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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    Agronomic and environmental studies of potato (Solanum tuberosum L.) and analysis of its value chain in Zimbabwe
    Svubure, O. - \ 2015
    Wageningen University. Promotor(en): Paul Struik; Anton Haverkort, co-promotor(en): J.M. Steyn. - Wageningen : Wageningen University - ISBN 9789462575646 - 220
    solanum tuberosum - aardappelen - waardeketenanalyse - voedselzekerheid - duurzaamheid (sustainability) - gebruiksefficiëntie - modellen - agronomie - akkerbouw - zimbabwe - solanum tuberosum - potatoes - value chain analysis - food security - sustainability - use efficiency - models - agronomy - arable farming - zimbabwe

    Keywords: Irish potato, food security, stakeholder analysis, sustainability indicators, Cool Farm Tool-Potato, yield gap, resource use efficiency, LINTUL-POTATO model, Zimbabwe.

    Oniward Svubure (2015). Agronomic and environmental studies of potato (Solanum tuberosum L.) and analysis of its value chain in Zimbabwe. PhD thesis, Wageningen University, The Netherlands, with English summary, 220 pp.

    Irish potato is food for more than a billion people worldwide. In Zimbabwe, Irish potato is becoming an important food crop. The government declared it a national strategic food security crop on 18 May 2012. This major policy pronouncement, qualified Irish potato for government initiated farmer support initiatives such as mechanisation and irrigation capacity building. The growing importance of potato as a food crop is prefaced on rising food insecurity in the country coupled with the impact of the radical land reform of 2000 on agricultural production. The land reform completely restructured commercial agriculture when about 96 % of the original 12.5 million ha of large-scale commercial farmland in 1980 was taken up for resettlement by 2010. Two resettlement models were used, the A1 and A2 resettlement models. The former resembles the communal area land allocation system while the later are self-contained small to medium scale farm units ranging about 35 to 300 ha. The newly resettled farmers have started growing potato adding to the already existing communal area and the few remaining large-scale commercial farmers. It is in this context that the potential of the new agrarian structure to sustainably increase Irish potato production was investigated. Increasing potato production on a sustainable basis will enable the crop to assert itself as a national strategic food security crop and help ease the food security challenges the country is grappling with. A grower survey was conducted on the cultural practices, input use, average yield, and infrastructure for potato production. The survey data was used to categorise the growers. Only growers with a minimum 5 years continuous potato growing experience were targeted making the data collected dependable. Grower resource footprints of land, water, biocides and nutrients were calculated based on the actual yield, Ya. Further, the Ya data collected were used to calculate the yield gap, YG, based on the yield of the best performing growers, Yh, simulated yield potential, Yp, and water-limited potential yield, Yw, of the respective agro-ecological areas. The LINTUL-POTATO model was used to estimate Yp, Yw and water need. This model simulates potential dry matter production based on radiation use efficiency of intercepted light by the potato crop. Another model, the Cool Farm Tool-Potato was used to further distinguish and appraise the production systems in terms of yields, inputs and efficient use of energy as reflected in their CO2 balances. The model calculates the contributions of various production operations to the total greenhouse gas (GHG) emission. Consequently, grower practices which contribute the most to the GHG emission were identified and generic mitigation measures for each production system were suggested. Realising the growing importance of sustainability issues in agricultural production and the scarcity of evaluation protocols in cropping systems, the study developed a framework that can be used to evaluate cropping systems. The framework was constructed using the potato-based cropping systems in the Eastern Highlands of Zimbabwe. Finally, instead of just focusing on the production related aspects only, the study also took into cognisance the need to understand the performance of the entire Irish potato sector in Zimbabwe. A value-chain analysis was therefore conducted to evaluate the performance the Irish potato sector in the country. Irish potato production in Zimbabwe is still low. Experts estimate annual production at nearly 120,000 t from around 6,000 ha. The large-scale commercial and the A2 resettlement are large-scale, high input and mechanised systems with an average potato area of 9 ha per planting. The communal area and A1 resettlement are smallholder low input systems with average potato area per planting of 0.8 ha and animal-drawn equipment is used. On resource use efficiencies, the actual tuber yield ranged from 8 – 35 t/ha across all systems representing a yield gap of over 77 %. Comparing with the simulated average potential yield, the mean actual yield observed ranged from 8 to 35 % of the simulated potential yield, translating to a yield gap of 65 to 92 %. Hence there is a large potential to increase potato production in these environments. The nutrient use efficiencies range were: 97 to 162 g potato g-1 N, 93–105 g potato g-1 P2O5 and 97–123 g potato g-1 K2O. This was anticipated because of the high synthetic fertiliser use and the low actual yields reported. The biocide use efficiencies ranged from 0.5 to 0.9 kg potato g-1 active ingredient (a.i.) fungicide, and 8 to 15 kg potato g-1 a.i. insecticide. Regarding water use, the average water use efficiency based on irrigation water and rainfall, ranged from 2 to 6 g potato l-1, while the simulated potential water use efficiency from irrigation and precipitation ranged from 9 to 17 g potato l-1. The large gap observed between actual and potential water use efficiency shows the scope to improve crop management practices to increase actual yield while lowering irrigation water. On the CO2 balance of the systems, a high carbon footprint was reported with an average of 251 kg CO2 eq./t potato. The least average carbon footprint was 216 kg CO2 eq./t potato for the communal area, while the A2 resettlement system had the highest of 286 kg CO2 eq./t potato. The high carbon footprint was anticipated as a reflection of the systems’ inefficiencies in terms of low yields and high input use. Focussing on the performance of the entire Irish potato sector, value chain analysis showed considerable levels of value-addition and gross profit of at least 13 % at each linkage. While the sector enjoys government policy support, major factors impacting on the value-chain performance relate to high potato production costs, low yields, and lack of farmer training. On the proposed framework on cropping sustainability, the indicator thresholds serve to monitor farmer progress as they improve their practices towards the desired direction of sustainability. This study demonstrated that there is tremendous potential to increase potato output and help ease the food insecurity challenges the country currently faces.

