Staff Publications

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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Multi-level socioecological drivers of agrarian change: Longitudinal evidence from mixed rice-livestock-aquaculture farming systems of Bangladesh
Aravindakshan, Sreejith ; Krupnik, Timothy J. ; Groot, Jeroen C.J. ; Speelman, Erika N. ; Amjath- Babu, T.S. ; Tittonell, Pablo - \ 2020
Agricultural Systems 177 (2020). - ISSN 0308-521X
Coastal systems are facing natural and human-driven change coupled with a rising population. With increasing shifts in socioecological conditions during the past several decades, it is important to understand how socioecological drivers at different hierarchical levels: -micro, -meso, and -macro affect coastal farming systems, which play a crucial role in the livelihoods of coastal dwellers. Mixed rice-livestock-aquaculture farming in Southern Bangladesh exemplifies the rapid change occurring in many of the world's coastal farming systems in response to these drivers. We used panel data observations from the above study area and modeled trajectories of farm typologies, and the impact of multi-level socioecological drivers by a novel approach. Our approach integrates: (1) a well-articulated conceptual frame of change observed using (2) a temporal view of the potential drivers, change process and farm type outcomes, with the twenty years panel data of 502 households that is analyzed by means of (3) multivariate statistics in conjunction with panel data models that operationalize the conceptual frame. Our approach allows (a) estimating dynamic effects over time that typically cannot be estimated in a cross-sectional data set, (b) distinguishing between time-invariant fixed and time dependent random effects of multi-level socioecological drivers, and (c) controlling for omitted variables to a certain extent. Considering farming systems both within and outside of polder embankment systems intended to protect against oceanic water intrusion, we found a gradual shift from heterogeneous, rice-livestock farm types to more homogenous farms with less livestock and more off-farm activities. Micro-level factors including farm plot fragmentation, farmers' experience in cropping, machinery, salinity and soil fertility were influencing changes in farming systems. Meso-level factors including markets, road infrastructure, labor availability, access to extension and land tenure also affect the trajectory of farming systems change. Among macro-level drivers, increasing population density positively and significantly influenced cropping intensity among farms outside polder systems. Within polders, a positive but non-significant trend was observed for the influence of population density on cropping intensity. Our data also indicate negative and significant influence of cyclonic storms on cropping intensity over time in both areas. Our results underscore the importance of accounting for multiple levels of socioecological drivers of change when developing appropriate policy options for sustainable development in South Asia's coastal farming systems.
At a crossroads: potential impacts and trade-offs of improved livestock feeding and forages in smallholder farming systems of East Africa
Paul, Birthe K. - \ 2019
Wageningen University. Promotor(en): P.A. Tittonell, co-promotor(en): J.C.J. Groot; M. Herrero. - Wageningen : Wageningen University - ISBN 9789463950640 - 257
Piecing together complexity: the co-evolution of agroecosystem patterns & natural resource management
Caulfield, Mark E. - \ 2019
Wageningen University. Promotor(en): Pablo A. Tittonell, co-promotor(en): Jeroen Groot; Stephen Sherwood. - Wageningen : Wageningen University - ISBN 9789463950688 - 203
Role and management of soil biodiversity for food security and nutrition; where do we stand?
Mujtar, V. El; Muñoz, N. ; Prack Mc Cormick, B. ; Pulleman, M. ; Tittonell, P. - \ 2019
Global Food Security 20 (2019). - ISSN 2211-9124 - p. 132 - 144.
Agriculture - Ecosystem services - Soil biota - Soil fauna - Soil food webs - Soil microorganisms

Soils host diverse communities that support and regulate ecosystem functions, thereby affecting plant production and resource use efficiencies. There is increasing evidence that agricultural intensification affects soil biodiversity (SBD) and such changes may impact on current and future food security. Here, we provide an overview of the state-of-the-art on the relations between agricultural management, SBD and food production. The potential of applying such knowledge to improve food security and nutrition is discussed. Biotechnological methods to describe impacts of agricultural practices on taxonomic and functional diversity of soil organisms are advancing rapidly. At the same time new understanding of soil-plant interactions has provided novel insights into the mechanisms by which soil organisms and plants co-regulate plant growth and defences, or affect food nutritional quality and safety. Yet, empirical studies on SBD – plant productivity relations often lead to results and applications that are crop and context specific. Translating knowledge on SBD into universally applicable soil management recommendations to enhance food production, and ultimately food security, remains challenging. Instead, we propose a holistic approach to SBD management that strengthens multiple ecosystem functions and provides ecological insurance.

