Decomposition of and nutrient release from ruminant manure on acid sandy soils in the Sahelian zone of Niger, West Africa

In ago-pastoral systems of the semi-arid West African Sahel, targeted applications of ruminant manure to the cropland is a widespread practice to maintain soil productivity. However, studies exploring the decomposition and mineralisation processes of manure under farmers' conditions are scarce. The present research in south-west Niger was undertaken to examine the role of micro-organisms and meso-fauna on in situ release rates of nitrogen (N), phosphorus (P) and potassium (K) from cattle and sheep-goat manure collected from village corrals during the rainy season. The results show tha (1) macro-organisms played a dominant role in the initial phase of manure decomposition; (2) manure decomposition was faster on crusted than on sandy soils; (3) throughout the study N and P release rates closely followed the dry matter decomposition; (4) during the first 6 weeks after application the K concentration in the manure declined much faster than N or P. At the applied dry matter rate of 18.8 Mg ha^-1, the quantities of N, P and K released from the manure during the rainy season were up to 10-fold larger than the annual nutrient uptake of pearl millet (Pennisetum glaucum L.), the dominant crop in the traditional agro-pastoral systems. The results indicate considerable nutrient losses with the scarce but heavy rainfalls which could be alleviated by smaller rates of manure application. Those, however, would require a more labour intensive system of corralling or manure distribution.

Causes of legume-rotation effects in increasing cereal yields across the Sudanian, Sahelian and Guinean zone of West Africa

On-farm experiments and pot trials were conducted on eight West African soils to explore the mechanisms governing the often reported legume rotation-induced cereal growth increases in this region. Crops comprised pearl millet (Pennisetum glaucum L.), sorghum (Sorghum bicolor Moench), maize (Zea mays L.), cowpea (Vigna unguiculata Walp.) and groundnut (Arachis hypogaea L.). In groundnut trials the observed 26 to 85% increases in total dry matter (TDM) of rotation cereals (RC) compared with continuous cereals (CC) in the 4th year appeared to be triggered by site- and crop-specific early season differences in nematode infestation (up to 6-fold lower in RC than in CC), enhanced Nmin and a 7% increase in mycorrhizal (AM) infection. In cowpea trials yield effects on millet and differences in nematode numbers, Nmin and AM were much smaller. Rhizosphere studies indicated effects on pH and acid phosphatase activity as secondary causes for the observed growth differences between RC and CC. In the study region legume-rotation effects on cereals seemed to depend on the capability of the legume to suppress nematodes and to enhance early N and P availability for the subsequent cereal.

Fliesslochformen und Gewindefurchen in dünne Bleche und Rohre aus Kupfer und Kupferlegierungen