    Climate Smart Agriculture: Synthesis of case studies in Ghana, Kenya and Zimbabwe
    Hengsdijk, H. ; Conijn, J.G. ; Verhagen, A. - \ 2015
    Wageningen : Wageningen UR (Report / Plant Research International 624) - 26
    stadslandbouw - biologische landbouw - duurzame landbouw - metriek stelsel - ghana - kenya - zimbabwe - engelssprekend afrika - agrarische productiesystemen - klimaatadaptatie - voedselveiligheid - urban agriculture - organic farming - sustainable agriculture - metric system - ghana - kenya - zimbabwe - anglophone africa - agricultural production systems - climate adaptation - food safety
    This study contributes to the current debate on climate smart agriculture and development in Africa, specifically in relation to farm size, food security and intensification in rain fed farming areas. Although the different analyses are rough, because of a combination of incomplete knowledge and limited data sets, the results places the prevailing development discussions in the context of CSA: Provides intensification a way out of poverty and contributes intensification to food security under climate change? How affects climate change crop yields and household income? Conflicts intensification with climate mitigation goals? These are some of the questions addressed for diverging case study areas in this study.
    The politics of IWRM in Southern Africa
    Mehta, L. ; Alba, R. ; Bolding, J.A. ; Denby, K. ; Derman, B. ; Hove, T. ; Manzungu, E. ; Movik, S. ; Prabhakaran, P. ; Koppen, B.M.C. - \ 2014
    International Journal of Water Resources Development 30 (2014)3. - ISSN 0790-0627 - p. 528 - 542.
    water-resources management - catchment management - developing-countries - zimbabwe - lessons
    This article offers an approach to the study of the evolution, spread and uptake of integrated water resources management (IWRM). Specifically, it looks at the flow of IWRM as an idea in international and national fora, its translation and adoption into national contexts, and the on-the-ground practices of IWRM. Research carried out in South Africa, Zimbabwe and Mozambique provides empirical insights into the politics of IWRM implementation in southern Africa, the interface between international and national interests in shaping water policies in specific country contexts, and the on-the-ground challenges of addressing equity, redress and the reallocation of water.
    Vulnerability and adaptation to climate variability and change in smallholder farming systems in Zimbabwe
    Rurinda, J. - \ 2014
    Wageningen University. Promotor(en): Ken Giller, co-promotor(en): P. Mapfumo; Mark van Wijk. - Wageningen : Wageningen University - ISBN 9789461739605 - 168
    klimaatverandering - kleine landbouwbedrijven - bedrijfssystemen - klimaatadaptatie - adaptatie - klimaat - gewasopbrengst - zimbabwe - climatic change - small farms - farming systems - climate adaptation - adaptation - climate - crop yield - zimbabwe

    Keywords: Climate change; Increased climate variability; Vulnerability; Smallholder farmers; Adaptation

    Climate change and increased climate variability are currently seen as the major constraints to the already stressed smallholder farming livelihood system in southern Africa. The main objectives of this study were first to understand the nature and sources of vulnerability of smallholder farmers to climate variability and change, and second to use this knowledge to evaluate possible farm-level management options that can enhance the adaptive capacity of smallholder farmers in the face of increased climate variability and long-term change in climate. The study was conducted in Makoni and Hwedza districts in eastern Zimbabwe. Local famers’ and expert empirical knowledge were combined using research tools that mainly included detailed field observations and surveys, systems analysis and field experimentation, and simulation modelling (the Agricultural Production Systems Simulator (APSIM)). To understand the nature and sources of vulnerability, long term climate data were analysed and farmers were interviewed individually and in groups. On-farm experimentation and simulation modelling were conducted to evaluate the impacts and interactions of adaptation options namely maize cultivar choice, staggered planting dates, and variable fertilizer rates, on maize yield under both short-term climate variability and long-term climate change. Another on-farm experiment was conducted to assess whether small grains (finger millet and sorghum) perform as well as maize under variable soil and rainfall conditions.

    The long-term rainfall and temperature analyses closely supports farmers’ perceptions that the total annual rainfall has so far not changed, but variability in the rainfall distribution within seasons has increased. The number of rain days has decreased, and the frequency of dry spells within season increased. The mean daily minimum temperature increased by 0.2°C per decade in Makoni, and by 0.5°C per decade in Hwedza, over the period from 1962 to 2000. The surface air temperature is further projected to increase significantly in Makoni and Hwedza, by 2100. The impacts of rising temperatures and increased rainfall variability among smallholder households were highly differentiated because different households depend on varied farming livelihood sub-systems, which were exposed uniquely to aspects of climatic risk. For example, livestock production was sensitive to drought due to lack of feed, affecting resource-endowed farmers, who often own relatively large herds of cattle. Crop production was more sensitive to increased rainfall variability, affecting especially farmers with intermediate resource endowment. Availability of wild fruits and social safety nets were affected directly and indirectly by extreme temperatures and increased rainfall variability, impacting the livelihoods of poorer farmers. Farmers have also access to different biophysical and socioeconomic resources such as fertilizer and farm labour inputs, and as a result they respond variedly to impacts of a changing climate. Thus, alongside climate variability and change, farmers also faced biophysical and socioeconomic challenges, and these challenges had strong interactions with adaptation options to climate change.

    Experimentation in this studydemonstrated that the maize cultivars currently on the market in Zimbabwe, and in many parts of southern Africa, exhibit narrow differences in maturity time such that they do not respond differently to prolonged dry spells. The yield performance for all three cultivars is projected to be similar in future change in climates, consistent with results from the experiments.In the current cropping system farmers can select any cultivar available on the market without a yield penalty. However, with climate change none of the available cultivars will be able to compensate for the decline in yield. Greater maize grain yields were obtained with both the early (25 October – 20 November) and normal (21 November – 15 December) plantings, with no significant differences between these planting windows(e.g. on average 5 t ha-1 in Makoni, and 3 t ha-1 in Hwedza for the high fertilization rate).Contrary to previous research findings, there is a reasonably wide planting window in which good yields can be obtained if the rains start on time, but if the start of the rains is delayed until after the beginning of December planting should be done as soon as possible. Regardless of the amount of fertilizer applied, yields were reduced strongly when planting was substantially delayed by four weeks after the start of the rainy season. Maize yielded more than finger millet and sorghum even when rainfall was poor in the 2010/2011 season. For example, maize yielded 2.4 t ha-1 compared with 1.6 t ha-1 for finger millet and 0.4 t ha-1 for sorghum in the 2010/2011 rainfall season in Makoni. Finger millet and sorghum failed to emerge unless fertilizer was applied. Application of manure alone failed to address this challenge of poor emergence until fertilizer was added. Sorghum suffered critical yield losses due to bird damage. The better performance of maize over finger millet and sorghum suggested that the recommendation to substitute small grains for maize as a viable adaptation option to a changing climate, will neither be the best option for robust adaptation nor attractive for farmers in southern Africa. Alternatively spreading crops across the farm and in time can be a viable strategy to spread climatic risk as well as improve human nutrition. Poor soil fertility constrained yield more strongly than rainfall and late planting, as demonstrated by the large yield gap (> 1.2 t ha-1) between the unfertilized and fertilized cultivars even in the poor rainfall season (2010/2011).

    Fertilization increased yield significantly under both the baseline and future climates particularly when planting before mid-December.The maize response to mineral nitrogen is, however, projected to decline as climate changes, although effects only become substantial towards the end of the 21st Century. Soil fertility management is therefore likely to be a major entry point for increasing the adaptive capacity of smallholder farmers to climate change and increased climate variability. However, management of factors related to both nutrient resource access and farmers decisions to enhance resource use efficiencies are critical if agriculture is to be used as robust adaptation options to climate change by smallholder in Southern Africa.

