Methodological innovations in estimating the (inverse) relationship between farm productivity and farm size in a developing economy: a case study of Burundi

We use a nonparametric estimation of the production function to investigate the relationship between farm productivity and farming scale in poor smallholder agricultural systems in the north of Burundi. Burundi is one of the poorest countries in the world, with a predominant small scale subsistence farming sector. A Kernel regression is used on data of mixed cropping systems to study the determinants of production including different factors that have been identified in literature as missing variables in the testing of the inverse relationship such as soil quality, location and household heterogeneity. Household data on farm activities and crop production was gathered among 640 households in 2007 in two Northern provinces of Burundi. Four production models were specified each with different control variables. For the relatively small farms, we find clear evidence of an inverse relationship. The relatively large farms show a different pattern. Returns to scale are found to be farm scale dependent. Parametric Cobb-Douglass models tend to over-simplify the debate on returns to scale because of not accounting for the different effects of large farms. Other factors that significantly positively affect production include the soil quality and production orientation towards banana or cash crop production. Production seems to be negatively affected by field fragmentation.inverse relationship, farm size, nonparametric, Burundi, Agricultural and Food Policy, Community/Rural/Urban Development, Environmental Economics and Policy, D24, O13, Q12, Q18,

Challenging Small-scale Farming, A Non-parametric Analysis of the (Inverse) Relationship Between Farm Productivity and Farm Size in Burundi

We use a nonparametric estimation of the production function to investigate the relation- ship between farm productivity and farming scale in poor smallholder agricultural systems in the north of Burundi. Burundi is one of the poorest countries in the world, with a predominant small scale subsistence farming sector. A Kernel regression is used on data of mixed cropping systems to study the determinants of production including different factors that have been identified in literature as missing variables in the testing of the inverse relationship such as soil quality, location and household heterogeneity. Household data on farm activities and crop production was gathered among 640 households in 2007 in two Northern provinces of Burundi. Four production models were specified each with different control variables. For the relatively small farms, we find clear evidence of an inverse relationship. The relatively large farms show a different pattern. Returns to scale are found to be farm scale dependent. Parametric Cobb-Douglass models tend to over-simplify the debate on returns to scale because of not accounting for the different effects of large farms. Other factors that significantly positively affect production include the soil quality and production orientation towards banana or cash crop production. Production seems to be negatively affected by field fragmentation.inverse relationship, farm size, nonparametric, Burundi, Farm Management, Productivity Analysis,

Recovering from conflict: an analysis of food production in Burundi

This paper deals with the devastating food insecurity in two densely populated provinces in the north of Burundi as a result of overpopulation and low production capacity in the aftermath of conflict. We compare data that was collected in the Ngozi and Muyinga Province in 2007 with data of households interviewed on the same hills in 1996. Households live from subsistence farming, erratic surplus sales, sales of coffee and banana and occasional off- and non-farm work. We find that not only did production levels decrease but also total factor productivity (Malmquist indices calculated with DEA approach) dropped in 83% of the hills between 1996 and 2007.food security, post-conflict, Central Africa, Burundi, subsistence farming, poverty trap, International Development,

Dynamic Metabolic Flux Analysis Demonstrated on Cultures Where the Limiting Substrate Is Changed from Carbon to Nitrogen and Vice Versa

The main requirement for metabolic flux analysis (MFA) is that the cells are in a pseudo-steady state, that there is no accumulation or depletion of intracellular metabolites. In the past, the applications of MFA were limited to the analysis of continuous cultures. This contribution introduces the concept of dynamic MFA and extends MFA so that it is applicable to transient cultures. Time series of concentration measurements are transformed into flux values. This transformation involves differentiation, which typically increases the noisiness of the data. Therefore, a noise-reducing step is needed. In this work, polynomial smoothing was used. As a test case, dynamic MFA is applied on Escherichia coli cultivations shifting from carbon limitation to nitrogen limitation and vice versa. After switching the limiting substrate from N to C, a lag phase was observed accompanied with an increase in maintenance energy requirement. This lag phase did not occur in the C- to N-limitation case

Phenotypes induced by NM causing α-skeletal muscle actin mutants in fibroblasts, Sol 8 myoblasts and myotubes

