yield sensitivity to abiotic stresses in semi-arid central Tanzania, Eastern Africa
(Sustainability, 2019-08) Silungwe, F.R; Graef, F; Bellingrath-Kimura, S.D; Chilagane, E; Tumbo, S.D; Kahimba, F.C; Lana, M.A
Drought and heat-tolerant crops, such as Pearl millet (Pennisetum glaucum), are priority crops for fighting hunger in semi-arid regions. Assessing its performance under future climate scenarios is critical for determining its resilience and sustainability. Field experiments were conducted over two consecutive seasons (2015/2016 and 2016/2017) to determine the yield responses of the crop (pearl millet variety “Okoa”) to microdose fertilizer application in a semi-arid region of Tanzania. Data from the experiment were used to calibrate and validate the DSSAT model (CERES Millet). Subsequently, the model evaluated synthetic climate change scenarios for temperature increments and precipitation changes based on historic observations (2010–2018). Temperature increases of +0.5 to +3.0 ◦C (from baseline), under non-fertilized (NF) and fertilizer microdose (MD) conditions were used to evaluate nine planting dates of pearl millet from early (5 December) to late planting (25 February), based on increments of 10 days. The planting date with the highest yields was subjected to 49 synthetic scenarios of climate change for temperature increments and precipitation changes (of −30% up to +30% from baseline) to simulate yield responses. Results show that the model reproduced the phenology and yield, indicating a very good performance. Model simulations indicate that temperature increases negatively affected yields for all planting dates under NF and MD. Early and late planting windows were more negatively affected than the normal planting window, implying that temperature increases reduced the length of effective planting window for achieving high yields in both NF and MD. Farmers must adjust their planting timing, while the timely availability of seeds and fertilizer is critical. Precipitation increases had a positive effect on yields under all tested temperature increments, but Okoa cultivar only has steady yield increases up to a maximum of 1.5 ◦C, beyond which yields decline. This informs the need for further breeding or testing of other cultivars that are more heat tolerant. However, under MD, the temperature increments and precipitation change scenarios are higher than under NF, indicating a high potential of yield improvement under MD, especially with precipitation increases. Further investigation should focus on other cropping strategies such as the use of in-field rainwater harvesting and heat-tolerant cultivars to mitigate the effects of temperature increase and change in precipitation on pearl millet yield.
Multi-Disciplinary North-South Collaboration in Participatory Action Research on Food Value Chains: a German-Tanzanian Case Study on Perceptions, Experiences and Challenges
(Springer, 2018) Graef, F; Mutabazi, K.D; Sieber, S; Asch, F; Makoko, B; Bonatti, M; Brüntrup, M; Gornott, C; Herrmann, L; Herrmann, R; Kaburire, L; Kahimba, F.C; Kimaro, A; Kuntosch, A; König, H.J
Upgrading local food value chains is a promising approach to invigorating African food systems. This endeavour warrants multi-disciplinary North-South collaboration and partnerships through participatory action research (PAR) to help leverage appropriate upgrading strategies (UPSs) with a focus on local stakeholders. The more disciplines, cultures,and partner institutions that are involved, the more a project will present challenges in terms of communication and coordinating activities. Our aim was to determine the costs and investigate whether PAR with a multi-disciplinary approach was feasible in rural Tanzania with over 600 local stakeholders and more than 100 scientists. This article presents a self-evaluation of the collaboration and communication of project scientists during their research activities. Despite the overall high satisfaction, the more complex and complicated PAR activities required more cooperation, instructions and communication among the project scientists than had been anticipated in this multi-disciplinary, multi-cultural, and multi–institutional context, resulting in greater tension and dissatisfaction. The findings indicate that this type of large multidisciplinary PAR is challenging in terms of flexibility in the planning of research activities, the administration of finances, and cross-cultural communication. Potential avenues to overcome these obstacles include a) more communication on PAR activities across cultures to develop a shared vocabulary; b) developing other modes of shared responsibility for a more horizontal collaboration; and c) more face-to-face cross-cultural activities to overcome cultural, disciplinary and geographical distance.