    Water management for rainfed maize in semi-arid Zimbabwe
    Nyakudya, I.W. - \ 2014
    Wageningen University. Promotor(en): Leo Stroosnijder. - Wageningen : Wageningen University - ISBN 9789461738981 - 148
    waterbeheer - zea mays - regenafhankelijke landbouw - akkerbouw - semi-aride klimaatzones - zimbabwe - grondbewerking gericht op bodemconservering - water management - zea mays - rainfed agriculture - arable farming - semiarid zones - zimbabwe - conservation tillage
    The potential of carbon sequestration to mitigate against climate change in forests and agro ecosystems of Zimbabwe
    Mujuru, L. - \ 2014
    Wageningen University. Promotor(en): Rik Leemans, co-promotor(en): Marcel Hoosbeek. - Wageningen : Wageningen University - ISBN 9789461739285 - 209
    koolstofvastlegging - klimaatverandering - bossen - agro-ecosystemen - mitigatie - koolstofvastlegging in de bodem - koolstofcyclus - koolstof - zimbabwe - carbon sequestration - climatic change - forests - agroecosystems - mitigation - soil carbon sequestration - carbon cycle - carbon - zimbabwe

    Climate change adversely affects human livelihoods and the environment through alteration of temperatures, rainfall patterns, sea level rise and ecosystem productivity. Developing countries are more vulnerable to climate change because they directly depend on agriculture and natural ecosystem products for their livelihoods. Mitigation of climate change impacts includes practices that can store carbon (C) in soil and biomass thus, reducing concentrations of atmospheric carbon dioxide (CO2) and other greenhouse gasses. In addition, planted and natural forests that store large amounts of C, can become key resources for mitigating and reducing vulnerability to climate change, whilst infertile agricultural soils require large amounts of chemical and/or organic fertilisers to improve productivity. Increasing awareness about climate change mitigation has led to realisation of a need for sustainable land management practices and promoting soil C sequestration to reduce the greenhouse effects.

    The C storage potential of agricultural soils is compounded by conventional tillage practices, covering large areas with only small portions of fields dedicated to conservation farming practices. Maintaining soil and crop productivity under these agricultural systems becomes a major challenge especially in rain-fed arid and semi-arid regions, characterised by long annual dry spells. Conservation tillage practices, such as no-till and reduced tillage, have been reported to increase soil organic carbon (SOC) stocks in agricultural systems as they reduce soil disturbance, whereas conventional tillage has been criticised for causing soil C losses, accelerating soil erosion and displacing of soil nutrients, despite benefits, such as reduced soil compaction, weed control and preparation of favourable seedbed, which have been reported under conventional tillage. The identification of appropriate agricultural management practices is critical for realisation of the benefits of Soil C sequestration and reducing emissions from agricultural activities.

    This thesis was planned to improve our understanding on how tillage, fertilisation, tree planting or natural forest conservation can enhance C sequestration and thus mitigate climate change. The main goal was to quantify the influence of tillage, fertilisation and plantation forestry practices on C and N dynamics in bulk soil and density separated soil organic matter (SOM) fractions relative natural forest. Tillage treatments under reduced tillage (RP), no tillage (DS) and conventional tillage (CT) were compared with natural forests (NF) in sandy Haplic Arenosols and clayey Rhodic Ferralsols. Impacts of fertilisation were assessed from three fertility treatments; unfertilised control (control), nitrogen fertiliser (N Fert) and nitrogen fertiliser plus cattle manure (N Fert + manure) in conventionally tilled fields on Arenosols (sandy soil) and Luvisols (clayey soil) along two soil fertility gradients. Similarly, C and N storage in tree farming was studied using a Pinus patula chronosequence. Soil sampling followed randomised complete block design with four replications in agricultural systems and two replicates in each plantation age stands and natural forest. Sodium polytungstate (density 1.6 g cm-3) was used to isolate organic matter into free light fraction (fLF), occluded light fraction (oLF) and mineral associated heavy fraction (MaHF). Carbon an N were analysed by dry combustion and C and N stocks calculated using bulk density, depth and C and N concentration. The RothC model was used to match density separated fractions with conceptual model pools for agricultural and natural forest soils.

    Findings from tillage studies showed significantly larger C and N stocks in natural forests than tillage systems despite the open access use of the natural forests. The C and N stocks were significantly lower in sandy than clayey soils. At 0–10 cm depth, SOC stocks increased under CT, RP and DS by 0.10, 0.24, 0.36 Mg ha−1yr−1 and 0.76, 0.54, 0.10 Mg ha−1yr−1 on sandy and clayey soils respectively over a four year period while N stocks decreased by 0.55, 0.40, 0.56 Mg ha−1yr−1 and 0.63, 0.65, 0.55 Mg ha−1yr−1 respectively. Under prevailing climatic and management conditions, improvement of residue retention could be a major factor that can distinguish the potential of different management practices for C sequestration.

    Among the fertility treatments, there were significantly higher SOC and TON stocks under N Fert and N Fert + manure at 0-10 cm soil depth in Luvisols. Although this effect was not significant at 20-30 cm and 30-50 cm depth. On Arenosols, N Fert had highest C and N at all depths except at 0-10 cm. The storage of C and N on Luvisols, followed: control < N Fert < N Fert + manure whereas Arenosols had control < N Fert + manure < N Fert. Compared with control, N Fert and N Fert + manure enhanced fLF C on homefields and outfields by 19%, 24% and 9%, 22% on Luvisols and 17%, 26% and 26%, 26% respectively on Arenosols. Homefields on Luvisols, under N Fert and N Fert + manure had similar equilibrium levels, which were 2.5 times more than control.

    Forests play a major role in regulating the rate of increase of global atmospheric CO2 storing C in soil and biomass although the C storage potential varies with forest type and plant species composition. In this research, storage of C and N were highest in moist forest and lowest in the Miombo woodland. In both natural and planted forests, above ground tree biomass was the major ecosystem C pool followed by forest floor’s humus (H) layer. The mineral soil had 45%, 31% and 24% of SOC stored at the 0–10, 10–30 and 30–60 cm soil depths respectively. Stand age affected C and N storage significantly having an initial decline after establishment recovering rapidly up to 10 years, after which it declined and increased again by 25 years. Average soil C among the Pinus compartments was 12 kg m-2, being highest at 10 years and lowest in the 1 year old stands. Organic N was also highest at 10 years and least at 25 years. The proportional mass of fLF and oLF in Miombo woodlands was similar while the other stands had higher fLF than oLF. The highest LF was in the moist forest. In the Pinus patula stands the fLF C contributed between 22−25%, the oLF C contributed 8−16% and MaHF C contributed between 60−70% to total SOC. Carbon in MaHF and oLF increased with depth while the fLF decreased with depth in all except the 1 and the 10 year old stands. Conversion of depleted Miombo woodlands to pine plantations can yield better C gains in the short and long run whilst moist forests provide both carbon and biodiversity. Where possible moist forests should be conserved and enrichment planting done in degraded areas to sustain them and if possible the forests can be considered as part of future projects on reduced emission from deforestation and degradation (REDD+). It is believed that REDD+ can promote both conservation and socio economic welfare, including poverty alleviation by bringing together the development of the forest and climate change link in African forests and woodlands. The focus on the monetary valuation and payment for environmental services can contribute to the attraction of political support for soil conservation. Developing countries therefore, need to formulate enabling economic and institutional land management policies that have positive impacts on poverty alleviation, food security and environmental sustainability.

