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Exploring Mechanisms to Restore Fertility of Degraded Lixisols for Enhanced Crop Productivity under Smallholder Farmer Management Systems
No full textCroplands in smallholder farming areas of Southern Africa are in a degraded state, with most cereal and legume crops yielding less than 1 t ha-1 of grain. Restoring productivity of these degraded croplands is therefore key to intensifying crop production to meet household food and nutritional security needs. The objective of this study was to evaluate sequences of integrated soil fertility management (ISFM) technology components for rehabilitation of degraded sandy soils and intensification of maize (Zea mays L.)-based cropping systems in Hwedza and Makoni smallholder farming areas in Eastern Zimbabwe. Farmer participatory research approaches, laboratory characterization, remote sensing and Geographic Information Systems were first employed to formulate criteria for assessing degradation of croplands. Second, field experiments were conducted to evaluate alternate sequences of ISFM options based on nitrogen (N)-fixing green manure and grain legumes, low quality organic resources and mineral N and phosphorus (P) fertilizers for rehabilitating the degraded croplands. Third, biophysical data generated from field experimentation were combined with simulation modelling to best-fit the ISFM sequences to different resource categories of farmers. Farmers delineated croplands as productive, moderately productive, degraded and severely degraded based on common indicator weeds, crop performance and soil physical attributes. Overall, laboratory-based soil chemical and biological properties, and most of the weed species closely matched farmer categorization. Spatially, forty percent of the arable land was classified as degraded to severely degraded. Over a 3-year period, rehabilitation of the degraded sandy soils was positively influenced by high quality organic resource application and P fertilization. Indigenous legumes and sunnhemp (Crotalaria juncea L.) planted on otherwise degraded soils, with addition of mineral P fertilizer, led to higher biomass C and N production than under natural fallow. A combination of biomass generated under indigenous legume fallow (indifallow) and sunnhemp fallow, and cattle manure increased soil basal respiration and microbial biomass. Maize grain yields averaged 2.5 t ha-1 under the legume-based sequences compared with 1 t ha-1 under continuous fertilized maize and natural fallow-based options. Over a 4-year period, ISFM sequences based on cattle manure/woodland litter-, NP fertilizer- and legume-based rotations accumulated the highest maize and soyabean grain yields. This was largely explained by a significant accumulation of soil P. These sequences were more productive than farmers’ designated most-and least-productive fields. Cattle manure-based sequences gave the highest cumulative crop yields, while sunnhemp-based sequences attained the highest increase in soil P. Based on costs of seed, fertilizers and labour, the ISFM sequences gave better financial returns than the farmers’ most-and least-productive fields. When assessed over a 49-year period (1962-2011) using Agricultural Production Systems Simulator (APSIM) under agronomic management of different resource categories of farmers, simulated maize yields of the ISFM sequencing options averaged 3.8, 2.4 and 1.8 t ha-1 for resource-endowed, resource-intermediate and resource-constrained households, respectively. The major conclusions from this study were as follows: (i) ethnopedological approaches could aid assessment of soil degradation on smallholder farms to inform decision-making, (ii) degraded croplands are not beyond remedy, and ISFM sequences based on herbaceous legumes are potential entry points to rehabilitate them and (iii) ISFM sequences are a suitable option for intensifying smallholder cropping systems in Southern Africa through increasing crop yields to meet energy and protein requirements of households, and allowing for systematic allocation of the often limited and variable nutrient, seed and labour resources in space and time
Exploring mechanisms to restore fertility of degraded lixisols for enhanced crop productivity under Smallholder Farmer Management Systems
No full textCroplands in smallholder farming areas of Southern Africa are in a degraded state, with most cereal and legume crops yielding less than 1 t ha-1 of grain. Restoring productivity of these degraded croplands is therefore key to intensifying crop production to meet household food and nutritional security needs. The objective of this study was to evaluate sequences of integrated soil fertility management (ISFM) technology components for rehabilitation of degraded sandy soils and intensification of maize (Zea mays L.)-based cropping systems in Hwedza and Makoni smallholder farming areas in Eastern Zimbabwe. Farmer participatory research approaches, laboratory characterization, remote sensing and Geographic Information Systems were first employed to formulate criteria for assessing degradation of croplands. Second, field experiments were conducted to evaluate alternate sequences of ISFM options based on nitrogen (N)-fixing green manure and grain legumes, low quality organic resources and mineral N and phosphorus (P) fertilizers for rehabilitating the degraded croplands. Third, biophysical data generated from field experimentation were combined with simulation modelling to best-fit the ISFM sequences to different resource categories of farmers. Farmers delineated croplands as productive, moderately productive, degraded and severely degraded based on common indicator weeds, crop performance and soil physical attributes. Overall, laboratory-based soil chemical and biological properties, and most of the weed species closely matched farmer categorization. Spatially, forty percent of the arable land was classified as degraded to severely degraded. Over a 3-year period, rehabilitation of the degraded sandy soils was positively influenced by high quality organic resource application and P fertilization. Indigenous legumes and sunnhemp (Crotalaria juncea L.) planted on otherwise degraded soils, with addition of mineral P fertilizer, led to higher biomass C and N production than under natural fallow. A combination of biomass generated under indigenous legume fallow (indifallow) and sunnhemp fallow, and cattle manure increased soil basal respiration and microbial biomass. Maize grain yields averaged 2.5 t ha-1 under the legume-based sequences compared with 1 t ha-1 under continuous fertilized maize and natural fallow-based options. Over a 4-year period, ISFM sequences based on cattle manure/woodland litter-, NP fertilizer- and legume-based rotations accumulated the highest maize and soyabean grain yields. This was largely explained by a significant accumulation of soil P. These sequences were more productive than farmers’ designated most-and least-productive fields. Cattle manure-based sequences gave the highest cumulative crop yields, while sunnhemp-based sequences attained the highest increase in soil P. Based on costs of seed, fertilizers and labour, the ISFM sequences gave better financial returns than the farmers’ most-and least-productive fields. When assessed over a 49-year period (1962-2011) using Agricultural Production Systems Simulator (APSIM) under agronomic management of different resource categories of farmers, simulated maize yields of the ISFM sequencing options averaged 3.8, 2.4 and 1.8 t ha-1 for resource-endowed, resource-intermediate and resource-constrained households, respectively. The major conclusions from this study were as follows: (i) ethnopedological approaches could aid assessment of soil degradation on smallholder farms to inform decision-making, (ii) degraded croplands are not beyond remedy, and ISFM sequences based on herbaceous legumes are potential entry points to rehabilitate them and (iii) ISFM sequences are a suitable option for intensifying smallholder cropping systems in Southern Africa through increasing crop yields to meet energy and protein requirements of households, and allowing for systematic allocation of the often limited and variable nutrient, seed and labour resources in space and time.,1. The European Union through the African Conservation Tillage Network (ACT) under the Agroecology-based Aggradation–Conservation Agriculture: Tailoring innovations to combat food insecurity in semiarid Africa (ABACO) project to SOFECSA.