Nitrogen and Phosphorus Fertilizer Micro-doses on Maize and Its Effect on P-foriability: An evidence from Sub-humid Farming Systems, Tanzania
(ournal of Economics, Management and Trade, 2018) Saidia, P.S; Graef, F; Rweyemamu, C.L; Kahimba, F.C; Semoka, J.M.R; Kimaro, A.A; Mwinuka, L; Mutabazi, K.D; Sieber, S
Despite a high productive potential for many best bet agricultural technologies, there is a low rate of adoption from farmers. Recommendations of improved technologies such as fertilizer use based on agronomic data without economic analysis contributes to this low adoption rate. The purpose of this study was to evaluate the profitability of selected fertilizer types and rates in maize production in a sub-humid farming system. A field experiment was conducted to investigate costs and revenue of fertilizer types and rates applied on maize farms using a split-plot layout under randomized complete block design. The phosphate fertilizers trialed were local Minjingu Mazao (MM), diammonium phosphate (DAP) and triple super phosphate (TSP), urea was used to supply nitrogen. Fertilizer rates were micro-doses at 12.5%, 25%, 50% and 75% compared to control and recommended rates. Local MM at 75% micro-dosing produced the highest net benefit 3.0 – 3.5 million Tanzanian Shillings per hectare (TZS/ha) followed by 2.7 – 2.9 million TZS/ha from TSP at recommended rates and DAP at a 75% micro-dose rate under subsistence farming. Micro-dosing fertilizer at 25% and 50% produced the highest benefit-cost ratio under both commercial and subsistence farming conditions. Micro-dosing at a rate of 12.5% was more profitable than the control rate and farm profitability increased towards 25% and 50%, thereafter decreasing as application approached the recommended rate. Adoption of micro-dosing fertilizer at 12.5% could be an entry point to fertilizer use and to later be advanced to 25% and 50% micro-dosing rates which are more profitable under smallholder farming systems in sub-humid tropics.
Soil moisture management and fertilizer micro-dosing on yield and land utilization efficiency of inter-cropping maize-pigeon-pea in sub humid Tanzania
(Elsevier, 2019-07) Saidia, P.S; Rweyemamu, C.L; Semoka, J.M.R; Kimaro, A.A; Germer, J; Asch, F; Kahimba, F.C; Graef, F; Lagweni, P.P
Principally caused by soil water stress and declining soil fertility, low crop productivity results in both food and income insecurity. The eﬀects of nitrogen and phosphorus fertilizer micro-dosing with inter-row rainwater harvesting practices for maize and pigeon-pea inter-cropping on yield and land use efciency are inadequately documented in sub humid tropics. A feld experiment on sandy loam soils in sub humid conditions using a splitsplit plot design was conducted. Plots used in situ rainwater harvesting practices of tied ridges, open ridges, and ﬂat cultivation. Sub-plots were sole maize, sole pigeon-pea, and 1:1 maize-pigeon pea inter-cropping. The subsub plots were control, fertilizer (N and P) application at the micro-dose level, and recommended rates. Tied ridges signifcantly (p < 0.001) conserved more soil moisture than ﬂat cultivation at 30 cm depth after ten days of rainfall. Ridges increased maize yield by 0.3 t ha−1 over ﬂat cultivation. Fertilizer application signifcantly (p < 0.001) increased maize yield by 1.12 t ha−1 with micro-dosing and by 1.60 t ha−1 with recommended rates over the control. Combining tied ridges and fertilizer signifcantly (p < 0.040) increased maize yield by 132–156% compared to ﬂat cultivation without fertilizer. Reﬂecting a land equivalent ratio, land use efciency was 67–122% higher in inter-cropping than sole crop. Tied ridges conserved more soil moisture than ﬂat cultivation, enhancing fertilizer use efciency that improved crop yields and land equivalent ratio under intercropping. This strategy could increase food availability and income generation under smallholder farming systems in sub-humid tropic areas.