Grazing management for more resilient mixed livestock farming systems on native grasslands of southern South America
Modernel, Pablo ; Picasso, Valentin ; Carmo, Martin Do; Rossing, Walter A.H. ; Corbeels, Marc ; Soca, Pablo ; Dogliotti, Santiago ; Tittonell, Pablo - \ 2019
Grass and Forage Science (2019). - ISSN 0142-5242
drought - grazing management - livestock farming systems - native grasslands - resilience - Rio de la Plata grasslands

Droughts in southern South America affect grazing systems in many ways. They reduce biomass productivity; decrease livestock feed intake, weight and reproductive performance; increase farmers’ costs; and reduce farm income. It was hypothesized that simple grazing management variables affect the resilience of grazing systems to droughts at the paddock and farm scales. The effects of grazing management on herbage and animal production were assessed at paddock level, and how technological and structural variables relate to the production and economic performances at farm level. Results of a grazing experiment controlling herbage allowance at paddock level showed that resistance of herbage accumulation and animal live weight to drought was significantly higher for paddocks with higher pre-drought herbage allowance than for those managed to low herbage allowance treatments. A strong positive linear relationship was found between pre-drought herbage height and resistance of herbage accumulation rate (p <.01). In a longitudinal study of nine farms in Uruguay, resistance of cow pregnancy rate to drought was positively correlated with cow pregnancy rate (r =.72, p =.02) and farm net income (r =.78, p =.02), and negatively correlated with sheep-to-cattle ratio (r = −.80, p =.01). These correlations suggest that farms with higher incomes and low proportions of sheep in the herd withstand drought better (in terms of pregnancy rate). Four common regional production strategies were identified that react differently when farmers face drought, and these results can aid farmers in those regions to design more resilient mixed livestock farming systems and can inform policymakers about effective strategies for mitigating drought impacts in the region.

Motivations for the use of sustainable intensification practices among smallholder farmers in Tanzania and Malawi
Jambo, Isaac Jonathan ; Groot, Jeroen C.J. ; Descheemaeker, Katrien ; Bekunda, Mateete ; Tittonell, Pablo - \ 2019
NJAS Wageningen Journal of Life Sciences 89 (2019). - ISSN 1573-5214
External drivers - Farming constraints - Farming systems - Self determination theory - Sustainable development - Technology adoption

Agricultural techniques and technologies that could foster sustainable intensification of farming (hereafter: SI practices) can originate from existing farm practices, from the adoption of externally suggested new practices, or from an adaptation of existing or new practices. The rate at which farmers use SI practices is often low and influenced by on-farm biophysical and socio-economic conditions. There is a narrow understanding of the role of motivations and the balance between external incentives and intrinsic motivations for use of SI practices. We analysed the role of intrinsic and extrinsic motivations among 246 sampled households alongside the perceived benefits and constraints from SI practices in five districts of Malawi and Tanzania. Our results showed that farmer decisions were not exclusively dependent on external incentives, but also on intrinsic values which farmers attach to their production resources and farming practices. Despite various benefits perceived, farmers highlighted the lack of financial resources as a major constraint to the use of externally proposed SI practices. While we hypothesized that intrinsic motivation would be much stronger than extrinsic in influencing decisions to use SI practices, our results demonstrated equal importance of intrinsic and extrinsic motivations in influencing the number of SI practices which smallholder farmers used. We suggest explicitly addressing both intrinsic and extrinsic motivations in further research in combination with socio-economic and biophysical variables to give a better reflection of what drives farmers’ decisions to use more sustainable farming practices. We argue that the design of SI research programs should support motivations of diversified farmers to participate in such programs. Emphasising farmers’ autonomy, a key to intrinsic motivation, can stimulate ownership of SI projects and smoothen the process of adoption, adaptation and use of SI practices by farmers, and is expected to reduce the mismatch between proposed practices and farmers’ expectations.