<p>Abstract</p> <p>Background</p> <p>Nemaline myopathy is a neuromuscular disorder characterized by the presence of nemaline bodies in patient muscles. 20% of the cases are associated with α-skeletal muscle actin mutations. We previously showed that actin mutations can cause four different biochemical phenotypes and that expression of NM associated actin mutants in fibroblasts, myoblasts and myotubes induces a range of cellular defects.</p> <p>Findings</p> <p>We conducted the same biochemical experiments for twelve new actin mutants associated with nemaline myopathy. We observed folding and polymerization defects. Immunostainings of these and eight other mutants in transfected cells revealed typical cellular defects such as nemaline rods or aggregates, decreased incorporation in F-actin structures, membrane blebbing, the formation of thickened actin fibres and cell membrane blebbing in myotubes.</p> <p>Conclusion</p> <p>Our results confirm that NM associated α-actin mutations induce a range of defects at the biochemical level as well as in cultured fibroblasts and muscle cells.</p

Earlier initiation of antiretroviral treatment coincides with an initial control of the HIV-1 sub-subtype F1 outbreak among men-having-sex-with-men in Flanders, Belgium

Human immunodeficiency virus type 1 (HIV-1) non-B subtype infections occurred in Belgium since the 1980s, mainly amongst migrants and heterosexuals, whereas subtype B predominated in men-having-sex-with-men (MSM). In the last decade, the diagnosis of F1 sub-subtype in particular has increased substantially, which prompted us to perform a detailed reconstruction of its epidemiological history. To this purpose, the Belgian AIDS Reference Laboratories collected HIV-1 pol sequences from all sub-subtype F1-infected patients for whom genotypic drug resistance testing was requested as part of routine clinical follow-up. This data was complemented with HIV-1 pol sequences from countries with a high burden of F1 infections or a potential role in the global origin of sub-subtype F1. The molecular epidemiology of the Belgian subtype F1 epidemic was investigated using Bayesian phylogenetic inference and transmission dynamics were characterized based on birth-death models. F1 sequences were retained from 297 patients diagnosed and linked to care in Belgium between 1988 and 2015. Phylogenetic inference indicated that among the 297 Belgian F1 sequences, 191 belonged to a monophyletic group that mainly contained sequences from people likely infected in Belgium (OR 26.67, 95% CI 9.59-74.15), diagnosed in Flanders (OR 7.28, 95% CI 4.23-12.53), diagnosed at a recent stage of infection (OR 7.19, 95% CI 2.88-17.95) or declared to be MSM (OR 34.8, 95% CI 16.0-75.6). Together with a Spanish clade, this Belgian clade was embedded in the genetic diversity of Brazilian subtype F1 strains and most probably emerged after one or only a few migration events from Brazil to the European continent before 2002. The origin of the Belgian outbreak was dated back to 2002 (95% higher posterior density 2000-2004) and birth-death models suggested that its extensive growth had been controlled (Re < 1) by 2012, coinciding with a time period where delay in antiretroviral treatment initiation substantially declined. In conclusion, phylogenetic reconstruction of the Belgian HIV-1 sub-subtype F1 epidemic illustrates the introduction and substantial dissemination of viral strains in a geographically restricted risk group that was most likely controlled by effective treatment as prevention.publishersversionpublishe

Phosphorus-efficient soybean germplasm as an entry point to integrated soil fertility management in Western Kenya