This thesis in Thermal Flow Drilling and Flowtap in thin metal sheet and pipes of copper and copper alloys had as objectives to know the comportment of copper and copper alloys sheet metal during the Thermal Flow Drill processes with normal tools, to know the best Speed and Feed machine data for the best bushing quality, to known the best Speed for Form Tapping processes and to know the best bush long in pure copper pipes for water solar interchange equipment. Thermal Flow Drilling (TFD) and Form Tapping (FT) is one of the research lines of the Institute of Production and Logistics (IPL) at University of Kassel. At December 1995, a work meeting of IPL, Santa Catarina University, Brazil, Buenos Aires University, Argentine, Tarapacá University (UTA), Chile members and the CEO of Flowdrill B.V. was held in Brazil. The group decided that the Manufacturing Laboratory (ML) of UTA would work with pure copper and brass alloys sheet metal and pure copper pipes in order to develop a water interchange solar heater. The Flowdrill BV Company sent tools to Tarapacá University in 1996. In 1999 IPL and the ML carried out an ALECHILE research project promoted by the DAAD and CONICyT in copper sheet metal and copper pipes and sheet metal a-brass alloys. The normal tools are lobed, conical tungsten carbide tool. When rotated at high speed and pressed with high axial force into sheet metal or thin walled tube generated heat softens the metal and allows the drill to feed forward produce a hole and simultaneously form a bushing from the displacement material. In the market exist many features but in this thesis is used short and longs normal tools of TFD. For reach the objectives it was takes as references four qualities of the frayed end bushing, where the best one is the quality class I. It was used pure copper and a-brass alloys sheet metals, with different thickness. It was used different TFD drills diameter for four thread type, from M-5 to M10. Similar to the Aluminium sheet metals studies it was used the predrilling processes with HSS drills around 30% of the TFD diameter (1,5 – 3,0 mm D). In the next step is used only 2,0 mm thick metal sheet, and 9,2 mm TFD diameter for M-10 thread. For the case of pure commercial copper pipes is used for ¾” inch diameter and 12, 8 mm (3/8”) TFD drill for holes for 3/8” pipes and different normal HSS drills for predrilling processes. The chemical sheet metal characteristics were takes as reference for the material behaviour. The Chilean pure copper have 99,35% of Cu and 0,163% of Zinc and the Chilean a-brass alloys have 75,6% of Cu and 24,0% of Zinc. It is used two German a-brass alloys; Nº1 have 61,6% of Cu, 36,03 % of Zinc and 2,2% of Pb and the German a-brass alloys Nº2 have 63,1% of Cu, 36,7% of Zinc and 0% of Pb. The equipments used were a HAAS CNC milling machine centre, a Kistler dynamometer, PC Pentium II, Acquisition card, TESTPOINT and XAct software, 3D measurement machine, micro hardness, universal test machine, and metallographic microscope. During the test is obtained the feed force and momentum curves that shows the material behaviour with TFD processes. In general it is take three phases. It was possible obtain the best machining data for the different sheet of copper and a-brass alloys thick of Chilean materials and bush quality class I. In the case of a-brass alloys, the chemical components and the TFD processes temperature have big influence. The temperature reach to 400º Celsius during the TFD processes and the a-brass alloys have some percents of Zinc the bush quality is class I. But when the a-brass alloys have some percents of Lead who have 200º C melting point is not possible to obtain a bush, because the Lead gasify and the metallographic net broke. During the TFD processes the recrystallization structures occur around the Copper and a-brass alloy bush, who gives more hardness in these zones. When the threads were produce with Form Tapping processes with Flowtap tools, this hardness amount gives a high limit load of the thread when hey are tested in a special support that was developed for it. For eliminated the predrilling processes with normal HSS drills it was developed a compound tool. With this new tool it was possible obtain the best machining data for quality class I bush. For the copper pipes it is made bush without predrilling and the quality class IV was obtained. When it is was used predrilling processes, quality classes I bush were obtained. Then with different HSS drill diameter were obtained different long bush, where were soldering with four types soldering materials between pipes with 3/8” in a big one as ¾”. Those soldering unions were tested by traction test and all the 3/8” pipes broken, and the soldering zone doesn’t have any problem. Finally were developed different solar water interchange heaters and tested. As conclusions, the present Thesis shows that the Thermal Flow Drilling in thinner metal sheets of cooper and cooper alloys needs a predrilling process for frayed end quality class I bushings, similar to thinner sheets of aluminium bushes. The compound tool developed could obtain quality class I bushings and excludes predrilling processes. The bush recrystalization, product of the friction between the tool and the material, the hardness grows and it is advantageous for the Form Tapping. The methodology developed for commercial copper pipes permits to built water solar interchange heaters.

Evaluating partial root-zone irrigation and mulching in okra (Abelmoschus esculentus L.) under a sub-humid tropical climate

The field experiments were conducted to compare the alternate partial root-zone irrigation (APRI) with and without black plastic mulch (BPM) with full root-zone irrigation (FRI) in furrow-irrigated okra (Abelmoschus esculentus L. Moench) at Bhubaneswar, India. APRI means that one of the two neighbouring furrows was alternately irrigated during consecutive watering. FRI was the conventional method where every furrow was irrigated during each watering. The used irrigation levels were 25% available soil moisture depletion (ASMD), 50% ASMD, and 75% ASMD. The plant growth and yield parameters were observed to be significantly (p < 0.05) higher with frequent irrigation (at 25% ASMD) under all irrigation strategies. However, APRI + BPM produced the maximum plant growth and yield using 22% and 56% less water over APRI without BPM and FRI, respectively. The highest pod yield (10025 kg ha^-1) was produced under APRI at 25% ASMD + BPM, which was statistically at par with the pod yield under APRI at 50% ASMD + BPM. Irrigation water use efficiency (IWUE), which indicates the pod yield per unit quantity of irrigation water, was estimated to be highest (12.3 kg m^-3) under APRI at 50% ASMD + BPM, followed by APRI at 25% ASMD + BPM. Moreover, the treatment APRI at 50% ASMD + BPM was found economically superior to other treatments, generating more net return (US $ 952 ha^-1) with higher benefit–cost ratio (1.70).

Squeezed thermal phonons precurse nonthermal melting of silicon as a function of fluence

A femtosecond-laser pulse can induce ultrafast nonthermal melting of various materials along pathways that are inaccessible under thermodynamic conditions, but it is not known whether there is any structural modification at fluences just below the melting threshold. Here, we show for silicon that in this regime the room-temperature phonons become thermally squeezed, which is a process that has not been reported before in this material. We find that the origin of this effect is the sudden femtosecond-laser-induced softening of interatomic bonds, which can also be described in terms of a modification of the potential energy surface. We further find in ab initio molecular-dynamics simulations on laser-excited potential energy surfaces that the atoms move in the same directions during the first stages of nonthermal melting and thermal phonon squeezing. Our results demonstrate how femtosecond-laser-induced coherent fluctuations precurse complete atomic disordering as a function of fluence. The common underlying bond-softening mechanism indicates that this relation between thermal squeezing and nonthermal melting is not material specific.