Banana leaf pruning to facilitate annual legume intercropping as an intensification strategy in the East African highlands
Ocimati, W. ; Ntamwira, J. ; Groot, J.C.J. ; Taulya, G. ; Tittonell, P. ; Dhed'a, B. ; Asten, P. van; Vanlauwe, B. ; Ruhigwa, B. ; Blomme, G. - \ 2019
European Journal of Agronomy 110 (2019). - ISSN 1161-0301
Banana - Intercrop - Leaf pruning - Legume - LER - Revenue

Banana leaf pruning is a common practice to facilitate intercropping with legumes on farmers’ fields. It is however not clear if this practice improves farmers land-use and economic efficiency, especially after full canopy formation. To analyze pruning effects, three legumes viz. bush bean (Phaseolus vulgaris L), climbing bean (Phaseolus vulgaris L) and soybean (Glycine max), were planted under three banana leaf pruning levels in which four, seven and all fully grown leaves were retained. Sole banana or legume plots served as controls. Each treatment combination was replicated three times. Banana growth and yield attributes were measured for the plant and first ratoon crops while legume biomass and yields determined over five consecutive cropping seasons. Significant (P < 0.001) reductions in banana growth and yield were associated with leaf pruning. Banana yield reductions of 31% and 10% for the four- and seven-leaf retention treatments, respectively occurred. The vigorous intercrops (climbing beans and soybeans) more often depressed the growth and yield of banana. Legume grain and biomass yields increased with leaf pruning levels. Weed biomass and associated management costs increased with decline in shade intensity. The land-use efficiency measured using the land equivalence ratio (LER) was far lower in the treatment with four-leaves (1.10) compared to when all leaves were retained (1.4) but higher (1.54) for the seven-leaf treatment. Severe banana leaf pruning could thus be detrimental to banana performance and inefficient. Moderate banana leaf pruning could however be promoted were land is limiting and farmers want to maximize diversity/nutrition. However, the highest values for gross revenue and benefit-cost ratio were realized for sole banana-all-leaf retention treatment due to a higher labor productivity and lower input costs attributed to the perennial nature of banana. The higher economic efficiency in sole banana plots suggests that reliance on LER only may be insufficient for guiding intercropping decisions.

Landscape composition overrides field level management effects on maize stemborer control in Ethiopia
Kebede, Yodit ; Bianchi, Felix J.J.A. ; Baudron, Frédéric ; Tittonell, Pablo - \ 2019
Agriculture, Ecosystems and Environment 279 (2019). - ISSN 0167-8809 - p. 65 - 73.
African ecosystem - Busseola Fusca - Landscape ecology - Lepidoptera (Noctuidae)

Lepidopteran stemborers are a serious pest of maize in Africa. While farmers have adopted cultural control practices at the field scale, it is not clear how these practices affect stemborer infestation levels and how their efficacy is influenced by landscape context. The aim of this 3-year study was to assess the effect of field and landscape factors on maize stemborer infestation levels and maize productivity. Maize infestation levels, yield and biomass production were assessed in 33 farmer fields managed according to local practices. When considering field level factors only, plant density was positively related to stemborer infestation level. During high infestation events, length of tunnelling was positively associated with planting date and negatively with the botanical diversity of hedges. However, the proportion of maize crop in the surrounding landscape was strongly and positively associated with length of tunnelling at 100, 500, 1000 and 1500 m radius, and overrode field level management factors when considered together. Maize grain yield was positively associated with plant density and soil phosphorus content, and not negatively associated with the length of tunnelling. Our findings highlight the need to consider a landscape approach for stemborer pest management, but also indicate that maize is tolerant to low and medium infestation levels of stemborers.

The risk posed by Xanthomonas wilt disease of banana : Mapping of disease hotspots, fronts and vulnerable landscapes
Ocimati, Walter ; Bouwmeester, Hein ; Groot, Jeroen C.J. ; Tittonell, Pablo ; Brown, David ; Blomme, Guy - \ 2019
PLoS ONE 14 (2019)4. - ISSN 1932-6203