A spiral of ever-decreasing soil fertility is threatening the livelihoods of smallholder farmers in Western Kenya. While high population pressure leads to the cutback of fallow periods, the use of large amounts of fertilizers is neither within reach of resource-poor farmers nor sustainable on the long term because of finite phosphate rock reserves. A realistic approach to increase production levels and to counteract soil fertility decline is integrated soil fertility management (ISFM), which combines improved germplasm with judicious use of mineral fertilizers and organic amendments. As nitrogen (N) is the most limiting nutrient in most agricultural systems, the cultivation of legumes, which can fix N from atmospheric N2, may reverse the downward trend in soil fertility, and legumes therefore play an important role in ISFM. However, many soils in Western Kenya are characterized by low P availability and high P-sorption. Legumes such as soybean (Glycine max) are particularly sensitive to P deficiency as nodulation and N fixation largely depend on P supply. In this context, the selection and development of soybean genotypes that are adapted to low P conditions is highly needed. Plants can adapt to P-limiting conditions through the development of P-uptake enhancing root traits (P uptake efficiency) or through a change in physiological processes that affect the use of P in the plant tissue (P utilization efficiency). The objectives of this study were to assess variation in P uptake and utilization efficiencies among soybean genotypes, to investigate the occurrence of root characteristics that contribute to P uptake efficiency, and to evaluate how the incorporation of P-efficient soybean germplasm into ISFM systems may improve soil fertility and P fertilizer use efficiency. First, a methodological framework was implemented to compare plant growth at low P supply among soybean genotypes that largely differ in yield potential at high P supply. A distinction was made between P productivity , measured as absolute biomass or grain yield at a given suboptimal P level, and P efficiency , measured as biomass or grain yield at suboptimal P relative to corresponding values at optimal P. In addition, a new index, the suboptimal P tolerance index (SPTIbiomass) , was introduced by multiplying P productivity and P efficiency. With regard to P uptake, a similar terminology was adopted (P uptake productivity, P uptake efficiency and SPTIuptake). A pot trial was set up to evaluate variation in these low P tolerance indices among 40 soybean genotypes at early growth stages. Further, the response of 20 soybean genotypes to suboptimal and optimal levels of P fertilizer application was evaluated in a multi-location field trial in Western Kenya. In the pot trial, a 2-fold variation in P uptake productivity and a 2.5-fold variation in P uptake efficiency among genotypes was observed, but no variation in P efficiency and the SPTIbiomass could be demonstrated. In the field trial, a significant 2-fold variation in P efficiency and 6-fold variation in SPTIbiomass among genotypes was observed. P uptake efficiency and P utilization efficiency correlated negatively in the pot trial, which indicated that a trade-off exists between both components of P efficiency. Strong positive correlations between P efficiency and P uptake efficiency in both the pot and the field trial demonstrated that variation in overall P efficiency is determined by factors affecting P uptake rather than P utilization. Furthermore, we showed that the use of different indices results in a different ranking of genotypes. In the pot trial, variation in biomass production attributed to the inherent potential (biomass yield under optimal conditions) was eliminated by ranking genotypes in terms of the SPTI, while the same was achieved in the field by ranking in terms of P efficiency.The contribution of different root traits to variation in P uptake efficiency among soybean genotypes grown in a P-deficient Ferralsol was investigated by regression analysis and mechanistic modeling. Eight genotypes were grown in a pot trial at suboptimal and optimal P availability. Root hair growth was visualized by growing plants in a novel agar system where P intensity was buffered by Al2O3 nanoparticles. In the pot trial, P uptake did not vary among the genotypes at optimal P supply but differed about 2-fold at suboptimal P. The genotypes differed in P uptake efficiency but not in P utilization efficiency. Variation among genotypes was observed for several root characteristics that affect P uptake, such as the root to shoot ratio, root diameter, colonization by arbuscular mycorrhizal fungi, and root hair length and density. Regression analysis and mechanistic modeling indicated that P uptake efficiencies were to a large extent related to root hair development (length and density) and, to a lower extent, to colonization by mycorrhizal fungi. Sensitivity analysis showed that root hairs can directly increase P uptake with maximally 36% (through P uptake at the root hair level). Indications were found that the indirect effect of root hairs on P uptake (improved P uptake leading to improved root growth, in turn leading to enhanced P uptake) exceeded the direct effect. Breeding for improved root hair development is suggested as a promising way to increase P uptake efficiency of soybean.Growth and P uptake of 5 soybean genotypes at a suboptimal rate of poorly soluble rock P was compared to that at an equal rate of water-soluble P in 2 moderately acid, P-deficient soils with different P buffering capacity. Mucuna (Mucuna pruriens), which is known for its ability to mobilize sparingly available P, was grown as a reference species. Depending on the genotype, the biomass of soybean at a suboptimal amount of rock P relative to that at an equal rate of soluble P varied between 53 and 86%. The results suggested that mucuna mobilizes sparingly available P through rhizosphere-modifying processes, while soybean is able to take up similar amounts of P through the development of a larger root system. A different ranking of the genotypes in terms of P efficiency was obtained in the 2 soils, indicating that several P uptake-enhancing mechanisms play a role while the relative benefits of such mechanisms depend on the soil physicochemical characteristics.Lastly, we evaluated the response of 5 soybean genotypes to increasing levels of P fertilizer under field conditions in terms of P uptake, N fixation and grain yields, and determined the rotation effect of these genotypes on a subsequent maize crop in terms of N and P nutrition (the N effect and the P effect ). P application increased P uptake, nodulation, N fixation and grain yields, and the soybean genotypes differed largely in P productivity. The results demonstrated that N balances after a season of soybean cropping and N effects of soybean on a subsequent maize crop do not necessarily increase when P rates are increased. Further, no differences in N effects among genotypes and no P effects of soybean on maize were observed. However, we showed that even on strongly P-fixing soils, residual effects of P applied to soybean can largely overcome P limitations to a subsequent maize crop. When P was applied solely to the soybean crop, the total P recovery (P taken up by soybean and maize in percentage of applied P), was significantly higher when P-productive genotypes were incorporated in the rotation. Hence, despite the absence of differences among genotypes in effects on the N and P nutrition of a subsequent maize crop, P fertilizer use efficiency in a soybean-maize rotation can be increased by incorporating P-productive soybean genotypes.status: publishe