    Soil C models are used to predict impacts of land management on C storage. The RothC 2.63 model was used for estimating SOC stock under selected land management practices on the clayey and sandy soils of Zimbabwe. There is greater potential to store more C in clayey soils than sandy soils and in practices that receive more organic inputs. Results show that the RothC model pool of HUM + IOM is related to the measured MaHF from density fractionation and that the model can be used to estimate SOC stock changes on Zimbabwean agricultural and forest soils. The relationship between equilibrium levels estimated by the RothC model and those estimated using the Langmuir equation was good. A 1.5˚ C rise in temperature was found to cause the A and B systems on clayey soils to sequester more C. The results also show that, when holding all the other factors constant, the model is sufficiently sensitive to a rise in temperatures with sandy soils reaching an equilibrium much earlier than clayey soils. The modelling approach represents one of the most promising methods for the estimation of SOC stock changes and allowed us to evaluate the changes in SOC in the past period on the basis of measured data. However, since the data were obtained from short term experiments (4−9 years), further ground validation can be hampered by the lack of long-term experimental trials in the southern African region. The deficiency of adequate experimental sites also limits further work on model uncertainties. The understanding soil quality and dynamics however, helps to design sustainable agricultural systems, while achieving the urgently needed win-win situation in enhancing productivity and sequestering C.

    Panarchy rules? : rethinking resilience of agroecosystems
    Apeldoorn, D.F. van - \ 2014
    Wageningen University. Promotor(en): Ken Giller, co-promotor(en): Kasper Kok; Marthijn Sonneveld. - Wageningen : Wageningen University - ISBN 9789461739179 - 137
    agro-ecosystemen - duurzaamheid (sustainability) - bedrijfssystemen - organisch bodemmateriaal - wiskundige modellen - systeemanalyse - nederland - zimbabwe - agroecosystems - sustainability - farming systems - soil organic matter - mathematical models - systems analysis - netherlands - zimbabwe

    This thesis explores the applicability of the resilience perspective on agro-ecosystems dynamics. It start out by using the five heuristics of the resilience perspective on intensive agricultural systems. Simulations with a dynamic farm model suggest that conventional farming short cuts the adaptive cycle leading to an ‘incremental adaptation’ trap. Panarchy is therefore claimed as a leading heuristic to understand long-term dynamics and current management characteristics. This interaction of long-term dynamics with current management leads to an asymmetry in the landscape. This asymmetry leads to windows of opportunities for farmers. However, disregarding the cross-scale nature of the asymmetry might also lead to a cascade of events that undermine the resilience of the landscape as whole. The cross-scale interactions of landscape dynamics and farm management suggest a co-evolution of production intensity and landscape pattern. Moreover trajectories of intensification might even be linked to certain tipping points of combinations of landscape characteristics and management. Therefore the landscape asymmetry might yield insight in agro-ecosystem functioning. The landscape asymmetry potentially provides a level of self-organisation above the farm. However, identifying the asymmetry appeared to be problematic. Next to scale issues, the current pattern does not necessary result from current management, leading to a de-coupling of pattern and process. A re-coupling of management and landscape asymmetry can exploit positive feedbacks. I suggest the use of identity to locate asymmetries and to use space-time substitutions to experiment with the typical slow variables that shape the asymmetry.

    The theory developed in this thesis is grounded on empirical farm management data and dynamical model simulation of intensive dairy farming in the Netherlands and small-holder systems in Zimbabwe.

