Nodulation and nitrogen fixation in promiscuous and non promiscuous soybean (Glycine max (L.) Merrill) varieties in Eastern Kenya

Soil nitrogen deficiency is a major factor limiting soybean production. This problem can be alleviated by the use of nitrogen fertilizers which on the other hand adversely affect the environment, are expensive and unaffordable to most peasant farmers. Alternatively, attention is being paid to improving soil nitrogen through the use of environmental friendly biological nitrogen fixation of soybeans in an attempt to develop sustainable cropping systems. There is however inadequate knowledge on estimates of nitrogen fixation by soybean varieties in Kenya. In light of this, growth experiments were designed to investigate biological nitrogen fixation in promiscuous and non promiscuous soybeans. Results from the field experiment showed that the two promiscuous soybean varieties (TGx 1869 and TGx 1893) nodulated better than the non promiscuous Gazelle. Uninoculated Gazelle did not produce any nodule while uninoculated TGx 1869 and TGx 1893 nodulated with indigenous soil rhizobia. Inoculation affected nodulation since there was a significantly higher mean nodule number in inoculated soybeans (highest in TGx 1869 IN – 76) as compared to uninoculated (highest in TGx 1869 – UNC - 21) and(0.0) in nitrogen treated soybeans at podding. Inoculated soybeans had higher shoot dry weight (highest in TGx 1893 IN - 19.30 g) than uninoculated soybeans (highest in TGx 1869 UNC - 13.50 g) .Stover biomass was higher in inoculated soybeans (13.07 g) than in uninoculated treatments (6.91 g). Although there was no significant difference in seed dry weight of inoculated (14.10 g) and uninoculated (8.11 g), inoculated soybeans had higher seed dry weight. The inoculated TGx varieties had higher seed dry weight (TGx 1869 at 12.94 g and TGx 1893 at 14.10 g) than Gazelle (10.12 g). There is need to adopt growing of promiscuous TGx varieties and to exploit biological nitrogen fixation with the view of increasing soybean yields and decreasing overdependence on nitrogen fertilizers for sustainable agriculture.Key words: Bradyrhizobia, Soybean, Glycine cross, inoculation, nodulation, promiscuous, TGx, nitrogen fixation

Evaluation of the CSM-CROPGRO-Soybean model for dual-purpose soyabean in Kenya

Limited information is available on the potential performance of introduced dual purpose varieties across different Kenyan soils and agro-ecological environments and consistency across sites and seasons. Crop simulation modeling offers an opportunity to explore the potential of and select introduced cultivars for new areas before establishing costly and time-consuming field trials. Dual purpose soybeans were introduced due to their ability to improve soils and at the same time provide substantial grain yields. The objective of this study was to derive genetic coefficients of recently introduced dual purpose soybean varieties and to explore the reliability of the Cropping System Model (CSM)-CROPGRO-Soybean model in simulating phenology and yield of the dual purpose varieties under different environments. Field trials for seven varieties were conducted across three sites in two seasons and data on phenology and management, soil characteristics and weather was collected and used in the CROPGRO model. A stepwise procedure was used in the calibration of the model to derive the genetic coefficients. Two sets of data from Kakamega and Kitale were used in calibration process while 2006 data for Kakamega and Msabaha, were used for evaluation of the model. The derived genetic coefficients provided simulated values of various development and growth parameters that were in good agreement with their corresponding observed values for most parameters. Model evaluation with independent data sets gave similar results. The differences among the cultivars were also expressed through the differences in the derived genetic coefficients. CROPGRO was able to accurately predict growth, phenology and yield. The model predicted the first flowering dates to within 2¿3 days of the observed values, the first pod dates within 3 days of the observed values and yields within 5¿300 kg ha-1 of the observed yields. The genetic coefficients derived in CROPGRO model can, therefore, be used to predict soybean yield and phenology of the dual purpose soybean varieties across different agro-ecological zones. (Résumé d'auteur

Taming the Heat Flux Problem: Advanced Divertors Towards Fusion Power

The next generation fusion machines are likely to face enormous heat exhaust problems. In addition to summarizing major issues and physical processes connected with these problems, we discuss how advanced divertors, obtained by modifying the local geometry, may yield workable solutions. We also point out that: (1) the initial interpretation of recent experiments show that the advantages, predicted, for instance, for the X-divertor (in particular, being able to run a detached operation at high pedestal pressure) correlate very well with observations, and (2) the X-D geometry could be implemented on ITER (and DEMOS) respecting all the relevant constraints. A roadmap for future research efforts is proposed

Higher fusion power gain with profile control in DIII-D tokamak plasmas

Strong shaping, favourable for stability and improved energy confinement, together with a significant expansion of the central region of improved confinement in negative central magnetic shear target plasmas, increased the maximum fusion power produced in DIII-D by a factor of 3. Using deuterium plasmas, the highest fusion power gain, the ratio of fusion power to input power, Q, was 0.0015, corresponding to an equivalent Q of 0.32 in a deuterium-tritium plasma, which is similar to values achieved in tokamaks of larger size and magnetic field. A simple transformation relating Q to the stability parameters is presented

Higher fusion power gain with profile control in DIII-D tokamak plasmas

Strong shaping, favourable for stability and improved energy confinement, together with a significant expansion of the central region of improved confinement in negative central magnetic shear target plasmas, increased the maximum fusion power produced in DIII-D by a factor of 3. Using deuterium plasmas, the highest fusion power gain, the ratio of fusion power to input power, Q, was 0.0015, corresponding to an equivalent Q of 0.32 in a deuterium-tritium plasma, which is similar to values achieved in tokamaks of larger size and magnetic field. A simple transformation relating Q to the stability parameters is presented

Improved understanding of physics processes in pedestal structure, leading to improved predictive capability for ITER

Joint experiment/theory/modelling research has led to increased confidence in predictions of the pedestal height in ITER. This work was performed as part of a US Department of Energy Joint Research Target in FY11 to identify physics processes that control the H-mode pedestal structure. The study included experiments on C-Mod, DIII-D and NSTX as well as interpretation of experimental data with theory-based modelling codes. This work provides increased confidence in the ability of models for peeling-ballooning stability, bootstrap current, pedestal width and pedestal height scaling to make correct predictions, with some areas needing further work also being identified. A model for pedestal pressure height has made good predictions in existing machines for a range in pressure of a factor of 20. This provides a solid basis for predicting the maximum pedestal pressure height in ITER, which is found to be an extrapolation of a factor of 3 beyond the existing data set. Models were studied for a number of processes that are proposed to play a role in the pedestal ne and Te profiles. These processes include neoclassical transport, paleoclassical transport, electron temperature gradient turbulence and neutral fuelling. All of these processes may be important, with the importance being dependent on the plasma regime. Studies with several electromagnetic gyrokinetic codes show that the gradients in and on top of the pedestal can drive a number of instabilities. © 2013 IAEA, Vienna