Banana production landscapes in the African Great Lakes Region (AGLR) have been under immense pressure from Xanthomonas wilt (XW) disease over the past two decades. XW, first reported on banana in central Uganda and eastern DR Congo in 2001, has since spread to the entire AGLR. XW is currently spreading westwards from hot spots in eastern DR Congo highlands, putting the plantain (Musa AAB genome) belt of central and west Africa at risk. In-depth understanding of the key variables responsible for disease spread, current hotspots, and vulnerable landscapes is crucial for disease early warning and management. We mapped aggregated disease distribution and hotspots in the AGLR and identified vulnerable landscapes across African banana production zones. Available data on disease prevalence collected over 11 years was regressed against environmental and expert developed covariates to develop the AGLR XW hotspots map. For the Africa-wide risk map, precipitation, distance to hotspots, degree of trade in fresh banana products, production zone interconnectedness and banana genotype composition were used as covariates. In the AGLR, XW was mainly correlated to precipitation and disease/banana management. Altitude and temperature had unexpectedly low effects, possibly due to an overriding impact of tool-mediated spread which is part of the management covariate. In the AGLR, the eastern part of DR Congo was a large hotspot with highest vulnerability. Apart from endemic zones in the AGLR and Ethiopia, northern Mozambique was perceived as a moderate risk zone mainly due to the predominance of ‘Bluggoe’ (Musa ABB type) which is highly susceptible to insect-vectored transmission. Presence of XW hotspots (e.g. eastern DR Congo) and vulnerable areas with low (e.g. north-western Tanzania) or no disease (e.g. Congo basin, western DR Congo and northern Mozambique) pressure suggest key areas where proactive measures e.g. quarantines and information sharing on XW diagnosis, epidemiology, and control could be beneficial.

Hide and seek: management and landscape factors affecting maize stemborers Busseola fusca (Fuller) infestation levels in Ethiopia
Kebede, Yodit - \ 2019
Wageningen University. Promotor(en): P.A. Tittonell, co-promotor(en): F.J.J.A. Bianchi; Frédéric Baudron. - Wageningen : Wageningen University - ISBN 9789463435864 - 176
On smallholder farm and farmer diversity
Michalscheck, Mirja - \ 2019
Wageningen University. Promotor(en): P. A. Tittonell, co-promotor(en): J.C.J. Groot. - Wageningen : Wageningen University - ISBN 9789463434102 - 380
Livestock farming systems on South American native grasslands: when production meets conservation
Modernel, Pablo - \ 2018
Wageningen University. Promotor(en): P.A. Tittonell, co-promotor(en): M. Corbeels; W.A.H. Rossing; S. Dogliotti Moro. - Wageningen : Wageningen University - ISBN 9789463435291 - 237
Understanding farm diversity to promote agroecological transitions
Teixeira, Heitor Mancini ; Berg, Leonardo van den; Cardoso, Irene Maria ; Vermue, Ardjan J. ; Bianchi, Felix J.J.A. ; Peña-Claros, Marielos ; Tittonell, Pablo - \ 2018
Sustainability 10 (2018)12. - ISSN 2071-1050
Agroecological practice - Participatory action research - Participatory farm typology - Peasant - Statistical farm typology

Agroecology is increasingly promoted by scientists, non-governmental organisations (NGO's), international organisations and peasant movements as an approach to foster the transition to sustainable and equitable food systems. The challenges to agroecological transitions are not the same for all farmers, as they can face different social and bio-physical conditions. We developed a farm typology combining participatory and quantitative methodologies to assess and categorise farm diversity and its implications for developing strategies to promote agroecological transitions. The participatory typology was developed during workshops to acquire insights on local farmers' perceptions and knowledge, and to generate hypotheses on family farm diversity. The participatory-based hypotheses were tested in the quantitative farm characterisation, which provided information on household characteristics, production strategies, land use, participation in public policies and extension services. Farms were located in Zona da Mata, Minas Gerais, Brazil, which harbour a wide diversity of farmers and where different actors have been engaged in agroecological transitions for the past 30 years. Our main findings were: (i) In the face of agroecological transitions, farmers differ in their management strategies, practices and principles; (ii) farmers identified as agroecological typically had stronger engagements in a network composed of farmers' organisations, universities and NGO's; (iii) agroecological farms showed great potential to provide a wide range of ecosystem services as they featured a higher crop diversity and a higher number of crops for self-consumption; (iv) to promote agroecology, it is crucial to recognise peasant knowledge, to change the dominant discourse on agriculture through social movement dynamics, and to generate support from public policies and funds; and (v) participatory and quantitative methodologies can be combined for more precise and relevant assessments of agroecological transitions.