    Comparative assessment of maize, finger millet and sorghum for household food security in the face of increasing climatic risk
    Rurinda, J. ; Mapfumo, P. ; Wijk, M.T. van; Mtambanengwe, F. ; Rufino, M.C. ; Chikowo, R. ; Giller, K.E. - \ 2014
    European Journal of Agronomy 55 (2014). - ISSN 1161-0301 - p. 29 - 41.
    southern africa - soil fertility - pearl-millet - sandy soil - zimbabwe - variability - management - adaptation - productivity - agriculture
    Questions as to which crop to grow, where, when and with what management, will be increasingly challenging for farmers in the face of a changing climate. The objective of this study was to evaluate emergence, yield and financial benefits of maize, finger millet and sorghum, planted at different dates and managed with variable soil nutrient inputs in order to develop adaptation options for stabilizing food production and income for smallholder households in the face of climate change and variability. Field experiments with maize, finger millet and sorghum were conducted in farmers’ fields in Makoni and Hwedza districts in eastern Zimbabwe for three seasons: 2009/10, 2010/11 and 2011/12. Three fertilization rates: high (90 kg N ha-1, 26 kg P ha-1, 7 t ha-1 manure), low (35 kg N ha-1, 14 kg P ha-1, 3 t ha-1 manure) and a control (zero fertilization); and three planting dates: early, normal and late, were compared. Crop emergence for the unfertilized finger millet and sorghum was 70% for the fertilized treatments. In contrast, the emergence for maize (a medium-maturity hybrid cultivar, SC635), was >80% regardless of the amount of fertilizer applied. Maize yield was greater than that of finger millet and sorghum, also in the season (2010/11) which had poor rainfall distribution. Maize yielded 5.4 t ha-1 compared with 3.1 t ha-1 for finger millet and 3.3 t ha-1 for sorghum for the early plantings in the 2009/10 rainfall season in Makoni, a site with relatively fertile soils. In the poorer 2010/11 season, early planted maize yielded 2.4 t ha-1, against 1.6 t ha-1 for finger millet and 0.4 t ha-1 for sorghum in Makoni. Similar yield trends were observed on the nutrient-depleted soils in Hwedza, although yields were less than those observed in Makoni. All crops yielded significantly more with increasing rates of fertilization when planting was done early or in what farmers considered the ‘normal window’. Crops planted early or during the normal planting window gave comparable yields that were greater than yields of late-planted crops. Water productivity for each crop planted early or during the normal window increased with increase in the amount of fertilizer applied, but differed between crop type. Maize had the highest water productivity (8.0 kg dry matter mm-1 ha-1) followed by sorghum (4.9 kg mm-1 ha-1) and then finger millet (4.6 kg mm-1 ha-1) when a high fertilizer rate was applied to the early-planted crop. Marginal rates of return for maize production were greater for the high fertilization rate (>50%) than for the low rate (100%) than for the high rate (
    Improving the efficiency of use of small amounts of nitrogen and phosphorus fertilizer on smallholders maize in Central Malawi
    Kamanga, B.C.G. ; Waddington, S.R. ; Almekinders, C.J.M. ; Giller, K.E. - \ 2014
    Experimental Agriculture 50 (2014)2. - ISSN 0014-4797 - p. 229 - 249.
    soil fertility - simulating response - mucuna-pruriens - management - dynamics - zimbabwe - crop - africa - model
    Mineral fertiliser is a scarce input for smallholder maize farmers in Malawi. A recent provision of small amounts of subsidised fertilisers by government programmes to farmers throughout Malawi has increased fertiliser access and raised maize production, but fertiliser management and yield responses frequently remain poor. To seek ways to use the fertiliser more efficiently, we analysed the effects of low rates of N (15 or 30 kg N ha-1) and P (9 kg P ha-1) fertiliser in combination with improved weed management on maize yields in experiments on 12 smallholder farms in Chisepo, central Malawi. Several indices of N and P use efficiency were computed from the above-ground crop components and nutrient contents. Maize yield simulations were conducted using long-term rainfall records in the APSIM crop-soil system model. NP fertiliser significantly (p <0.001) raised maize grain yield from 0.65 to 1.5 t ha-1, and twice-weeding fertilised maize significantly (p <0.001) raised maize yields by 0.4 t ha-1 compared with weeding once (0.9 t ha-1). The agronomic efficiency of applied fertiliser N (AEN) averaged 19.3 kg grain kg N-1 with one weeding but doubled to 38.7 kg with the additional weeding. The physiological efficiency of applied N (PEN) was 40.7 kg grain kg-1 N uptake. APSIM predicted that similar or larger maize yield responses to 15 or 30 kg N ha-1 can be expected in 8 out of 10 years in areas with similar rainfall patterns to Chisepo. A financial analysis showed that the application of these small amounts of fertiliser was economic even when fertiliser was purchased from the open market, provided the crop was adequately weeded. Participatory assessments helped farmers understand the increased efficiency of fertiliser use possible with additional weeding, although some farmers reported difficulty implementing this recommendation due to competing demands for labour. We conclude that to raise the productivity and sustainability of fertiliser support programmes in Malawi, initiatives should be introduced to help identify and educate farmers on the major drivers of productivity in their systems.
    Vegetation factors influencing density and distribution of wild large herbivores in a southern African savannah
    Gandiwa, E. - \ 2014
    African Journal of Ecology 52 (2014)3. - ISSN 0141-6707 - p. 274 - 283.
    gonarezhou-national-park - distribution patterns - ungulate diversity - semiarid savanna - water sources - zimbabwe - heterogeneity - populations - elephant - habitat
    Understanding factors influencing large herbivore densities and distribution in terrestrial ecosystems is a fundamental goal of ecology. This study examined environmental factors influencing the density and distribution of wild large herbivores in Gonarezhou National Park, Zimbabwe. Vegetation and surface water were predicted to have a stronger influence than anthropogenic-related disturbances (livestock grazing, fires, settlements and poaching) on the density and distribution of wild large herbivores. Aerial survey data for seven common wild large herbivores conducted in 2007 and 2009 and environmental data were collected. Only grass cover explained a significant proportion of the variation in large herbivore densities and distribution. Moreover, only two species densities significantly differed across the Gonarezhou, namely impala and zebra. In contrast, buffalo, elephant, giraffe, kudu and nyala densities did not differ significantly across the Gonarezhou. Overall, the findings only partly support the study prediction. The study results suggest the need to further investigate the roles of environmental factors at smaller scales in order to tease out their relative strengths in influencing density and distribution of large herbivores.
    Understanding the impact and adoption of conservation agriculture in Africa: a multi-scale analysis
    Corbeels, M. ; Graaff, J. de; Hycenth Ndah, T. ; Penot, E. ; Baudron, F. ; Naudin, K. ; Andrieu, N. ; Chirat, G. ; Schuler, J. ; Nyagumbo, I. ; Rusinamhodzi, L. ; Traore, K. ; Mzoba, H.D. ; Adolwa, I.S. - \ 2014
    Agriculture, Ecosystems and Environment 187 (2014). - ISSN 0167-8809 - p. 155 - 170.
    crop residues - soil quality - productivity - zimbabwe - maize - yield - intensification - tillage - poverty - systems
    Conservation agriculture (CA) is increasingly promoted in Africa as an alternative for coping with the need to increase food production on the basis of more sustainable farming practices. Success with adopting CA on farms in Africa has been limited, despite more than two decades of research and development investments. Through analyzing past and on-going CA experiences in a set of case studies, this paper seeks to better understand the reasons for the limited adoption of CA and to assess where, when and for whom CA works best. CA is analyzed and understood within a framework that distinguishes the following scales of analysis: field, farm, village and region. CA has a potential to increase crop yields in the fields, especially under conditions of erratic rainfall and over the long-term as a result of a gradual increase of overall soil quality. The impact on farm income with the practice of CA on some fields of the farm is far less evident, and depends on the type of farm. The lack of an immediate increase in farm income with CA explains in many cases the non-adoption of CA. Smallholders have often short-term time horizons: future benefits do not adequately outweigh their immediate needs. Another key factor that explains the limited CA adoption in mixed crop-livestock farming systems is the fact that crop harvest residues are preferably used as fodder for livestock, preventing their use as soil cover. Finally, in most case studies good markets for purchase of inputs and sale of produce – a key prerequisite condition for adoption of new technologies – were lacking. The case studies show clear evidence for the need to target end users (not all farmers are potential end user of CA) and adapt CA systems to the local circumstances of the farmers, considering in particular the farmer's investment capacity in the practice of CA and the compatibility of CA with his/her production objectives and existing farming activities. The identification of situations where, when and for whom CA works will help future development agents to better target their investments with CA.
    Fermentation characteristics of yeasts isolated from traditionally fermented masau (Ziziphus mauritiana) fruits
    Nyanga, L.K. ; Nout, M.J.R. ; Smid, E.J. ; Boekhout, C. ; Zwietering, M.H. - \ 2013
    International Journal of Food Microbiology 166 (2013)3. - ISSN 0168-1605 - p. 426 - 432.
    saccharomyces-cerevisiae - volatile compounds - wine yeasts - immobilized cells - grape varieties - zimbabwe - strains - metabolism - acid - evolution
    Yeast strains were characterized to select potential starter cultures for the production of masau fermented beverages. The yeast species originally isolated from Ziziphus mauritiana (masau) fruits and their traditionally fermented fruit pulp in Zimbabwe were examined for their ability to ferment glucose and fructose using standard broth under aerated and non-aerated conditions. Most Saccharomyces cerevisiae strains were superior to other species in ethanol production. The best ethanol producing S. cerevisiae strains, and strains of the species Pichia kudriavzevii, Pichia fabianii and Saccharomycopsis fibuligera were tested for production of flavor compounds during fermentation of masau fruit juice. Significant differences in the production of ethanol and other volatile compounds during fermentation of masau juice were observed among and within the four tested species. Alcohols and esters were the major volatiles detected in the fermented juice. Trace amounts of organic acids and carbonyl compounds were detected. Ethyl hexanoate and ethyl octanoate were produced in highest amounts as compared to the other volatile compounds. S. cerevisiae strains produced higher amounts of ethanol and flavor compounds as compared to the other species, especially fatty acid ethyl esters that provide the major aroma impact of freshly fermented wines. The developed library of characteristics can help in the design of mixtures of strains to obtain a specific melange of product functionalities. Keywords: Masau juice; Fermentation; Yeast; Volatile compounds; Flavor; Wine
    African wildlife and people : finding solutions where equilibrium models fail
    Poshiwa, X. - \ 2013
    Wageningen University. Promotor(en): Herbert Prins; Ekko van Ierland, co-promotor(en): Ignas Heitkonig; Rolf Groeneveld. - Wageningen : Wageningen UR - ISBN 9789461737618 - 173
    wild - extensieve weiden - evenwicht - droogte - mensen - herbivoren - vee - verstoring - ecologische verstoring - zimbabwe - afrika - wildlife - rangelands - equilibrium - drought - people - herbivores - livestock - disturbance - ecological disturbance - zimbabwe - africa

