An evaluation of conventional and no-tillage systems on soil physical conditions.

Thesis (M.Sc.)-University of Natal, Pietermaritzurg, 2003.The use of no-tillage (NT) system has increased in the past few years in South Africa, but its effects on soil physical conditions have not been adequately documented. This study was undertaken to ascertain these effects, as compared to Conventional tillage (CT) system. Several sites were selected in the Bergville and Winterton areas of the midlands of KwaZulu-Natal, and at the Cedara Agricultural Research Station. NT generally increased bulk density in the topsoil and this altered total porosity and poresize distribution. Water retention, organic C and aggregate stability were increased under NT, partly due to the maintenance of the mulch cover on the surface soil. Organic C and aggregate stability were positively correlated with each other. Differences in bulk density between tillage systems with soil depth did not clearly indicate where soil compaction had occurred. Significant differences in soil compaction between treatments were, however, illustrated by changes in soil penetration resistance (SPR), especially at the. 150 mm depth. In addition, depending on the soil type, SPR was greater in the topsoil under NT than CT. It was suggested that conversion from CT to NT was carried out when the topsoil of the CT-fields was structurally poor, due to a previous history of continuous CT. Tractor traffic under CT and repeated tillage when the soil was wet had, in some cases, resulted in the formation of a compacted layer at the depth of cultivation. In clay soils, this has resulted in subsoil compaction. The formation of compacted layers caused major changes to pore size distribution and continuity and this resulted in substantially reduced hydraulic conductivity, infiltration rate,air-filled porosity and air permeability. It was concluded that compacted subsoil layers need to be broken up prior to conversion from CT to NT, and that compaction in the surface soil under NT has occurred and, in some cases, this will be a limitation to crop production. The use of minimum tillage systems should be considered and researched in these cases.Page 69 (colour photographs) missing from origina

Effects of antibiotic resistance, drug target attainment, bacterial pathogenicity and virulence, and antibiotic access and affordability on outcomes in neonatal sepsis: an international microbiology and drug evaluation prospective substudy (BARNARDS)

Background Sepsis is a major contributor to neonatal mortality, particularly in low-income and middle-income countries (LMICs). WHO advocates ampicillin–gentamicin as first-line therapy for the management of neonatal sepsis. In the BARNARDS observational cohort study of neonatal sepsis and antimicrobial resistance in LMICs, common sepsis pathogens were characterised via whole genome sequencing (WGS) and antimicrobial resistance profiles. In this substudy of BARNARDS, we aimed to assess the use and efficacy of empirical antibiotic therapies commonly used in LMICs for neonatal sepsis. Methods In BARNARDS, consenting mother–neonates aged 0–60 days dyads were enrolled on delivery or neonatal presentation with suspected sepsis at 12 BARNARDS clinical sites in Bangladesh, Ethiopia, India, Pakistan, Nigeria, Rwanda, and South Africa. Stillborn babies were excluded from the study. Blood samples were collected from neonates presenting with clinical signs of sepsis, and WGS and minimum inhibitory concentrations for antibiotic treatment were determined for bacterial isolates from culture-confirmed sepsis. Neonatal outcome data were collected following enrolment until 60 days of life. Antibiotic usage and neonatal outcome data were assessed. Survival analyses were adjusted to take into account potential clinical confounding variables related to the birth and pathogen. Additionally, resistance profiles, pharmacokinetic–pharmacodynamic probability of target attainment, and frequency of resistance (ie, resistance defined by in-vitro growth of isolates when challenged by antibiotics) were assessed. Questionnaires on health structures and antibiotic costs evaluated accessibility and affordability. Findings Between Nov 12, 2015, and Feb 1, 2018, 36 285 neonates were enrolled into the main BARNARDS study, of whom 9874 had clinically diagnosed sepsis and 5749 had available antibiotic data. The four most commonly prescribed antibiotic combinations given to 4451 neonates (77·42%) of 5749 were ampicillin–gentamicin, ceftazidime–amikacin, piperacillin–tazobactam–amikacin, and amoxicillin clavulanate–amikacin. This dataset assessed 476 prescriptions for 442 neonates treated with one of these antibiotic combinations with WGS data (all BARNARDS countries were represented in this subset except India). Multiple pathogens were isolated, totalling 457 isolates. Reported mortality was lower for neonates treated with ceftazidime–amikacin than for neonates treated with ampicillin–gentamicin (hazard ratio [adjusted for clinical variables considered potential confounders to outcomes] 0·32, 95% CI 0·14–0·72; p=0·0060). Of 390 Gram-negative isolates, 379 (97·2%) were resistant to ampicillin and 274 (70·3%) were resistant to gentamicin. Susceptibility of Gram-negative isolates to at least one antibiotic in a treatment combination was noted in 111 (28·5%) to ampicillin–gentamicin; 286 (73·3%) to amoxicillin clavulanate–amikacin; 301 (77·2%) to ceftazidime–amikacin; and 312 (80·0%) to piperacillin–tazobactam–amikacin. A probability of target attainment of 80% or more was noted in 26 neonates (33·7% [SD 0·59]) of 78 with ampicillin–gentamicin; 15 (68·0% [3·84]) of 27 with amoxicillin clavulanate–amikacin; 93 (92·7% [0·24]) of 109 with ceftazidime–amikacin; and 70 (85·3% [0·47]) of 76 with piperacillin–tazobactam–amikacin. However, antibiotic and country effects could not be distinguished. Frequency of resistance was recorded most frequently with fosfomycin (in 78 isolates [68·4%] of 114), followed by colistin (55 isolates [57·3%] of 96), and gentamicin (62 isolates [53·0%] of 117). Sites in six of the seven countries (excluding South Africa) stated that the cost of antibiotics would influence treatment of neonatal sepsis