Enhancing agroecosystem productivity with woody perennials in semi-arid West Africa. A meta-analysis
Félix, Georges F. ; Scholberg, Johannes M.S. ; Clermont-Dauphin, Cathy ; Cournac, Laurent ; Tittonell, Pablo - \ 2018
Agronomy for Sustainable Development 38 (2018)6. - ISSN 1774-0746
Agroforestry - Mulch - Sahel - Shrub-crop associations - Woody amendments

Soil degradation in semi-arid West Africa can be reversed through an intensified application of organic matter, especially on coarse soils. Woody perennials have been promoted in the region to secure organic matter sources and improve soil productive capacity, yet the mechanisms by which perennials provide benefits to soils and crops remain poorly understood, and no effective, generalizable agronomic recommendations exist. Here, we reviewed the effects of trees and shrubs on soil properties and on crop yields in semi-arid West Africa (1000 mm year−1). Specific objectives of this meta-analysis were to (i) describe and (ii) quantify the effects of the presence of woody perennials and of ramial wood amendments on crop productivity and soil characteristics, and (iii) identify general recommendations on the integration of perennials with crops. An iterative keyword search was conducted to gather relevant literature. The search string consisted of four parts: source, practice, responses, and countries of interest. In total, 26 references on agroforestry parklands and 21 on woody amendments were included in the meta-database (314 entries, 155 for parklands, and 159 for ramial wood). We show that (1) the presence of shrubs and trees on agricultural fields had an overall positive but variable effect on soil total C (i.e. + 20 to 75%); (2) millet and sorghum yields were often higher in the presence of shrubs (− 25 to + 120%); (3) more variability was observed in the presence of trees (− 100 to + 200%); and (4) the use of shrub- and tree-based ramial wood resulted in equal or higher cereal yields as compared to the control (− 30 to + 100%). Upscaling the use of biodiversity-driven processes in farming systems of West Africa may provide benefits to overall ecosystems, but species’ choice and trade-offs perceived at the farm level, including labour management and low ramial wood availability, should be addressed through future research.

Risks posed by intercrops and weeds as alternative hosts to xanthomonas campestris pv. Musacearum in Banana Fields
Ocimati, Walter ; Were, Evans ; Groot, Jeroen C.J. ; Tittonell, Pablo ; Nakato, Gloria Valentine ; Blomme, Guy - \ 2018
Frontiers in Plant Science 9 (2018). - ISSN 1664-462X
Alternative host - Banana - Cannaspp - Maize - Millet - Sorghum - Xanthomonas campestris pv. musacearum - Xanthomonas wilt

Alternative host plants are important in the survival and perpetuation of several crop pathogens and have been suspected to play a role in the survival of Xanthomonas campestris pv. musacearum (Xcm) and perpetuation of Xanthomonas wilt (XW) disease of banana and enset. This study determined the potential risk posed by two weeds (Canna spp. and wild sorghum) and common banana intercrops (maize, millet, sorghum, taro, and sugarcane) as alternative hosts to Xcm. The study employed screenhouse experiments, laboratory procedures and diagnosis of banana fields in XW-affected landscapes. Typical XW symptoms were only observed in artificially inoculated Canna sp., with an incidence of 96%. Leaf lesions characteristic of xanthomonads occurred on millet (50%) and sorghum (35%), though the plants recovered. No symptoms occurred in maize, sugarcane, taro or wild sorghum. However, Xcm was recovered from all these plant species, with higher recoveries in Canna sp. (47%), millet (27%), sugarcane (27%), and wild sorghum (25%). Only isolates recovered from Canna sp., millet, sorghum and wild sorghum caused disease in banana plantlets. The presence and incidence of XW on-farm was positively associated with the presence of susceptible ABB Musa genotypes and negatively with number of banana cultivars on farm and household access to training on XW management. Only 0.02% of field sampled Canna spp. plants had Xcm. Risk posed by Canna spp. on-farm could be limited to tool transmission as it has persistent floral bracts that prevent insect-mediated infections. Given the high susceptibility, perennial nature and propagation through rhizomes of Canna sp., it could pose a moderate-high risk, thus warranting some attention in the management of XW disease. Sugarcane could offer a low-moderate risk due to its perennial nature and propagation through rhizomes while risk from maize, millet, and sorghum was deemed zero-low due to their annual nature, wind-mediated mode of pollination and propagation through seed. Understanding the interactions of a crop pathogen with other plants is thus important when diversifying agroecosystems. The study findings also suggest other factors such as cultivar composition and management of the disease at farm and landscape level to be important in the perpetuation of XW disease.

