Assessment of strip tillage systems for maize production in semi-arid Ethiopia: effects on grain yield and water balance

International audienceThe traditional tillage implement, the Maresha plow, and the tillage systems that require repeated and cross plowing have caused poor rainfall partitioning, land degradation and hence low water productivity in Ethiopia. Conservation tillage could alleviate these problems. However, no-till can not be feasible for smallholder farmers in semi-arid regions of Ethiopia because of difficulties in maintaining soil cover due to low rainfall and communal grazing and because of high costs of herbicides. Strip tillage systems may offer a solution. This study was initiated to test strip tillage systems using implements that were modified forms of the Maresha plow, and to evaluate the impacts of the new tillage systems on water balance and grain yields of maize (Zea mays XX). Experiments were conducted in two dry semi arid areas called Melkawoba and Wulinchity, in the central Rift Valley of Ethiopia during 2003?2005. Strip tillage systems that involved cultivating planting lines at a spacing of 0.75 m using the Maresha plow followed by subsoiling along the same lines (STS) and without subsoiling (ST) were compared with the traditional tillage system of 3 to 4 times plowing with the Maresha plow (CONV). Soil moisture was monitored to a depth of 1.8 m using Time Domain Reflectometer while surface runoff was measured using rectangular trough installed at the bottom of each plot. STS resulted in the least surface runoff (Qs=17 mm-season?1), the highest transpiration (T=196 mm-season?1), the highest grain yields (Y=2130 kg-ha?1) and the highest water productivity using total evaporation (WPET=0.67 kg-m?3) followed by ST (Qs=25 mm-season?1, T=178 mm-season?1, Y=1840 kg-ha?1, WPET=0.60 kg-m?3) and CONV (Qs=40 mm-season?1,T=158 mm-season?1, Y=1720 kg-ha?1, WPET=0.58 kg-m?3). However, when the time between the last tillage operation and planting of maize was more than 26 days, the reverse occurred. There was no statistically significant change in soil physical and chemical properties after three years of experimenting with different tillage systems

Routine Violence Risk Assessment in Community Forensic Mental Healthcare

We developed a method for periodic monitoring of violence risk, as part of routine community forensic mental healthcare. The feasibility of the method was tested, as well as its predictive validity for violent and risk enhancing behavior in the subsequent months. Participants were 83 clients who received forensic psychiatric home treatment, and six case managers. The method proved feasible and informative. Violent and risk enhancing behavior could be predicted to a reasonable extent (AUC = .77, 95% CI = .70-.85; respectively .76, .70-.82). Dynamic risk factors had an incremental predictive value over static factors in the prediction of violent behavior (OR = 4.30, 1.72-10.73). The professional judgment of the case managers added further predictive power (OR = 2.16, 1.40-3.33), corroborating the structured professional judgment approach. Finally, unmet needs for care of the client were associated with a reduced risk for violent and risk enhancing behavior (OR = .80, 0.69-0.93, and 0.84, 0.72-0.97). This latter finding suggests that in cases with unmet needs the case manager saw opportunities to do something about the risk. Currently we are testing whether using the method actually prevents violence. Copyright (C) 2009 John Wiley & Sons, Ltd

A distributed stream temperature model using high resolution temperature observations

International audienceDistributed temperature data are used as input and as calibration data for an energy based temperature model of a first order stream in Luxembourg. A DTS (Distributed Temperature Sensing) system with a fiber optic cable of 1500 m was used to measure stream water temperature with 1 m resolution each 2 min. Four groundwater inflows were identified and quantified (both temperature and relative discharge). The temperature model calculates the total energy balance including solar radiation (with shading effects), longwave radiation, latent heat, sensible heat and river bed conduction. The simulated temperature is compared with the observed temperature at all points along the stream. Knowledge of the lateral inflow appears to be crucial to simulate the temperature distribution and conversely, that stream temperature can be used successfully to identify sources of lateral inflow. The DTS fiber optic is an excellent tool to provide this knowledge

Dopant compensation in alloyed CH3NH3PbBr3-xClx perovskite single crystals for gamma-ray spectroscopy

Organic–inorganic halide perovskites (OIHPs) bring an unprecedented opportunity for radiation detection with their defect-tolerance nature, large mobility–lifetime product, and simple crystal growth from solution. Here we report a dopant compensation in alloyed OIHP single crystals to overcome limitations of device noise and charge collection, enabling γ-ray spectrum collection at room temperature. CH3NH3PbBr3 and CH3NH3PbCl3 are found to be p-type and n-type doped, respectively, whereas dopant-compensated CH3NH3PbBr2.94Cl0.06 alloy has over tenfold improved bulk resistivity of 3.6 × 109 Ω cm. Alloying also increases the hole mobility to 560 cm2 V−1 s−1, yielding a high mobility–lifetime product of 1.8 × 10−2 cm2 V−1. The use of a guard ring electrode in the detector reduces the crystal surface leakage current and device dark current. A distinguishable 137Cs energy spectrum with comparable or better resolution than standard scintillator detectors is collected under a small electric field of 1.8 V mm−1 at room temperature

Efficient photogeneration of charge carriers in silicon nanowires with a radial doping gradient

From electrodeless time-resolved microwave conductivity measurements, the efficiency of charge carrier generation, their mobility, and decay kinetics on photo-excitation were studied in arrays of Si nanowires grown by the vapor-liquid-solid mechanism. A large enhancement in the magnitude of the photoconductance and charge carrier lifetime are found depending on the incorporation of impurities during the growth. They are explained by the internal electric field that builds up, due to a higher doped sidewalls, as revealed by detailed analysis of the nanowire morphology and chemical composition

Twenty-Three Unsolved Problems in Hydrology (UPH) – a Community Perspective

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come