Optimizing Arabica coffee production systems in Rwanda : a multiple-scale analysis

The Government of Rwanda would like to improve farming livelihood through the sustainable production of high quality coffee. This would be a win-win situation because improving farming livelihoods also provides increased export earnings. In order to fulfil this, the Government of Rwanda needs to design and support policies which sustain this growth. This can be achieved through an improvement programme of soil fertility and reduction of soil erosion, among other strategies. The programme should identify suitable areas for Arabica coffee production and assess sustainable land management technologies to improve soil fertility and reduce soil erosion to create conditions for optimizing production of high quality coffee. This PhD project contributes to those objectives. Experimental field measurements were conducted to assess the effects of mulch application on improving soil properties and reducing soil erosion, thus positively impacting yields. Assessments were made for three agro-ecological zones of Rwanda, namely the highlands, the central plateau and the shores of Lake Kivu. The thesis covers a GIS Spatial analysis of coffee production systems at national level (chapters 2 and 3); at system and farm levels. It assessed the effects of best practices on soil erosion and soil fertility (chapters 4 and 5); and then it recommended best upscaling practices for a country level (chapters 3, 4, 5 and 6). Chapter 2 also reviewed coffee growing conditions, systems and soil management practices in Rwanda. Data showed that growing conditions are confined to an altitude range of 1,400 - 1,900 m a.s.l., an annual rainfall regime of 1,500 - 1,600 mm, a temperature class of 18 – 22 °C, and an average sunlight amount of 2,000 - 2,400 hours per year. Coffee is mainly grown along the shores of Lake Kivu, on the plateau in the central part of Rwanda, and in the Mayaga region located in the Southern-East part of the country. In these areas, coffee is mainly cultivated on moderate slopes and soils with low fertility. Coffee requires deep and finely-textured soils, which are well drained, aerated with moderate acidity (i.e. pH of 4.5 - 6.0) and moderate-to-high fertility. Many of the coffee farming lands in Rwanda do not accommodate these ideal conditions, e.g. steep slopes or scattered coffee plots intercropped with annual crops. Steep slopes, in particular, deplete soil fertility through soil erosion. The thesis looked at how mulching can assist with erosion control, improve soil properties and boost yields in such farming situations. Chapter 3 assessed suitable areas for sustainably growing Arabica coffee, potential production zones, their productivity levels and the prediction of potential coffee yields. Results showed that coffee production zones cover about 32,000 ha, or about 2.3% of all cultivated lands in the country. About 21% of the country has a moderate yield potential, ranging between 1.0 and 1.6 t coffee ha-1, mainly around the Central Plateau; 70% has a low yield potential (< 1.0 t coffee ha-1) mainly in the Eastern semi-dry lowlands and very cold highlands of the North-West of the country. Only 9% of the country has a high yield potential of 1.6 to 2.4 t ha-1, particularly around the shores of the Lake Kivu. The results have some variances depending upon the location and variable conditions in terms of agro-ecological zones. Chapter 4 discusses the positive effects of different types of mulch. Again, the success of each area showed to be site-specific, with significant effects using a mixture of mulches composed of crop residues applied at a rate of above 20 t ha-1, where soil erodibility was reduced significantly (up-to 91%). Clay content and silt particles are also noted to play a part. In fact, the association of soil organic carbon with clay and silt particles may be related to the amount of organic carbon that can be mobilised to saturate the clay and silt fractions on a particular soil texture. Chapter 5 reports the positive effects of mulch on availability of soil nutrients to improve soil fertility and coffee yields. The amount of nutrient contents released after mulching was regulated by the amount of mulch biomass, the quality and type of mulch used, the climatic conditions and soil properties. Significant effects were obtained with a mixture of different types of mulch applied at a rate of above 20 t ha-1. Success results were also site-specific and additional application of inorganic fertiliser was recommended to obtain coffee yields of above 1.9 t ha-1. The inorganic fertiliser rates differ for each agro-ecological zone and soil type. The sustainability of coffee productivity could be ensured by intensifying the use of mineral fertilisers, but there are limited financial resources. Chapter 6 presents a synthesis of our research findings and conclusions of the previous chapters. It highlights sustainable best land management practices that help to improve and optimise coffee productivity in smallholder farming systems. This chapter also presents key policy strategies and recommendations to improve coffee productivity of smallholder farmers in Rwanda. Besides the research results, conclusions and recommendations, the chapter highlights also a number of topics that remain to be addressed in order to understand more clearly the effects of mulching on soil fertility improvement and reduced soil erodibility, such as: (i) predicting coffee productivity through mapping of soil fertility indicators, (ii) modelling soil erosion of scattered smallholder coffee farms at micro-catchment level, and (iii) assessing the quality and the effects of the organic mulches applied in small scale coffee farming systems, accounting for related costs and benefits for the farmer