    Grazing systems, covering about half of the terrestrial surface, tend to be either equilibrial or non-equilibrial in nature, largely depending on the environmental stochasticity.The equilibrium model perspective stresses the importance of biotic feedbacks between herbivores and their resource, while the non-equilibrium model perspective stresses stochastic abiotic factors as the primary drivers of vegetation and herbivore dynamics.In semi-arid and arid tropical systems, environmental stochasticity is rather high, making the systems essentially non-equilibrial in nature, suggesting that feedback between livestock and vegetation is absent or at least severely attenuated for much of the time. In southern Africa, range and livestock management however, has been built around the concept of range condition class and the practices of determining carrying capacities and manipulating livestock numbers and grazing seasons to influence range condition. This management approach is derived from the equilibrium or climax concept of Clementsian succession. The erratic and variable rainfall in many pastoral areas of Africa poses a fundamental challenge to this conventional notion of carrying capacity in range management. This realization has caused a shift towards models that embrace non-equilibrium dynamics in ecosystems. The main concern is that application of the range model may contribute to mismanagement and degradation of some rangeland ecosystems. However, only a few studies in rangelands have empirically tested the non-equilibrium hypothesis leading to the debate on rangeland dynamics remaining unresolved.

    Across the savannas of Africa, grasslands are being changed into cultivation due to increasing human population, at the expense of decreasing wildlife populations. African savannas however, still contain pockets of wilderness surviving as protected areas, but even there, species richness of large mammals is decreasing. The inevitable result is the loss of most of the wild plants and animals that occupy these natural habitats, at the same time threatening the well-being of the inhabitants of these savannas. Hence, to facilitate the management of arid and semi-arid savannas for both biological conservation and sustainable use (improving human welfare) an improved understanding of the complex dynamics of these savannas is critical. Furthermore, it is widely recognized that a high level of uncertainty typifies the lives of rural farmers in developing countries.Non-equilibrium dynamics bring additional uncertainty and risk to the system.However, attempts to understand efficient and sustainable ways to improve biodiversity and human welfare in systems showing non-equilibrium dynamics have been rare.The behaviour of non-equilibrium systems is characterised as more dynamic and less predictable than equilibrium systems. Therefore, non-equilibrium dynamics in dryland ecosystems present a different kind of management problem for both livestock and wildlife systems since their management has been dictated by the equilibrium assumption. Additionally, loss of biodiversity is regarded today as one of the great unsolved environmental problems.Faced with this biodiversity crisis, the challenge is to find ways to respond in a flexible way to deal with uncertainty and surprises brought about by non-equilibrium dynamics.

    In this thesis I use a bioeconomic approach in analyzing the implications of non-equilibrium dynamics for the efficient and sustainable management of wildlife and livestock in dryland grazing systems. The study area for this thesis is southeastern lowveld of Zimbabwe.

    In chapter 2, I investigate the role of abiotic and biotic factors in determining plant species composition. While early studies emphasized the importance of edaphic and environmental controls on plant species distribution and spatial variation in vegetation composition, recent studies have documented the importance of both natural and anthropogenic disturbances in this respect. At a regional scale vegetation structure (i.e., grass/tree ratio) and species composition in savannas is largely determined by precipitation, whereas at the nested landscape-scale vegetation structure and composition is more prominently determined by geologic substrate, topography, fire and herbivory. Chapter 2, shows that at the landscape scale, abiotic variables such as rainfall and soil fertility override the effect of humans and livestock on the herbaceous and the woody plant composition.

    Then, in Chapter 3, I ask the question whether there is something like non-equilibrium and what are the impacts of such dynamics on cattle herd dynamics? I studied the relevance of non-equilibrium theory to my study area by testing whether annual changes in cattle numbers showed the presence of crashes and if so, what were the factors best explaining those crashes and what age and sex classes of cattle were most vulnerable to such crashes? Chapter 3 showed that crashes in annual cattle numbers were evident and were best explained by rainfall and NDVI and their lags. Immigration i.e., movement in of animals was also an important factor in years when rainfall was below the threshold and so it was a possible source of cattle recovery after a crash together with high calving rates. In years when rainfall was above the rainfall threshold, NDVI explained more variation in annual changes of livestock. The impacts of crashes were greater on calves than other cattle age categories thus explaining why there are legacy effects (lags) in cattle numbers that can only partly be offset by cattle purchases from elsewhere because of poverty or lack of surplus stock elsewhere. These findings make the southeastern lowveld system to be dominated by non-equilibrium dynamics.

    The welfare of local people is the issue that I focused on in my economic section of this thesis (Chapters 4 and 5). I addressed the question of how risks of fluctuations in household income can be managed in order to improve human welfare. The expectation was that in systems exhibiting non-equilibrium dynamics people can improve their welfare by exploiting a combination of wildlife and agricultural activities (livestock and cropping) in their attempts to reduce fluctuations in their annual welfare. This would be possible if the risks in wildlife and agro-pastoral systems were sufficiently different. Exploiting different sources of income requires efficient allocation of resources. The most prominent resource is land and land varies spatially in quality and ecological resources require spatial connectivity. Therefore the spatial dimension is important in this allocation.

    In Chapter 4 I asked the question: To what extent can wildlife income buffer rural households’ incomes against fluctuations in rainfall? I studied the extent to which wildlife derived income can buffer local households’ income against fluctuations due to rainfall. The addition of wildlife as an asset for rural farmers’ portfolio of assets showed that wildlife can be used as a hedge asset to offset risk from agricultural production without compromising on return. However, the power of diversification using wildlife is limited because revenues from agriculture and wildlife assets were positively correlated. However, the correlation was very weak (only 0.4 and the explained variance thus only be 16 %) which gives ample scope for buffering. Therefore, revenues from wildlife have potential to reduce household income fluctuations due to drought, but only to a limited extent.

    In Chapter 5 the question was: From a theoretical perspective, can wildlife income have an insurance value to local people? I used a modelling approach to study the extent to which wildlife income offers an insurance value to local people against fluctuating annual rainfall. Findings did not support the common assertion that wildlife can offer insurance to local people against income fluctuations due to rainfall fluctuations. The failure by wildlife income to offer insurance value to local people could be explained by high costs of harvesting the wildlife resource and high densities of both human and livestock populations in southeastern lowveld.As corollary I draw the conclusion that wildlife cannot pay its way in these rangelands as long as there are high densities of people as shown in Chapter 5. Definitely wildlife income becomes insufficient if long-term sustainability of wildlife resources is considered.

    Chapter 6, finally synthesizes the conclusions that can be drawn from the preceding chapters and puts the issues addressed in a broader context. In summary, this thesis shows evidence of non-equilibrium dynamics in semi-arid grazing systems. Furthermore, the small contribution of wildlife income to local people’s welfare goes to show the widely shared view that financial rewards generated through integrated conservation and development programmes such as CAMPFIRE have generally been seen as insufficient. This led me to suggest that if we have a moral or ethical obligation to protect wildlife species, then an important way for people to meet their aspirations economically was suggested by Malthus.

