239 research outputs found
Design and evaluation of a no-tillage seeder for small scale vegetable production using a two-wheeled tractor in Coahuila, Mexico
Currently used conventional tillage systems for small-scale vegetable production in the region of Saltillo, Coahuila, Mexico require a considerable amount of hand labor, energy and materials for all activities. Seedbed preparation can require up to 60% of the total production cost in some systems in Mexico. Further, soil is degraded and eroded due to the system. Conservation tillage may reduce costs and prevent soil degradation, but appropriate tools, such as, no-tillage seeders for small-scale farmers are not available. This papers reports on the design and construction of a prototype of a no-tillage seeder for small-scale conservation tillage using a 2-wheeled tractor. Three main functions received particular attention: opening of the soil, placing seed and/or fertilizer and closing the slot. Because of its vapor conservation and good seedling emergence, tools to create T-shaped slots were chosen, with adapted depth control and closing and covering devices. A systematic design process was applied in order to reach the required decisions. Function diagrams were defined from where morphologic charts guided the selection of the configuration of the seeder. A preliminary evaluation included testing of two furrow opener disc types (notched and fluted), and four crop residue levels, 0, 30, 60 and 100%, with respect to performance of the seeder. An evaluation showed that with low cover amounts a consistent and firm seed cover was obtained, but emergence quality decreased due to insufficient residue cover. The notched disc had a better performance than the fluted disc. The inverted T-shape in the soil was not always sustained due to technical flaws. It was possible to build a prototype under 2000 dollars with basic tools in a local workshop. Further research will focus on the biological performance and improvement of the mechanical components and performance
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
Infiltration, runoff and drainage in the Sudano-Sahelian zone
We present a brief overview of methods suitable
for measuring or estimating infiltration. runoff or drainage.
Since an exhaustive mrvior is not fcaaibie in the context
of this paper, the emphasis h on field methods which are
not too complicated or expensive, and suitable for use in
the Sudano Sahelian zone. Methods for measurements over
large areas, e.& catchments. are not included. Obviously, for
natural events where interception of rainfall by the
vegetation can be ignored. Idbation and runoff together
equal precipitation: onh. two of the three procuacs need be
quantified to quantib the other. For each method a brief
dewription is given, together with a suitable reference for
further information
Retention of Antimicrobial Activity in Plaque and Saliva following Mouthrinse Use in vivo
The aim of this study was to determine the contribution of plaque and saliva towards the prolonged activity, also called substantivity, of three antimicrobial mouthrinses (Listerine (R), Meridol (R), Crest Pro Health (R)), used in combination with a toothpaste (Prodent Coolmint (R)). Volunteers brushed for 4 weeks with a toothpaste without antimicrobial claims, while during the last 2 weeks half of the volunteers used an antimicrobial mouthrinse in addition to brushing. At the end of the experimental period, plaque and saliva samples were collected 6 h after oral hygiene, and bacterial concentrations and viabilities were determined. The contribution of plaque and saliva towards substantivity was assessed by combining plaque obtained after mechanical cleaning only with plaque and saliva obtained after additional use of an antimicrobial rinse. Subsequently, resulting viabilities of the combined plaques were determined. The viabilities of plaque samples after additional rinsing with mouthrinses were lower than of plaque obtained after mechanical cleaning only, regardless of the rinse involved. Moreover, plaque collected 6 h after rinsing with antimicrobial mouthrinses contained a surplus of antimicrobial activity. Only Listerine showed decreased vi
The concept of remembrance in Walter Benjamin
This thesis argues that the role played by the concept of remembrance (Eingedenken)
in Walter Benjamin's 'theory of the knowledge of history' and in his engagement with
Enlightenment universal history, is a crucial one. The implications of Benjamin's
contention that history's 'original vocation' is 'remembrance' have hitherto gone
largely unnoticed. The following thesis explores the meaning of the concept of
remembrance and assesses the significance of this proposed link between history and
memory, looking at both the mnemonic aspect of history and the historical facets of
memory. It argues that by mobilising the simultaneously destructive and constructive
capacities of remembrance, Benjamin sought to develop a critical historiography
which would enable a radical encounter with a previously suppressed past. In so doing
he takes up a stance (explicit and implicit) towards existing philosophical conceptions
of history, in particular the idea of universal history found in German Idealism.
Benjamin reveals an intention to retain the epistemological aspirations of universal
history whilst ridding that approach of its apologetic moment. He criticises existing
conceptions of history on the basis that each assumes homogeneous time to be the
framework in which historical events occur. Insight into the distinctive temporality of
remembrance proves to be the touchstone for this critique, and provides a paradigm
for a very different conception of time. The thesis goes on to determine what is valid
and what is problematic both in this concept of remembrance and in the theory of
historical knowledge which it informs, by subjecting both to the most cogent
criticisms which can be levelled at them. What emerges is not only the importance of
this concept for an understanding of Benjamin's philosophy but the pertinence of this
concept for any philosophical account of memory
Vee(n)houderij : rendabel mobiel melken in het Westelijk veenweidegebied
Over de problematiek van de melkveehouderij in het veengebied. Mobiele melkstal, mobiel melken in de regio Woerden - Bodegrave
Comment on Spracklandus Hoser, 2009 (Reptilia, Serpentes, ELAPIDAE): request for confirmation of the availability of the generic name and for the nomenclatural validation of the journal in which it was published (Case 3601; see BZN 70: 234–237; 71: 30–38, 133–135, 181–182, 252–253)
Effects of liposomal-curcumin on five opportunistic bacterial strains found in the equine hindgut - preliminary study
Author Correction: The global distribution of tetrapods reveals a need for targeted reptile conservation
- …