Rôle du paludisme dans l'efficience technique des producteurs de coton du nord de la Côte-d'Ivoire

The Malaria Effects on Technical Efficiency of Cotton Growers in Northern Côte d'Ivoire This article assess the role of malaria on the agricultural development and more precisely on technical efficiency in the context of cotton crop in the Korhogo region in the North of Côte d'Ivoire. The stochastic frontier production function incorporating a model for technical inefficiency effects (Battese and Coelli, 1995) was applied in order to check the hypothesis that the efficiency deviations between farmers should be explained by the disparity of the presence and the severity of malaria infection among the farmers and their family. Field data was collected by the authors between March 1997 and February 1998 on 700 rural households living in three production systems differently exposed to the malaria risk. Three malaria indicators were used. There were the prevalence, in the active (11-55 years old) family members of the farm, of parasitemia, high and very high densities of Plasmodium falciparum. The results of the model and the distribution of farm efficiency according to the presence and the severity of malaria infection obviously determine a critical threshold above which malaria has a negative effect on technical efficiency in the cotton crop. Then, farm households in which the proportion of actives with a high density of Plasmodium falciparum (more than 499 parasites/pl of blood) was higher or equal to 25 %, were less efficient than the farm households in which this density is lower.L'objet de cet article est d'estimer le rôle du paludisme sur le développement agricole, et plus précisément sur l'efficience technique dans la culture du coton dans la zone de savane de la région de Korhogo au nord de la Côte-d'lvoire. Le modèle de frontière de production stochastique à effets de l'efficience incorporés, proposé par Battese et Coelli (1995), permet de tester l'hypothèse selon laquelle les écarts d'efficience entre les exploitants sont, entre autres facteurs, liés à une présence différenciée du paludisme au sein des exploitations familiales. Les données nécessaires à l'analyse sont issues d'une série d'enquêtes conduites par les auteurs entre mars 1997 et février 1998 auprès d'environ 700 exploitations familiales agricoles réparties dans trois systèmes de production différemment exposés au risque palustre. Trois indicateurs d'infection palustre sont utilisés et concernent la prévalence, dans la population active 499 parasites/pl de sang) est supérieure ou égale à 25 %, sont moins efficientes, toutes choses égales par ailleurs, que les familles où cette densité est plus faible ou nulle.Audibert Martine, Mathonnat Jacky, Henry Marie-Claire, Nzeyimana Innocent. Rôle du paludisme dans l'efficience technique des producteurs de coton du nord de la Côte-d'Ivoire. In: Revue d'économie du développement, 7e année N°4, 1999. Santé et développement : analyses économétriques. pp. 121-148

Relationship between measured and predicted Arabica coffee yields – cross validation using ordinary kriging (Predicted Arabica coffee yield index – CYI (t ha⁻¹) = 0.71x + 0.33; Mean Prediction Error – MPE = 0.0187; Root Mean Square Prediction Error – RMSE = 0.278; Root Mean Square Standardized Prediction Error – RMSSE = 0.99; Mean Standardized Prediction Error - MSE = 0.036; Coefficient of determination – R² = 0.73; Average Standard Error –Avg. SE = 0.291; Sample points, n = 121).

<p>Relationship between measured and predicted Arabica coffee yields – cross validation using ordinary kriging (Predicted Arabica coffee yield index – CYI (t ha⁻¹)  =  0.71x + 0.33; Mean Prediction Error – MPE  =  0.0187; Root Mean Square Prediction Error – RMSE  =  0.278; Root Mean Square Standardized Prediction Error – RMSSE  = 0.99; Mean Standardized Prediction Error - MSE  =  0.036; Coefficient of determination – R² = 0.73; Average Standard Error –Avg. SE = 0.291; Sample points, n = 121).</p

Data Set for GIS-based multi-criteria analysis for Arabica coffee expansion in Rwanda

<p>This project file contains row research data and result data that have been used for the paper entitled "GIS-based multi-criteria analysis for Arabica coffee expansion in Rwanda" by Innocent Nzeyimana, Alfred E. Hartemink, Violette Geissen. </p> <p>http://dx.doi.org/10.6084/m9.figshare.1128594- See more at: http://figshare.com/preview/_preview/1128594#sthash.QkGK7m8Y.dpuf</p