    Factors affecting domestic water consumption in rural households upon access to improved water supply: insights from the Wei River Basin, China
    Fan, L. ; Liu, G. ; Wang, F. ; Geissen, V. ; Ritsema, C.J. - \ 2013
    PLoS ONE 8 (2013)8. - ISSN 1932-6203
    path-coefficient analysis - developing-countries - sensitivity-analysis - use patterns - zimbabwe - behavior - disease - storage - home
    Comprehensively understanding water consumption behavior is necessary to design efficient and effective water use strategies. Despite global efforts to identify the factors that affect domestic water consumption, those related to domestic water use in rural regions have not been sufficiently studied, particularly in villages that have gained access to improved water supply. To address this gap, we investigated 247 households in eight villages in the Wei River Basin where three types of improved water supply systems are implemented. Results show that domestic water consumption in liters per capita per day was significantly correlated with water supply pattern and vegetable garden area, and significantly negatively correlated with family size and age of household head. Traditional hygiene habits, use of water appliances, and preference for vegetable gardening remain dominant behaviors in the villages with access to improved water supply. Future studies on rural domestic water consumption should pay more attention to user lifestyles (water appliance usage habits, outdoor water use) and cultural backgrounds (age, education).
    The numbers game in wildlife conservation: changeability and framing of large mammal numbers in Zimbabwe
    Gandiwa, E. - \ 2013
    Wageningen University. Promotor(en): Herbert Prins; Cees Leeuwis, co-promotor(en): Ignas Heitkonig. - S.l. : s.n. - ISBN 9789461737465 - 204
    wildbescherming - zoogdieren - jachtdieren - populatiedynamica - populatie-ecologie - populatiebiologie - jagen - wild - zimbabwe - wildlife conservation - mammals - game animals - population dynamics - population ecology - population biology - hunting - wildlife - zimbabwe

    Wildlife conservation in terrestrial ecosystems requires an understanding of processes influencing population sizes. Top-down and bottom-up processes are important in large herbivore population dynamics, with strength of these processes varying spatially and temporally. However, up until recently the role of human-induced top-down and bottom-up controls have received little attention. This is despite the fact that almost all terrestrial ecosystems are influenced by human activities thereby likely altering the natural control of animal populations. Therefore, in this thesis, the role of natural and human-induced controls in influencing large herbivore populations and how human controls (i.e., policy instruments, incentives and provisions) influence human activities and wildlife conservation in a semi-arid African savanna ecosystem are investigated. This study primarily focuses on Gonarezhou National Park (hereafter, Gonarezhou), Zimbabwe and adjacent areas. Zimbabwe experienced an economic crisis and political instability between 2000 and 2008 following the land reforms that started in 2000 which were widely covered in the mass media.

    The results indicated a weak synchrony in rainfall and drought occurrence (natural bottom-up process) in areas within the same “climatic” region, and variable responses of large herbivore species to the 1992 severe drought with most large herbivore species’ populations declining following the 1992 drought and increasing thereafter. Therefore, droughts are important in influencing large herbivore populations in semi-arid ecosystems. Furthermore, the results showed variation in the intensity of illegal hunting (top-down human control) which was associated with variation in law enforcement efforts in Gonarezhou. Law enforcement efforts in Gonarezhou were strengthened in 2004 following the employment of additional patrol rangers which resulted in increased park coverage and a decline in recorded illegal activities. Thus, the results show that political instability and economic collapse does not necessarily lead to increased illegal hunting in situations where policy instruments, such as laws, are enforced.

    A higher perceived effectiveness of Communal Areas Management Programme for Indigenous Resources (CAMPFIRE - a community-based program that allows local people living in communal areas near protected areas in Zimbabwe to financially benefit from using the wildlife resources within their area) was partly associated with a decline in human-wildlife conflicts. In addition, local communities with higher perceived effectiveness of CAMPFIRE programs partly had more favourable attitudes towards problematic wild animals. Moreover, the results showed that in the 1990s, the majority of newspaper articles highlighted that wildlife conservation in Zimbabwe was largely successful. However, following the land reforms that occurred in 2000, the international media lost interest in wildlife conservation in Zimbabwe, as evidenced by a sharp decline in published articles. Also, the frames changed in the international media with the “political unrest and land reform” blame frame becoming more dominant, and nature conservation was portrayed more negatively. The change in media frames shows that there was a spill-over effect from the political domain into wildlife conservation following Zimbabwe’s land reforms in 2000.

    Overall, this study provides new insights on the processes influencing large herbivore population dynamics in human-dominated semi-arid savanna ecosystems which consist of diverse wildlife management regimes and also illuminates the importance of media framing and (mis-)representation of wildlife conservation issues following political instability, crisis or societal unrest. With these findings, it is concluded that natural bottom-up processes (e.g., droughts) influence large herbivore population dynamics whereas policy instruments, incentives, provisions and societal frames mainly have a top-down effect on wild large herbivore populations in savanna ecosystems.