Unpacking the push-pull system : Assessing the contribution of companion crops along a gradient of landscape complexity
Kebede, Yodit ; Baudron, Frédéric ; Bianchi, Felix ; Tittonell, Pablo - \ 2018
Agriculture, Ecosystems and Environment 268 (2018). - ISSN 0167-8809 - p. 115 - 123.
Africa - Agroecology - Biocontrol - Busseola fusca (Fuller) - Ethiopia - Generalist predators - Habitat management - Landscape - Lepidoptera: Noctuidae

The push-pull system, a stimulo-deterrent cropping strategy consisting of intercropping cereals with herbaceous legumes and surrounded by fodder grasses, is presented as a promising crop diversification strategy for smallholder farmers in Africa as it may contribute to maize stemborer Busseola fusca (Fuller) suppression, while improving soil fertility and providing feed for livestock. The push-pull system has often been assessed at plot level and as a package (e.g., Maize + Desmodium + Napier grass). However, it is unclear how the system performs in different landscape settings or when companion crops are changed to better meet household needs. Here we evaluate the potential of the push-pull system to suppress maize stemborer infestations in three landscapes in the Rift Valley region of Ethiopia along a gradient of landscape complexity. Within each landscape, experimental plots were established on four representative smallholder farms. At each farm we used a split-plot factorial design with main plots surrounded or not by Napier grass, and subplots consisting of sole maize, maize-bean or maize-Desmodium. We assessed stemborer infestation level and maize grain and stover yields during two years, as well as natural enemies abundance and egg predation at two maize development stages in the second year. In the simple landscape, which was dominated by maize, all treatments had high stemborer infestation levels, irrespective of within-field crop diversity; the presence of Napier grass was associated with higher predator abundance, while egg predation rates were the highest in the maize-bean intercrop. In the intermediate complexity landscape, subplots with sole maize had higher stemborer infestation levels compared to maize-bean or maize-Desmodium. In the complex landscape, infestation levels were low in all treatments. However, none of these effects led to significant differences in maize grain and stover yields among treatments in any of the landscapes. The benefits of the push-pull system accrued from the companion crops (bean, Desmodium and Napier), rather than from stemborer suppression per se. Our findings highlight the importance of the surrounding landscape in mediating the performance of the push-pull system, provide new insights on the contribution of the different components of push-pull system and can guide the design of ecologically intensive agroecosystems.

Use and management of biodiversity by smallholder farmers in semi-arid West Africa
Félix, Georges F. ; Diedhiou, Ibrahima ; Garff, Marie Le; Timmermann, Cristian ; Clermont-Dauphin, Cathy ; Cournac, Laurent ; Groot, Jeroen C.J. ; Tittonell, Pablo - \ 2018
Global Food Security 18 (2018). - ISSN 2211-9124 - p. 76 - 85.
Agroforestry - Ecological engineering - Intercropping - Nutritional functional diversity - Termites

Strategies that strengthen and use biodiversity are crucial for sustained food production and livelihoods in semi-arid West Africa. The objective of this paper was to examine the role of biodiversity in sustaining diverse forms of multifunctional farming practices while at the same time providing ecological services to subsistence-oriented farming families in the region of study through mechanisms as (a) crop species diversification, (b) management of spatial heterogeneity, and (c) diversification of nutrition-sensitive landscapes. Our analysis shows that crop associations between cereals and legumes or between perennials and annuals, have overall positive effects on soil characteristics and often improve crop yields. Soil heterogeneity is produced by woody perennials and termites. Local management provides opportunities to collect a diversity of nutrition-rich species year-round and sustain household nutrition.

Ramial wood amendments (Piliostigma reticulatum) mitigate degradation of tropical soils but do not replenish nutrient exports
Félix, Georges F. ; Clermont-Dauphin, Cathy ; Hien, Edmond ; Groot, Jeroen C.J. ; Penche, Aurélien ; Barthès, Bernard G. ; Manlay, Raphaël J. ; Tittonell, Pablo ; Cournac, Laurent - \ 2018
Land Degradation and Development 29 (2018)8. - ISSN 1085-3278 - p. 2694 - 2706.
adaptation - farmer innovation - Sahel - shrub material - termites