Dairy farms typology and management of animal genetic resources in the peri-urban zone of Bamako (Mali)

Facing growth in demand, dairy production in peri-urban areas of developing countries is changing rapidly. To characterise this development around Bamako (Mali), this study establishes a typology of dairy production systems with a special focus on animal genetic resources. The survey included 52 dairy cattle farms from six peri-urban sites. It was conducted in 2011 through two visits, in the dry and harvest seasons. The median cattle number per farm was 17 (range 5-118) and 42% of farmers owned cropland (8.3 +/- 7.3 ha, minimum 1 ha, maximum 25 ha). Feeding strategy was a crucial variable in farm characterisation, accounting for about 85% of total expenses. The use of artificial insemination and a regular veterinary follow-up were other important parameters. According to breeders’ answers, thirty genetic profiles were identified, from local purebreds to different levels of crossbreds. Purebred animals raised were Fulani Zebu (45.8%), Maure Zebu (9.2%), Holstein (3.0%), Azawak Zebu (1.3%), Mere Zebu (0.5%) and Kuri taurine (0.1%). Holstein crossbred represented 30.5% of the total number of animals (19.0% Fulani-Holstein, 11.2% Maure-Holstein and 0.3% Kuri-Holstein). Montbéliarde, Normande and Limousin crossbreds were also found (6.6%, 0.7% and 0.3%, respectively). A multivariate analysis helped disaggregate the diversity of management practices. The high diversity of situations shows the need for consideration of typological characteristics for an appropriate intervention. Although strongly anchored on local breeds, the peri-urban dairy systems included a diversity of exotic cattle, showing an uncoordinated quest of breeders for innovation. Without a public intervention, this dynamic will result in an irremediable erosion of indigenous animal genetic resources.

Atomistic-continuum modeling of ultrafast laser-induced melting of silicon targets

In this work, we present an atomistic-continuum model for simulations of ultrafast laser-induced melting processes in semiconductors on the example of silicon. The kinetics of transient non-equilibrium phase transition mechanisms is addressed with MD method on the atomic level, whereas the laser light absorption, strong generated electron-phonon nonequilibrium, fast heat conduction, and photo-excited free carrier diffusion are accounted for with a continuum TTM-like model (called nTTM). First, we independently consider the applications of nTTM and MD for the description of silicon, and then construct the combined MD-nTTM model. Its development and thorough testing is followed by a comprehensive computational study of fast nonequilibrium processes induced in silicon by an ultrashort laser irradiation. The new model allowed to investigate the effect of laser-induced pressure and temperature of the lattice on the melting kinetics. Two competing melting mechanisms, heterogeneous and homogeneous, were identified in our big-scale simulations. Apart from the classical heterogeneous melting mechanism, the nucleation of the liquid phase homogeneously inside the material significantly contributes to the melting process. The simulations showed, that due to the open diamond structure of the crystal, the laser-generated internal compressive stresses reduce the crystal stability against the homogeneous melting. Consequently, the latter can take a massive character within several picoseconds upon the laser heating. Due to the large negative volume of melting of silicon, the material contracts upon the phase transition, relaxes the compressive stresses, and the subsequent melting proceeds heterogeneously until the excess of thermal energy is consumed. A series of simulations for a range of absorbed fluences allowed us to find the threshold fluence value at which homogeneous liquid nucleation starts contributing to the classical heterogeneous propagation of the solid-liquid interface. A series of simulations for a range of the material thicknesses showed that the sample width we chosen in our simulations (800 nm) corresponds to a thick sample. Additionally, in order to support the main conclusions, the results were verified for a different interatomic potential. Possible improvements of the model to account for nonthermal effects are discussed and certain restrictions on the suitable interatomic potentials are found. As a first step towards the inclusion of these effects into MD-nTTM, we performed nanometer-scale MD simulations with a new interatomic potential, designed to reproduce ab initio calculations at the laser-induced electronic temperature of 18946 K. The simulations demonstrated that, similarly to thermal melting, nonthermal phase transition occurs through nucleation. A series of simulations showed that higher (lower) initial pressure reinforces (hinders) the creation and the growth of nonthermal liquid nuclei. For the example of Si, the laser melting kinetics of semiconductors was found to be noticeably different from that of metals with a face-centered cubic crystal structure. The results of this study, therefore, have important implications for interpretation of experimental data on the kinetics of melting process of semiconductors.