    Manage or convert Boswellia woodlands? Can frankincense production payoff?
    Dejene, T. ; Lemenih, M. ; Bongers, F. - \ 2013
    Journal of Arid Environments 89 (2013). - ISSN 0140-1963 - p. 77 - 83.
    forest products - south-africa - dry forests - papyrifera - ethiopia - environment - zimbabwe - trade
    African dry forests provide non-timber forest products (NTFPs) of high commercial value, such as frankincense and gum arabic. Nonetheless, their deforestation and conversion to croplands is intensifying. Expected higher financial return from crop production is a main driver of conversion, but research supporting this underlying claim is scarce. We compared the financial returns for two crop production options (sesame and cotton) and forest use, in a dry forest area known for its frankincense production in northern Ethiopia. Net revenue was highest for sesame and lowest for cotton agricultural use. The forest based revenue was intermediate. The revenues from the crop production options were more sensitive to a range of uncertainties than the forest land use. Our results show that forest land use that includes commercial NTFPs is financially competitive to some commercial crop options and offers returns of better reliability. The hypothesis that forest based revenues are lower than crop based ones is not supported by our results. Therefore, the continued deforestation of dry forests cannot be explained by lower returns alone, but other factors such as awareness, market access, property right and institutional issues may also play a role to drive deforestation and conversion of dry forests to croplands.
    Conservation Agriculture in mixed crop–livestock systems: Scoping crop residue trade-offs in Sub-Saharan Africa and South Asia
    Valbuena, D.F. ; Erenstein, O. ; Homann-Kee Tui, S. ; Abdoulaye, T. ; Claessens, L.F.G. ; Duncan, A.J. ; Gerard, B. ; Rufino, M. ; Teufel, N. ; Wijk, M.T. van - \ 2012
    Field Crops Research 132 (2012). - ISSN 0378-4290 - p. 175 - 184.
    smallholder farming systems - soil fertility management - pressure - food - productivity - strategies - community - dynamics - patterns - zimbabwe
    Conservation Agriculture (CA) is being advocated to enhance soil health and sustain long term crop productivity in the developing world. One of CA's key principles is the maintenance of soil cover often by retaining a proportion of crop residues on the field as mulch. Yet smallholder crop–livestock systems across Africa and Asia face trade-offs among various options for crop residue use. Knowledge of the potential trade-offs of leaving more residues as mulch is only partial and the objective of this research is to address some of these knowledge gaps by assessing the trade-offs in contrasting settings with mixed crop–livestock systems. The paper draws from village surveys in 12 sites in 9 different countries across Sub-Sahara Africa and South Asia. Sites were clustered into 3 groups along the combined population and livestock density gradients to assess current crop residue management practices and explore potential challenges to adopting mulching practices in different circumstances. Results show that although high-density sites face higher potential pressure on resources on an area basis, biomass production tends to be more substantial in these sites covering demands for livestock feed and allowing part of the residues to be used as mulch. In medium-density sites, although population and livestock densities are relatively lower, biomass is scarce and pressure on land and feed are high, increasing the pressure on crop residues and their opportunity cost as mulch. In low-density areas, population and livestock densities are relatively low and communal feed and fuel resources exist, resulting in lower potential pressure on residues on an area basis. Yet, biomass production is low and farmers largely rely on crop residues to feed livestock during the long dry season, implying substantial opportunity costs to their use as mulch. Despite its potential benefit for smallholder farmers across the density gradient, the introduction of CA-based mulching practices appears potentially easier in sites where biomass production is high enough to fulfil existing demands for feed and fuel. In sites with relatively high feed and fuel pressure, the eventual introduction of CA needs complementary research and development efforts to increase biomass production and/or develop alternative sources to alleviate the opportunity costs of leaving some crop residues as mulch.
    Yeasts preservation: alternatives for lyophilisation
    Nyanga, L.K. ; Nout, M.J.R. ; Smid, E.J. ; Boekhout, T. ; Zwietering, M.H. - \ 2012
    World Journal of Microbiology and Biotechnology 28 (2012)11. - ISSN 0959-3993 - p. 3239 - 3244.
    ziziphus-mauritiana - starter cultures - trehalose - viability - fermentation - survival - efficacy - zimbabwe - storage - fruits
    The aim of the study was to compare the effect of two low-cost, low technology traditional methods for drying starter cultures with standard lyophilisation. Lyophilised yeast cultures and yeast cultures preserved in dry rice cakes and dry plant fibre strands were examined for viable cell counts during 6 months storage at 4 and 25 °C. None of the yeast cultures showed a significant loss in viable cell count during 6 months of storage at 4 °C upon lyophilisation and preservation in dry rice cakes. During storage at 25 °C in the dark, yeast cultures preserved in dry rice cakes, and lyophilised cultures of Saccharomyces cerevisiae and Issatchenkia orientalis showed no significant loss of viable cells up to 4 months of storage. Yeast cultures preserved in dry plant fibre strands had the greatest loss of viable count during the 6 months of storage at 25 °C. Preservation of yeasts cultures in dry rice cakes provided better survival during storage at 4 °C than lyophilisation. The current study demonstrated that traditional methods can be useful and effective for starter culture preservation in small-scale, low-tech applications.
    The production-ecological sustainability of cassava, sugarcane and sweet sorghum cultivation for bioethanol in Mozambique
    Vries, S.C. de; Ven, G.W.J. van de; Ittersum, M.K. van; Giller, K.E. - \ 2012
    Global change biology Bioenergy 4 (2012)1. - ISSN 1757-1693 - p. 20 - 35.
    term crop response - fertilizer phosphorus - organic-matter - fuel ethanol - management - energy - residues - soils - zimbabwe - nitrogen
    We present an approach for providing quantitative insight into the production-ecological sustainability of biofuel feedstock production systems. The approach is based on a simple crop-soil model and was used for assessing feedstock from current and improved production systems of cassava for bioethanol. Assessments were performed for a study area in Mozambique, a country considered promising for biomass production. Our focus is on the potential role of smallholders in the production of feedstock for biofuels. We take cassava as the crop for this purpose and compare it with feedstock production on plantations using sugarcane, sweet sorghum and cassava as benchmarks. Production-ecological sustainability was defined by seven indicators related to resource-use efficiency, soil quality, net energy production and greenhouse gas (GHG) emissions. Results indicate that of the assessed systems, sugarcane performed better than cassava, although it requires substantial water for irrigation. Targeted use of nutrient inputs improved sustainability of smallholder cassava. Cassava production systems on more fertile soils were more sustainable than those on less fertile soils; the latter required more external inputs for achieving the same output, affecting most indicators negatively and reducing the feasibility for smallholders. Cassava and sweet sorghum performed similarly. Cassava production requires much more labour per hectare than production of sugarcane or sweet sorghum. Production of bioethanol feedstock on cultivated lands was more sustainable and had potential for carbon sequestration, avoiding GHG emissions from clearing natural vegetation if new land is opened.
    Elephants of democracy : an unfolding process of resettlement in the Limpopo National Park
    Milgroom, J. - \ 2012
    Wageningen University. Promotor(en): Cees Leeuwis; Ken Giller, co-promotor(en): J.L.S. Jiggins. - S.l. : s.n. - ISBN 9789461732699 - 322
    nationale parken - natuurbescherming - ontwikkelingsprojecten - politiek - natuurbeleid - wildbescherming - invloeden - inheemse volkeren - bevolkingsverplaatsing - zuid-afrika - zimbabwe - mozambique - national parks - nature conservation - development projects - politics - nature conservation policy - wildlife conservation - influences - indigenous people - resettlement - south africa - zimbabwe - mozambique
    The proposed paper will focus on the process of displacement taking place in the context of the creation of the Limpopo National Park in Mozambique. This park is part of the Great Limpopo Transfrontier Park, which also includes the Kruger National Park (South Africa) and Gonarezhou National Park (Zimbabwe). The creation of the Limpopo National Park – which involved the translocation of more than 3000 animals from Kruger park to Limpopo park, including more than a hundred elephants – is strongly associated by some local residents with political developments following the cease-fire in 1992 and the increased regional cooperation since South Africa’s transition to democracy in 1994. The paper will describe how the establishment of the larger transfrontier park resulted in pressure on the Mozambican government to favour the model of a national park over other conservation options that might have better accommodated the interests of local communities. About 26 000 people are currently living in the Limpopo National Park; about 6000 of whom are in the process of being resettled to an area southeast of the park. The Mozambican government and donors funding the creation of the park have maintained that no forced relocation will take place. However, the pressure created by restrictions on livelihood strategies resulting from park regulations, and the increased presence of wildlife has forced some communities to ‘accept’ the resettlement option. The paper will describe the negotiation process about alternative locations and compensation packages for the communities to be resettled, involving park officials, local and international NGOs, and communities. An analysis will be presented of the power struggles between those parties, but also of the internal contradictions and conflicts that each of the parties experience. Furthermore, an often neglected aspect will be explored, namely that of the possible consequences of resettlement for the hosting communities outside of the park
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