2. Rockefeller Foundation
3. Deutscher Akademischer Austausch Dienst (DAAD
Point of no return? Rehabilitating desgraded soils for increased crop productivity on samllholder farmas in eastern Zimbabwe
No full textSoil degradation is a major threat to Southern Africa's agricultural production. Crops show generally weak responses to mineral fertilizers on degraded soils. A three-year study was conducted between 2009 and 2012 on smallholder farms in eastern Zimbabwe to explore entry points for rehabilitating degraded croplands using principles of integrated soil fertility management (ISFM) supported through farmers' local knowledge of soils. Participatory research approaches were first used to investigate farmers' understanding of soil degradation and the commonly used local diagnostic indicators. Farmers' determinants of degraded soils centered on crop performance, indicator weed species and soil physical attributes, and matched laboratory parameters. Overall, physical and chemical properties of the degraded soils were significantly lower than reported values for productive sandy soils in Zimbabwe. Evaluated on ten degraded field sites of corresponding catenary positions and similar slope, the main ISFM options involved nitrogen-fixing herbaceous legumes planted in the first year, with subsequent addition of cattle manure in the second year. In the third year, the influence of the ISFM options on maize productivity and changes in soil biological activity were then evaluated. Phosphorus was applied every year under each sequence. The controls were natural fallow and continuous maize. The treatments were randomly assigned to plots at each of the experimental sites and replicated across farms. Above-ground biomass carbon (C) and nitrogen (N) accumulation was 3038 kg ha− 1 and 203 kg ha− 1, respectively, under 1-year indigenous legume fallow (indifallow) against 518 kg C ha− 1 and 14 kg N ha− 1 under 1-year natural fallow. Two-year indifallow produced approximately three times the biomass N attained under the 2-year natural fallow. When all the treatments were planted to a maize test crop in the third year, herbaceous legume-based sequences showed the highest response to mineral fertilizer N compared with natural fallow-based sequences and continuous fertilized maize. A regression of maize yields against mineral N fertilizer showed a maximum yield of 2.5 t ha− 1 under the herbaceous legume-based sequences against 1 t ha− 1 under continuous fertilized maize and natural fallow-based options following addition of 120 kg ha− 1 of mineral N fertilizer. ‘Green-start’, a Crotalaria juncea L. (sunnhemp)-based sequence, and ‘Indifallow-start 1’, an indigenous legume-based sequence, gave the highest microbial biomass C (MBC) of 243 mg kg− 1 soil compared with 187 mg kg− 1 soil under continuous maize. Microbial biomass N showed a similar trend. Under ‘Green-start’ and ‘Indifallow-start 1’, MBC to organic C ratio averaged 7; about one and half times more than under natural fallow-based sequences and continuous fertilized maize. Consistent with microbial biomass, soil carbon dioxide (CO2) emission under ‘Green-start’ and ‘Indifallow-start 1’ was 22% higher than under natural fallow-based sequences. Continuous maize treatments gave higher metabolic quotients (qCO2) than legume-based sequences, indicating a lower microbial efficiency under the former. We concluded that short-term restoration of productivity of degraded sandy soils should focus on high quality organic resource application and P fertilization to stimulate microbial activity and induce responses to mineral fertilizers. When coupled to P fertilization, herbaceous legume-based ISFM sequences provide a potential entry point for reversing soil degradation and offer opportunities for increasing crop productivity in dominant smallholder farming systems of Zimbabwe and other parts of Southern Africa.Fil: Nezomba, Hatirarami. University of Zimbabwe. Department of Soil Science and Agricultural Engineering; Zimbabwe. University of Zimbabwe. Soil Fertility Consortium for Southern; ZimbabweFil: Mtambanengwe, Florence. University of Zimbabwe. Department of Soil Science and Agricultural Engineering; Zimbabwe. University of Zimbabwe. Soil Fertility Consortium for Southern; ZimbabweFil: Tittonell, Pablo Adrian. Wageningen University and Research Centre; Holanda. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; ArgentinaFil: Mapfumo, Paul. University of Zimbabwe. Department of Soil Science and Agricultural Engineering; Zimbabwe. University of Zimbabwe. Soil Fertility Consortium for Southern; Zimbabw
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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