Restoring degraded soils to support food production is a major challenge for West African smallholders who have developed local innovations to counter further degradation. The objective of this study was to evaluate a local farmer's technique that uses ramial wood (RW) as soil amendment (Piliostigma reticulatum shrub). Three treatments were applied in an experimental plot in Burkina Faso: control (no amendment), low RW (3 Mg fresh mass·ha−1·yr−1), and high RW (12 Mg fresh mass·ha−1·yr−1). RW was chipped to <5-cm pieces and either buried or mulched. Topsoil carbon (C), nitrogen (N), and phosphorus (P) in control and low-RW treatments declined after 7 years of continuous sorghum cultivation. Use of high-RW amendment stabilized soil C content while N and P declined, thus not replenishing nutrient exports. Net contribution to soil C in the layer measuring 0–15 cm was 15% of the applied C in the high-RW amendments. Although biomass and grain yields were higher in high-RW treatments, crop productivity declined throughout the experiment for all treatments. Termite casts on RW treatments evidenced the potential role of wood-foraging termites in diluting the impact of RW on soil fertility build-up and soil water content. We conclude that mitigating soil degradation under semiarid conditions in Burkina Faso would require large amounts of woody amendments, particularly if the level of termite activity is high. Additional nutrient sources would be needed to compensate for removal in exported products so that biomass and grain production can be stabilized or increased.

An Evaluation of the Loss-on-Ignition Method for Determining the Soil Organic Matter Content of Calcareous Soils
Hoogsteen, M.J.J. ; Lantinga, E.A. ; Bakker, E.J. ; Tittonell, P.A. - \ 2018
Communications in Soil Science and Plant Analysis 48 (2018)13. - ISSN 0010-3624 - p. 1541 - 1552.
Calcite analysis procedures - ignition temperature - sample weight

The Loss-on-Ignition (LOI) method is widely employed for measuring the organic matter (OM) content of soil samples. There is a risk of carbonate losses when calcareous soil samples are analyzed through LOI, but this has never been investigated in detail. Moreover, a worldwide standard protocol for determining the carbonate content of soils is not available. The aims of this study were (i) to evaluate two commonly employed carbonate analysis procedures using calcareous and non-calcareous soil samples: the gravimetric method with (GMF) and without (GM) the addition of the antioxidant iron(II) chloride (FeCl2) and the acetic acid dissolution procedure (AAD); (ii) to evaluate the effect of ignition temperature on losses of pure calcite, calcite-quartz and calcareous soil samples. We found that the average apparent carbonate content of the non-calcareous soils was greatest for the GMF method followed by the AAD procedure. The GM method showed the smallest apparent carbonate contents. For the calcite-quartz sand mixture, ignition losses started at 600°C and increased with temperature in a sigmoidal way. LOI values stabilized at 750°C when 80% of the carbon dioxide was released. We recommend the GM procedure for carbonate analysis because the apparent carbonate contents of the non-calcareous soil samples were smallest. Furthermore, we recommend an LOI temperature of 550°C because at this ignition temperature 99.8% of the total calcite fraction remains in the soil samples.

Capturing farm diversity with hypothesis-based typologies : An innovative methodological framework for farming system typology development
Alvarez, Stéphanie ; Timler, Carl J. ; Michalscheck, Mirja ; Paas, Wim ; Descheemaeker, Katrien ; Tittonell, Pablo ; Andersson, Jens A. ; Groot, Jeroen C.J. - \ 2018
PLoS ONE 13 (2018)5. - ISSN 1932-6203

Creating typologies is a way to summarize the large heterogeneity of smallholder farming systems into a few farm types. Various methods exist, commonly using statistical analysis, to create these typologies. We demonstrate that the methodological decisions on data collection, variable selection, data-reduction and clustering techniques can bear a large impact on the typology results. We illustrate the effects of analysing the diversity from different angles, using different typology objectives and different hypotheses, on typology creation by using an example from Zambia’s Eastern Province. Five separate typologies were created with principal component analysis (PCA) and hierarchical clustering analysis (HCA), based on three different expert-informed hypotheses. The greatest overlap between typologies was observed for the larger, wealthier farm types but for the remainder of the farms there were no clear overlaps between typologies. Based on these results, we argue that the typology development should be guided by a hypothesis on the local agriculture features and the drivers and mechanisms of differentiation among farming systems, such as biophysical and socio-economic conditions. That hypothesis is based both on the typology objective and on prior expert knowledge and theories of the farm diversity in the study area. We present a methodological framework that aims to integrate participatory and statistical methods for hypothesis-based typology construction. This is an iterative process whereby the results of the statistical analysis are compared with the reality of the target population as hypothesized by the local experts. Using a well-defined hypothesis and the presented methodological framework, which consolidates the hypothesis through local expert knowledge for the creation of typologies, warrants development of less subjective and more contextualized quantitative farm typologies.

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